Diagnostic Accuracy of High-Resolution Multidetector CT Compared to MRI in Local Staging of Rectal Cancer: A Prospective Study

Diagnostic Accuracy of High-Resolution Multidetector CT Compared to MRI in Local Staging of Rectal Cancer: A Prospective Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Diagnostic Accuracy of High-Resolution Multidetector CT Compared to MRI in Local Staging of Rectal Cancer: A Prospective Study Islam Haney Shawali, Yomna Dokmak, Mohamed Tamer Mohamed Mostafa, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7364470/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Magnetic resonance imaging (MRI) remains the gold standard for local staging of rectal cancer due to its superior soft-tissue contrast. However, its limited accessibility, high cost, and potential for delay in imaging workflows, particularly in low-resource settings, necessitate the exploration of alternative modalities. Recent advances in multidetector computed tomography (MDCT) allow for high-resolution multiplanar imaging that may be suitable for local rectal staging Purpose: To evaluate the diagnostic accuracy of high-resolution MDCT for local staging of rectal cancer, compared to MRI Methods: This prospective study included 40 patients with biopsy-confirmed rectal carcinoma. All underwent pelvic MRI and contrast-enhanced MDCT with an optimized early venous phase protocol. Imaging findings were compared across T stage, N stage, circumferential resection margin (CRM) involvement, and detection of distant metastases. MRI served as the reference standard. Agreement between modalities was assessed using weighted kappa statistics; diagnostic accuracy parameters were calculated for MDCT Results: MDCT demonstrated excellent concordance with MRI for T3–T4 staging (κ = 0.82), with 100% sensitivity and 95% overall accuracy. CRM assessment showed perfect agreement between modalities (κ = 1.0). For nodal staging, MDCT achieved a kappa value of 0.73, with a sensitivity of 100% and specificity of 77%. Distant metastases were detected in 4 patients (10%) by MDCT but missed on MRI. MDCT over-staged early-stage tumors in several cases Conclusion: High-resolution MDCT, when performed with a standardized protocol, provides excellent diagnostic accuracy for local staging of advanced rectal cancer and offers additional benefit in systemic assessment. It represents a valuable alternative when MRI is unavailable or delayed. Rectal cancer MRI MDCT T staging N staging Circumferential resection margin High-resolution CT Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Background Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second leading cause of cancer-related death globally. Approximately one-third of CRC cases originate in the rectum, with over 40% of rectal tumors located within 6 cm of the anal verge [ 1 ]. Accurate local staging is essential for determining the optimal therapeutic approach, particularly in guiding decisions regarding neoadjuvant chemoradiotherapy (NACRT) and surgical planning. The advent of total mesorectal excision (TME) and the use of NACRT for locally advanced rectal cancer have significantly improved patient outcomes by reducing local recurrence rates and enhancing overall survival [ 2 ]. Accurate assessment of tumor depth (T stage), nodal involvement (N stage), and circumferential resection margin (CRM) involvement is crucial for predicting resectability and tailoring treatment strategies [ 3 ]. Magnetic resonance imaging (MRI) is currently regarded as the gold standard for local staging of rectal cancer due to its superior soft tissue contrast and multiplanar imaging capabilities [ 4 ]. It plays a pivotal role in evaluating tumor extension beyond the rectal wall and assessing the relationship to the mesorectal fascia (MRF). However, in resource-limited settings, the routine use of MRI is often hindered by restricted availability, high costs, and long waiting lists, which can lead to delays in initiating treatment [ 5 , 6 ]. In Egypt and many developing countries, the number of MRI scanners per capita is critically low, with only two MRI units available per million people, significantly below international benchmarks [ 7 ]. Moreover, MRI services are often prioritized for neurological and musculoskeletal applications, further limiting access for oncologic imaging. Computed tomography (CT), in contrast, is widely available and commonly used for metastatic screening in colorectal cancer patients. Technological advancements in multidetector CT (MDCT), such as thin-slice collimation, rapid acquisition, and multiplanar reconstruction, have enhanced CT’s capability in local tumor assessment [ 8 ]. Several studies have demonstrated the potential of MDCT in evaluating advanced rectal cancer, particularly for T3–T4 tumors and CRM involvement [ 9 ]. Nevertheless, CT remains less reliable for accurately staging early T1–T2 tumors and assessing lymph node involvement due to its limited soft tissue contrast resolution [ 10 ]. Standardizing high-resolution CT protocols, including early venous phase imaging, may improve diagnostic performance and offer a practical alternative where MRI access is constrained. Against this background, the current study aimed to evaluate the diagnostic accuracy of high-resolution MDCT in the local staging of rectal cancer, using MRI as the reference standard. We specifically assessed the agreement between MDCT and MRI in determining T stage, N stage, CRM involvement, and detection of distant metastases. Methods Study Design and Population This prospective study was conducted at Kasr Al-Ainy Hospital between October 2022 and May 2023. A total of 40 patients with histopathologically confirmed rectal adenocarcinoma were consecutively enrolled. Inclusion criteria were: age ≥ 18 years and biopsy-proven rectal carcinoma. Exclusion criteria included contraindications to iodinated contrast media (e.g., severe renal impairment, history of contrast allergy), pregnancy, and body habitus exceeding CT gantry weight limits [ 11 ]. All patients underwent both high-resolution pelvic MRI and contrast-enhanced multidetector computed tomography (MDCT) within a maximum interval of 7 days. MRI was used as the reference standard for local staging. Ethical approval was obtained from the Institutional Review Board (IRB), and informed consent was acquired from all participants. CT Imaging Protocol MDCT examinations were performed using a 128-slice CT scanner (GE, 128-detector mode). Patients underwent mild bowel preparation with 1 liter of polyethylene glycol the night before the scan and were