Srinivasa Prasad - Academia.edu (original) (raw)

Papers by Srinivasa Prasad

Korean journal of radiology : official journal of the Korean Radiological Society

We evaluated the association between patients' weight and abdominal cross-sectional dimension... more We evaluated the association between patients' weight and abdominal cross-sectional dimensions and CT image quality. We prospectively evaluated 39 cancer patients aged more than 65 years with multislice CT scan of abdomen. All patients underwent equilibrium phase contrast-enhanced abdominal CT with 4 slices (from top of the right kidney) obtained at standard tube current (240-280 mA). All other scanning parameters were held constant. Patients' weight was measured just prior to the study. Cross-sectional abdominal dimensions such as circumference, area, average anterior abdominal wall fat thickness and, anteroposterior and transverse diameters were measured in all patients. Two subspecialty radiologists reviewed randomized images for overall image quality of abdominal structures using 5- point scale. Non-parametric correlation analysis was performed to determine the association of image quality with patients' weight and cross-sectional abdominal dimensions. A statisticall...

RadioGraphics, 2004

See www.rsna .org/education /rg_cme.html. LEARNING OBJECTIVES After reading this article and taki... more See www.rsna .org/education /rg_cme.html. LEARNING OBJECTIVES After reading this article and taking the test, the reader will be able to: Ⅲ Describe CT angiographic and MR angiographic techniques in evaluating the hepatic vasculature. Ⅲ Identify normal hepatic vasculature and anatomic variants that may influence patient selection or surgical technique for liver surgery.

American Journal of Roentgenology, 2002

OBJECTIVE. We hypothesized that radiation doses for abdominal CT could be reduced by adjusting th... more OBJECTIVE. We hypothesized that radiation doses for abdominal CT could be reduced by adjusting the dose for a patient's weight and cross-sectional abdominal dimensions, with the resultant scans still being of diagnostic quality. SUBJECTS AND METHODS. Using a multidetector CT scanner, we prospectively studied 39 patients who were 65 years and older who had a known history of cancer. After performing a diagnostic contrast-enhanced CT examination, we obtained four slices each (centered at the top of the right kidney) at a standard radiation dose (240-300 mA) and at a 50% reduced dose (120-150 mA) at a constant kilovoltage of 140. Scans were obtained during a single breath-hold, with a 2.5-mm detector configuration and a slice pitch of 6:1. Reconstructed slice thickness was 5 mm. In a blinded review, two radiologists rated the randomized CT scans for overall image quality and anatomic details of liver, spleen, adrenal glands, kidneys, pancreas, and abdominal wall, using a 5point scale (1 = unacceptable, 2 = substandard, 3 = acceptable, 4 = above average, and 5 = superior). Patients' weight and abdominal circumference, area, and anteroposterior and transverse diameters were correlated with image quality of scans obtained at standard-dose and 50% reduced-dose CT. Statistical analysis of the data was performed using Wilcoxon's signed rank test. RESULTS. Overall, the image quality score was significantly higher (p < 0.005) on the scans obtained with standard-dose CT. No statistically significant difference in image quality was noted in the 50% reduced-and standard-dose CT scans in patients who weighed less than 180 lb, or 81 kg, (p > 0.05) and who had a transverse abdominal diameter of less than 34.5 cm (p > 0.05), an anteroposterior diameter of less than 28 cm (p > 0.05), a cross-sectional circumference of less than 105 cm (p > 0.05), and a cross-sectional area of less than 800 cm 2 (p > 0.05). Good interobserver agreement (p > 0.5) was found between the two reviewing radiologists. CONCLUSION. Abdominal CT scan quality appears to be acceptable even with a 50% reduction in radiation dose except in patients with large anthropometric measurements. A reduction in CT radiation dose is possible if the tube current is optimized for the patient's weight and abdominal dimensions.

American Journal of Roentgenology, 2002

OBJECTIVE. The purpose of our study was to evaluate the performance of CT angiography using multi... more OBJECTIVE. The purpose of our study was to evaluate the performance of CT angiography using multidetector CT (MDCT) for preoperative vascular evaluation in candidates who were scheduled for liver neoplasm resection. SUBJECTS AND METHODS. Forty-two consecutive subjects with malignant liver tumors scheduled for resection were studied with multiphase MDCT. The first 22 subjects underwent both multiphase MDCT angiography and catheter angiography before surgery. The subsequent 20 subjects underwent only preoperative CT angiography. Postprocessing was performed, and the images were analyzed for the depiction of arterial, portal vein, and hepatic vein anatomy and for the identification of important vascular variants. The postprocessing findings were compared and correlated with the findings from catheter angiography (22/42) or intraoperative sonography (42/42) and surgery (42/42). RESULTS. Arterial anomalies were detected on the images of 17 of 42 patients, including a replaced right hepatic artery in five, replaced left hepatic artery in six, accessory right and left hepatic arteries in two, common trunk for the celiac and superior mesenteric arteries in one, and early bifurcation of the celiac artery in one. In 22 patients in whom catheter angiography confirmation was available, the number of arteries and almost all the significant anomalies were correctly identified on CT angiography (accuracy, 97%; sensitivity, 94%; specificity, 100%). In the subset of 20 patients who underwent MDCT angiography without catheter angiography confirmation, all clinically relevant information was provided by CT angiography. The portal and hepatic vein anatomy and the relationships of the liver tumors to the neighboring venous structures were shown on CT. CONCLUSION. Multidetector CT provides valuable preoperative information about hepatic vascular architecture and can be used as a noninvasive alternative to catheter angiography before oncologic liver surgery.

