Walter Romano

Graph cuts with invariant object-interaction priors: application to intervertebral disc segmentation

This study investigates novel object-interaction priors for graph cut image segmentation with application to intervertebral disc delineation in magnetic resonance (MR) lumbar spine images. The algorithm optimizes an original cost function which constrains the solution with learned prior knowledge about the geometric interactions between different objects in the image. Based on a global measure of similarity between distributions, the proposed priors are intrinsically invariant with respect to translation and rotation. We further introduce a scale variable from which we derive an original fixed-point equation (FPE), thereby achieving scale-invariance with only few fast computations. The proposed priors relax the need of costly pose estimation (or registration) procedures and large training sets (we used a single subject for training), and can tolerate shape deformations, unlike template-based priors. Our formulation leads to an NP-hard problem which does not afford a form directly amenable to graph cut optimization. We proceeded to a relaxation of the problem via an auxiliary function, thereby obtaining a nearly real-time solution with few graph cuts. Quantitative evaluations over 60 intervertebral discs acquired from 10 subjects demonstrated that the proposed algorithm yields a high correlation with independent manual segmentations by an expert. We further demonstrate experimentally the invariance of the proposed geometric attributes. This supports the fact that a single subject is sufficient for training our algorithm, and confirms the relevance of the proposed priors to disc segmentation.

Evaluation of MRI-TRUS Fusion Versus Cognitive Registration Accuracy for MRI-Targeted, TRUS-Guided Prostate Biopsy

OBJECTIVE The purpose of this article is to compare transrectal ultrasound (TRUS) biopsy accuracies of operators with different levels of prostate MRI experience using cognitive registration versus MRI-TRUS fusion to assess the preferred method of TRUS prostate biopsy for MRI-identified lesions. SUBJECTS AND METHODS; One hundred patients from a prospective prostate MRI-TRUS fusion biopsy study were reviewed to identify all patients with clinically significant prostate adenocarcinoma (PCA) detected on MRI-targeted biopsy. Twenty-five PCA tumors were incorporated into a validated TRUS prostate biopsy simulator. Three prostate biopsy experts, each with different levels of experience in prostate MRI and MRI-TRUS fusion biopsy, performed a total of 225 simulated targeted biopsies on the MRI lesions as well as regional biopsy targets. Simulated biopsies performed using cognitive registration with 2D TRUS and 3D TRUS were compared with biopsies performed under MRI-TRUS fusion. RESULTS Two-dimensional and 3D TRUS sampled only 48% and 45% of clinically significant PCA MRI lesions, respectively, compared with 100% with MRI-TRUS fusion. Lesion sampling accuracy did not statistically significantly vary according to operator experience or tumor volume. MRI-TRUS fusion-naïve operators showed consistent errors in targeting of the apex, midgland, and anterior targets, suggesting that there is biased error in cognitive registration. The MRI-TRUS fusion expert correctly targeted the prostate apex; however, his midgland and anterior mistargeting was similar to that of the less-experienced operators. CONCLUSION MRI-targeted TRUS-guided prostate biopsy using cognitive registration appears to be inferior to MRI-TRUS fusion, with fewer than 50% of clinically significant PCA lesions successfully sampled. No statistically significant difference in biopsy accuracy was seen according to operator experience with prostate MRI or MRI-TRUS fusion.

Regression Segmentation for

Clinical routine often requires to analyze spinal images of multiple anatomic structures in multiple anatomic planes from multiple imaging modalities ( M3). Unfortunately, existing methods for segmenting spinal images are still limited to one specific structure, in one specific plane or from one specific modality ( S3). In this paper, we propose a novel approach, Regression Segmentation, that is for the first time able to segment M3 spinal images in one single unified framework. This approach formulates the segmentation task innovatively as a boundary regression problem: modeling a highly nonlinear mapping function from substantially diverse M3 images directly to desired object boundaries. Leveraging the advancement of sparse kernel machines, regression segmentation is fulfilled by a multi-dimensional support vector regressor (MSVR) which operates in an implicit, high dimensional feature space where M3 diversity and specificity can be systematically categorized, extracted, and handled. The proposed regression segmentation approach was thoroughly tested on images from 113 clinical subjects including both disc and vertebral structures, in both sagittal and axial planes, and from both MRI and CT modalities. The overall result reaches a high dice similarity index (DSI) 0.912 and a low boundary distance (BD) 0.928 mm. With our unified and expendable framework, an efficient clinical tool for M3 spinal image segmentation can be easily achieved, and will substantially benefit the diagnosis and treatment of spinal diseases.