instructed to fast for at least 6 hours prior to the examination. Intravenous contrast material (iopromide, 350 mg/mL) was administered at a dose of 1–1.5 mL/kg, with an injection rate of 4 mL/s. Image acquisition was performed during the early venous phase (EVP), 40 seconds post-injection. Acquisition parameters included: Collimation: 0.5 mm Pitch: 0.8 Field of view (FOV): limited to the region from the sigmoid colon to the perineum (approximately 16 cm). These protocol adjustments were adopted based on previous studies demonstrating enhanced tumor-tissue contrast and better delineation of the circumferential resection margin (CRM) using EVP imaging [ 8 , 13 ] MRI Protocol (for Comparison) Pelvic MRI was performed using a 1.5 Tesla scanner equipped with a phased-array body coil. Patients were imaged in the supine position without rectal filling. The imaging protocol included: Axial, sagittal, and coronal T2-weighted sequences. Diffusion-weighted imaging (DWI). Post-contrast sequences when deemed necessary. Parameters evaluated on MRI included tumor location, depth of invasion (T stage), nodal status (N stage), and CRM involvement, following standardized rectal cancer staging protocols [ 4 , 12 ] Image Analysis and Staging Evaluation Two abdominal radiologists, each with over 10 years of experience in oncologic imaging, independently reviewed the MRI and CT scans in a blinded manner. The following parameters were assessed for each modality: Tumor location and extent. T stage. Nodal status (N stage). Circumferential resection margin (CRM) involvement. Presence of distant or non-regional lymph node metastases. Discrepancies between reviewers were resolved by consensus Statistical Analysis Statistical analyses were performed using IBM SPSS software version 26.0 (IBM Corp., Armonk, NY, USA). Diagnostic agreement between MDCT and MRI was evaluated using weighted kappa (κ) statistics. The strength of agreement was interpreted as follows: < 0.20: Poor 0.21–0.40: Fair 0.41–0.60: Moderate 0.61–0.80: Good 0.80: Very Good [ 14 ]. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic accuracy of MDCT were calculated, using MRI as the reference. Receiver operating characteristic (ROC) curve analysis was conducted to assess the discriminative ability of MDCT in differentiating early (T1–T2) from advanced (T3–T4) disease stages Results Study Population Characteristics The study included 40 patients (20 males and 20 females) with histologically confirmed rectal adenocarcinoma. The mean age was 47.5 ± 13.4 years (range: 17–74 years) (Table 1) . All patients completed both MRI and MDCT examinations without adverse events. T Staging Agreement between MDCT and MRI MRI identified 2 patients as T1, 9 as T2, 18 as T3, and 11 as T4. MDCT demonstrated excellent agreement with MRI in identifying advanced T3 and T4 tumors. All 18 T3 tumors and 11 T4 tumors were correctly identified by MDCT. However, MDCT over-staged the 2 T1 tumors as T2, and 6 out of 9 T2 tumors were over-staged as T3. The diagnostic agreement is detailed in Table 2 The sensitivity, specificity, and overall diagnostic accuracy of MDCT for detecting T3–T4 tumors were 100%, 77.7%, and 95%, respectively. The weighted kappa (κ) value for T staging was 0.82, indicating very good agreement. Representative cases demonstrating T3 and overstaged T2 tumors are shown in Figs. 1 and 3 , respectively "The overall distribution of T staging by MRI and MDCT is illustrated in Figs. 5 and 7 . Nodal Staging MRI identified 9 patients as N0, 10 as N1, and 21 as N2. MDCT correctly identified most cases of N2 disease but showed a tendency to overstaged N0 and N1 nodes: 2 N0 cases were over-staged as N1. 7 N1 cases were over-staged as N2. (Table 3) MDCT achieved a sensitivity of 100%, specificity of 77%, and an overall accuracy of 95% for nodal staging. The weighted kappa value was 0.73, indicating good agreement between MDCT and MRI. A case example of N2b nodal involvement is presented in Fig. 2 "The distribution of nodal staging by MRI and MDCT is visualized in Figs. 6 and 8 , respectively. Circumferential Resection Margin (CRM) Both MDCT and MRI demonstrated identical CRM status across all cases. CRM involvement was noted in 23 patients (57.5%), while 17 patients (42.5%) had a clear CRM. (Table 4) The kappa statistic for CRM assessment was 1.0, reflecting perfect agreement between MDCT and MRI. Distant Metastasis Detection MDCT identified distant metastases in 4 patients (10%), presenting as non-regional lymphadenopathy. These findings were not detected on MRI, leading to upstaging in these cases. The agreement between MRI and MDCT for detecting distant metastases was poor (κ = 0.00). An illustrative case of metastatic lymph node detection by CT, not seen on MRI, is shown in Fig. 4 . Receiver Operating Characteristic (ROC) Curve Analysis ROC analysis confirmed the robust performance of MDCT in discriminating advanced (T3–T4) from early (T1–T2) disease. The area under the curve (AUC) was 0.91 (95% CI: 0.84–0.98), indicating excellent diagnostic capability. Sensitivity and specificity for T3–T4 disease were 100% and 77.7%, respectively. Summary of Diagnostic Performance A comprehensive summary of MDCT's diagnostic performance for T staging, N staging, CRM assessment, and metastasis detection is provided in (Table 6 ) . Comparative charts of MRI and MDCT staging agreement are shown in Figs. 9 and 10 . Discussion This study evaluated the diagnostic performance of high-resolution multidetector computed tomography (MDCT) in the local staging of rectal cancer, using magnetic resonance imaging (MRI) as the reference standard. Our findings demonstrate that MDCT, when performed with an optimized early venous phase protocol, shows excellent agreement with MRI in assessing advanced T stages (T3–T4) and circumferential resection margin (CRM) involvement. However, MDCT remains less reliable in accurately staging early tumors (T1–T2) and in lymph node evaluation. Accurate local staging of rectal cancer is essential for determining appropriate treatment strategies, particularly in selecting candidates for neoadjuvant chemoradiotherapy (NACRT) and for surgical planning. The introduction of total mesorectal excision (TME) and the routine use of NACRT have significantly improved patient outcomes by reducing local recurrence rates [ 2 ]. MRI is widely considered the gold standard for locoregional staging due to its superior soft tissue contrast and multiplanar imaging capability, particularly in assessing mesorectal fascia (MRF) and CRM involvement [ 3 , 4 ]. Our study demonstrated a sensitivity