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Biomedical subjects

Shanker Raja

Publications and source records attributed to Shanker Raja.

7 recordsLinked to original sources
PubMed2006

FDG PET scan in a primitive neuroectodermal tumor.

Primitive peripheral neuroectodermal tumor (PNET) is a rare tumor that often arises in soft tissue. Magnetic resonance imaging is a good diagnostic tool that can establish the extent of disease. The utility of positron emission tomography (PET) using F-18-fluoro-2-deoxy-D-glucose (FDG) in the diagnostic work-up and staging of PNET has not been well established. We present a case of PNET of the right upper extremity that did not show FDG uptake despite its large size and aggressive nature.

Adult↗
PubMed2005

Automated 3-dimensional elastic registration of whole-body PET and CT from separate or combined scanners.

UNLABELLED: Registration and fusion of whole-body functional PET and anatomic CT is significant for accurate differentiation of viable tumors from benign masses, radiotherapy planning and monitoring treatment response, and cancer staging. Whole-body PET and CT acquired on separate scanners are misregistered because of differences in patient positions and orientations, couch shapes, and breathing protocols. Although a combined PET/CT scanner removes many of these misalignments, breathing-related nonrigid mismatches still persist. METHODS: We have developed a new, fully automated normalized mutual information-based 3-dimensional elastic image registration technique that can accurately align whole-body PET and CT images acquired on stand-alone scanners as well as a combined PET/CT scanner. The algorithm morphs the PET image to align spatially with the CT image by generating an elastic transformation field by interpolating quaternions and translations from multiple 6-parameter rigid-body registrations, each obtained for hierarchically subdivided image subvolumes. Fifteen whole-body (spanning thorax and abdomen) PET/CT image pairs acquired separately and 5 image pairs acquired on a combined scanner were registered. The cases were selected on the basis of the availability of both CT and PET images, without any other screening criteria, such as a specific clinical condition or prognosis. A rigorous quantitative validation was performed by evaluating algorithm performance in the context of variability among 3 clinical experts in the identification of up to 32 homologous anatomic landmarks. RESULTS: The average execution time was 75 and 45 min for images acquired using separate scanners and combined scanner, respectively. Visual inspection indicated improved matching of homologous structures in all cases. The mean registration accuracy (5.5 and 5.9 mm for images from separate scanners and combined scanner, respectively) was found comparable to the mean interexpert difference in landmark identification (5.6 +/- 2.4 and 6.6 +/- 3.4 mm, respectively). The variability in landmark identification did not show statistically significant changes on replacing any expert by the algorithm. CONCLUSION: We have presented a new and automated elastic registration algorithm to correct for nonrigid misalignments in whole-body PET/CT images as well as improve the "mechanical" registration of a combined PET/CT scanner. The algorithm performance was on par with the average opinion of 3 experts.

Algorithms↗
PubMed2004

Radionuclide evaluation of pleural-peritoneal shunt before pleurodesis.

OBJECTIVES: Talc pleurodesis can be offered to patients with hepatic hydrothorax. The authors wanted to determine their patient's eligibility for talc pleurodesis by excluding a pleural-peritoneal shunt. MATERIALS AND METHODS: The authors measured the size of the talc particles and matched them with the radionuclide particle size. After injecting radiopharmaceutical into the pleura, the authors imaged the abdomen for possible migration. RESULTS: In their patient, there was no migration of radionuclide from the thorax into the abdomen. CONCLUSION: Injecting radionuclide into the thoracic cavity and then imaging for an extended period of time is one way to determine whether the patient has a pleural-peritoneal shunt.

Aged↗
PubMed2003

Mutual information-based multimodality registration of cardiac ultrasound and SPECT images: a preliminary investigation.