M^{3}

Diminished vascular endothelial function results in decreased vasodilator capacity and is associated with erectile dysfunction (ED) in patients afflicted with type 2 diabetes. The current study was designed to evaluate whether daily use of sildenafil could alter endothelial function and improve penile rigidity in a group of patients with diabetic ED. A double-blind, placebo-controlled, prospective trial was conducted with 24 men with type 2 diabetes who were randomized into 2 groups: one receiving daily sildenafil (50 mg, n = 12) and the other placebo (n = 12) for 10 weeks. Erectile function was captured subjectively using the International Index of Erectile Function (IIEF-5), and endothelial function was objectively monitored via brachial artery flow-mediated dilation. Among the placebo and sildenafil groups, there were no significant differences in average patient age, time from type 2 diabetes diagnosis, duration of ED, or baseline IIEF-5 scores. Past medical histories, including smoking, alcohol consumption, hypertension, and hyperlipidemia, were also similar. At the conclusion of the 10-week trial, patients who received daily sildenafil had significantly improved erectile rigidity as captured by IIEF-5 (P < .001) and increased endothelial function via brachial artery flow-mediated dilation (P < .01). Endothelial function in men with type 2 diabetes was enhanced with daily sildenafil. Improved erectile rigidity and enhanced vascular circulation was noted after 10 weeks of daily sildenafil use.

Spinal Images

Background The association of pulmonary sequestration and nonimmune fetal hydrops reportedly carries a very poor prognosis for survival. We describe three newborns with good outcomes despite the diagnosis of pulmonary sequestration; two cases were associated with hydrops fetalis and one with isolated fetal ascites. Cases Two neonates with severe hydrops fetalis had pulmonary sequestration diagnosed postnatally. A third infant presented early in gestation with marked fetal ascites that regressed spontaneously before delivery; this infant also had pulmonary sequestration. Despite severe respiratory insufficiency requiring aggressive management, all three infants survived after surgical resection of the sequestered lung mass. Conclusion These cases demonstrate the difficulties associated with antenatal counseling regarding long-term prognosis for infants with nonimmune hydrops and pulmonary sequestration. With optimal care in a tertiary perinatal center, a less pessimistic outlook than previously described in the literature may be appropriate.

Daily Use of Sildenafil Improves Endothelial Function in Men With Type 2 Diabetes

OBJECTIVE To evaluate the feasibility, safety, and short-term efficacy of bilateral uterine artery occlusion, using a transvaginal Doppler-guided vascular clamp as a minimally invasive therapy for symptomatic uterine leiomyomas. METHODS We conducted two prospective, non-randomized, phase I pilot studies (Canadian Task Force Classification II-2) at a university-affiliated teaching hospital. Between June 2004 and May 2005, 30 premenopausal women with symptomatic uterine leiomyomas underwent bilateral uterine artery occlusion using a transvaginal Doppler-guided vascular clamp. Bilateral uterine artery occlusion was performed for 5.8 +/- 1.4 hours in the first 17 patients (Group 1) and from 6 to 9 hours (mean 7.05 +/- 1.0 hours) in the latter 13 patients (Group 2). Outcome measures included dominant fibroid volume (cm(3)), uterine volume (cm(3)), and improvement of menorrhagia at one, three, and six months. RESULTS Bilateral occlusion of the uterine arteries was achieved in all 30 patients. In Group 1, the Ruta Menorrhagia Severity Scores decreased from baseline by 16%, 22% and 39% at one, three, and six months respectively. The dominant fibroid (DF) and uterine volumes decreased by 24% and 16% respectively at six months. In Group 2, the Ruta scores changed from baseline by +3%, -24%, and -42% at one, three, and six months respectively. The DF and uterine volumes decreased by 29% and 16%, respectively at six months. CONCLUSION Following bilateral uterine artery occlusion using a transvaginal Doppler clamp, the dominant fibroid volume decreased by an average of 24%, uterine volume decreased by 12%, and menorrhagia symptoms were reduced by up to 42%. Uterine artery occlusion may provide the gynaecologist with an alternative to uterine artery embolization (UAE). The system is simple, easy to apply, and short-term efficacy may be equivalent to UAE.