of 100% and specificity of 77.7% for MDCT in detecting advanced T3–T4 tumors ( Table 6 ) , with a weighted kappa (κ) value of 0.82. These results are in line with Ramanan et al. [ 2 ], who reported similar diagnostic accuracy of MDCT in the local staging of rectal cancer. The use of thin collimation and multiplanar reformation in MDCT likely contributed to this enhanced diagnostic performance [ 8 ]. However, MDCT exhibited limitations in accurately staging early tumors. In our series, both T1 tumors were overstaged as T2, and 6 out of 9 T2 tumors were overstaged as T3. This tendency to overstage early lesions is consistent with previous studies by Heo et al. [ 8 ] and Lokuhetty et al. [ 6 ], who attributed this issue to CT's inability to reliably distinguish between true tumor infiltration and desmoplastic or fibrotic reactions in the perirectal fat. Such overstaging may potentially lead to overtreatment. Nodal staging remains a diagnostic challenge for both MDCT and MRI. In our study, MDCT demonstrated good agreement with MRI (κ = 0.73) as outlined in Table 6 but tended to overstaged N0 and N1 nodes. This is comparable to the findings of Al-Sukhni et al. [ 10 ], who reported that MRI has a pooled sensitivity of 77% for nodal metastasis detection, with CT performing similarly when size and morphological criteria are used. The inability of both modalities to detect micrometastases in morphologically benign lymph nodes remains a known limitation [ 15 ]. A notable strength of MDCT in our study was its perfect agreement with MRI in CRM assessment (κ = 1.0) (Table 4) . CRM involvement is a critical prognostic factor in rectal cancer, and its accurate preoperative assessment is vital for surgical planning. Similar findings were reported by Ramanan et al. [ 2 ], emphasizing the capability of high-resolution MDCT in CRM evaluation when standardized protocols are applied. Additionally, MDCT detected distant metastases in 10% of cases, which were not identified by MRI as shown to Table 5 and exemplified in Fig. 4 . These metastases were in non-regional lymph nodes, underscoring the benefit of whole-body CT imaging in systemic assessment. This dual capability of MDCT—local and systemic evaluation—may provide a practical advantage, especially in resource-limited settings. In Egypt, the availability of MRI scanners remains critically low, with only two units per million population [ 7 ]. Consequently, the routine use of MRI for rectal cancer staging is often impractical. In such scenarios, MDCT, when optimized with appropriate protocols, could serve as a feasible alternative for local staging of advanced rectal cancer, while simultaneously providing metastatic screening [ 5 ]. Nevertheless, certain limitations of this study must be acknowledged. Firstly, the sample size was relatively small (n = 40), limiting statistical power and generalizability. Secondly, MRI was used as the reference standard instead of histopathology. Although MRI is widely accepted for local staging, histopathological correlation remains the definitive benchmark. Thirdly, inter- and intra-observer variability were not assessed, which could influence staging interpretations in borderline cases. Lastly, emerging imaging techniques such as dual-energy CT, perfusion imaging, and artificial intelligence-based tools were not evaluated in this study, though they hold promise for improving diagnostic accuracy, particularly in early-stage tumors and nodal assessment [ 12 ]. Conclusion High-resolution MDCT demonstrated very good agreement with MRI for local staging of advanced rectal cancer (T3–T4) and showed excellent accuracy in CRM assessment. Although MDCT was less reliable for early T-stage tumors and nodal staging, its overall performance in advanced disease was promising. In resource-constrained settings where MRI access is limited, optimized MDCT protocols may serve as a practical alternative for comprehensive staging of rectal cancer. Incorporating MDCT into preoperative workflows could enhance patient triage, minimize diagnostic delays, and support timely treatment planning. Larger, multicenter studies with histopathological correlation are warranted to validate these findings and to explore emerging technologies that may overcome current limitations. Abbreviations • AUC Area Under the Curve • CI Confidence Interval • CRC Colorectal Cancer • CRM Circumferential Resection Margin • CT Computed Tomography • DWI Diffusion – Weighted Imaging • EVP Early Venous Phase • FOV Field of View • MDCT Multidetector Computed Tomography • MF Mesorectal Fascia • MRI Magnetic Resonance Imaging • NACRT Neoadjuvant Chemoradiotherapy • NPV Negative Predictive Value • PPV Positive Predictive Value • ROC Receiver Operating Characteristic • TME Total Mesorectal Excision Declarations Ethics approval and consent to participate: • Written informed consent was signed by all patients before the high resolution CT examination. The study is approved by the medical committee of the faculty of medicine Cairo University. Reference number is available. Consent for publication: • All adult patients included in this research (≥ 18 years of age) gave written informed consent to publish the data contained within this study. Funding: not applicable (no funding) Author Contribution I.S: Conceptualization, Study Design, Data Acquisition, Radiological Image Interpretation, Manuscript Drafting, Critical Revision of the Manuscript.M.M: Clinical Data Collection, Surgical Correlation, Methodology, and Contribution to Manuscript Writing.B.M: Radiological Image Review, Data Validation, Manuscript Editing, Visualization (Figures and Tables Preparation).Y.D: Data collection, Study Design, Data Acquisition, Radiological Image Interpretation, Manuscript Drafting. References Prashanth R, Balaraj BM, Patil N, Sowmya P. Evaluation of rectal cancer using imaging modalities: A review. J Clin Diagn Res. 2019;13(10):TE01–TE05. Ramanan V, Basha SH, Baskar S, Karthikeyan VS, Kalayarasan R. Diagnostic accuracy of MDCT in the local staging of rectal cancer compared to MRI: A prospective comparative study. Indian J Radiol Imaging. 2021;31(3):483–491. Nancy M, Schmid-Tannwald C, Bani Hani M, Sah BR, Vetter M, Weishaupt D. MRI in rectal cancer: Standard and emerging techniques. Clin Radiol. 2020;75(5):364–374. Magan AA, Rankin SC, Haseeb MA. MRI in rectal cancer: Staging and restaging evaluation. BMJ Open Gastroenterol. 2020;7:e000407. Ortega P, Rocha R. Cost-effectiveness of MRI versus CT for staging of rectal cancer in developing countries. Radiol Bras. 2019;52(4):245–251. Lokuhetty D, White VA, Watanabe R, Cree IA. WHO Classification of Tumours: Digestive System Tumours. 