T2 Shading and T2 Dark Spot Sign in the Diagnosis of Endometriotic Cysts

“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.[] T2 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.[] The 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.[]

The 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. Inclusion criteria Lesions showing homogeneous echogenicity on sonography without any evidence of solid vascular component Lesions with size >3 cm. Exclusion criteria Lesions with size <3 cm Lesions showing evidence of solid component on sonography Lesions showing postcontrast administration enhancement. Imaging techniques Ultrasonography Sonography was done using Logic P5 (GE healthcare, USA). The various characteristics noted were as: Size of the lesion Location (right versus left) Number of lesions Echogenicity of the lesion Presence of solid component on color Doppler study. Magnetic resonance imaging MRI was done using 1.5 Tesla Magnetom machine (Siemens Healthcare, Germany). The protocol followed in the study is as; T1-weighted images in the sagittal, axial, and coronal planes T1 fat-saturated images in axial, coronal, and sagittal planes T2-weighted images in axial, coronal, and sagittal planes TRIM sagittal and axial images T1 fat-saturated postcontrast administration images in sagittal, axial, and coronal planes. The images were analyzed for the following features. Size and number of the lesions Presence of T2 shading and T2 dark spot sign Presence of enhancement on postcontrast administration images. The 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.

and Observations In 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. Of the 64 patients, 58 were unmarried females with only six were married females. The age group of the patients is depicted in [Table 1]. Out 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. Most 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]. The 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. The 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. The 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. The 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. [Figures 123] show the various MR features noticed in the study patients.

MRI 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.[] The 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.[] Togashi 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. T2 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.[] T2 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.[] Dias 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.

This 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. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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