Pulse-Inversion US Imaging of Testicular Ischemia: Quantitative and Qualitative Analyses in a Rabbit Model

Comparison of Contrast-enhanced Ultrasound and Contrast-enhanced Magnetic Resonance Imaging in the Assessment of Infant Hip Perfusion and Prediction of Proximal Femoral Growth Disturbance Following Closed and Open Reduction for Developmental Dysplasia of the Hip: A Preliminary Study

OBJECTIVE

Proximal femoral growth disturbance (PFGD) is a significant complication associated with surgical treatment of infant hip dislocation. Contrast-enhanced magnetic resonance imaging (CEMRI) has been utilized to assess perfusion in these hips and avoid PFGD. Contrast-enhanced ultrasound (CEUS) is an imaging technique utilized to evaluate perfusion in other organs. The aims of this study were to compare perfusion of dysplastic infant hips with CEUS and CEMRI after surgical treatment and to determine whether CEUS was as effective as CEMRI at predicting PFGD.

METHODS

A retrospective analysis of patients undergoing closed or open reduction for infant hip dislocation between 2012 and 2019 was performed. All patients underwent intraoperative CEUS and postoperative CEMRI to assess femoral epiphyseal perfusion using intravenous contrast. Perfusion status was rated as normal, partially decreased, or globally decreased in both modalities. Agreement in perfusion status between CEUS and CEMRI was assessed. Patients were followed for a minimum of 2 years postoperatively and assessed for PFGD.

RESULTS

Eighteen patients (28% males) underwent closed or open reduction at an average age of 8 months (3 to 16 mo). The agreement in perfusion status between CEUS and CEMRI was substantial (α = 0.74). Patients were followed for a median of 3 years. PFGD developed in 3 hips (17%). For the detection of PFGD, both imaging modalities performed very well and with no difference in the diagnostic utility of CEUS compared with CEMRI. Considering normal perfusion alone the accuracy, sensitivity, and specificity for CEUS were 83%, 100%, and 80%, and for CEMRI were 78%, 100%, and 73%, respectively. Considering global decreased perfusion alone, the accuracy, sensitivity, and specificity for CEUS were 94%, 67%, and 100%, and for CEMRI were 89%, 67%, and 93%, respectively.

CONCLUSIONS

CEUS is a viable intraoperative method to assess infant hip perfusion. This pilot study appears to be comparable to CEMRI at visualizing perfusion of infant hips and as good or better in predicting PFGD after hip reduction. Prospective studies of this imaging technique should be performed to confirm the findings of this retrospective review.

LEVEL OF EVIDENCE

Level II-development diagnostic criteria on the basis of consecutive patients (with generally preferred standard).

Translational research in pediatric contrast-enhanced ultrasound

The role of contrast-enhanced ultrasound (CEUS) imaging is being widely explored by various groups for its use in the pediatric population. Clinical implementation of new diagnostic or therapeutic techniques requires extensive and meticulous preclinical testing and evaluation. The impact of CEUS will be determined in part by the extent to which studies are oriented specifically toward a pediatric population. Rather than simply applying principles and techniques used in the adult population, these studies are expected to advance and augment preexisting knowledge with pediatric-specific information. To further develop this imaging modality for use in children, pediatric-focused preclinical research is essential. In this paper we describe the development and implementation of the pediatric-specific preclinical animal and phantom models that are being used to evaluate CEUS with the goal of clinical translation to children.

Multiparametric US for scrotal diseases

Multiparametric US is increasingly recognized as a valuable problem-solving technique in scrotal pathologies. Compared to conventional Doppler modes, contrast-enhanced ultrasonography (CEUS) has higher sensitivity in assessing the presence or absence of flows, and to improve differentiation between poorly vascularized tumors and non-neoplastic, avascular lesions. Characterization of benign and malignant complex cysts is improved. In trauma patients, CEUS can help evaluating the viability of testicular parenchyma. In patients with severe epididymo-orchitis, it allows unequivocal assessment of post-inflammatory ischemic changes and abscess formation. CEUS does not add significantly to conventional Doppler modes in spermatic cord torsion. Attempt of differentiating benign and malignant tumors remains a research tool. In the clinical practice, elastography has a limited role for tumor characterization. The majority of malignant tumors are stiff at elastography, but they may display soft areas, or appear globally soft. A quantitative evaluation of testicular stiffness is feasible using shear-wave elastography. Potential clinical applications for elastographic modes could include work-up of infertile patients.

