Salil Soman

Textural Kinetics: A Novel Dynamic Contrast-Enhanced (DCE)-MRI Feature for Breast Lesion Classification

Dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) of the breast has emerged as an adjunct imaging tool to conventional X-ray mammography due to its high detection sensitivity. Despite the increasing use of breast DCE-MRI, specificity in distinguishing malignant from benign breast lesions is low, and interobserver variability in lesion classification is high. The novel contribution of this paper is in the definition of a new DCE-MRI descriptor that we call textural kinetics, which attempts to capture spatiotemporal changes in breast lesion texture in order to distinguish malignant from benign lesions. We qualitatively and quantitatively demonstrated on 41 breast DCE-MRI studies that textural kinetic features outperform signal intensity kinetics and lesion morphology features in distinguishing benign from malignant lesions. A probabilistic boosting tree (PBT) classifier in conjunction with textural kinetic descriptors yielded an accuracy of 90%, sensitivity of 95%, specificity of 82%, and an area under the curve (AUC) of 0.92. Graph embedding, used for qualitative visualization of a low-dimensional representation of the data, showed the best separation between benign and malignant lesions when using textural kinetic features. The PBT classifier results and trends were also corroborated via a support vector machine classifier which showed that textural kinetic features outperformed the morphological, static texture, and signal intensity kinetics descriptors. When textural kinetic attributes were combined with morphologic descriptors, the resulting PBT classifier yielded 89% accuracy, 99% sensitivity, 76% specificity, and an AUC of 0.91.

Medical Students’ Preferences in Radiology Education: A Comparison Between the Socratic and Didactic Methods Utilizing PowerPoint Features in Radiology Education

RATIONALE AND OBJECTIVES The Socratic method has long been a traditional teaching method in medicine and law. It is currently accepted as the standard of teaching in clinical wards, while the didactic teaching method is widely used during the first 2 years of medical school. There are arguments in support of both styles of teaching. MATERIALS AND METHODS After attending a radiology conference demonstrating different teaching methods, third-year and fourth-year medical students were invited to participate in an online anonymous survey. RESULTS Of the 74 students who responded, 72% preferred to learn radiology in an active context. They preferred being given adequate time to find abnormalities on images, with feedback afterward from instructors, and they thought the best approach was a volunteer-based system of answering questions using the Socratic method in the small group. They desired to be asked questions in a way that was constructive and not belittling, to realize their knowledge deficits and to have daily pressure to come prepared. The respondents thought that pimping was an effective teaching tool, supporting previous studies. CONCLUSIONS When teaching radiology, instructors should use the Socratic method to a greater extent. Combining Socratic teaching with gentle questioning by an instructor through the use of PowerPoint is a preferred method among medical students. This information is useful to improve medical education in the future, especially in radiology education.

Durable Response to Crizotinib in a MET-Amplified, KRAS-Mutated Carcinoma of Unknown Primary

Background: Carcinoma of unknown primary (CUP) accounts for 3-5% of all adult solid tumors. An extensive search for the anatomic site of origin is often undertaken in an attempt to tailor systemic treatment, but the latter often has limited efficacy - especially in the setting of an initial treatment failure. Molecularly targeted therapy is an emerging approach that may offer greater efficacy and less toxicity but is most likely to be effective when pairing a tumor harboring a sensitizing genomic alteration with an agent directed at the altered gene product. We report a patient with a CUP harboring a MET amplification with a complete metabolic response to crizotinib despite also harboring a KRAS mutation. Methods: Genomic profiling was performed using a clinical next-generation-sequencing-based assay, FoundationOne®, in a CAP-accredited laboratory certified by Clinical Laboratory Improvement Amendments (Foundation Medicine, Cambridge, Mass., USA). Results: The CUP harbored both MET amplification (16 copies) and a KRAS G12V mutation. The patient was treated with crizotinib, a MET inhibitor, and has experienced a complete normalization of tumor metabolic activity for more than 19 months. Conclusions: Genomic profiling of CUP may reveal clinically meaningful genomic alterations that can guide targeted therapy decision-making. The use of this approach should be studied prospectively as a strategy for the effective treatment of CUP patients and for avoiding resource-intensive workups to identify the tumor site of origin.