5th ed. Lyon: IARC Press; 2019. Ogbole GI, Adeyomoye AA, Badu-Peprah A, Mensah Y, Nzeh DA. Survey of magnetic resonance imaging availability in West Africa. Pan Afr Med J. 2018;30:240. Heo SH, Kim JW, Shin SS, Jeong YY, Kang HK. Multidetector-row CT for preoperative staging of rectal cancer: Usefulness in evaluating local invasion. J Comput Assist Tomogr. 2015;39(3):143–150. Ramanan V, Basha SH, Baskar S, Karthikeyan VS, Kalayarasan R. Diagnostic accuracy of MDCT for CRM assessment. Indian J Radiol Imaging. 2021;31(3):483–491. Al-Sukhni E, Milot L, Fruitman M, Beyene J, Victor JC, Brown G, et al. Diagnostic accuracy of MRI for assessment of T category, lymph node metastases, and circumferential resection margin involvement in patients with rectal cancer: A systematic review and meta-analysis. Ann Surg Oncol. 2012;19(7):2212–2223. Ahmed AS, Abd-El-Fattah ME, Fouda MA, Fathy M. Colorectal cancer in Egypt: Epidemiological and pathological overview. World J Colorectal Surg. 2013;3(2). doi: 10.13107/j.wjcs.2013.06.005 . Bipat S, Glas AS, Slors JF, Zwinderman AH, Bossuyt PM, Stoker J. Rectal cancer: Local staging and assessment of lymph node involvement with endoluminal US, CT, and MR imaging—a meta-analysis. Radiology. 2004;232(3):773–783. Winter DC, Sheahan K, O’Connell PR. MRI accuracy in nodal staging of rectal cancer—a systematic review. Colorectal Dis. 2007;9(3):209–216. Altman DG. Practical statistics for medical research. London: Chapman & Hall; 1991. Beets-Tan RG, Beets GL. Rectal cancer: Review with emphasis on MR imaging. Radiology. 2004;232(2):335–346 Tables Table 1 to 6 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Tables.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7364470","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":549841578,"identity":"00d019d0-3572-4fef-95b4-061b41bea9f7","order_by":0,"name":"Islam Haney 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9","display":"","copyAsset":false,"role":"figure","size":30959,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Fig.9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7364470/v1/eb2a3beadf2bc7869e8378d8.jpg"},{"id":96918029,"identity":"3db9f987-10d5-4db9-b7d4-57dc88d9f30f","added_by":"auto","created_at":"2025-11-27 14:11:01","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":25153,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"fig.10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7364470/v1/63ffe389ce89fe172ff8cd1a.jpg"},{"id":100623295,"identity":"9c020f8a-17c3-422f-9de7-194b0b9db315","added_by":"auto","created_at":"2026-01-19 18:47:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1244195,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7364470/v1/2738e9ab-74cb-4afc-8a87-bbebb9f88793.pdf"},{"id":96800617,"identity":"ef9e09de-d559-4f0e-9ecb-9a1805e7d5e9","added_by":"auto","created_at":"2025-11-26 08:38:10","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":20156,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-7364470/v1/423754c705ca6086f2b8b1e4.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eDiagnostic Accuracy of High-Resolution Multidetector CT Compared to MRI in Local Staging of Rectal Cancer: A Prospective Study\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eColorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second leading cause of cancer-related death globally. Approximately one-third of CRC cases originate in the rectum, with over 40% of rectal tumors located within 6 cm of the anal verge [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Accurate local staging is essential for determining the optimal therapeutic approach, particularly in guiding decisions regarding neoadjuvant chemoradiotherapy (NACRT) and surgical planning.\u003c/p\u003e\u003cp\u003eThe advent of total mesorectal excision (TME) and the use of NACRT for locally advanced rectal cancer have significantly improved patient outcomes by reducing local recurrence rates and enhancing overall survival [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Accurate assessment of tumor depth (T stage), nodal involvement (N stage), and circumferential resection margin (CRM) involvement is crucial for predicting resectability and tailoring treatment strategies [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eMagnetic resonance imaging (MRI) is currently regarded as the gold standard for local staging of rectal cancer due to its superior soft tissue contrast and multiplanar imaging capabilities [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. It plays a pivotal role in evaluating tumor extension beyond the rectal wall and assessing the relationship to the mesorectal fascia (MRF). However, in resource-limited settings, the routine use of MRI is often hindered by restricted availability, high costs, and long waiting lists, which can lead to delays in initiating treatment [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn Egypt and many developing countries, the number of MRI scanners per capita is critically low, with only two MRI units available per million people, significantly below international benchmarks [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Moreover, MRI services are often prioritized for neurological and musculoskeletal applications, further limiting access for oncologic imaging.\u003c/p\u003e\u003cp\u003eComputed tomography (CT), in contrast, is widely available and commonly used for metastatic screening in colorectal cancer patients. Technological advancements in multidetector CT (MDCT), such as thin-slice collimation, rapid acquisition, and multiplanar reconstruction, have enhanced CT\u0026rsquo;s capability in local tumor assessment [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Several studies have demonstrated the potential of MDCT in evaluating advanced rectal cancer, particularly for T3\u0026ndash;T4 tumors and CRM involvement [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNevertheless, CT remains less reliable for accurately staging early T1\u0026ndash;T2 tumors and assessing lymph node involvement due to its limited soft tissue contrast resolution [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Standardizing high-resolution CT protocols, including early venous phase imaging, may improve diagnostic performance and offer a practical alternative where MRI access is constrained.