Krishna Juluru

Intra-abdominal pressure mechanism for stabilizing the lumbar spine

Currently, intra-abdominal pressure (IAP) is thought to provide stability to the lumbar spine but the exact principles have yet to be specified. A simplified physical model was constructed and theoretical calculations performed to illustrate a possible intra-abdominal pressure mechanism for stabilizing the spine. The model consisted of an inverted pendulum with linear springs representing abdominal and erector spinae muscle groups. The IAP force was simulated with a pneumatic piston activated with compressed air. The critical load of the model was calculated theoretically based on the minimum potential energy principle and obtained experimentally by increasing weight on the model until the point of buckling. Two distinct mechanisms were simulated separately and in combination. One was antagonistic flexor extensor muscle coactivation and the second was abdominal muscle activation along with generation of IAP. Both mechanisms were effective in stabilizing the model of a lumbar spine. The critical load and therefore the stability of the spine model increased with either increased antagonistic muscle coactivation forces or increased IAP along with increased abdominal spring force. Both mechanisms were also effective in providing mechanical stability to the spine model when activated simultaneously. Theoretical calculation of the critical load agreed very well with experimental results (95.5% average error). The IAP mechanism for stabilizing the lumbar spine appears preferable in tasks that demand trunk extensor moment such as lifting or jumping. This mechanism can increase spine stability without the additional coactivation of erector spinae muscles.

Lumbar spine stability can be augmented with an abdominal belt and/or increased intra-abdominal pressure.

Abstract The increased intra-abdominal pressure (IAP) commonly observed when the spine is loaded during physical activities is hypothsized to increase lumbar spine stability.The mechanical stability of the lumbar spine is an important consideration in low back injury prevention and rehabilitation strategies. This study examined the effects of raised IAP and an abdominal belt on lumbar spine stability. Two hypotheses were tested: (1) An increase in IAP leads to increased lumbar spine stability, (2) Wearing an abdominal belt increases spine stability. Ten volunteers were placed in a semi-seated position in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplished by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexion, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gastric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of the following two factors: belt or no belt and three levels of IAP (0, 40, and 80% of maximum). The belt and raised IAP increased trunk stiffness in all directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IAP levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness depending on the IAP level and the direction of exertion. In all three directions, the EMG activity of all 12 trunk muscles increased significantly due to the elevated IAP. The belt had no effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lumbar erector spinae in flexion, whose activities decreased. The results indicate that both wearing an abdominal belt and raised IAP can each independently, or in combination, increase lumbar spine stability. However, the benefits of the belt must be interpreted with caution in the context of the decreased activation of a few trunk extensor muscles.

Transcatheter arterial chemoembolization of liver tumors: effects of embolization protocol on injectable volume of chemotherapy and subsequent arterial patency.

AbstractThe purpose of this study was to determine whether transcatheter arterial chemoembolization (TACE) protocol affects the total volume of chemotherapy injected into the liver as well as subsequent arterial patency. A total of 160 patients with primary or secondary liver cancer were treated with 3 different chemoembolization protocols at a single institution. Data were analyzed retrospectively. Group 1 (n = 36) consisted of slurry of chemotherapy, oil and polyvinyl alcohol particles (PVA), group 2 (n = 91), chemotherapy and oil followed by PVA, and group 3 (n = 33), chemotherapy and oil followed by Gelfoam pledgets. The total volume of chemotherapy injected into the liver was recorded. Arterial patency was determined during subsequent chemoembolizations. The mean percentage of total intended chemotherapy dose administered was 54.6% for group 1, 75.3% for group 2, and 80.6% for group 3. Arterial patency at follow-up angiography was 56% for group 1, 74% for group 2, and 81% for group 3. The slurry protocol (group 1) significantly reduced arterial patency and injectable volume of chemotherapy during TACE.

Computed tomography imaging of Gastrointestinal stromal tumors with pathology correlation

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that typically arise in association with the muscularis propria of gastrointestinal (GI) tract wall. They occur most frequently in the stomach (60%) but also can occur in the small bowel (30%) or elsewhere, including the colon and rectum (5%) and esophagus (<5%). In addition, a GIST may occur as a primary tumor of the omentum, mesentery, or retroperitoneum. They account for 1%-3% of gastric neoplasms, 20% of small bowel tumors, and 0.2%-1% of colorectal tumors. These tumors arise pathologically from the wall of the GI tract and can be characterized as benign, borderline, or with low or high malignant potential based on the pathologic appearance. Computed tomography (CT) plays an important role for the diagnosis and staging of these neoplasms because it can identify the tumor and assess for local spread or distant metastases. This article reviews the role of CT in the detection and characterization of GISTs. The optimal CT technique for visualization of small bowel tumors is reviewed, and a variety of GISTs are illustrated. Pathologic correlation is also included.

Quality Initiatives MR Imaging in Patients at Risk for Developing Nephrogenic Systemic Fibrosis: Protocols, Practices, and Imaging Techniques to Maximize Patient Safety

Nephrogenic systemic fibrosis (NSF) is a rare but potentially debilitating or even fatal fibrosing condition that most often affects the skin but is now also recognized to involve multiple organs. The first report on NSF was published in 1997, and there is mounting evidence that this condition is associated with renal failure and the administration of large amounts of gadolinium. Although gadolinium-enhanced magnetic resonance (MR) imaging was once considered one of the safer imaging procedures, concerns over NSF have led the radiology community to rethink its imaging practices. Several noncontrast angiographic techniques based on fast spin-echo, gradient-echo, phase-contrast, and inversion-recovery principles are currently available. These techniques allow MR angiography to be performed safely, even in patients at risk for developing NSF. When use of gadolinium-based contrast material is necessary for diagnosis, it is possible to reduce total gadolinium administration through the use of agents with higher relaxivity, time-resolved imaging, high-field-strength magnets, and body compression devices. Management of NSF also requires an understanding of the risk factors of this disease and developing an institutional policy for identifying and testing at-risk patients.

