ROLE OF DIFFUSION-WEIGHTED MAGNETIC RESONANCE IMAGING IN DETECTION OF NON- PALPABLE UNDESCENDED TESTES

Manar M. Nasr MD 1 , Wael Abdulghaffar MD 1 and Ahmad Yassin, MRCS 2 . 1. Department of Diagnostic and Interventional radiology, Mansoura University Hospital, 3511212 El-Gomhoreya street, Mansoura, Egypt. 2. Pediatric surgery Department, Maternity and Children Hospital. Mozdalifa road, 6521. Holy Makah, Saudi Arabia. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History


ISSN: 2320-5407
Int. J. Adv. Res. 5 (7), 1367-1374 1368 Diagnosis and management of non palpable testes is a very difficult dilemma and it is mandatory to be achieved to reach the best chance of proper testicular function; including normal hormonal secretions for normal future fertility. On the other hand, accurate diagnosis is very crucial to avoid malignant transformation (4,5). Ultrasonography (US) is simple method of diagnosis of non-palpable testes in children and for surgical planning preoperatively. Many studies concluded that the accuracy of US was not satisfactory (6). Different radiological diagnostic procedures before laparoscopic intervention for non-palpable testis are still controversial regarding the cost benefit ratio. All imaging procedure for the assessment of non-palpable testis are needed to identify their location accurately and assess the viability before surgical interference.
MRI sequences including Fat suppressed T2 and diffusion weighted imaging (DWI); which depend on the Brownian motion of water molecules to provide tissue contrast could be helpful (7). DWI can be performed with MRI sequences at the same setting and it can provide more accurate additional information for non-palpable testes in comparison with conventional MRI alone (7).
The accuracy of detection of the location of a nonpalpable testis with MRI and ultrasound are similar about (85% and 84% respectively) (6,8). Many recent studies have noted that combining DWI with routine MRI sequences improves the diagnostic accuracy of the procedure (9)(10)(11)(12)(13)(14)(15)(16)(17). At DWI, the testes show high signal intensity due to their high cellular density. DWI in addition to routine MRI sequences can improve the sensitivity and specificity of the technique in detecting non palpable testes located intra-abdominally (7).

Objective:-
The aim of our study was to assess the benefit of adding DWI to conventional MRI in the detection of nonpalpable undescended testes.

Materials and Methods:-Patient Populations:-
Between April 2014 and May 2017, Forty one male patients (age range, 6 months-16 years; mean age, 9 years) with undescended testes were included in our study. Patients were imaged using conventional MRI, and DWI. Written informed consent was obtained from all patients' parents before MRI.
Diffusion-weighted MR imaging was performed using a single-shot spin-echo echo planar imaging (EPI) sequence with the b factors of 50, 400, and 800 s/mm 2 along the three orthogonal planes. In order to improve signal-to-noise ratio and for easier patient compliance, DWI under free-breathing was performed; using the following technical parameters TR = 6200 ms, TE = 95 ms, matrix = 125 x 192, slices thickness = 5 mm with inter-slice gap = 20%, FOV = 40 cm, and the average = 4. Acquisition time for the three different b factors was about 3.0 minute. The parallel imaging algorithms (GRAPPA), with an acceleration factor of 2, were added to reduce the acquisition time. Spectral fat saturation was employed systematically to suppress the chemical-shift artifacts. 1369
All the seventeen intracanalicular testes and the eighteen intra-abdominal testes were identified by preoperative combined assessment involving conventional MRI (T1-and T2-weighted imaging, fat-suppressed T2-weighted imaging) and DWI (table 1).
On conventional MR images, testes were detected as elliptic areas of hypointense SI on T1-weighted images and hyperintense on T2-weighted images in their anatomical locations. On DWI, the testes have high signal intensity, therefore at DWI, the pelvi-abdominal region was scanned for focal areas of hyperintensity. Elliptic areas of hyperintensity were considered as testes and recorded. Their locations were classified into two anatomic regions: intracanalicular (Testes close to and below the internal inguinal ring) and intraabdominal (Testes above the internal ring).
On our combined conventional MR images and DW images, conventional sequences were referred to for anatomic location of the hyperintense elliptic areas on the DW images. On DW images, testes were considered the focal areas of hyperintensity that did not represent T2 shine through from fluid-containing structures, on the other hand, hyperintensity due to susceptibility artifacts around bowel loops containing air were dismissed and not considered testes (18).
In our study, all testes were intra-abdominal. Three could not be identified, out of them, 2 were intra-abdominal atrophic testis and one ended blindly at the cord structure intra-abdominally (vanishing testis) as confirmed by surgical findings (fig 5). The following table summarizes the identification of nonpalpable undescended testes in our study in comparison with laparoscopic findings ( Table 2).
The sensitivity and specificity values for conventional MRI versus laparoscopic findings were 89.1 and 100% respectively. The overall prediction accuracy was 89.4% while the sensitivity and specificity values for the conventional MRI with addition of DWI versus laparoscopic findings were 94.6%, and 100% respectively. The overall prediction accuracy was 94.7%.