\u003c/p\u003e\u003cp\u003eAgainst this background, the current study aimed to evaluate the diagnostic accuracy of high-resolution MDCT in the local staging of rectal cancer, using MRI as the reference standard. We specifically assessed the agreement between MDCT and MRI in determining T stage, N stage, CRM involvement, and detection of distant metastases.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy Design and Population\u003c/h2\u003e\u003cp\u003eThis prospective study was conducted at Kasr Al-Ainy Hospital between October 2022 and May 2023. A total of 40 patients with histopathologically confirmed rectal adenocarcinoma were consecutively enrolled. Inclusion criteria were: age\u0026thinsp;\u0026ge;\u0026thinsp;18 years and biopsy-proven rectal carcinoma. Exclusion criteria included contraindications to iodinated contrast media (e.g., severe renal impairment, history of contrast allergy), pregnancy, and body habitus exceeding CT gantry weight limits [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAll patients underwent both high-resolution pelvic MRI and contrast-enhanced multidetector computed tomography (MDCT) within a maximum interval of 7 days. MRI was used as the reference standard for local staging.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003cp\u003ewas obtained from the Institutional Review Board (IRB), and informed consent was acquired from all participants.\u003c/p\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eCT Imaging Protocol\u003c/h3\u003e\n\u003cp\u003eMDCT examinations were performed using a 128-slice CT scanner (GE, 128-detector mode). Patients underwent mild bowel preparation with 1 liter of polyethylene glycol the night before the scan and were instructed to fast for at least 6 hours prior to the examination.\u003c/p\u003e\u003cp\u003eIntravenous contrast material (iopromide, 350 mg/mL) was administered at a dose of 1\u0026ndash;1.5 mL/kg, with an injection rate of 4 mL/s. Image acquisition was performed during the early venous phase (EVP), 40 seconds post-injection.\u003c/p\u003e\u003cp\u003eAcquisition parameters included:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eCollimation: 0.5 mm\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePitch: 0.8\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eField of view (FOV): limited to the region from the sigmoid colon to the perineum (approximately 16 cm).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThese protocol adjustments were adopted based on previous studies demonstrating enhanced tumor-tissue contrast and better delineation of the circumferential resection margin (CRM) using EVP imaging [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/p\u003e\n\u003ch3\u003eMRI Protocol (for Comparison)\u003c/h3\u003e\n\u003cp\u003ePelvic MRI was performed using a 1.5 Tesla scanner equipped with a phased-array body coil. Patients were imaged in the supine position without rectal filling. The imaging protocol included:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAxial, sagittal, and coronal T2-weighted sequences.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eDiffusion-weighted imaging (DWI).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePost-contrast sequences when deemed necessary.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eParameters evaluated on MRI included tumor location, depth of invasion (T stage), nodal status (N stage), and CRM involvement, following standardized rectal cancer staging protocols [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/p\u003e\n\u003ch3\u003eImage Analysis and Staging Evaluation\u003c/h3\u003e\n\u003cp\u003eTwo abdominal radiologists, each with over 10 years of experience in oncologic imaging, independently reviewed the MRI and CT scans in a blinded manner. The following parameters were assessed for each modality:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eTumor location and extent.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eT stage.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eNodal status (N stage).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eCircumferential resection margin (CRM) involvement.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePresence of distant or non-regional lymph node metastases.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eDiscrepancies between reviewers were resolved by consensus\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eStatistical analyses were performed using IBM SPSS software version 26.0 (IBM Corp., Armonk, NY, USA). Diagnostic agreement between MDCT and MRI was evaluated using weighted kappa (κ) statistics. The strength of agreement was interpreted as follows:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.20: Poor\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e0.21\u0026ndash;0.40: Fair\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e0.41\u0026ndash;0.60: Moderate\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e0.61\u0026ndash;0.80: Good\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e0.80: Very Good [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eSensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall diagnostic accuracy of MDCT were calculated, using MRI as the reference. Receiver operating characteristic (ROC) curve analysis was conducted to assess the discriminative ability of MDCT in differentiating early (T1\u0026ndash;T2) from advanced (T3\u0026ndash;T4) disease stages\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003eStudy Population Characteristics\u003c/h2\u003e\u003cp\u003eThe study included 40 patients (20 males and 20 females) with histologically confirmed rectal adenocarcinoma. The mean age was 47.5\u0026thinsp;\u0026plusmn;\u0026thinsp;13.4 years (range: 17\u0026ndash;74 years) \u003cb\u003e(Table\u0026nbsp;1)\u003c/b\u003e. All patients completed both MRI and MDCT examinations without adverse events.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eT Staging Agreement between MDCT and MRI\u003c/h3\u003e\n\u003cp\u003eMRI identified 2 patients as T1, 9 as T2, 18 as T3, and 11 as T4. MDCT demonstrated excellent agreement with MRI in identifying advanced T3 and T4 tumors.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAll 18 T3 tumors and 11 T4 tumors were correctly identified by MDCT.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eHowever, MDCT over-staged the 2 T1 tumors as T2, and 6 out of 9 T2 tumors were over-staged as T3. The diagnostic agreement is detailed in \u003cb\u003eTable\u0026nbsp;2\u003c/b\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe sensitivity, specificity, and overall diagnostic accuracy of MDCT for detecting T3\u0026ndash;T4 tumors were 100%, 77.7%, and 95%, respectively. The weighted kappa (κ) value for T staging was 0.82, indicating very good agreement.