BACKGROUND: Ultrasound (US) and single photon emission computed tomography (SPECT) are the two most commonly prescribed procedures for diagnosing coronary artery disease (CAD). We have demonstrated the feasibility of multimodality registration of two-dimensional (2D) and three-dimensional (3D) cardiac US images with cardiac SPECT images with an aim to simultaneously present the complementary anatomical and perfusion information from the two modalities. We have also tested the clinicians' assessment of the clinical adequacy of the registered images. METHODS AND RESULTS: We have demonstrated temporal and spatial registration for nine sets of cardiac US and SPECT cine loops covering the entire cardiac cycle. Temporal alignment was performed by interpolation of existing SPECT images at cardiac phases corresponding to available US images. Spatial registration was performed in 3D image space using a mutual information-based approach. Experts from echocardiography and nuclear medicine determined the clinical utility of the registration by rating each registration on a scale of 1 to 5, a rating of 3 or above indicating clinical utility. 2DUS-SPECT registration (five cases) received an average rating of 4.2, whereas 3DUS-SPECT registration (four cases) received an average rating of 2.85. By one-sample t test, the overall evaluations (mean 3.58) were greater than the pre-specified clinical cut-off of 3 with p < 0.05, indicating likelihood of clinical utility. CONCLUSION: Our method demonstrates the feasibility of registering cardiac US and SPECT images in their present as well as possible future forms. Such registration has the potential to provide a more accurate and powerful tool for diagnosing CAD.

Clinical Protocols↗
PubMed2003

Ictal urinary urge: further evidence for lateralization to the nondominant hemisphere.

PURPOSE: To determine the lateralizing value of ictal urinary urgency. METHODS: A retrospective database search was performed for patients with ictal urinary urgency admitted to the Epilepsy Monitoring Unit at the Cleveland Clinic between 1994 and 2001. RESULTS: Six patients were identified; intracarotid amytal test demonstrated left hemispheric speech dominance in five cases. The sixth patient continued to speak during right temporal seizures. EEG and imaging data supported right temporal or frontotemporal epilepsy in all six cases. Two patients were seizure free after focal right hemispheric resection. CONCLUSIONS: Ictal urinary urge appears to be a lateralizing sign for nondominant temporal lobe epilepsy.

Adult↗
PubMed2003

Neocortical temporal FDG-PET hypometabolism correlates with temporal lobe atrophy in hippocampal sclerosis associated with microscopic cortical dysplasia.

PURPOSE: Medically intractable temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS), with or without cortical dysplasia (CD), is associated with atrophy of the hippocampal formation and regional fluorodeoxyglucose positron-emission tomography (FDG-PET) hypometabolism. The relation between areas of functional and structural abnormalities is not well understood. We investigate the relation between FDG-PET metabolism and temporal lobe (TL) and hippocampal atrophy in patients with histologically proven isolated HS and HS associated with CD. METHODS: Twenty-three patients underwent en bloc resection of the mesial and anterolateral neocortical structures. Ten patients were diagnosed with isolated HS; 13 patients had associated microscopic CD. Temporal lobe volumes (TLVs) and hippocampal volumes were measured. Magnetic resonance imaging (MRI) and PET were co-registered, and regions of interest (ROIs) determined as gray matter of the mesial, lateral, and anterior temporal lobe. RESULTS: All patients (HS with or without CD) had significant ipsilateral PET hypometabolism in all three regions studied (p < 0.0001). In patients with isolated HS, the most prominent hypometabolism was in the anterior and mesial temporal lobe, whereas in dual pathology, it was in the lateral temporal lobe. TLVs and hippocampal volumes were significantly smaller on the epileptogenic side (p < 0.05). The PET asymmetries ipsilateral/contralateral to the epileptogenic zone and TLV asymmetries correlated significantly for the anterior and lateral temporal lobes (p < 0.05) in the HS+CD group, but not in the isolated HS group. Mesial temporal hypometabolism was not significantly different between the two groups. CONCLUSIONS: Temporal neocortical microscopic CD with concurrent HS is associated with more prominent lateral temporal metabolic dysfunction compared with isolated HS in TL atrophy. Further studies are needed to confirm these findings and correlate the PET hypometabolic patterns with outcome data in patients operated on for HS with or without CD.

Adolescent↗