Growing indications for CEUS: The kidney, testis, lymph nodes, thyroid, prostate, and small bowel

Contrast enhanced ultrasonography (CEUS) is increasingly used for non-hepatic applications as well, so that nearly all organs have been investigated. Among them, there is a growing clinical use for a variety of pathologies of the kidney, testis, and small bowel. The possibility to differentiate benign from malignant nodes in cancer patients has been investigated. A new application is in the detection of sentinel nodes after intradermal microbubble injection. The need to distinguish thyroid nodules eligible for fine needle aspiration cytology has led to the use of CEUS in thyroid examinations as well. The potential of CEUS for prostate cancer detection has been extensively investigated, with encouraging initial results. Early promise, however, has not been fulfilled. New perspective regards evaluation of the extent of prostate tissue devascularization following ablative treatments.

Multi-planar dynamic contrast-enhanced ultrasound assessment of blood flow in a rabbit model of testicular torsion

To assess correlation between multi-planar, dynamic contrast-enhanced ultrasound (US) blood flow measurements and radiolabeled microsphere blood flow measurements, five groups of six rabbits underwent unilateral testicular torsion of 0°, 180°, 360°, 540° or 720°. Five US measurements per testis (three transverse/two longitudinal) were obtained pre-operatively and immediately and 4 and 8 h post-operatively using linear transducers (7-4 MHz/center frequency 4.5 MHz/10 rabbits; 9-3 MHz/center frequency 5.5 MHz/20 rabbits). Björck's linear least-squares method fit the rise phase of mean pixel intensity over a 7-s period for each time curve. Slope of fit and intervention/control US pixel intensity ratios were calculated. Means of transverse, longitudinal and combined transverse/longitudinal US ratios as a function of torsion degree were compared with radiolabeled microsphere ratios using Pearson's correlation coefficient, ρ. There was high correlation between the two sets of ratios (ρ ≥ 0.88, p ≤ 0.05), except for the transverse US ratio in the immediate post-operative period (ρ = 0.79, p = 0.11). These results hold promise for future clinical applications.

Safety of contrast-enhanced ultrasound in children for non-cardiac applications: a review by the Society for Pediatric Radiology (SPR) and the International Contrast Ultrasound Society (ICUS)

The practice of contrast-enhanced ultrasound in children is in the setting of off-label use or research. The widespread practice of pediatric contrast-enhanced US is primarily in Europe. There is ongoing effort by the Society for Pediatric Radiology (SPR) and International Contrast Ultrasound Society (ICUS) to push for pediatric contrast-enhanced US in the United States. With this in mind, the main objective of this review is to describe the status of US contrast agent safety in non-cardiac applications in children. The five published studies using pediatric intravenous contrast-enhanced US comprise 110 children. There is no mention of adverse events in these studies. From a European survey 948 children can be added. In that survey six minor adverse events were reported in five children. The intravesical administration of US contrast agents for diagnosis of vesicoureteric reflux entails the use of a bladder catheter. Fifteen studies encompassing 2,951 children have evaluated the safety of intravesical US contrast agents in children. A European survey adds 4,131 children to this group. No adverse events could be attributed to the contrast agent. They were most likely related to the bladder catheterization. The existing data on US contrast agent safety in children are encouraging in promoting the widespread use of contrast-enhanced US.

Ultrasound perfusion analysis combining bolus-tracking and burst-replenishment

A new signal model and processing method for quantitative ultrasound perfusion analysis is presented, called bolus-and-burst. The method has the potential to provide absolute values of blood flow, blood volume, and mean transit time. Furthermore, it provides an estimate of the local arterial input function which characterizes the arterial tree, allowing accurate estimation of the bolus arrival time. The method combines two approaches to ultrasound perfusion analysis: bolus-tracking and burst-replenishment. A pharmacokinetic model based on the concept of arterial input functions and tissue residue functions is used to model both the bolus and replenishment parts of the recording. The pharmacokinetic model is fitted to the data using blind deconvolution. A preliminary assessment of the new perfusion-analysis method is presented on clinical recordings.