\u003c/p\u003e\u003cp\u003eRepresentative cases demonstrating T3 and overstaged T2 tumors are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e, respectively\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\"The overall distribution of T staging by MRI and MDCT is illustrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eNodal Staging\u003c/h2\u003e\u003cp\u003eMRI identified 9 patients as N0, 10 as N1, and 21 as N2. MDCT correctly identified most cases of N2 disease but showed a tendency to overstaged N0 and N1 nodes:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e2 N0 cases were over-staged as N1.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e7 N1 cases were over-staged as N2.\u003cb\u003e(Table\u0026nbsp;3)\u003c/b\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eMDCT achieved a sensitivity of 100%, specificity of 77%, and an overall accuracy of 95% for nodal staging. The weighted kappa value was 0.73, indicating good agreement between MDCT and MRI.\u003c/p\u003e\u003cp\u003eA case example of N2b nodal involvement is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\"The distribution of nodal staging by MRI and MDCT is visualized in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e, respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eCircumferential Resection Margin (CRM)\u003c/h2\u003e\u003cp\u003eBoth MDCT and MRI demonstrated identical CRM status across all cases. CRM involvement was noted in 23 patients (57.5%), while 17 patients (42.5%) had a clear CRM. \u003cb\u003e(Table\u0026nbsp;4)\u003c/b\u003e\u003c/p\u003e\u003cp\u003e The kappa statistic for CRM assessment was 1.0, reflecting perfect agreement between MDCT and MRI.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eDistant Metastasis Detection\u003c/h2\u003e\u003cp\u003eMDCT identified distant metastases in 4 patients (10%), presenting as non-regional lymphadenopathy. These findings were not detected on MRI, leading to upstaging in these cases. The agreement between MRI and MDCT for detecting distant metastases was poor (κ\u0026thinsp;=\u0026thinsp;0.00).\u003c/p\u003e\u003cp\u003eAn illustrative case of metastatic lymph node detection by CT, not seen on MRI, is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eReceiver Operating Characteristic (ROC) Curve Analysis\u003c/h2\u003e\u003cp\u003eROC analysis confirmed the robust performance of MDCT in discriminating advanced (T3\u0026ndash;T4) from early (T1\u0026ndash;T2) disease. The area under the curve (AUC) was 0.91 (95% CI: 0.84\u0026ndash;0.98), indicating excellent diagnostic capability. Sensitivity and specificity for T3\u0026ndash;T4 disease were 100% and 77.7%, respectively.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eSummary of Diagnostic Performance\u003c/h2\u003e\u003cp\u003eA comprehensive summary of MDCT's diagnostic performance for T staging, N staging, CRM assessment, and metastasis detection is provided in (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003eComparative charts of MRI and MDCT staging agreement are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study evaluated the diagnostic performance of high-resolution multidetector computed tomography (MDCT) in the local staging of rectal cancer, using magnetic resonance imaging (MRI) as the reference standard. Our findings demonstrate that MDCT, when performed with an optimized early venous phase protocol, shows excellent agreement with MRI in assessing advanced T stages (T3\u0026ndash;T4) and circumferential resection margin (CRM) involvement. However, MDCT remains less reliable in accurately staging early tumors (T1\u0026ndash;T2) and in lymph node evaluation.\u003c/p\u003e\u003cp\u003eAccurate local staging of rectal cancer is essential for determining appropriate treatment strategies, particularly in selecting candidates for neoadjuvant chemoradiotherapy (NACRT) and for surgical planning. The introduction of total mesorectal excision (TME) and the routine use of NACRT have significantly improved patient outcomes by reducing local recurrence rates [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. MRI is widely considered the gold standard for locoregional staging due to its superior soft tissue contrast and multiplanar imaging capability, particularly in assessing mesorectal fascia (MRF) and CRM involvement [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOur study demonstrated a sensitivity of 100% and specificity of 77.7% for MDCT in detecting advanced T3\u0026ndash;T4 tumors \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e, with a weighted kappa (κ) value of 0.82. These results are in line with Ramanan et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], who reported similar diagnostic accuracy of MDCT in the local staging of rectal cancer. The use of thin collimation and multiplanar reformation in MDCT likely contributed to this enhanced diagnostic performance [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eHowever, MDCT exhibited limitations in accurately staging early tumors. In our series, both T1 tumors were overstaged as T2, and 6 out of 9 T2 tumors were overstaged as T3. This tendency to overstage early lesions is consistent with previous studies by Heo et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] and Lokuhetty et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], who attributed this issue to CT's inability to reliably distinguish between true tumor infiltration and desmoplastic or fibrotic reactions in the perirectal fat. Such overstaging may potentially lead to overtreatment.\u003c/p\u003e\u003cp\u003eNodal staging remains a diagnostic challenge for both MDCT and MRI. In our study, MDCT demonstrated good agreement with MRI (κ\u0026thinsp;=\u0026thinsp;0.73) as outlined in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e6\u003c/span\u003e but tended to overstaged N0 and N1 nodes. This is comparable to the findings of Al-Sukhni et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], who reported that MRI has a pooled sensitivity of 77% for nodal metastasis detection, with CT performing similarly when size and morphological criteria are used. The inability of both modalities to detect micrometastases in morphologically benign lymph nodes remains a known limitation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eA notable strength of MDCT in our study was its perfect agreement with MRI in CRM assessment (κ\u0026thinsp;=\u0026thinsp;1.0) \u003cb\u003e(Table\u0026nbsp;4)\u003c/b\u003e. CRM involvement is a critical prognostic factor in rectal cancer, and its accurate preoperative assessment is vital for surgical planning. Similar findings were reported by Ramanan et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], emphasizing the capability of high-resolution MDCT in CRM evaluation when standardized protocols are applied.