Medical student educationMedical Students’ Preferences in Radiology Education: A Comparison Between the Socratic and Didactic Methods Utilizing PowerPoint Features in Radiology Education

RATIONALE AND OBJECTIVES The Socratic method has long been a traditional teaching method in medicine and law. It is currently accepted as the standard of teaching in clinical wards, while the didactic teaching method is widely used during the first 2 years of medical school. There are arguments in support of both styles of teaching. MATERIALS AND METHODS After attending a radiology conference demonstrating different teaching methods, third-year and fourth-year medical students were invited to participate in an online anonymous survey. RESULTS Of the 74 students who responded, 72% preferred to learn radiology in an active context. They preferred being given adequate time to find abnormalities on images, with feedback afterward from instructors, and they thought the best approach was a volunteer-based system of answering questions using the Socratic method in the small group. They desired to be asked questions in a way that was constructive and not belittling, to realize their knowledge deficits and to have daily pressure to come prepared. The respondents thought that pimping was an effective teaching tool, supporting previous studies. CONCLUSIONS When teaching radiology, instructors should use the Socratic method to a greater extent. Combining Socratic teaching with gentle questioning by an instructor through the use of PowerPoint is a preferred method among medical students. This information is useful to improve medical education in the future, especially in radiology education.

The impact of depression on veterans with PTSD and traumatic brain injury: a diffusion tensor imaging study

A significant proportion of military personnel deployed in support of Operation Enduring Freedom and Operation Iraqi Freedom were exposed to war-zone events associated with traumatic brain injury (TBI), depression (DEP) and posttraumatic stress disorder (PTSD). The co-occurrence of TBI, PTSD and DEP in returning Veterans has recently increased research and clinical interest. This study tested the hypothesis that white matter abnormalities are further impacted by depression. Of particular relevance is the uncinate fasciculus (UF), which is a key fronto-temporal tract involved in mood regulation, and the cingulum; a tract that connects to the hippocampus involved in memory integration. Diffusion tensor imaging (DTI) was performed on 25 patients with a combination of PTSD, TBI and DEP and 20 patients with PTSD and TBI (no DEP). Microstructural changes of white matter were found in the cingulum and UF. Fractional anisotropy (FA) was lower in Veterans with DEP compared to those without DEP.

Improved T2* Imaging without Increase in Scan Time: SWI Processing of 2D Gradient Echo

BACKGROUND AND PURPOSE: 2D gradient-echo imaging is sensitive to T2* lesions (hemorrhages, mineralization, and vascular lesions), and susceptibility-weighted imaging is even more sensitive, but at the cost of additional scan time (SWI: 5–10 minutes; 2D gradient-echo: 2 minutes). The long acquisition time of SWI may pose challenges in motion-prone patients. We hypothesized that 2D SWI/phase unwrapped images processed from 2D gradient-echo imaging could improve T2* lesion detection. MATERIALS AND METHODS: 2D gradient-echo brain images of 50 consecutive pediatric patients (mean age, 8 years) acquired at 3T were retrospectively processed to generate 2D SWI/phase unwrapped images. The 2D gradient-echo and 2D SWI/phase unwrapped images were compared for various imaging parameters and were scored in a blinded fashion. RESULTS: Of 50 patients, 2D gradient-echo imaging detected T2* lesions in 29 patients and had normal findings in 21 patients. 2D SWI was more sensitive than standard 2D gradient-echo imaging in detecting T2* lesions (P < .0001). 2D SWI/phase unwrapped imaging also improved delineation of normal venous structures and nonpathologic calcifications and helped distinguish calcifications from hemorrhage. A few pitfalls of 2D SWI/phase unwrapped imaging were noted, including worsened motion and dental artifacts and challenges in detecting T2* lesions adjacent to calvaria or robust deoxygenated veins. CONCLUSIONS: 2D SWI and associated phase unwrapped images processed from standard 2D gradient-echo images were more sensitive in detecting T2* lesions and delineating normal venous structures and nonpathologic mineralization, and they also helped distinguish calcification at no additional scan time. SWI processing of 2D gradient-echo images may be a useful adjunct in cases in which longer scan times of 3D SWI are difficult to implement.

Improving the robustness of pseudo-continuous arterial spin labeling to off-resonance and pulsatile flow velocity.