Application of a second-generation US contrast agent in infants and children--a European questionnaire-based survey

BACKGROUND

No US contrast agent (US-CA) is currently licensed for use in children.

OBJECTIVE

To survey the off-label use in children of a second-generation US-CA.

MATERIALS AND METHODS

Questionnaires were e-mailed to European paediatric radiologists, who were asked about their experience with the second-generation US-CA Sonovue® (Bracco, Milan, Italy). Number of examinations per indication and adverse effects were recorded. Examinations were categorised by intravenous or intracavitary use of US-CA.

RESULTS

Out of 146 respondents, 88 stated that they did not perform contrast-enhanced US in children, but 36 of these (44%) would appreciate paediatric approval. Forty-five centres reported 5,079 examinations in children (age mean: 2.9 years; range: birth-18 years, M/F: 1/ 2.8). The majority (4,131 [81%] in 29 centres) were intravesical applications. The minority (948 [19%] in 30 centres) were intravenous applications. No adverse effects had been recorded from intravesical use. Six minor adverse effects (skin reaction, unusual taste, hyperventilation) had been recorded after five intravenous studies (0.52%).

CONCLUSION

Responses suggest a favourable safety profile of this second-generation US-CA in children. It also demonstrates a demand for such US-CA from paediatric radiologists.

Contrast-enhanced sonography in blunt scrotal trauma()

The scope of this study was to determine whether contrast-enhanced ultrasonography (CEUS), compared with basic US, can increase diagnostic confidence and provide relevant information on blunt scrotal trauma. Over a period of 75 months we examined 40 patients seen consecutively for blunt scrotal trauma using high-resolution US, color-power Doppler, low mechanical index CEUS, and power Doppler after IV administration of contrast medium (SonoVue(®)). In the 24 cases that were positive, concordance between basal US and CEUS findings was grade 0 (absent) in 4 cases, grade 1 (low) in 3, grade 2 (moderate) in 8, and grade 3 (high) in 9. The relevance of the additional information provided by CEUS was classified as follows: high in 4/40 (10%), moderate 7/40 (17,5%), low 13/40 (32,5%), none in 14/40 (35%). Our findings demonstrate that CEUS is appreciably more sensitive in detecting damage caused by blunt scrotal trauma, particularly small lesions. It is also useful for differential diagnosis and marginalization of corpuscular fluid collections, fractures, and above all ruptures, which require immediate surgery. In our series 2 out of 3 (67%) patients with testicular rupture were diagnosed only by CEUS. We feel that the use of CEUS can significantly improve diagnostic confidence in cases of closed scrotal trauma although these conclusions need to be confirmed in larger case series.

Role of contrast enhanced ultrasound in acute scrotal diseases

OBJECTIVE

To evaluate the efficacy of contrast-enhanced ultrasound (CEUS) in patients with acute scrotal pain not defined at ultrasound (US) with colour Doppler .

METHODS

CEUS was carried out in 50 patients with acute scrotal pain or scrotal trauma showing testicular lesion of undefined nature at US. The accuracy of US and CEUS findings versus definitive diagnosis (surgery or follow-up) was calculated.

RESULTS

Twenty-three patients had a final diagnosis of testicular tumour, three abscess, eight focal infarction, seven trauma, three testicular torsion, one haematoma. Five patients were negative. Thirty-five patients were operated (23 testicular tumours, six trauma, three testicular torsion, one abscess, one focal infarction, and one haematoma) and 15 underwent medical treatment or were discharged. US provided a definitive diagnosis in 34/50 as compared to the 48/50 patients diagnosed at CEUS. Sensitivity and specificity were 76% and 45% for US and 96% and 100% for CEUS respectively.

CONCLUSIONS

CEUS was more accurate in the final diagnosis compared to US, potentially reducing the need for further imaging. In particular CEUS can be proposed in emergency in cases where US diagnosis remains inconclusive, namely in infarction, and trauma, when testicular torsion cannot be ruled out, and in identifying testicular mass.

Acute segmental testicular infarction at contrast-enhanced ultrasound: early features and changes during follow-up

OBJECTIVE

The purpose of this retrospective study was to assess whether contrast-enhanced ultrasound is useful for characterization of acute segmental testicular infarction.