Circulation, 2002

Three closely linked lines of research have now merged. In the 1980s, concepts crystallized on th... more Three closely linked lines of research have now merged. In the 1980s, concepts crystallized on the role of lipids (eg, oxidized LDL, elevated cholesterol) in the genesis of atherosclerotic plaque. In the 1990s, use of antiplatelet agents proved that platelet aggregation caused ...

Radiology, 2003

PURPOSE: To evaluate a histogram analysis method for differentiating adrenal adenoma from metasta... more PURPOSE: To evaluate a histogram analysis method for differentiating adrenal adenoma from metastasis at computed tomography (CT). MATERIALS AND METHODS: In a retrospective review of 2 years of clinical CT records, 223 adrenal adenomas in 193 patients (115 with contrast material-enhanced CT, 43 with unenhanced and enhanced CT, and 35 with unenhanced CT) and 31 metastases (25 patients with enhanced CT) were found. In 158 patients with adenomas at enhanced CT, diagnosis was based on stable mass size for more than 1 year (n ϭ 135) and characteristic signal intensity decrease at chemical shift magnetic resonance imaging (n ϭ 23). In 35 patients with adenomas at unenhanced CT, mean attenuation was 10 HU or less. Diagnosis of all metastases was based on rapid growth of a mass or new mass in less than 6 months in patients with cancer. Adrenal metastases with extensive necrosis were excluded. Histogram analysis was performed in a circular region of interest (ROI) for mean attenuation, number of pixels, and range of pixel attenuation for all pixels and for the subset of pixels with less than 0 HU ("negative" pixels). Correlation between mean attenuation and percentage negative pixels was calculated. RESULTS: Negative pixels were present in all 74 unenhanced adenomas with mean attenuation of 10 HU or less and in 14 of 16 unenhanced adenomas with mean attenuation above 10 HU. Of 184 enhanced adenomas, only 20 had mean attenuation of 10 HU or less, but 97 contained negative pixels (77 of these 97 masses had mean attenuation above 10 HU). Increase in percentage negative pixels was highly correlated with decrease in mean attenuation of both unenhanced and enhanced adenomas. None of the adrenal metastases had mean attenuation of 10 HU or less or contained negative pixels. CONCLUSION: The histogram method is far more sensitive than the 10-HU threshold method for diagnosis of adrenal adenomas at enhanced CT, with specificity maintained at 100%.

RadioGraphics, 2012

There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate cha... more There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate characteristic epidemiologic and histopathologic features and natural histories. These masses may be classified into five distinct subgroups using a pattern-based approach that takes anatomic distribution and certain imaging characteristics into account, allowing greater accuracy in their detection and characterization and helping to optimize patient management. The five groups are cystic (serous and mucinous epithelial neoplasms, pelvic lymphangioma, tailgut cyst, ancient schwannoma), vascular or hypervascular (solitary fibrous tumor, paraganglioma, pelvic arteriovenous malformation, Klippel-Trénaunay-Weber syndrome, extraintestinal GIST [gastrointestinal stromal tumor]), fat-containing (lipoma, liposarcoma, myelolipoma, presacral teratoma), calcified (calcified lymphocele, calcified rejected transplant kidney, rare sarcomas), and myxoid (schwannoma, plexiform neurofibroma, myxoma).Cross-sectional imaging modalities help differentiate the more common gynecologic neoplasms from more unusual masses. In particular, the tissue-specific multiplanar capability of high-resolution magnetic resonance imaging permits better tumor localization and internal characterization, thereby serving as a road map for surgery. ©

RadioGraphics, 2012

Urinary bladder cancer is a heterogeneous disease with a variety of pathologic features, cytogene... more Urinary bladder cancer is a heterogeneous disease with a variety of pathologic features, cytogenetic characteristics, and natural histories. It is the fourth most common cancer in males and the tenth most common cancer in females. Urinary bladder cancer has a high recurrence rate, necessitating long-term surveillance after initial therapy. Early detection is important, since up to 47% of bladder cancer-related deaths may have been avoided. Conventional computed tomography (CT) and magnetic resonance (MR) imaging are only moderately accurate in the diagnosis and local staging of bladder cancer, with cystoscopy and pathologic staging remaining the standards of reference. However, the role of newer MR imaging sequences (eg, diffusionweighted imaging) in the diagnosis and local staging of bladder cancer is still evolving. Substantial advances in MR imaging technology have made multiparametric MR imaging a feasible and reasonably accurate technique for the local staging of bladder cancer to optimize treatment. In addition, whole-body CT is the primary imaging technique for the detection of metastases in bladder cancer patients, especially those with disease that invades muscle. Abbreviations: ADC = apparent diffusion coefficient, FIESTA = fast imaging employing steady-state acquisition, FOV = field of view, GRE = gradient-echo, SE = spin-echo, 3D = three-dimensional, TURBT = transurethral resection of bladder tumor

