Relative blood volume measurements by magnetic resonance imaging facilitate detection of testicular torsion

18F-PEG1-Vinyl Sulfone-Labeled Red Blood Cells as Positron Emission Tomography Agent to Image Intra-Abdominal Bleeding

¹⁸F-Labeled blood pool agents (BPAs) have attracted great attention for identifying bleeding sites. However, many BPAs are not sufficiently evaluated partially due to the limitations of labeling methods. In our previous work, we noticed that ¹⁸F-PEG1-vinyl sulfone (¹⁸F-VS) could efficiently label red blood cells (RBCs) ex vivo and in situ. However, its application as BPA is not fully evaluated. In this study, we systematically explored the feasibility of using ¹⁸F-VS-labeled RBCs as a positron emission tomography (PET) BPA for intra-abdominal bleeding diagnosis. In brief, we first optimized the labeling conditions, which lead to an 80% labeling yield of RBCs after incubating with ¹⁸F-VS in phosphate-buffered saline (PBS) at 37°C for 20 min. ¹⁸F-VS-labeled RBCs were found to be stable in vitro, which could simplify its transportation/storage for in vivo applications. In normal rat PET study, the cardiovascular system could be clearly imaged up to 5 h post injection (p.i.). An intra-abdominal hemorrhage rat model demonstrated that the ¹⁸F-VS-labeled RBCs clearly showed the dynamic changes of extravascular radioactivity due to intra-abdominal hemorrhage. Validation in the model of gastrointestinal bleeding clearly demonstrated the great potential of using ¹⁸F-VS-labeled RBCs as a BPA, which could be further evaluated in future studies.

Role of diffusion weighted magnetic resonance imaging in a rat model of testicular torsion

OBJECTIVE

The purpose of this study was to investigate the usefulness of diffusion-weighted imaging (DWI) in the detection of different degrees of testicular torsion (TT) at the 8th hour and testicular salvageability at the 24th hour of torsion.

METHODS

31 rats were randomly classified into 4 groups. In Group 1 (sham-control group), the left testicle was kept outside and replaced. Left testicles were kept outside and twisted 360° in Group 2, 720° in Group 3 and 1080° in Group 4. Later, DWI was performed at 8th and 24th hours. After DWI, bilateral radical orchiectomy and histopathological examination were performed. Apparent diffusion coefficient (ADC) maps were obtained with b-factors of 0 and 800 s mm^-2. Comparisons of ADC values and damage in testicles were performed with Kruskal-Wallis test.

RESULTS

Sensitivity of DWI in the diagnosis of TT was 12.5% for 360° torsion, 100% for 720° torsion and 1080° torsion at the 8th hour of torsion. Mean ADC values of the left testicles increased significantly at the 24th hour of torsion in Groups 3 and 4. All testicles in Groups 3 and 4 were observed to be irrecoverable on histopathological examination.

CONCLUSION

Increased ADC values in the affected testicle may represent irreversible tissue damage. So, immediate surgery is not required at this stage, which may reduce morbidity and mortality caused by immediate surgery and anaesthesia. Advances in knowledge: TT can be diagnosed easily by DWI without administrating any contrast material. DWI findings in the affected testicle may represent testicular salvageability.

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.

Magnetic Resonance Imaging of Acute Scrotum

Background and Aims:

The aim of the pilot study was to evaluate the feasibility of dynamic contrast enhanced (CE)-magnetic resonance imaging (MRI) in the detection of testicular ischemia and its ability to differentiate testicle torsion from other causes of acute scrotum.

Material and Methods:

Seventeen boys or young men with an acute scrotum were included in the prospective study during the time period from October 2001 to December 2005. The median age of the patients was 16,4 (7–44) years. The duration of the symptoms preceding the MRI study varied from six hours to 30 days. The study protocol included physical examination by a surgeon, laboratory tests and Doppler ultrasound (DUS) and finally testicles were imaged by using a 1,5 T MRI scanner; T1-weighted and diffusion weighted images were produced. The gadolinium uptake, reported as the region of interest (ROI) perfusion values and presented as curves, was compared between the affected and contralateral testicle. In testicles with normal blood circulation the ROI values increased during the imaging time. Nine patients were operated on, because the spermatic cord torsion could not be excluded by clinical or DUS findings.

Results and Conclusions:

All the normal testicles gave increasing ROI values meanwhile all three testicles with torsion gave constantly low values referring to no perfusion. Other causes of acute scrotum, such as epididymitis and torsion of testicular appendage seemed to be related with normal perfusion. Dynamic CE-MRI seems to show reliably ischemia of testicle and thus it may be helpful in selecting patients with acute scrotum for urgent operation.

Dynamic contrast-enhanced subtraction magnetic resonance imaging in diagnostics of testicular torsion

OBJECTIVES

To retrospectively correlate the magnetic resonance imaging (MRI) diagnosis with the surgical findings and/or clinical outcomes in patients presenting with an acute scrotum.

METHODS

From January 1997 to June 2004, 39 selected patients presenting with an acute scrotum underwent dynamic contrast-enhanced subtraction MRI as a 24-hour stand-by examination. The MRI diagnosis was based solely on the presence or absence of testicular contrast enhancement, without respect to the clinical history or physical examination findings.

RESULTS

Contrast enhancement of the affected and normal testes could be accurately compared in all cases. The MRI diagnosis was testicular torsion (no testicular contrast enhancement, n = 13), nonspecific (reduced to normal enhancement, n = 10), appendiceal torsion (n = 3), and epididymitis (n = 13). The surgical findings and/or subsequent clinical outcomes showed that MRI diagnosis of testicular torsion was accurate in all 13 cases. Furthermore, exploration revealed testicular torsion in 1 case with very little enhancement. The sensitivity and specificity of MRI in the diagnosis of testicular torsion was 93% (13 of 14) and 100% (25 of 25), respectively. Although MRI detected testicular perfusion, 5 of the 6 patients with clinical suspicion of intermittent torsion underwent surgical exploration.

CONCLUSIONS

MRI is a highly accurate imaging modality for the diagnosis of testicular torsion. However, it could not be used to rule out intermittent torsion and the clinical use of negative findings for an MRI torsion test was less than 100% specificity. Because this was a preliminary retrospective study, the true clinical value of MRI should be evaluated by prospective studies.

Continuous arterial spin-labeling perfusion magnetic resonance imaging of the human testis1

RATIONALE AND OBJECTIVES

The purpose of this study was to determine if continuous arterial spin-labeling perfusion magnetic resonance imaging could be used to detect testicular perfusion in human subjects.

MATERIALS AND METHODS

Continuous arterial spin-labeling magnetic resonance perfusion imaging was performed in seven normal male volunteers and in one patient with a painful scrotum following vasectomy.

RESULTS

Normal testicular blood flow was demonstrated in 14 of 14 normal testes in seven volunteers, as well as in two normally perfused testes in the post-vasectomy patient. A change in the steady state magnetization was observed in all of the normally perfused testes of the seven volunteers.

CONCLUSION

It is possible to detect blood flow to the normally perfused testes using noninvasive spin-labeling perfusion magnetic resonance imaging. This modality could potentially, in future investigations, be used to image patients with suspected testicular torsion and resultant testicular ischemia.