Disscusion:-
Many diagnostic procedures to identify the nonpalpable testis; including sonography, CT, MRI, and laparoscopy have been used and many trials were done to assess their benifits. Laparoscopy has been considered the most reliable and accurate diagnostic procedure for the identification of nonpalpable testes however being an invasive procedure is the main disadvantage [6].
In contrary to CT, MRI is not an ionizing radiating technique therefore, it is more preferable imaging modality with much less side effects for pediatric patients. Undescended testes have the same magnetic resonance signal characteristics as scrotal testes. They are low signal intensity on T1-weighted images and high intensity of T2weighted images. Kanemoto et al concluded that in spite of considering the high sensitivity and specificity of MRI in comparison with ultrasound in detection of undescended testes, the inability to detect a testis does not completely exclude its absence (19). They studied the role of MRI in detecting of nonpalpable testis and they noted that MRI have an accuracy of 85%, sensitivity of 86%, and specificity of 79% (6).
Desireddiet al. reported that, the accuracy of detecting a viable testis by conventional MRI, was 74% with positive predictive value 70%, and negative predictive value 44% (20).

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In our study, the sensitivity and specificity values for conventional MRI versus laparoscopic findings were 89.1 and 100% respectively. The prediction accuracy was 89.4%. Our result of conventional MRI has a relatively high sensitivity and specificity as compared with previous studies due to using of routing axial & coronal T2 fat suppression in our study.
DWI is a non-invasive method to visualize changes in the translational motion of water molecules and providing better tissue contrast than conventional MRI (7). Many factors can affect DWI signals including the viscosity of fluid which is the main histological feature (21,22), changes in the ratio between intra-and extracellular fluid (23), as well as tissue cellularity (24).
In our study, adding DWI to conventional MRI sequences was increasing the sensitivity of detection of the location of nonpalpable testes from 89.1% to 94.6 % and was increasing the overall accuracy from 89.4 % to 94.7 %. It also increased the confidence of diagnosis as DWI confirm the information obtained from conventional MRI due to suppression of fluid in bowel and nulling the signal of blood vessels.
Kantarci et al, relayed on two observers with different experience in interpreting the MRI findings, they concluded that sensitivity of conventional MRI alone was 85% for both observers; accuracy was 86% for observer 1 and 84% for observer 2. After adding DWI to conventional MRI techniques, the sensitivity and accuracy were increased for both observers (sensitivity, 0.91 and 0.88 and accuracy, 0.92 and 0.86). That means by adding DW technique the performance of both observer greatly improved in detecting the undescended testes (25).
Kato et al, using MRI fat suppressed T2-wieghted and DWI for detecting nonpalpable testes pre operatively. They found that the sensitivity was 100%, the positive predictive value was 96.3%, the specificity was 97.3% and the negative predictive value was 100% in all cases in which they performed orchidopexy, including 13 intraabdominal and 13 intracanalicular testes. Therefore, they mentioned that these techniques greatly facilitate the detection of intra-abdominal and intracanalicular testes with high certainty (26). The results of previous studies (25-26) are in agreement with results of our study.

Conclusion:-
In conclusion, DWI being easy to obtain and easy to evaluate in short time, it yields information that complements conventional MRI findings, improving identification and location of nonpalpable undescended testes. We recommend the use of DWI in addition to conventional MRI to increase the preoperative sensitivity and accuracy of identifying and locating nonpalpable testes.