RadioGraphics, 2010

Renal cystic diseases in adults are a heterogeneous group of disorders characterized by the prese... more Renal cystic diseases in adults are a heterogeneous group of disorders characterized by the presence of multiple cysts in the kidneys. These diseases may be categorized as hereditary, acquired, or developmental on the basis of their pathogenesis. Hereditary conditions include autosomal dominant polycystic kidney disease, medullary cystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis. Acquired conditions include cystic kidney disease, which develops in patients with end-stage renal disease. Developmental cystic diseases of the adult kidney include localized renal cystic disease, multicystic dysplastic kidney, and medullary sponge kidney. In recent years, many molecular and cellular mechanisms involved in the pathogenesis of renal cystic diseases have been identified. Hereditary renal cystic diseases are characterized by genetic mutations that lead to defects in the structure and function of the primary cilia of renal tubular epithelial cells, abnormal proliferation of tubular epithelium, and increased fluid secretion, all of which ultimately result in the development of renal cysts. A better understanding of these pathophysiologic mechanisms is now providing the basis for the development of more targeted therapeutic drugs for some of these disorders. Cross-sectional imaging provides useful information for diagnosis, surveillance, prognostication, and evaluation of treatment response in renal cystic diseases. ©

RadioGraphics, 2010

Mesenchymal neoplasms of the kidney in adults cover a wide spectrum with characteristic ontogeny ... more Mesenchymal neoplasms of the kidney in adults cover a wide spectrum with characteristic ontogeny and histologic findings and variable biologic profiles and imaging findings. Benign mesenchymal renal tumors include angiomyolipoma, leiomyoma, hemangioma, lymphangioma, juxtaglomerular cell tumor, renomedullary interstitial cell tumor (medullary fibroma), lipoma, solitary fibrous tumor, and schwannoma. Malignant renal tumors of mesenchymal origin include leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, osteosarcoma, synovial sarcoma, fibrosarcoma, malignant fibrous histiocytoma, and solitary fibrous tumor. Cross-sectional imaging findings for mesenchymal renal tumors in adults are varied. Although angiomyolipomas and lipomas show macroscopic fat, lymphangiomas are cystic in appearance. Renal hemangioma may show phleboliths and a characteristic enhancement pattern. Leiomyoma typically arises from the capsule and causes buckling of the renal cortex. Although osteosarcoma may demonstrate characteristic dense ossification, most renal sarcomas demonstrate imaging features that are indistinguishable from the more common renal cell carcinoma. Although some renal mesenchymal tumors have typical imaging findings, biopsy is warranted to establish a definitive diagnosis. Awareness of the various mesenchymal renal tumors and familiarity with their imaging findings permit optimal patient management. ©

RadioGraphics, 2014

■ Describe the anatomy of the porta hepatis and its adjacent peritoneal reflections. ■ Discuss th... more ■ Describe the anatomy of the porta hepatis and its adjacent peritoneal reflections. ■ Discuss the wide array of diseases that affect the porta hepatis and its role as a pathway for disease spread. ■ Identify the role of imaging in diagnosis and management of diseases of the porta hepatis.

RadioGraphics, 2011

Note: This copy is for your personal non-commercial use only. To order presentation-ready copies ... more Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.

RadioGraphics, 2008

The perirenal space, located between the anterior and the posterior renal fasciae, is shaped like... more The perirenal space, located between the anterior and the posterior renal fasciae, is shaped like an inverted cone with an apex that extends into the iliac fossa. Perirenal tumors and pseudotumors primarily originate either from the kidney or as part of a systemic disease process and have characteristic histopathologic features and biologic behavior. The lesions may be classified on the basis of their distribution and imaging features as solitary soft-tissue masses (renal cell carcinoma, lymphangioma, hemangioma, and leiomyoma), rindlike soft-tissue lesions (lymphoma, retroperitoneal fibrosis, and Erdheim-Chester disease), masses containing macroscopic fat (angiomyolipoma, liposarcoma, myelolipoma, and extramedullary hematopoiesis), and multifocal soft-tissue masses (metastases, plasma cell tumors). Because of overlap in imaging findings among these diverse perirenal lesions, a definitive diagnosis in most cases can be established only at histopathologic analysis. However, an imaging pattern-based approach may facilitate the diagnosis and optimal management of perirenal tumors and pseudotumors. ©

RadioGraphics, 2005

After reading this article and taking the test, the reader will be able to: Ⅲ Describe the crosss... more After reading this article and taking the test, the reader will be able to: Ⅲ Describe the crosssectional imaging appearances of tumors of the renal medulla. Ⅲ Illustrate the gross and histopathologic features of neoplasms of the renal medulla and correlate these findings with radiologic characteristics.

RadioGraphics, 2005

This article meets the criteria for 1.0 category 1 credit toward the AMA Physician's Recognition ... more This article meets the criteria for 1.0 category 1 credit toward the AMA Physician's Recognition Award. To obtain credit, see www.rsna.org/education/rg_cme.html.

RadioGraphics, 2006

After reading this article and taking the test, the reader will be able to: Ⅲ Describe the histol... more After reading this article and taking the test, the reader will be able to: Ⅲ Describe the histologic spectrum of common and uncommon renal cell carcinomas. Ⅲ Identify the imaging features of different histologic subtypes of renal cell carcinoma. Ⅲ Discuss correlation of the imaging findings of various histologic subtypes of renal cell carcinoma with the gross and microscopic findings.