\u003c/p\u003e\u003cp\u003eAdditionally, MDCT detected distant metastases in 10% of cases, which were not identified by MRI as shown to \u003cb\u003eTable\u0026nbsp;5\u003c/b\u003e and exemplified in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e4\u003c/span\u003e. These metastases were in non-regional lymph nodes, underscoring the benefit of whole-body CT imaging in systemic assessment. This dual capability of MDCT\u0026mdash;local and systemic evaluation\u0026mdash;may provide a practical advantage, especially in resource-limited settings.\u003c/p\u003e\u003cp\u003eIn Egypt, the availability of MRI scanners remains critically low, with only two units per million population [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Consequently, the routine use of MRI for rectal cancer staging is often impractical. In such scenarios, MDCT, when optimized with appropriate protocols, could serve as a feasible alternative for local staging of advanced rectal cancer, while simultaneously providing metastatic screening [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNevertheless, certain limitations of this study must be acknowledged. Firstly, the sample size was relatively small (n\u0026thinsp;=\u0026thinsp;40), limiting statistical power and generalizability. Secondly, MRI was used as the reference standard instead of histopathology. Although MRI is widely accepted for local staging, histopathological correlation remains the definitive benchmark. Thirdly, inter- and intra-observer variability were not assessed, which could influence staging interpretations in borderline cases. Lastly, emerging imaging techniques such as dual-energy CT, perfusion imaging, and artificial intelligence-based tools were not evaluated in this study, though they hold promise for improving diagnostic accuracy, particularly in early-stage tumors and nodal assessment [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eHigh-resolution MDCT demonstrated very good agreement with MRI for local staging of advanced rectal cancer (T3\u0026ndash;T4) and showed excellent accuracy in CRM assessment. Although MDCT was less reliable for early T-stage tumors and nodal staging, its overall performance in advanced disease was promising.\u003c/p\u003e\u003cp\u003eIn resource-constrained settings where MRI access is limited, optimized MDCT protocols may serve as a practical alternative for comprehensive staging of rectal cancer. Incorporating MDCT into preoperative workflows could enhance patient triage, minimize diagnostic delays, and support timely treatment planning. Larger, multicenter studies with histopathological correlation are warranted to validate these findings and to explore emerging technologies that may overcome current limitations.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; AUC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eArea Under the Curve\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; CI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eConfidence Interval\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; CRC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eColorectal Cancer\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; CRM\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eCircumferential Resection Margin\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; CT\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eComputed Tomography\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; DWI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eDiffusion\u003c/b\u003e\u0026ndash;\u003cb\u003eWeighted Imaging\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; EVP\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eEarly Venous Phase\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; FOV\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eField of View\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; MDCT\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eMultidetector Computed Tomography\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; MF\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eMesorectal Fascia\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; MRI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eMagnetic Resonance Imaging\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; NACRT\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eNeoadjuvant Chemoradiotherapy\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; NPV\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eNegative Predictive Value\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; PPV\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003ePositive Predictive Value\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; ROC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eReceiver Operating Characteristic\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; TME\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eTotal Mesorectal Excision\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e\u003cp\u003e \u0026bull; Written informed consent was signed by all patients before the high resolution CT examination. The study is approved by the medical committee of the faculty of medicine Cairo University. Reference number is available.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003cp\u003e\u0026bull; All adult patients included in this research (\u0026ge;\u0026thinsp;18 years of age) gave written informed consent to publish the data contained within this study.\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003enot applicable (no funding)\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eI.S: Conceptualization, Study Design, Data Acquisition, Radiological Image Interpretation, Manuscript Drafting, Critical Revision of the Manuscript.M.M: Clinical Data Collection, Surgical Correlation, Methodology, and Contribution to Manuscript Writing.B.M: Radiological Image Review, Data Validation, Manuscript Editing, Visualization (Figures and Tables Preparation).Y.D: Data collection, Study Design, Data Acquisition, Radiological Image Interpretation, Manuscript Drafting.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePrashanth R, Balaraj BM, Patil N, Sowmya P. Evaluation of rectal cancer using imaging modalities: A review. J Clin Diagn Res. 2019;13(10):TE01\u0026ndash;TE05.