Nonimmune hydrops fetalis, pulmonary sequestration, and favorable neonatal outcome

PURPOSE To compare the accuracy of biopsy with two-dimensional (2D) transrectal ultrasonography (US) with that of biopsy with conventional three-dimensional (3D) transrectal US and biopsy with guided 3D transrectal US in the guidance of repeat prostate biopsy procedures in a prostate biopsy simulator. MATERIALS AND METHODS The institutional review board approved this retrospective study. Five residents and five experts performed repeat biopsies with a biopsy simulator that contained the transrectal US prostate images of 10 patients who had undergone biopsy. Simulated repeat biopsies were performed with 2D transrectal US, conventional 3D transrectal US, and guided 3D transrectal US (an extension of 3D transrectal US that enables active display of biopsy targets). The modalities were compared on the basis of time per biopsy and how accurately simulated repeat biopsies could be guided to specific targets. The probability for successful biopsy of a repeat target was calculated for each modality. RESULTS Guided 3D transrectal US was significantly (P < .01) more accurate for simulated biopsy of repeat targets than was 2D or 3D transrectal US, with a biopsy accuracy of 0.86 mm +/- 0.47 (standard deviation), 3.68 mm +/- 2.60, and 3.60 mm +/- 2.57, respectively. Experts had a 70% probability of sampling a prior biopsy target volume of 0.5 cm(3) with 2D transrectal US; however, the probability approached 100% with guided 3D transrectal US. Biopsy accuracy was not significantly different between experts and residents for any modality; however, experts were significantly (P < .05) faster than residents with each modality. CONCLUSION Repeat biopsy of the prostate with 2D transrectal US has limited accuracy. Compared with 2D transrectal US, the biopsy accuracy of both experts and residents improved with guided 3D transrectal US but did not improve with conventional 3D transrectal US.

Transvaginal Doppler-Guided Uterine Artery Occlusion for the Treatment of Symptomatic Fibroids: Summary Results From Two Pilot Studies

Clinical intracranial ultrasound (US) is performed as a standard of care on neonates at risk of intraventricular hemorrhaging (IVH) and is also used after a diagnosis to monitor for potential ventricular dilation. However, it is difficult to estimate the volume of ventricles with 2D US due to their irregular shape. We developed a 3D US system to be used as an adjunct to a clinical system to investigate volumetric changes in the ventricles of neonates with IVH. Our system has been found have an error of within 1% of actual distance measurements in all three directions and volume measurements of manually segmented volumes from phantoms were not statistically significantly different from the actual values (p>0.3). Interobserver volume measurements of the lateral ventricles in a patient with grade III IVH found no significant differences between measurements. There is the potential to use this system in IVH patients to monitor the progression of ventriculomegaly over time.

Repeat Prostate Biopsy Accuracy: Simulator-based Comparison of Two- and Three-dimensional Transrectal US Modalities

Manuscript received January 01, 1899. Date of current version July 29, 2015. Z. Wang is with the GE Healthcare, London, ON, N5Y 0A3 Canada (e-mail: zhijie.wang@ge.com). X. Zhen is with the Department of Biophisics, Western University, London, ON, N6A 3L7 Canada (e-mail: zhenxt@gmail.com). K. Tay is with the London Health Sciences Centre, London, ON, N6A 5W9 Canada (e-mail: kengyeow.tay@lhsc.on.ca). S. Osman and W. Romano are with the Department of Medical Imaging, Western University, London, ON, N6A 3K7 Canada (e-mail: said.osman@sjhc. london.on.ca; wmromano@rogers.com). S. Li is with the GE Healthcare, London, ON, N5Y 0A3 Canada (e-mail: shuo.li@ge.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TMI.2015.2472836 REFERENCES

Development of a 3D ultrasound system to investigate post-hemorrhagic hydrocephalus in pre-term neonates

Abstract. The aim of this study is to compare longitudinal two-dimensional (2-D) and three-dimensional (3-D) ultrasound (US) estimates of ventricle size in preterm neonates with posthemorrhagic ventricular dilatation (PHVD) using quantitative measurements of the lateral ventricles. Cranial 2-D US and 3-D US images were acquired from neonatal patients with diagnosed PHVD within 10 min of each other one to two times per week and analyzed offline. Ventricle index, anterior horn width, third ventricle width, and thalamo-occipital distance were measured on the 2-D images and ventricle volume (VV) was measured from 3-D US images. Changes in the measurements between successive image sets were also recorded. No strong correlations were found between VV and 2-D US measurements (R2 between 0.69 and 0.36). Additionally, weak correlations were found between changes in 2-D US measurements and 3-D US VV (R2 between 0.13 and 0.02). A trend was found between increasing 2-D US measurements and 3-D US-based VV, but this was not the case when comparing changes between 3-D US VV and 2-D US measurements. If 3-D US-based VV provides a more accurate estimate of ventricle size than 2-D US measurements, moderate–weak correlations with 3-D US suggest that monitoring preterm patients with PHVD using 2-D US measurements alone might not accurately represent whether the ventricles are progressively dilating. A volumetric measure (3-D US or MRI) could be used instead to more accurately represent changes.