Proceedings of the National Academy of Sciences, 2003

We earlier reported that the soluble form of the CD40 ligand (sCD40L), is involved in thrombosis ... more We earlier reported that the soluble form of the CD40 ligand (sCD40L), is involved in thrombosis by stabilizing platelet thrombi. In this article, we have determined the mechanism by which this protein affects platelet biology. Addition of sCD40L to washed platelets was found to activate the receptor function of α IIb β 3 as measured by the induction of fibrinogen binding and the formation of platelet microparticles. Mutation in the KGD sequence (D117E) of sCD40L, the α IIb β 3 -binding domain in the N terminus of the protein resulted in a loss of the platelet-stimulatory activity of this protein. Integrilin, a α IIb β 3 antagonist, but not an antibody to CD40 that blocked the ligand-binding activity, inhibited these platelet-stimulatory events. CD40 -/- platelets bound fibrinogen and formed microparticles similar to WT platelets, again indicating that CD40 is not involved in sCD40L-induced platelet activation. Exposure of platelets to sCD40L, but not D117E-sCD40L-coated surfaces, i...

Proceedings of the National Academy of Sciences, 2005

Enzymes of the blood coagulation pathway enhance the inflammatory response leading to endothelial... more Enzymes of the blood coagulation pathway enhance the inflammatory response leading to endothelial dysfunction, accounting, in part, for the vascular complications occurring in sepsis and cardiovascular disease. The responses of endothelial cell activation include induction of the expression of tissue factor (TF), a membrane glycoprotein that promotes thrombosis, and of E-selectin, a cell adhesion molecule that promotes inflammation. In this report, we demonstrate synergistic interactions between the coagulation factor Xa (fXa) and the proinflammatory cytokines TNF, IL-1β, and CD40L, leading to enhanced expression of TF and E-selectin in endothelial cells. A detailed analysis of the molecular pathways that could account for this activity of fXa showed that fXa inhibited the cytokine-induced expression of dual specificity phosphatases, MAP kinase phosphatase-L, -4, -5, and -7, blocking a negative regulatory effect on c-Jun N-terminal kinase. The synergistic interaction between fXa and...

Nature Medicine, 2002

CD40L (also known as CD154 and gp39) is a transmembrane protein and member of the tumor necrosis ... more CD40L (also known as CD154 and gp39) is a transmembrane protein and member of the tumor necrosis factor (TNF) family. It is expressed on cells of the immune system (activated CD4 + T cells, mast cells, basophils, eosinophils and natural killer cells) 1 and on activated platelets 2. The receptor for CD40L, CD40, from the TNF receptor family, is widely distributed, primarily on cells of the vasculature. Several immune functions for CD40L have been reported; the most prominent is in isotype switching during the immune response. Mutations in the gene encoding CD40L lead to a human pathology termed X-linked hyper-immunoglobulin-M syndrome 3. Ligation of CD40 by CD40L also has a role in the pathogenesis of atherosclerosis 4. Although the etiology of these responses may result from immune deficiency, the inflammatory activity of CD40L on platelets and other cells within the vasculature has also been considered as CD40L induces the expression of chemokines (monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and IL-8), pro-inflammatory adhesion molecules (vascular cellular adhesion molecule-1, intracellular adhesion molecule-1 and P-selectin), and tissue factor (TF), and downregulates the expression of thrombomodulin in vascular cells 5-7. CD40L is shed from stimulated lymphocytes generating soluble CD40L (sCD40L), and is actively released following platelet stimulation 8 and during acute coronary thrombosis 9. A recent study shows that the proteolytic cleavage of CD40L from platelets is stimulated by its binding to CD40 which is expressed constitutively on platelets 8. Although a precise role for sCD40L remains to be determined, two activities have been observed. First, sCD40L in serum of individuals with acute coronary thrombotic syndromes has been shown to be pro-inflammatory. In addition, sCD40L may promote coagulation as it induces TF expression on monocytes 10,11 , similar to an activity of soluble Pselectin 12. Soluble P-selectin in plasma promotes coagulation by causing the formation of TF-containing microparticles 13 , and CD40L could have similar activity. sCD40L also contains a KGD sequence 14 , a known binding motif specific for α IIb β 3 (ref. 15), the major platelet integrin. In addition, antibodies against CD40L induce thrombotic events in primates and humans 16. Here we report a direct role for CD40L in high-shear platelet thrombosis that depends on a novel interaction of sCD40L with β 3 integrins in platelets. Instability of large CD40L-/thrombi in mesenteric arterioles Thrombus formation in ferric chloride (FeCl 3)-induced injury of mesenteric arterioles of CD40L-/mice was compared with that of wild-type mice using intravital microscopy 17,18. Arterioles of 60-100-µm diameter with a shear rate of approximately 1300 per second were used. There was no difference in either initial adhesion of single platelets (97 ± 26 per min in CD40L-/versus 101 ± 24 per min in wild-type mice) or in the times required for first thrombus growth in wild-type and CD40L-/mice (Fig. 1a). However, in CD40L-/mice, large thrombi frequently ruptured and embolized, an event rarely seen in wild-type vessels (Fig. 1b), leading to a delay in vessel occlusion (Fig. 1c). Histological examination of the thrombi formed showed lower platelet density in the absence of CD40L (Fig. 1d), which probably contributed to the fragility of the thrombi. Platelets express 600-1,000 copies of CD40L (data not shown) and platelet activation is known to cause release of soluble CD40L (refs. 8,9). Therefore we investigated whether the soluble form of CD40L (rsCD40L) could restore the normal thrombotic process in CD40L-/vessels. Infusion of 1.6 mg/kg of rsCD40L just

