{"paper_id":"c97c110f-231c-4b3c-b8f8-2958dd534fac","body_text":"Introduction\n“T2Shading sign” indicates T2 shortening (hypointensity) in an adnexal cyst which is hyperintense on T1-weighted images. This is an important feature of endometriotic cysts. It can be either focal of diffuse, however, the most common manifestation is complete loss of signal intensity or dependent layering with a hypointense fluid layering.[]\nT2 dark spots refer to discrete, profoundly hypointense foci in the hemorrhagic cystic lesion on T2-weighted images. Their presence is specific for the diagnosis of endometriotic cysts and may be present alongside T2 shading or alone.[]\nThe T2 shortening results due to mixing of recurrent hemorrhage in an endometriotic cyst with high concentration of protein and iron. At sonography, the classic image of an endometrioma is that of a cystic mass with diffuse low-level echoes. The magnetic resonance imaging (MRI) features of endometrioma include either multiple cysts with T1 hyperintensity or one/more cysts with T1 hypertintensityand hypointensity (T2 shading) on T2-weighted images.[]\nMaterials and Methods\nThe present prospective study was conducted in our department over a period of 1 year from October 2017 to September 2018. During this period, MRI was done in suspected cases of endometriosis on ultrasonography. The magnetic resonance (MR) images were analyzed for the presence of T2 shading and T2 dark spot sign. The results were compared with the postoperative final diagnosis of endometriosis to determine the sensitivity and specificity of these two signs in the diagnosis of endometriosis.\nInclusion criteria\nLesions showing homogeneous echogenicity on sonography without any evidence of solid vascular component\nLesions with size >3 cm.\nExclusion criteria\nLesions with size <3 cm\nLesions showing evidence of solid component on sonography\nLesions showing postcontrast administration enhancement.\nImaging techniques\nUltrasonography\nSonography was done using Logic P5 (GE healthcare, USA). The various characteristics noted were as:\nSize of the lesion\nLocation (right versus left)\nNumber of lesions\nEchogenicity of the lesion\nPresence of solid component on color Doppler study.\nMagnetic resonance imaging\nMRI was done using 1.5 Tesla Magnetom machine (Siemens Healthcare, Germany). The protocol followed in the study is as;\nT1-weighted images in the sagittal, axial, and coronal planes\nT1 fat-saturated images in axial, coronal, and sagittal planes\nT2-weighted images in axial, coronal, and sagittal planes\nTRIM sagittal and axial images\nT1 fat-saturated postcontrast administration images in sagittal, axial, and coronal planes.\nThe images were analyzed for the following features.\nSize and number of the lesions\nPresence of T2 shading and T2 dark spot sign\nPresence of enhancement on postcontrast administration images.\nThe final postoperative histopathological diagnosis was obtained. In the final study, only those patients who underwent operative resection of the lesions were included in the study.\nResults and Observations\nIn the present study, 87 patients were evaluated by sonography and 78 underwent MRI. Of the 78 patients, only 64 underwent surgical resection. The final results were based on the sonographic, MRI, and postoperative diagnosis of 64 patients.\nOf the 64 patients, 58 were unmarried females with only six were married females.\nThe age group of the patients is depicted in [Table 1].\nOut of 64 patients, 48 presented with a history of lower abdominal pain and dysmenorrhea. Six patients had a history of irregular menses and ten patients had combined history of lower abdominal pain, dysmenorrheal, and irregular menses.\nMost of the patients included in the final study had lesion measuring 4.5–6 cm (n = 38) and in these patients, ten patients had more than one lesion [Table 2].\nThe various MR features of the lesions included in the final study are presented in [Table 3], whereas [Table 4] shows the postoperative diagnosis of the 64 patients included in the final study.\nThe sensitivity, specificity, and other statistical parameters with regard to the utility of T2 shading and T2 dark spot sign in the diagnosis of endometriosis were calculated using 2 × 2 tables.