MATERIALS AND METHODS

Twenty men with acute scrotal pain and suspected segmental testicular infarction underwent contrast-enhanced ultrasound. Three patients underwent orchiectomy. For the other patients, the final diagnosis was based on the absence of tumor markers and a change in the size or shape of the tumor during follow-up. Forty-nine color Doppler ultrasound studies (16 within 24 hours of the onset of pain; 14, 2-17 days after pain onset; 19 after 1 month or more), and 38 contrast-enhanced ultrasound studies (13 within 24 hours after pain onset; nine, 2-17 days; 16 after 1 month or more) were performed.

RESULTS

Fourteen of 16 lesions examined within 24 hours were oval, and two were wedge shaped. Eight lesions were isoechoic to the testis, six were hypoechoic, and two had mixed echogenicity. Twelve lesions were avascular and four were hypovascular at color Doppler examination. Contrast-enhanced ultrasound showed avascular parenchymal lobules in all cases and without perilesional rim enhancement in 12 of 13 studies. Two to 17 days after the symptoms appeared, contrast-enhanced ultrasound showed avascular lobules in all cases and perilesional rim enhancement in eight examinations. After 1 month or more, contrast-enhanced ultrasound depicted intralesional vascular spots in 12 of 14 infarcts. Perilesional enhancement was absent.

CONCLUSION

Recognition of lobular morphologic characteristics and the presence of perilesional rim enhancement at contrast-enhanced ultrasound can increase confidence in the diagnosis of segmental testicular infarction compared with reliance on gray-scale and color Doppler findings. Changes in lesion features during follow-up confirm the differential diagnosis from other testicular lesions and allow conservative management.

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.

Imaging of the acute scrotum: is there a place for contrast-enhanced ultrasonography?

PURPOSE

To present and evaluate the findings of contrast-enhanced ultrasonography (CEUS) in typical cases of acute painful scrotum.

MATERIALS AND METHODS

Nineteen patients aged from 19 to 61 years old were included in the study. All patients underwent grey-scale and color Doppler ultrasonography (US) of the scrotum, followed by imaging after i.v. administration of 2.4 mL of a second generation ultrasound contrast agent (microbubbles of sulphur hexafluoride). ? dedicated, contrast-sensitive technique was used (Contrast Tissue Imaging - CnTI). The diagnosis was confirmed surgically in 6 cases while in the remaining 8 cases it was based on the combination of clinical, imaging and laboratory findings.

RESULTS

The final diagnosis was testicular torsion (n = 4), epididymitis (n = 2, one of the cases complicated by abscess), testicular abscess (n = 1), scrotal abscess (n = 1), testicular trauma of varying severity (n = 6). Five out of 19 cases were true negatives: neither clinical examination nor laboratory tests revealed any pathology. CEUS showed complete lack of enhancement in all cases of torsion, permitting a rapid and definitive diagnosis. In the cases of infection complicated by abscesses, CEUS delineated the lesions much better than the combination of B-mode/Color Doppler US. The severely traumatized testicles showed minimal, inhomogeneous or patchy enhancement, while cases of minor trauma showed no significant enhancement defects. Hematomas were presented as non-enhancing lesions.

CONCLUSION

Generally, there was no advantage over Doppler US as has been previously shown. However, CEUS can be used supplementary to traditional Doppler US in the investigation of blunt testicular trauma especially when there is uncertainty in diagnosis after appropriate clinical and radiographic evaluations occurs. Further studies are required to clearly define the indications of this method.

Assessment of tissue perfusion by contrast-enhanced ultrasound

Contrast-enhanced ultrasound (CEUS) with microbubble contrast agents is a new imaging technique for quantifying tissue perfusion. CEUS presents several advantages over other imaging techniques in assessing tissue perfusion, including the use of microbubbles as blood-pool agents, portability, availability and absence of exposure to radiation or nuclear tracers. Dedicated software packages are necessary to quantify the echo-signal intensity and allow the calculation of the degree of tissue contrast enhancement based on the accurate distinction between microbubble backscatter signals and native tissue background. The measurement of organ transit time after microbubble injection and the analysis of tissue reperfusion kinetics represent the two fundamental methods for the assessment of tissue perfusion by CEUS. Transit time measurement has been shown to be feasible and has started to become accepted as a clinical tool, especially in the liver. The loudness of audio signals from spectral Doppler analysis is used to generate time-intensity curves to follow the wash-in and wash-out of the microbubble bolus. Tissue perfusion may be quantified also by analysing the replenishment kinetics of the volume of microbubbles after their destruction in the imaged slice. This allows to obtain semiquantitative parameters related to local tissue perfusion, especially in the heart, brain, and kidneys.