Korean journal of radiology : official journal of the Korean Radiological Society

We evaluated the association between patients' weight and abdominal cross-sectional dimension... more We evaluated the association between patients' weight and abdominal cross-sectional dimensions and CT image quality. We prospectively evaluated 39 cancer patients aged more than 65 years with multislice CT scan of abdomen. All patients underwent equilibrium phase contrast-enhanced abdominal CT with 4 slices (from top of the right kidney) obtained at standard tube current (240-280 mA). All other scanning parameters were held constant. Patients' weight was measured just prior to the study. Cross-sectional abdominal dimensions such as circumference, area, average anterior abdominal wall fat thickness and, anteroposterior and transverse diameters were measured in all patients. Two subspecialty radiologists reviewed randomized images for overall image quality of abdominal structures using 5- point scale. Non-parametric correlation analysis was performed to determine the association of image quality with patients' weight and cross-sectional abdominal dimensions. A statisticall...

RadioGraphics, 2004

See www.rsna .org/education /rg_cme.html. LEARNING OBJECTIVES After reading this article and taki... more See www.rsna .org/education /rg_cme.html. LEARNING OBJECTIVES After reading this article and taking the test, the reader will be able to: Ⅲ Describe CT angiographic and MR angiographic techniques in evaluating the hepatic vasculature. Ⅲ Identify normal hepatic vasculature and anatomic variants that may influence patient selection or surgical technique for liver surgery.

American Journal of Roentgenology, 2002

OBJECTIVE. We hypothesized that radiation doses for abdominal CT could be reduced by adjusting th... more OBJECTIVE. We hypothesized that radiation doses for abdominal CT could be reduced by adjusting the dose for a patient's weight and cross-sectional abdominal dimensions, with the resultant scans still being of diagnostic quality. SUBJECTS AND METHODS. Using a multidetector CT scanner, we prospectively studied 39 patients who were 65 years and older who had a known history of cancer. After performing a diagnostic contrast-enhanced CT examination, we obtained four slices each (centered at the top of the right kidney) at a standard radiation dose (240-300 mA) and at a 50% reduced dose (120-150 mA) at a constant kilovoltage of 140. Scans were obtained during a single breath-hold, with a 2.5-mm detector configuration and a slice pitch of 6:1. Reconstructed slice thickness was 5 mm. In a blinded review, two radiologists rated the randomized CT scans for overall image quality and anatomic details of liver, spleen, adrenal glands, kidneys, pancreas, and abdominal wall, using a 5point scale (1 = unacceptable, 2 = substandard, 3 = acceptable, 4 = above average, and 5 = superior). Patients' weight and abdominal circumference, area, and anteroposterior and transverse diameters were correlated with image quality of scans obtained at standard-dose and 50% reduced-dose CT. Statistical analysis of the data was performed using Wilcoxon's signed rank test. RESULTS. Overall, the image quality score was significantly higher (p < 0.005) on the scans obtained with standard-dose CT. No statistically significant difference in image quality was noted in the 50% reduced-and standard-dose CT scans in patients who weighed less than 180 lb, or 81 kg, (p > 0.05) and who had a transverse abdominal diameter of less than 34.5 cm (p > 0.05), an anteroposterior diameter of less than 28 cm (p > 0.05), a cross-sectional circumference of less than 105 cm (p > 0.05), and a cross-sectional area of less than 800 cm 2 (p > 0.05). Good interobserver agreement (p > 0.5) was found between the two reviewing radiologists. CONCLUSION. Abdominal CT scan quality appears to be acceptable even with a 50% reduction in radiation dose except in patients with large anthropometric measurements. A reduction in CT radiation dose is possible if the tube current is optimized for the patient's weight and abdominal dimensions.

American Journal of Roentgenology, 2002

OBJECTIVE. The purpose of our study was to evaluate the performance of CT angiography using multi... more OBJECTIVE. The purpose of our study was to evaluate the performance of CT angiography using multidetector CT (MDCT) for preoperative vascular evaluation in candidates who were scheduled for liver neoplasm resection. SUBJECTS AND METHODS. Forty-two consecutive subjects with malignant liver tumors scheduled for resection were studied with multiphase MDCT. The first 22 subjects underwent both multiphase MDCT angiography and catheter angiography before surgery. The subsequent 20 subjects underwent only preoperative CT angiography. Postprocessing was performed, and the images were analyzed for the depiction of arterial, portal vein, and hepatic vein anatomy and for the identification of important vascular variants. The postprocessing findings were compared and correlated with the findings from catheter angiography (22/42) or intraoperative sonography (42/42) and surgery (42/42). RESULTS. Arterial anomalies were detected on the images of 17 of 42 patients, including a replaced right hepatic artery in five, replaced left hepatic artery in six, accessory right and left hepatic arteries in two, common trunk for the celiac and superior mesenteric arteries in one, and early bifurcation of the celiac artery in one. In 22 patients in whom catheter angiography confirmation was available, the number of arteries and almost all the significant anomalies were correctly identified on CT angiography (accuracy, 97%; sensitivity, 94%; specificity, 100%). In the subset of 20 patients who underwent MDCT angiography without catheter angiography confirmation, all clinically relevant information was provided by CT angiography. The portal and hepatic vein anatomy and the relationships of the liver tumors to the neighboring venous structures were shown on CT. CONCLUSION. Multidetector CT provides valuable preoperative information about hepatic vascular architecture and can be used as a noninvasive alternative to catheter angiography before oncologic liver surgery.

