Dynamic contrast-enhanced MR imaging of the scrotum: reality check

Dynamic contrast-enhanced MRI in the assessment of testicular perfusion in infertile men with clinical varicocele

BACKGROUND

Varicocele represents the most common correctable cause of male infertility. The presence of non-invasive imaging parameters providing evidence as to which patients with varicocele are at risk for infertility would be important.

PURPOSE

To explore the role of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) using semi-quantitative parameters in the assessment of testicular perfusion in infertile men with clinical varicocele.

MATERIAL AND METHODS

The study cohort included 11 infertile men with clinical varicocele and six controls, with prior paternity. Subtraction DCE-MRI was performed after gadolinium administration, using a three-dimensional fast field-echo sequence. Time-signal intensity curves were created and semi-quantitative parameters were calculated. The independent samples t-test was used to compare basic T1 perfusion parameters between infertile testes with clinical varicocele and normal testes. Logistic regression analysis was performed to assess the most significant predictor of the diagnosis of clinical varicocele.

RESULTS

Both testes with clinical varicocele and normal testes enhanced moderately and homogeneously, with a linear increase of enhancement throughout the examination. Higher mean values of maximum enhancement (P = 0.026), maximum relative enhancement (P = 0.024), and wash-in rate (P = 0.013) were detected in the testes of infertile men with clinical varicocele, compared to the normal population. The wash-in rate proved the most significant predictor of the diagnosis of clinical varicocele (P = 0.013).

CONCLUSION

DCE-MRI may provide a valuable insight into the testicular perfusion of infertile men with clinical varicocele. The wash-in rate proved a strong and independent predictor of the diagnosis of clinical varicocele.

An Overview of the Role of Multiparametric MRI in the Investigation of Testicular Tumors

Simple Summary

Although conventional ultrasonography remains the primary imaging modality for the assessment of testicular tumors, multiparametric MRI of the scrotum, which combines morphologic and functional data, serves as a powerful adjunct. Based on the recommendations issued by the Scrotal and Penile Imaging Working Group of the European Society of Urogenital Radiology, scrotal MRI is strongly recommended after equivocal US findings. In cases of testicular masses, the main clinical indications are as follows: lesion characterization when sonographic findings are non-diagnostic, discrimination between germ-cell and non-germ-cell testicular tumors, local staging of testicular tumors in patients who are candidates for testis-sparing surgery, and preoperative histological characterization of testicular germ-cell tumors in selected cases. This article aims to provide an overview of the role of multiparametric MRI in the investigation of testicular tumors.

Abstract

Conventional ultrasonography represents the mainstay of testis imaging. In cases in which ultrasonography is inconclusive, scrotal MRI using a multiparametric protocol may be used as a useful problem-solving tool. MRI of the scrotum is primarily recommended for differentiating between benign and malignant testicular masses when sonographic findings are ambiguous. This technique is also accurate in the preoperative local staging of testicular tumors and, therefore, is recommended in patients scheduled for testis-sparing surgery. In addition, MRI may provide valuable information regarding the histological characterization of testicular germ-cell tumors, in selected cases. Scrotal MRI may also help in the differentiation between testicular germ-cell neoplasms and non-germ-cell neoplasms. Axial T1-weighted imaging, axial and coronal T2-weighted imaging, axial diffusion-weighted imaging, and coronal subtracted dynamic contrast-enhanced imaging are the minimum requirements for scrotal MRI. A variety of MRI techniques—including diffusion tensor imaging, magnetization transfer imaging, proton MR spectroscopy, volumetric apparent diffusion coefficient histogram analysis, and MRI-based radiomics—are being investigated for testicular mass characterization, providing valuable supplementary diagnostic information. In the present review, we aim to discuss clinical indications for scrotal MRI in cases of testicular tumors, along with MRI findings of common testicular malignancies.

When to ask for an MRI of the scrotum

Background

Multiparametric MRI (mpMRI) of the scrotum has been established as a useful second‐line diagnostic tool for the investigation of scrotal diseases. Recently, recommendations on clinical indications for scrotal MRI were issued by the Scrotal and Penile Imaging Working Group of the European Society of Urogenital Radiology.

Objective

To update current research on when to ask for an MRI of the scrotum.

Methods

PubMed database was searched for original articles and reviews published during 2010–2021.

Results

Eighty‐three articles fulfilled the search criteria. Scrotal MRI is mainly recommended after inconclusive US findings or inconsistent with the clinical examination and should be asked in the following cases: differentiation between intratesticular and paratesticular lesions (in rare cases of uncertain US findings), characterization of paratesticular and intratesticular lesions (when US findings are indeterminate), discrimination between germ cell and sex cord‐stromal testicular tumors, local staging of testicular malignancies (in patients planned for testis‐sparing surgery), differentiation between seminomas and non‐seminomatous tumors (when immediate chemotherapy is planned and orchiectomy is delayed), assessment of acute scrotum and scrotal trauma (rarely needed, in cases of non‐diagnostic US findings) and detection and localization of undescended testes (in cases of inconlusive US findings). Although preliminary data show promising results in the evaluation of male infertility, no established role for mpMRI still exists.