The role of ultrasound in assessment of male fertility

Ultrasonography (US) is a widely used and well tolerated imaging modality for evaluation of pathologic conditions of the testes. Recent technical advances of US applications and post processing developments have enabled new aspects in the structural and functional analysis of testicular tissue and therefore male fertility. This review covers the most relevant approaches due to recent technical advances. Testicular volume measured by B-mode US correlated significantly with testicular function. Increased resistive index (RI) and pulsatility index (PI) of capsular branches of testicular arteries on unenhanced color Doppler US examination may be an indicator of impaired testicular microcirculation in patients with clinical varicocele. FSH was inversely correlated with testicular volume and directly correlated with testicular vascularization, suggesting that ultrasonographic and color Doppler scanning of the testes may be used, if a sperm count is not available, to indirectly assess the gonadal function. Perfusion mapping, performed with the use of color Doppler ultrasound, has shown for the first time that in patients suffering from azoospermia, sperm quality and quantity depend on tissue perfusion within the testicle. Testicular arterial blood flow was found to be significantly decreased in men with varicocele. This may be a reflection of the impaired microcirculation. Following decreased testicular arterial blood flow, impaired spermatogenesis may result from defective energy metabolism in the microcirculatory bed. Contrast-enhanced ultrasound (CEUS) imaging is potentially applicable to the investigation of vascular disorders of the testis. Pulse inversion (PI) US data can correctly determine relative testicular perfusion based on nonlinear curve fitting of the US backscatter intensity as a function of time and spectral analysis of the intensity time trace. PI imaging, compared with conventional Doppler US methods, provides superior assessment of perfusion in the setting of acute testicular ischemia. New contrast-enhanced US techniques like microvessel imaging (proposed by Philips) and CPS (proposed by Siemens-Acuson) allow for a better determination of tissue perfusion based on time intensity curves and an illustration of vessel distribution inside the testis. First results show a lower vessel density in atrophic testes and a difference in contrast dynamics in testes with impaired function. Real-time elastography, a method for illustration of tissue stiffness under real-time conditions, demonstrates different elasticity values dependent on testicular volume and function. Further studies will prove if these techniques can evolve into clinical practice.

Blood perfusion of the contralateral testis evaluated with contrast-enhanced ultrasound in rabbits with unilateral testicular torsion

The changes of blood perfusion of contralateral testis after unilateral testicular torsion remain controversial. In this study, 28 New Zealand white male rabbits were randomly divided into five groups. Group A (n = 8), the control group, underwent a sham operation on the unilateral testis without inducing testicular torsion. In groups B, C, and D (n = 5 each), unilateral testicular torsion was induced, and, after 3, 6 or 24 h, respectively, detorsion was performed. In group E (n = 5), permanent unilateral testicular torsion was applied. Contrast-enhanced ultrasound was used to observe the blood perfusion of the contralateral testis at the following stages: pre-torsion (preopration), immediately post-torsion (postopration), pre-detorsion, immediately post-detorsion, and late-stage post-detorsion (6-12 h post-detorsion in groups B-D) or at a similar time point (15-21 h post-torsion in group E). Time-intensity curves were generated, and the following parameters were derived and analyzed: arrival time, time to peak intensity, peak intensity, and half-time of the descending peak intensity. The analysis revealed that blood perfusion of the contralateral testis increased immediately after testicular torsion on the opposite side (P < 0.05), which increased with prolonged testicular torsion of the other testis. This research demonstrated that contrast-enhanced ultrasound was valuable in evaluating blood perfusion of the contralateral testis after unilateral testicular torsion.

Testicular Torsion: Twists and Turns

Testicular torsion is one of the common causes of acute scrotal pain. This review discusses the clinical and sonographic findings of intravaginal and extravaginal testicular torsion, including the normal sonographic and vascular anatomy of the testis. The role of color flow Doppler and spectral Doppler is also emphasized in the patient's complete, incomplete, and intermittent testicular torsion. Sonographic features of testicular torsion mimics, such as vasculitis, venous thrombosis, scrotal edema, and technical parameters, are also presented. A brief description of new developments such as contrast-enhanced ultrasound, dynamic contrast magnetic resonance imaging, and near-infrared imaging is included.