Circulation, 2002

Three closely linked lines of research have now merged. In the 1980s, concepts crystallized on th... more Three closely linked lines of research have now merged. In the 1980s, concepts crystallized on the role of lipids (eg, oxidized LDL, elevated cholesterol) in the genesis of atherosclerotic plaque. In the 1990s, use of antiplatelet agents proved that platelet aggregation caused ...

Radiology, 2003

PURPOSE: To evaluate a histogram analysis method for differentiating adrenal adenoma from metasta... more PURPOSE: To evaluate a histogram analysis method for differentiating adrenal adenoma from metastasis at computed tomography (CT). MATERIALS AND METHODS: In a retrospective review of 2 years of clinical CT records, 223 adrenal adenomas in 193 patients (115 with contrast material-enhanced CT, 43 with unenhanced and enhanced CT, and 35 with unenhanced CT) and 31 metastases (25 patients with enhanced CT) were found. In 158 patients with adenomas at enhanced CT, diagnosis was based on stable mass size for more than 1 year (n ϭ 135) and characteristic signal intensity decrease at chemical shift magnetic resonance imaging (n ϭ 23). In 35 patients with adenomas at unenhanced CT, mean attenuation was 10 HU or less. Diagnosis of all metastases was based on rapid growth of a mass or new mass in less than 6 months in patients with cancer. Adrenal metastases with extensive necrosis were excluded. Histogram analysis was performed in a circular region of interest (ROI) for mean attenuation, number of pixels, and range of pixel attenuation for all pixels and for the subset of pixels with less than 0 HU ("negative" pixels). Correlation between mean attenuation and percentage negative pixels was calculated. RESULTS: Negative pixels were present in all 74 unenhanced adenomas with mean attenuation of 10 HU or less and in 14 of 16 unenhanced adenomas with mean attenuation above 10 HU. Of 184 enhanced adenomas, only 20 had mean attenuation of 10 HU or less, but 97 contained negative pixels (77 of these 97 masses had mean attenuation above 10 HU). Increase in percentage negative pixels was highly correlated with decrease in mean attenuation of both unenhanced and enhanced adenomas. None of the adrenal metastases had mean attenuation of 10 HU or less or contained negative pixels. CONCLUSION: The histogram method is far more sensitive than the 10-HU threshold method for diagnosis of adrenal adenomas at enhanced CT, with specificity maintained at 100%.

RadioGraphics, 2012

There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate cha... more There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate characteristic epidemiologic and histopathologic features and natural histories. These masses may be classified into five distinct subgroups using a pattern-based approach that takes anatomic distribution and certain imaging characteristics into account, allowing greater accuracy in their detection and characterization and helping to optimize patient management. The five groups are cystic (serous and mucinous epithelial neoplasms, pelvic lymphangioma, tailgut cyst, ancient schwannoma), vascular or hypervascular (solitary fibrous tumor, paraganglioma, pelvic arteriovenous malformation, Klippel-Trénaunay-Weber syndrome, extraintestinal GIST [gastrointestinal stromal tumor]), fat-containing (lipoma, liposarcoma, myelolipoma, presacral teratoma), calcified (calcified lymphocele, calcified rejected transplant kidney, rare sarcomas), and myxoid (schwannoma, plexiform neurofibroma, myxoma).Cross-sectional imaging modalities help differentiate the more common gynecologic neoplasms from more unusual masses. In particular, the tissue-specific multiplanar capability of high-resolution magnetic resonance imaging permits better tumor localization and internal characterization, thereby serving as a road map for surgery. ©

RadioGraphics, 2012

Urinary bladder cancer is a heterogeneous disease with a variety of pathologic features, cytogene... more Urinary bladder cancer is a heterogeneous disease with a variety of pathologic features, cytogenetic characteristics, and natural histories. It is the fourth most common cancer in males and the tenth most common cancer in females. Urinary bladder cancer has a high recurrence rate, necessitating long-term surveillance after initial therapy. Early detection is important, since up to 47% of bladder cancer-related deaths may have been avoided. Conventional computed tomography (CT) and magnetic resonance (MR) imaging are only moderately accurate in the diagnosis and local staging of bladder cancer, with cystoscopy and pathologic staging remaining the standards of reference. However, the role of newer MR imaging sequences (eg, diffusionweighted imaging) in the diagnosis and local staging of bladder cancer is still evolving. Substantial advances in MR imaging technology have made multiparametric MR imaging a feasible and reasonably accurate technique for the local staging of bladder cancer to optimize treatment. In addition, whole-body CT is the primary imaging technique for the detection of metastases in bladder cancer patients, especially those with disease that invades muscle. Abbreviations: ADC = apparent diffusion coefficient, FIESTA = fast imaging employing steady-state acquisition, FOV = field of view, GRE = gradient-echo, SE = spin-echo, 3D = three-dimensional, TURBT = transurethral resection of bladder tumor