Conclusion

Multiparametric MRI of the scrotum, by assessing morphologic and functional data represents a valuable problem‐solving tool, helping to improve our understanding on the nature of scrotal pathology and the process of spermatogenesis. The technique may improve patient care and reduce the number of unnecessary surgical procedures.

Potential role of imaging in assessing harmful effects on spermatogenesis in adult testes with varicocele

Varicocele is characterized by an abnormal dilatation and retrograde blood flow in the spermatic veins. Varicocele is the leading correctable cause of male infertility. Although it is highly prevalent in infertile men, it is also observed in individuals with normal fertility. Determining which men are negatively affected by varicocele would enable clinicians to better select those men who will benefit from treatment. To assess the functional status of the testes in men with varicocele, color Doppler sonographic parameters were evaluated. Testicular arterial blood flow was significantly reduced in men with varicocele, reflecting an impairment of spermatogenesis. An improvement in the testicular blood supply was found after varicocelectomy on spectral Doppler analysis. Testicular contrast harmonic imaging and elastography might improve our knowledge about the influence of varicocele on intratesticular microcirculation and tissue stiffness, respectively, providing possible information on the early damage of testicular structure by varicocele. Magnetic resonance imaging (MRI), with measurement of apparent diffusion coefficient has been used to assess the degree of testicular dysfunction and to evaluate the effectiveness of varicocele repair. Large prospective studies are needed to validate the possible role of functional sonography and MRI in the assessment of early defects of spermatogenesis in testes with varicocele.

MR imaging of scrotum

Magnetic resonance (MR) imaging of the scrotum has been used as a valuable supplemental diagnostic modality in evaluating scrotal pathology, mostly recommended in cases of inconclusive sonographic findings. Because of the advantages of the technique, MR imaging of the scrotum may provide valuable information in the detection and characterization of various scrotal diseases. The technique may accurately differentiate intratesticular from extratesticular mass lesions and provide important information in the preoperative characterization of the histologic nature of scrotal masses. An accurate estimation of the local extent of testicular carcinomas in patients for whom testis-sparing surgery is planned is possible.

Dynamic contrast-enhanced subtraction MRI for characterizing intratesticular mass lesions

OBJECTIVE

The objective of our study was to analyze the enhancement patterns of various intratesticular mass lesions at dynamic contrast-enhanced subtraction MRI and assess the value of the technique in distinguishing between benign and malignant lesions.

MATERIALS AND METHODS

We retrospectively evaluated the records and images of 44 consecutive men (11 benign and 16 malignant intratesticular lesions) who presented to the department of urology with a variety of clinical symptoms and were referred for imaging. Dynamic contrast-enhanced subtraction MRI was performed using a 3D fast-field echo sequence after the administration of paramagnetic contrast medium. Patients were divided into three groups according to the final diagnosis: benign intratesticular lesions, malignant intratesticular lesions, and normal testes. The patterns of contrast enhancement of both the normal testes and the intratesticular lesions were evaluated. Time-signal intensity plots were created and classified according to shape: Type I presented a linear increase of contrast enhancement throughout the examination, type II showed an initial upstroke followed by either a plateau or a gradual increase in the late contrast-enhanced phase, and type III presented an initial upstroke followed by gradual washout of the contrast medium. The relative percentages of peak height, maximum time, and mean slope were also calculated.

RESULTS

Normal testes enhanced homogeneously with a type I curve. Most benign intratesticular lesions showed inhomogeneous or homogeneous contrast enhancement and a type II curve. Testicular carcinomas showed heterogeneous contrast enhancement with a type III curve. The relative percentages of maximum time to peak proved the most important discriminating factor in differentiating malignant from benign intratesticular masses (p < 0.001).

CONCLUSION

Dynamic contrast-enhanced MRI may be used to distinguish between benign and malignant intratesticular mass lesions.

Real-time sonoelastography for the evaluation of testicular lesions

PURPOSE

To evaluate the feasibility of using real-time sonoelastography (RTE) for the differentiation and characterization of testicular lesions.

MATERIALS AND METHODS

Institutional review board approval was obtained for this retrospective study, and the requirement to obtain informed consent was waived. Fifty patients (mean age, 42 years; age range, 18-81 years) with testicular lesions detected with gray-scale ultrasonography (US) and color and/or power Doppler US were evaluated with RTE between December 2004 and August 2010 to assess tissue elasticity of the testes. Stiff or "hard" lesions were suspected of being malignant. Testicular lesions with normal or decreased tissue stiffness ("soft" lesions) were considered benign. Findings from surgery and histopathologic examination were used as the reference standard in 34 cases, and findings from clinical and US follow-up were used as the reference standard in 16 cases. Sensitivity, specificity, negative predictive value, positive predictive value, and diagnostic accuracy were calculated.