Clinical and ultrasound features of segmental testicular infarction: Six-year experience from a single centre

The purpose was to analyse the aetiology and ultrasound appearances of segmental testicular infarction. Patients with focal testicular lesions underwent colour Doppler high frequency ultrasound. Segmental testicular infarction was defined as any focal area of altered reflectivity, with or without focal enlargement with absent or diminished colour Doppler flow, proven on histology or on follow-up exclusion of lesion progression. Patients were reviewed to document lesion shape, position, border definition, reflectivity and vascularity and correlated to presenting clinical symptoms and signs. Over a 6-year period 24 patients were defined as having segmental testicular infarction; median age was 37 years (range 16-82 years). All presented with a sudden onset of testicular pain. Of the patients, 14/24 (58.3%) had scrotal inflammatory disease, 5/24 (20.8%) had evidence of spermatic cord torsion, and three patients were termed idiopathic; 12/24 (50.0%) were of low reflectivity, 11/24 (45.8%) of mixed reflectivity, one of high reflectivity, 11/24 (45.8%) were wedge shaped, and 13/24 (54.2%) were round shaped. Of the patients, 8/24 (33.3%) demonstrated a mass effect, all with round-shaped lesions and with underlying epididymo-orchitis in seven. Absent colour Doppler flow was demonstrated in 20/24 (83.3%). Histology confirmed infarction in 8/24 (33.3%), and 12/24 (50.0%) had follow-up examinations without progression of the lesions. Segmental testicular infarction has characteristic ultrasound features, not always wedge-shaped, with reduced or absent vascularity of key importance. Awareness of the ultrasound features will allow for conservative management and avoid unnecessary orchidectomy.

Microbubble ultrasound contrast agents: an update

Microbubble contrast agents for ultrasound (US) have gained increasing interest in recent years, and contrast-enhanced US (CEUS) is a rapidly evolving field with applications now extending far beyond the initial improvements achieved in Doppler US. This has been achieved as a result of the safe profile and the increased stability of microbubbles persisting in the bloodstream for several minutes, and also by the availability of specialized contrast-specific US techniques, which allow a definite improvement in the contrast resolution and suppression of signal from stationary tissues. CEUS with low transmit power allows real-time scanning with the possibility of prolonged organ insonation. Several reports have described the effectiveness of microbubble contrast agents in many clinical applications and particularly in the liver, spleen, and kidneys. CEUS allows the assessment of the macrovasculature and microvasculature in different parenchymas, the identification and characterization of hepatic and splenic lesions, the depiction of septal enhancement in cystic renal masses, and the quantification of organ perfusion by the quantitative analysis of the echo-signal intensity. Other fields of application include the assessment of abdominal organs after traumas and the assessment of vesico-ureteral reflux in children. Finally, tumor-targeted microbubbles make possible the depiction of specific biologic processes.

Automated sonographic evaluation of testicular perfusion

Contrast-enhanced ultrasound (US) imaging is potentially applicable to the investigation of vascular disorders of the testis. We investigated the ability of two automated computer algorithms to analyse contrast-enhanced pulse inversion US data in a rabbit model of unilateral testicular ischaemia and to correctly determine relative testicular perfusion: nonlinear curve fitting of the US backscatter intensity as a function of time; and spectral analysis of the intensity time trace. We compared (i) five metrics based on the algorithmic data to testicular perfusion ratios obtained with radiolabelled microspheres, a reference standard; (ii) qualitative assessment of the US images by two independent readers blinded to the side of the experimental and control testes to the radiolabelled microsphere perfusion ratios; and (iii) results of the algorithmically-derived metrics to the qualitative assessments of the two readers. For the curve fit method, the algorithmically-derived metrics agreed with the reference standard in 54% to 68% of all cases. For the spectral method, the results agreed in 70% of all cases. The two readers agreed with the reference standard in 40% and 35% of all cases, respectively. These results suggest that automated methods of analysis may provide useful information in the assessment of testicular perfusion.