\nThe sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value, and accuracy of T2 shading signs in the diagnosis of endometriosis were 85.71%, 37.5%, 1.37%, 0.38%, 90.57%, 27.27%, and 79.69%, respectively.\nThe sensitivity, specificity, negative likelihood ratio, positive predictive value, negative predictive value, and accuracy of T2 dark spot sign in the diagnosis of endometriosis were 76.79%, 100%, 0.23%, 100%, 38.1%, and 79.19%, respectively.\n[Figures 123] show the various MR features noticed in the study patients.\nDiscussion\nMRI is an accurate method of assessing the adnexal lesions. T2 dark spot and T2 shading signs are important features on MR which help in the differentiation of endometriotic hemorrhagic lesions from other hemorrhagic lesions. It is due to T1 and T2 shortening that occurs in endometriotic lesions because of increased viscosity, increased concentration of proteins, and degraded blood products.[]\nThe present study results show that T2 shading sign has high sensitivity (85.71%) and T2 dark spot sign has high specificity (100%) in the diagnosis of endometriomas, and these results were in concordance with the results in the study by Corwin et al.[]\nTogashi et al. found in their study that multiple hyperintense lesions on T1-weighted images associated with or without T2 shading or single lesions with T2 shading showed sensitivity and specificity of 98% and 96%, respectively.[] In comparison, the present study showed T1 hyperintensity with a loss of signal on T2 images (T2 shading) showed sensitivity and specificity of 85.71% and 37.5%, respectively. In the present study, T1 hyperintensity was uniform with T2 dark spots seen on T2 images. T2 dark spots have sensitivity and specificity of 76.79% and 100%, respectively, in the study.\nT2 shading helps in the differentiation of hemorrhagic cysts from endometriomas. In hemorrhagic cysts, the retracted clots are short-lived and the resolution of the hemorrhagic cyst prevents these clots to cause T2 shortening in comparison to endometriotic cysts where chronic recurrent hemorrhage causes T2 shortening that results in T2 shading phenomenon.[]\nT2 dark spots refer to curvilinear, punctate, or focal hypointense foci on T2-weighted images that are adjacent to the wall of the endometriotic cysts. These result from the chronic and recurrent bleeding which causes desiccated and retracted clots which contain heavy concentrations of hemosiderin and protein.[]\nDias et al. in their study found that homogeneous T2 shading was the most prevalent finding in endometriomas.[] In the present study, we had excluded the lesions with solid or fat components and included only patients with hemorrhagic lesions. In the present study also, the endometriotic lesions were found to have homogenous T2 shading.\nConclusion\nThis study was conducted to determine the sensitivity and specificity of T2 dark spot and T2 shading sign in the diagnosis of endometriotic cysts. It was found that T2 shading sign is highly sensitive and T2 dark spot sign is highly specific for the diagnosis of endometriotic cysts. Preoperative MRI with demonstration of T2 shading and T2 dark spot signs greatly improve the preoperative diagnosis of endometriotic cysts which helps in the proper management of these cases.\nFinancial support and sponsorship\nNil.\nConflicts of interest\nThere are no conflicts of interest.\nREFERENCES\n- 1. Glastonbury CM. The shading sign Radiology. 2002;224:199–201\n- 2. Corwin MT, Gerscovich EO, Lamba R, Wilson M, McGahan JP. Differentiation of ovarian endometriomas from hemorrhagic cysts at MR imaging: Utility of the T2 dark spot sign Radiology. 2014;271:126–32\n- 3. Siegelman ES, Oliver ER. MR imaging of endometriosis: Ten imaging pearls Radiographics. 2012;32:1675–91\n- 4. Siegelman ES, Outwater EK. Tissue characterization in the female pelvis by means of MR imaging Radiology. 1999;212:5–18\n- 5. Togashi K, Nishimura K, Kimura I, Tsuda Y, Yamashita K, Shibata T, et al Endometrial cysts: Diagnosis with MR imaging Radiology. 1991;180:73–8\n- 6. Dias JL, Veloso Gomes F, Lucas R, Cunha TM. The shading sign: Is it exclusive of endometriomas? Abdom Imaging. 2015;40:2566–72\n- 7. Swaminathan SK. The T2-dark spot sign Abdom Radiol (NY). 2017;42:1614–5","source_license":"CC0","license_restricted":false}