RESULTS

Thirty-four of the 50 lesions (68%) were testicular tumors and 16 (32%) were of nontumorous origin. RTE showed the presence of hard lesions in all cases of testicular tumors and three cases of nontumorous lesions. Four lesions with an uncertain diagnosis when tested with gray-scale US and color and/or power Doppler US alone were soft at RTE and showed nontumorous character at follow-up. RTE showed a sensitivity of 100%, a specificity of 81%, a negative predictive value of 100%, a positive predictive value of 92%, and an accuracy of 94% in the diagnosis of testicular tumors.

CONCLUSION

RTE demonstrated all testicular tumors as lesions with increased tissue stiffness. Because of its higher specificity, RTE can provide additional information in cases with indeterminate US findings.

Contrast-enhanced, real-time volumetric ultrasound imaging of tissue perfusion: preliminary results in a rabbit model of testicular torsion

Contrast-enhanced ultrasound (US) imaging is potentially applicable to the clinical investigation of a wide variety of perfusion disorders. Quantitative analysis of perfusion is not widely performed, and is limited by the fact that data are acquired from a single tissue plane, a situation that is unlikely to accurately reflect global perfusion. Real-time perfusion information from a tissue volume in an experimental rabbit model of testicular torsion was obtained with a two-dimensional matrix phased array US transducer. Contrast-enhanced imaging was performed in 20 rabbits during intravenous infusion of the microbubble contrast agent Definity® before and after unilateral testicular torsion and contralateral orchiopexy. The degree of torsion was 0° in 4 (sham surgery), 180° in 4, 360° in 4, 540° in 4, and 720° in 4. An automated technique was developed to analyze the time history of US image intensity in experimental and control testes. Comparison of mean US intensity rate of change and of ratios between mean US intensity rate of change in experimental and control testes demonstrated good correlation with testicular perfusion and mean perfusion ratios obtained with radiolabeled microspheres, an accepted 'gold standard'. This method is of potential utility in the clinical evaluation of testicular and other organ perfusion.

MR imaging of testicular torsion: features of testicular hemorrhagic necrosis and clinical outcomes

PURPOSE

To determine whether emergency subtraction dynamic contrast-enhanced MR imaging (DCE-MRI) in combination with T2- and T2*-weighted imaging of the testis is useful in the evaluation of patients with testicular torsion.

MATERIALS AND METHODS

Fourteen patients with surgically proven testicular torsion were examined using preoperative emergency MRI, including T2-weighted, T2*-weighted, and DCE-MRI. The affected testis was examined histologically in eight patients who underwent orchiectomy, and by postoperative follow-up MRI in six patients who underwent orchiopexy. The diagnostic criteria for testicular torsion and detection of hemorrhagic necrosis in the affected testis in emergency MRI were decreased or no perfusion in DCE-MRI and a spotty and/or streaky pattern of low or very low signal intensity in T2- and T2*-weighted images. The intraoperative findings and clinical outcomes were also compared.

RESULTS

The histological findings and follow-up MR images revealed total or partial necrosis of the affected testis in 10 of the 14 patients. In the diagnosis of complete torsion, the sensitivities were 100% for DCE-MRI and 75% for T2- and T2*-weighted imaging. In the detection of testicular necrosis, T2- and T2*-weighted imaging showed the highest accuracy (100%), followed by 12-hour time from onset (93%), intraoperative findings (79%), and DCE-MRI (71%).

CONCLUSION

Emergency MRI can help diagnose testicular torsion and detect testicular necrosis when DCE-MRI is used in combination with T2- and T2*-weighted images.

Sonography of the scrotum

Ultrasonography (US) with a high-frequency (7.5-10-MHz) transducer has become the imaging modality of choice for examination of the scrotum. US examination can provide information valuable for the differential diagnosis of a variety of disease processes involving the scrotum that have similar clinical manifestations (eg, pain, swelling, or presence of mass). The pathologic condition that may be at the origin of such symptoms can vary from testicular torsion to infection to malignancy. The ability of color and power Doppler US to demonstrate testicular perfusion aids in reaching a specific diagnosis in patients with acute scrotal pain. This review covers the anatomy of the scrotum and the scanning protocol for scrotal US, as well as detailed descriptions of disease processes and their US appearances. Newly described conditions such as intratesticular varicoceles and other benign intratesticular cystic lesions are also discussed.

Scrotal imaging

Color Doppler ultrasound has been the mainstay for the evaluation of the scrotum in a variety of clinical settings. However, ultrasonography results are not always accurate or conclusive. Despite the high cost and limited availability, magnetic resonance imaging with the dynamic contrast-enhanced subtraction technique provides accurate information on morphology as well as blood flow. Infrared scrotal thermography increases accuracy in the diagnosis of varicocele. This article attempts to summarize recent advances in scrotal imaging with regard to testicular and extratesticular disorders.