RadioGraphics, 2010

Renal cystic diseases in adults are a heterogeneous group of disorders characterized by the prese... more Renal cystic diseases in adults are a heterogeneous group of disorders characterized by the presence of multiple cysts in the kidneys. These diseases may be categorized as hereditary, acquired, or developmental on the basis of their pathogenesis. Hereditary conditions include autosomal dominant polycystic kidney disease, medullary cystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis. Acquired conditions include cystic kidney disease, which develops in patients with end-stage renal disease. Developmental cystic diseases of the adult kidney include localized renal cystic disease, multicystic dysplastic kidney, and medullary sponge kidney. In recent years, many molecular and cellular mechanisms involved in the pathogenesis of renal cystic diseases have been identified. Hereditary renal cystic diseases are characterized by genetic mutations that lead to defects in the structure and function of the primary cilia of renal tubular epithelial cells, abnormal proliferation of tubular epithelium, and increased fluid secretion, all of which ultimately result in the development of renal cysts. A better understanding of these pathophysiologic mechanisms is now providing the basis for the development of more targeted therapeutic drugs for some of these disorders. Cross-sectional imaging provides useful information for diagnosis, surveillance, prognostication, and evaluation of treatment response in renal cystic diseases. ©

RadioGraphics, 2010

Mesenchymal neoplasms of the kidney in adults cover a wide spectrum with characteristic ontogeny ... more Mesenchymal neoplasms of the kidney in adults cover a wide spectrum with characteristic ontogeny and histologic findings and variable biologic profiles and imaging findings. Benign mesenchymal renal tumors include angiomyolipoma, leiomyoma, hemangioma, lymphangioma, juxtaglomerular cell tumor, renomedullary interstitial cell tumor (medullary fibroma), lipoma, solitary fibrous tumor, and schwannoma. Malignant renal tumors of mesenchymal origin include leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, osteosarcoma, synovial sarcoma, fibrosarcoma, malignant fibrous histiocytoma, and solitary fibrous tumor. Cross-sectional imaging findings for mesenchymal renal tumors in adults are varied. Although angiomyolipomas and lipomas show macroscopic fat, lymphangiomas are cystic in appearance. Renal hemangioma may show phleboliths and a characteristic enhancement pattern. Leiomyoma typically arises from the capsule and causes buckling of the renal cortex. Although osteosarcoma may demonstrate characteristic dense ossification, most renal sarcomas demonstrate imaging features that are indistinguishable from the more common renal cell carcinoma. Although some renal mesenchymal tumors have typical imaging findings, biopsy is warranted to establish a definitive diagnosis. Awareness of the various mesenchymal renal tumors and familiarity with their imaging findings permit optimal patient management. ©

RadioGraphics, 2014

■ Describe the anatomy of the porta hepatis and its adjacent peritoneal reflections. ■ Discuss th... more ■ Describe the anatomy of the porta hepatis and its adjacent peritoneal reflections. ■ Discuss the wide array of diseases that affect the porta hepatis and its role as a pathway for disease spread. ■ Identify the role of imaging in diagnosis and management of diseases of the porta hepatis.

RadioGraphics, 2011

Note: This copy is for your personal non-commercial use only. To order presentation-ready copies ... more Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.

RadioGraphics, 2008

The perirenal space, located between the anterior and the posterior renal fasciae, is shaped like... more The perirenal space, located between the anterior and the posterior renal fasciae, is shaped like an inverted cone with an apex that extends into the iliac fossa. Perirenal tumors and pseudotumors primarily originate either from the kidney or as part of a systemic disease process and have characteristic histopathologic features and biologic behavior. The lesions may be classified on the basis of their distribution and imaging features as solitary soft-tissue masses (renal cell carcinoma, lymphangioma, hemangioma, and leiomyoma), rindlike soft-tissue lesions (lymphoma, retroperitoneal fibrosis, and Erdheim-Chester disease), masses containing macroscopic fat (angiomyolipoma, liposarcoma, myelolipoma, and extramedullary hematopoiesis), and multifocal soft-tissue masses (metastases, plasma cell tumors). Because of overlap in imaging findings among these diverse perirenal lesions, a definitive diagnosis in most cases can be established only at histopathologic analysis. However, an imaging pattern-based approach may facilitate the diagnosis and optimal management of perirenal tumors and pseudotumors. ©

RadioGraphics, 2005

After reading this article and taking the test, the reader will be able to: Ⅲ Describe the crosss... more After reading this article and taking the test, the reader will be able to: Ⅲ Describe the crosssectional imaging appearances of tumors of the renal medulla. Ⅲ Illustrate the gross and histopathologic features of neoplasms of the renal medulla and correlate these findings with radiologic characteristics.

RadioGraphics, 2005

This article meets the criteria for 1.0 category 1 credit toward the AMA Physician's Recognition ... more This article meets the criteria for 1.0 category 1 credit toward the AMA Physician's Recognition Award. To obtain credit, see www.rsna.org/education/rg_cme.html.

RadioGraphics, 2006

After reading this article and taking the test, the reader will be able to: Ⅲ Describe the histol... more After reading this article and taking the test, the reader will be able to: Ⅲ Describe the histologic spectrum of common and uncommon renal cell carcinomas. Ⅲ Identify the imaging features of different histologic subtypes of renal cell carcinoma. Ⅲ Discuss correlation of the imaging findings of various histologic subtypes of renal cell carcinoma with the gross and microscopic findings.