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRamanan V, Basha SH, Baskar S, Karthikeyan VS, Kalayarasan R. Diagnostic accuracy of MDCT in the local staging of rectal cancer compared to MRI: A prospective comparative study. Indian J Radiol Imaging. 2021;31(3):483\u0026ndash;491.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNancy M, Schmid-Tannwald C, Bani Hani M, Sah BR, Vetter M, Weishaupt D. MRI in rectal cancer: Standard and emerging techniques. Clin Radiol. 2020;75(5):364\u0026ndash;374.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMagan AA, Rankin SC, Haseeb MA. MRI in rectal cancer: Staging and restaging evaluation. BMJ Open Gastroenterol. 2020;7:e000407.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOrtega P, Rocha R. Cost-effectiveness of MRI versus CT for staging of rectal cancer in developing countries. Radiol Bras. 2019;52(4):245\u0026ndash;251.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLokuhetty D, White VA, Watanabe R, Cree IA. WHO Classification of Tumours: Digestive System Tumours. 5th ed. Lyon: IARC Press; 2019.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOgbole GI, Adeyomoye AA, Badu-Peprah A, Mensah Y, Nzeh DA. Survey of magnetic resonance imaging availability in West Africa. Pan Afr Med J. 2018;30:240.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHeo SH, Kim JW, Shin SS, Jeong YY, Kang HK. Multidetector-row CT for preoperative staging of rectal cancer: Usefulness in evaluating local invasion. J Comput Assist Tomogr. 2015;39(3):143\u0026ndash;150.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRamanan V, Basha SH, Baskar S, Karthikeyan VS, Kalayarasan R. Diagnostic accuracy of MDCT for CRM assessment. Indian J Radiol Imaging. 2021;31(3):483\u0026ndash;491.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAl-Sukhni E, Milot L, Fruitman M, Beyene J, Victor JC, Brown G, et al. Diagnostic accuracy of MRI for assessment of T category, lymph node metastases, and circumferential resection margin involvement in patients with rectal cancer: A systematic review and meta-analysis. Ann Surg Oncol. 2012;19(7):2212\u0026ndash;2223.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAhmed AS, Abd-El-Fattah ME, Fouda MA, Fathy M. Colorectal cancer in Egypt: Epidemiological and pathological overview. World J Colorectal Surg. 2013;3(2). doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.13107/j.wjcs.2013.06.005\u003c/span\u003e\u003cspan address=\"10.13107/j.wjcs.2013.06.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBipat S, Glas AS, Slors JF, Zwinderman AH, Bossuyt PM, Stoker J. Rectal cancer: Local staging and assessment of lymph node involvement with endoluminal US, CT, and MR imaging\u0026mdash;a meta-analysis. Radiology. 2004;232(3):773\u0026ndash;783.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWinter DC, Sheahan K, O\u0026rsquo;Connell PR. MRI accuracy in nodal staging of rectal cancer\u0026mdash;a systematic review. Colorectal Dis. 2007;9(3):209\u0026ndash;216.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAltman DG. Practical statistics for medical research. London: Chapman \u0026amp; Hall; 1991.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBeets-Tan RG, Beets GL. Rectal cancer: Review with emphasis on MR imaging. Radiology. 2004;232(2):335\u0026ndash;346\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 to 6 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Rectal cancer, MRI, MDCT, T staging, N staging, Circumferential resection margin, High-resolution CT","lastPublishedDoi":"10.21203/rs.3.rs-7364470/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7364470/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground:\u003c/h2\u003e\u003cp\u003eMagnetic resonance imaging (MRI) remains the gold standard for local staging of rectal cancer due to its superior soft-tissue contrast. However, its limited accessibility, high cost, and potential for delay in imaging workflows, particularly in low-resource settings, necessitate the exploration of alternative modalities. Recent advances in multidetector computed tomography (MDCT) allow for high-resolution multiplanar imaging that may be suitable for local rectal staging\u003c/p\u003e\u003ch2\u003ePurpose:\u003c/h2\u003e\u003cp\u003eTo evaluate the diagnostic accuracy of high-resolution MDCT for local staging of rectal cancer, compared to MRI\u003c/p\u003e\u003ch2\u003eMethods:\u003c/h2\u003e\u003cp\u003eThis prospective study included 40 patients with biopsy-confirmed rectal carcinoma. All underwent pelvic MRI and contrast-enhanced MDCT with an optimized early venous phase protocol. Imaging findings were compared across T stage, N stage, circumferential resection margin (CRM) involvement, and detection of distant metastases. MRI served as the reference standard. Agreement between modalities was assessed using weighted kappa statistics; diagnostic accuracy parameters were calculated for MDCT\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e\u003cp\u003eMDCT demonstrated excellent concordance with MRI for T3\u0026ndash;T4 staging (κ\u0026thinsp;=\u0026thinsp;0.82), with 100% sensitivity and 95% overall accuracy. CRM assessment showed perfect agreement between modalities (κ\u0026thinsp;=\u0026thinsp;1.0). For nodal staging, MDCT achieved a kappa value of 0.73, with a sensitivity of 100% and specificity of 77%. Distant metastases were detected in 4 patients (10%) by MDCT but missed on MRI. MDCT over-staged early-stage tumors in several cases\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e\u003cp\u003eHigh-resolution MDCT, when performed with a standardized protocol, provides excellent diagnostic accuracy for local staging of advanced rectal cancer and offers additional benefit in systemic assessment. It represents a valuable alternative when MRI is unavailable or delayed.\u003c/p\u003e","manuscriptTitle":"Diagnostic Accuracy of High-Resolution Multidetector CT Compared to MRI in Local Staging of Rectal Cancer: A Prospective Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-26 08:38:05","doi":"10.21203/rs.3.rs-7364470/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a1a20c8a-5f31-48a3-b613-c55c14a4104f","owner":[],"postedDate":"November 26th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-19T18:38:28+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-26 08:38:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7364470","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7364470","identity":"rs-7364470","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}