To improve pseudo‐continuous arterial spin labeling (PCASL) robustness to off‐resonance and pulsatile blood flow velocity.

Volume of subclinical embolic infarct correlates to long-term cognitive changes after carotid revascularization

Objective: Carotid intervention is safe and effective in stroke prevention in appropriately selected patients. Despite minimal neurologic complications, procedure‐related subclinical microemboli are common and their cognitive effects are largely unknown. In this prospective longitudinal study, we sought to determine long‐term cognitive effects of embolic infarcts. Methods: The study recruited 119 patients including 46% symptomatic patients who underwent carotid revascularization. Neuropsychological testing was administered preoperatively and at 1 month, 6 months, and 12 months postoperatively. Rey Auditory Verbal Learning Test (RAVLT) was the primary cognitive measure with parallel forms to avoid practice effect. All patients also received 3T brain magnetic resonance imaging with a diffusion‐weighted imaging (DWI) sequence preoperatively and within 48 hours postoperatively to identify procedure‐related new embolic lesions. Each DWI lesion was manually traced and input into a neuroimaging program to define volume. Embolic infarct volumes were correlated with cognitive measures. Regression models were used to identify relationships between infarct volumes and cognitive measures. Results: A total of 587 DWI lesions were identified on 3T magnetic resonance imaging in 81.7% of carotid artery stenting (CAS) and 36.4% of carotid endarterectomy patients with a total volume of 29,327 mm3. Among them, 54 DWI lesions were found in carotid endarterectomy patients and 533 in the CAS patients. Four patients had transient postoperative neurologic symptoms and one had a stroke. CAS was an independent predictor of embolic infarction (odds ratio, 6.6 [2.1–20.4]; P < .01) and infarct volume (P = .004). Diabetes and contralateral carotid severe stenosis or occlusion had a trend of positive association with infarct volume, whereas systolic blood pressure ≥140 mm Hg had a negative association (P = .1, .09, and .1, respectively). There was a trend of improved RAVLT scores overall after carotid revascularization. Significantly higher infarct volumes were observed among those with RAVLT decline. Within the CAS cohort, infarct volume was negatively correlated with short‐ and long‐term RAVLT changes (P < .05). Conclusions: Cognitive assessment of procedure‐related subclinical microemboli is challenging. Volumes of embolic infarct correlate with long‐term cognitive changes, suggesting that microembolization should be considered a surrogate measure for carotid disease management.

Cord Compression due to Extramedullary Hematopoiesis in an Adolescent with Known Beta Thalassemia Major.

We describe a 16 year-old male with β thalassemia major and gait disturbances that had not been given blood transfusions due to a severe childhood transfusion reaction. Thoracic spine MRI demonstrated hematopoietic marrow throughout the spine and epidural masses causing cord compression consistent with extramedullary hematopoiesis (EMH). After treatment with steroids, radiotherapy and monitored blood transfusions, the patient demonstrated significant improvement of his paraspinal lesions and near complete resolution of his neurological symptoms. While EMH causing cord compression in adolescents is rare in the current era of bone marrow transplantation or chronic transfusions, it should be considered when thalassemia major patients present with neurological deficits. The well defined imaging features of EMH can play a central role in its diagnosis and management, especially because surgical and / or radiotherapeutic intervention are often considered in cases of failed medical treatment.

Rigid Registration of Echoplanar and Conventional Magnetic Resonance Images by Minimizing the Kullback-Leibler Distance

Functional Magnetic Resonance Imaging (fMRI) studies are derived from a time series of Echo-Planar images (EPIs). Compared to conventional Magnetic Resonance Images (MRIs), EPIs are of relatively poor quality for discerning anatomic features and are often registered with corresponding MRIs to map brain activity to neuroanatomy. In this paper we demonstrate the utility of a technique to register an EPI-MRI pair by minimizing the discrepancy between its joint intensity probability mass function (PMF) and a previously learned one for a properly registered EPI-MRI pair, using the Kullback-Leibler Distance (KLD). In probing experiments Joint Entropy (JE) and Mutual Information showed significant bias relative to KLD along the axial direction and JE along a rotation axis. A comparison of searches using random starting poses showed KLD to have lower final pose errors than JE. Results of variation on parameters of the KLD based EPI-MRI registration technique are also presented.