Proceedings of the National Academy of Sciences, 2003

We earlier reported that the soluble form of the CD40 ligand (sCD40L), is involved in thrombosis ... more We earlier reported that the soluble form of the CD40 ligand (sCD40L), is involved in thrombosis by stabilizing platelet thrombi. In this article, we have determined the mechanism by which this protein affects platelet biology. Addition of sCD40L to washed platelets was found to activate the receptor function of α IIb β 3 as measured by the induction of fibrinogen binding and the formation of platelet microparticles. Mutation in the KGD sequence (D117E) of sCD40L, the α IIb β 3 -binding domain in the N terminus of the protein resulted in a loss of the platelet-stimulatory activity of this protein. Integrilin, a α IIb β 3 antagonist, but not an antibody to CD40 that blocked the ligand-binding activity, inhibited these platelet-stimulatory events. CD40 -/- platelets bound fibrinogen and formed microparticles similar to WT platelets, again indicating that CD40 is not involved in sCD40L-induced platelet activation. Exposure of platelets to sCD40L, but not D117E-sCD40L-coated surfaces, i...

Proceedings of the National Academy of Sciences, 2005

Enzymes of the blood coagulation pathway enhance the inflammatory response leading to endothelial... more Enzymes of the blood coagulation pathway enhance the inflammatory response leading to endothelial dysfunction, accounting, in part, for the vascular complications occurring in sepsis and cardiovascular disease. The responses of endothelial cell activation include induction of the expression of tissue factor (TF), a membrane glycoprotein that promotes thrombosis, and of E-selectin, a cell adhesion molecule that promotes inflammation. In this report, we demonstrate synergistic interactions between the coagulation factor Xa (fXa) and the proinflammatory cytokines TNF, IL-1β, and CD40L, leading to enhanced expression of TF and E-selectin in endothelial cells. A detailed analysis of the molecular pathways that could account for this activity of fXa showed that fXa inhibited the cytokine-induced expression of dual specificity phosphatases, MAP kinase phosphatase-L, -4, -5, and -7, blocking a negative regulatory effect on c-Jun N-terminal kinase. The synergistic interaction between fXa and...

Nature Medicine, 2002

CD40L (also known as CD154 and gp39) is a transmembrane protein and member of the tumor necrosis ... more CD40L (also known as CD154 and gp39) is a transmembrane protein and member of the tumor necrosis factor (TNF) family. It is expressed on cells of the immune system (activated CD4 + T cells, mast cells, basophils, eosinophils and natural killer cells) 1 and on activated platelets 2. The receptor for CD40L, CD40, from the TNF receptor family, is widely distributed, primarily on cells of the vasculature. Several immune functions for CD40L have been reported; the most prominent is in isotype switching during the immune response. Mutations in the gene encoding CD40L lead to a human pathology termed X-linked hyper-immunoglobulin-M syndrome 3. Ligation of CD40 by CD40L also has a role in the pathogenesis of atherosclerosis 4. Although the etiology of these responses may result from immune deficiency, the inflammatory activity of CD40L on platelets and other cells within the vasculature has also been considered as CD40L induces the expression of chemokines (monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and IL-8), pro-inflammatory adhesion molecules (vascular cellular adhesion molecule-1, intracellular adhesion molecule-1 and P-selectin), and tissue factor (TF), and downregulates the expression of thrombomodulin in vascular cells 5-7. CD40L is shed from stimulated lymphocytes generating soluble CD40L (sCD40L), and is actively released following platelet stimulation 8 and during acute coronary thrombosis 9. A recent study shows that the proteolytic cleavage of CD40L from platelets is stimulated by its binding to CD40 which is expressed constitutively on platelets 8. Although a precise role for sCD40L remains to be determined, two activities have been observed. First, sCD40L in serum of individuals with acute coronary thrombotic syndromes has been shown to be pro-inflammatory. In addition, sCD40L may promote coagulation as it induces TF expression on monocytes 10,11 , similar to an activity of soluble Pselectin 12. Soluble P-selectin in plasma promotes coagulation by causing the formation of TF-containing microparticles 13 , and CD40L could have similar activity. sCD40L also contains a KGD sequence 14 , a known binding motif specific for α IIb β 3 (ref. 15), the major platelet integrin. In addition, antibodies against CD40L induce thrombotic events in primates and humans 16. Here we report a direct role for CD40L in high-shear platelet thrombosis that depends on a novel interaction of sCD40L with β 3 integrins in platelets. Instability of large CD40L-/thrombi in mesenteric arterioles Thrombus formation in ferric chloride (FeCl 3)-induced injury of mesenteric arterioles of CD40L-/mice was compared with that of wild-type mice using intravital microscopy 17,18. Arterioles of 60-100-µm diameter with a shear rate of approximately 1300 per second were used. There was no difference in either initial adhesion of single platelets (97 ± 26 per min in CD40L-/versus 101 ± 24 per min in wild-type mice) or in the times required for first thrombus growth in wild-type and CD40L-/mice (Fig. 1a). However, in CD40L-/mice, large thrombi frequently ruptured and embolized, an event rarely seen in wild-type vessels (Fig. 1b), leading to a delay in vessel occlusion (Fig. 1c). Histological examination of the thrombi formed showed lower platelet density in the absence of CD40L (Fig. 1d), which probably contributed to the fragility of the thrombi. Platelets express 600-1,000 copies of CD40L (data not shown) and platelet activation is known to cause release of soluble CD40L (refs. 8,9). Therefore we investigated whether the soluble form of CD40L (rsCD40L) could restore the normal thrombotic process in CD40L-/vessels. Infusion of 1.6 mg/kg of rsCD40L just