Corticomedullary Strain Ratio A Quantitative Marker for Assessment of Renal Allograft Cortical Fibrosis

To quantitatively assess the correlation between the corticomedullary strain ratio and cortical fibrosis in renal transplants.

Effects of Increased Image Noise on Image Quality and Quantitative Interpretation in Brain CT Perfusion

BACKGROUND AND PURPOSE: There is a desire within many institutions to reduce the radiation dose in CTP examinations. The purpose of this study was to simulate dose reduction through the addition of noise in brain CT perfusion examinations and to determine the subsequent effects on quality and quantitative interpretation. MATERIALS AND METHODS: A total of 22 consecutive reference CTP scans were identified from an institutional review board–approved prospective clinical trial, all performed at 80 keV and 190 mAs. Lower-dose scans at 188, 177, 167, 127, and 44 mAs were generated through the addition of spatially correlated noise to the reference scans. A standard software package was used to generate CBF, CBV, and MTT maps. Six blinded radiologists determined quality scores of simulated scans on a Likert scale. Quantitative differences were calculated. RESULTS: For qualitative analysis, the correlation coefficients for CBF (−0.34; P < .0001), CBV (−0.35; P < .0001), and MTT (−0.44; P < .0001) were statistically significant. Interobserver agreements in quality for the simulated 188-, 177-, 167-, 127-, and 44-mAs scans for CBF were 0.95, 0.98, 0.98, 0.95, and 0.52, respectively. Interobserver agreements in quality for the simulated CBV were 1, 1, 1, 1, and 0.83, respectively. For MTT, the interobserver agreements were 0.83, 0.86, 0.88, 0.74, and 0.05, respectively. For quantitative analysis, only the lowest simulated dose of 44 mAs showed statistically significant differences from the reference scan values for CBF (−1.8; P = .04), CBV (0.07; P < .0001), and MTT (0.46; P < .0001). CONCLUSIONS: From a reference CTP study performed at 80 keV and 190 mAs, this simulation study demonstrates the potential of a 33% reduction in tube current and dose while maintaining image quality and quantitative interpretations. This work can be used to inform future studies by using true, nonsimulated scans.

Strategic improvements for gross anatomy web-based teaching.

Current generations of graduate students have been immersed in technology from their early school years and have high expectations regarding digital resources. To better meet the expectations of Gross Anatomy students at our institution, electronic radiology teaching files for first-year coursework were organized into a web site. The web site was custom designed to provide material that directly correlated to the Gross Anatomy dissection and lectures. Quick links provided sets of images grouped by anatomic location. Additionally, Lab and Study Companions provided specific material for the students to review prior to and after lectures and gross dissections. Student opinions of this education resource were compared to student opinions of the prior years digital teaching files. The new content was ranked as more user friendly (3.1 points versus 2.3 points) and more useful for learning anatomy (3.3 points versus 2.6 points). Many students reported that using the web portal was critical in helping them to better understand relationships of anatomical structures. These findings suggest that a well-organized web portal can provide a user-friendly, valuable educational resource for medical students who are studying Gross Anatomy.

Facial Recognition Software Success Rates for the Identification of 3D Surface Reconstructed Facial Images: Implications for Patient Privacy and Security

Image de-identification has focused on the removal of textual protected health information (PHI). Surface reconstructions of the face have the potential to reveal a subject’s identity even when textual PHI is absent. This study assessed the ability of a computer application to match research subjects’ 3D facial reconstructions with conventional photographs of their face. In a prospective study, 29 subjects underwent CT scans of the head and had frontal digital photographs of their face taken. Facial reconstructions of each CT dataset were generated on a 3D workstation. In phase 1, photographs of the 29 subjects undergoing CT scans were added to a digital directory and tested for recognition using facial recognition software. In phases 2–4, additional photographs were added in groups of 50 to increase the pool of possible matches and the test for recognition was repeated. As an internal control, photographs of all subjects were tested for recognition against an identical photograph. Of 3D reconstructions, 27.5% were matched correctly to corresponding photographs (95% upper CL, 40.1%). All study subject photographs were matched correctly to identical photographs (95% lower CL, 88.6%). Of 3D reconstructions, 96.6% were recognized simply as a face by the software (95% lower CL, 83.5%). Facial recognition software has the potential to recognize features on 3D CT surface reconstructions and match these with photographs, with implications for PHI.

Visualization and segmentation of liver tumors using dynamic contrast MRI

Hepatocellular carcinoma (liver tumor) is one of the most common malignancies causing an estimated one million deaths annually, and the fastest growing form of cancer in the United States. Dynamic Contrast Enhanced MRI (DCE-MRI) is a useful way to characterize tumor response to contrast agent uptake, but the method still lacks maturity in terms of quantifying tumor burden and viability. We propose a semi-supervised technique for visualizing and measuring liver tumor burden and viability from DCE-MRI examinations. In order to solve the challenging segmentation problem, we exploit prior information about the spatio-temporal characteristics of DCE-MRI data, and perform k-means clustering in a hybrid intensity-spatial feature space.