Search PubMed⌕ Search

Biomedical subjects

R L Baron

Publications and source records attributed to R L Baron.

At least 55 records · Page 3Linked to original sources
PubMed1996

Cholangiographic features of biliary strictures after liver transplantation for primary sclerosing cholangitis: evidence of recurrent disease.

OBJECTIVE: Biliary strictures occur more frequently after liver transplantation for primary sclerosing cholangitis (PSC) than for other diseases. A hypothesized cause is recurrence of PSC in the liver graft. In our study, we compared cholangiographic features of biliary strictures after transplantation for PSC to those after transplantation for other diseases. MATERIALS AND METHODS: A study group of 32 PSC grafts in adults with biliary strictures was compared with a control group of 32 non-PSC grafts with strictures. Both groups were matched for the type of biliary anastomosis (choledochojejunostomy) and for the time interval between transplantation and stricture diagnosis. We then performed a blind retrospective review of cholangiograms in these 64 cases to evaluate for features of PSC. RESULTS: Location, number, and length of strictures and ductal dilatation were similar in the PSC and non-PSC groups. Mural irregularities of bile ducts were present in 15 of 32 (47%) PSC grafts compared with four of 32 (13%) in the control group (p=.005). Diverticulum-like outpouchings occurred in six of 32 (19%) PSC graft compared with one of 32 (3%) in the control group. An overall resemblance to PSC was observed in eight of 32 (25%) grafts in the PSC group compared with two of 32 (6%) in the control group. CONCLUSION: Mural irregularity and diverticulum-like outpouchings--findings suggestive of PSC--and an overall appearance resembling PSC occur more frequently in PSC transplants than in transplants for other diseases. These findings are consistent with the hypothesis that PSC may recur in liver transplants.

Adult↗
PubMed1996

Detecting hepatocellular carcinoma: value of unenhanced or arterial phase CT imaging or both used in conjunction with conventional portal venous phase contrast-enhanced CT imaging.

OBJECTIVE: Because rates of detection of hypervascular neoplasms by conventional dynamic incremental-bolus CT are lower than rates of detection of hypovascular tumors by CT and because both unenhanced CT imaging and arterial phase helical CT imaging may increase the detection of hypervascular tumors, such as hepatocellular carcinoma, we evaluated the value of unenhanced and arterial phase CT imaging used in conjunction with conventional portal venous phase CT imaging in patients with hepatocellular carcinoma. MATERIALS AND METHODS: Unenhanced and biphasic helical contrast-enhanced CT studies were performed on 81 patients with proven hepatocellular carcinoma. Arterial phase and portal venous phase images were obtained at 20-50 sec and at 60-100 sec, respectively. Three blinded readers evaluated portal venous phase images for the number of liver lesions. On separate dates, the readers compared the arterial phase images with the portal venous phase images and the unenhanced images with the portal venous phase images. The readers recorded the number of lesions that were seen on portal venous phase images and that were also detected on unenhanced or arterial phase images as well as the number of additional lesions seen on unenhanced or arterial phase images. Consensus readings of unenhanced, arterial phase, and portal venous phase images were obtained in the 42 patients who had definitive surgery or follow-up CT scans, documenting the total tumor burden in this patient subgroup. RESULTS: The readers identified 286-310 lesions on portal venous phase images. On unenhanced images, the readers identified 223-244 of the lesions seen on portal venous phase images and an additional 45-55 lesions that were not seen on portal venous phase images. Arterial phase imaging revealed 245-269 of the lesions seen on portal venous phase images and an additional 89-111 lesions that were not seen on portal venous images. The diagnosis of tumor was possible only on unenhanced images in two (3%) of 81 patients and only on arterial phase images in seven patients (9%). In the subset of 42 patients with proof of tumor burden, 157 proven lesions were found. Consensus readings identified 127 (81%) of these lesions on portal venous phase images, 98 (62%) of these lesions on unenhanced images, and 120 (76%) of these lesions on arterial phase images. Of the 30 lesions not seen on portal venous phase images, nine were seen on both unenhanced and arterial phase images, three were seen on unenhanced images only, and 18 were seen on arterial phase images only. CONCLUSION: In patients with known or suspected hepatocellular carcinoma, the use of unenhanced or arterial phase images or both in addition to conventional portal venous phase images resulted in more tumors being detected. The combination of arterial phase and portal venous phase images revealed significantly more hepatocellular carcinoma lesions than did the combination of unenhanced and portal venous phase images.

Adult↗
PubMed1996

Chondromyxoid fibroma.

Chondromyxoid fibroma is a rare benign tumor derived from cartilage. The classic site of involvement is usually the metaphyseal ends of the long tubular bones, such as the tibia. The majority of these tumors are seen in the lower extremities during the second and third decades of life. Local recurrence of the tumor in bone is not uncommon, while soft tissue recurrence is less frequent. Most younger patients and those with recurrent tumors tend to have the mucinous type. This case is somewhat classic in nature. The tumor was originally seen in the second decade of life and was of the mucinoid type. Bone grafting was necessary because of the size and location of the tumor.

Adult↗
PubMed1995

Does advanced cirrhosis with portosystemic shunting affect the value of CT arterial portography in the evaluation of the liver?

OBJECTIVE: The purpose of this study was to determine the extent to which reduced portal blood flow in patients with advanced cirrhosis affects contrast enhancement of the liver during CT arterial portography (CTAP). We postulated that reduced and/or irregular hepatic enhancement would limit the efficacy of CTAP for the detection of hepatic tumors in these patients. MATERIALS AND METHODS: We reviewed the records of 82 patients who had biopsy-proved advanced cirrhosis and who underwent CTAP. Three experienced radiologists evaluated the CTAP studies for adequacy of hepatic parenchymal enhancement. The presence or absence of varices also was documented in an attempt to select a subgroup of patients in whom CTAP showed better hepatic parenchymal enhancement. RESULTS: Forty-seven (57%) of 82 patients had inadequate hepatic parenchymal enhancement to allow an evaluation of the entire liver. Inadequacy was attributable to areas of hyperdense parenchymal enhancement, areas of diffuse nontumoral mottling, or zones of poor parenchymal enhancement (soft-tissue attenuation equal to that of the paraspinal muscle). Parenchymal enhancement was inadequate in 62% of patients with varices and in 28% of patients without demonstrable varices. CONCLUSION: Our results show that contrast enhancement of the liver during CTAP is altered significantly in patients with cirrhosis. Thus, it is likely that CTAP has limited usefulness for the detection or characterization of hepatic neoplasms in patients with cirrhosis.

Evaluation Studies as Topic↗
PubMed1995

Portal vein thrombosis in patients with cirrhosis: does sonographic detection of intrathrombus flow allow differentiation of benign and malignant thrombus?

OBJECTIVE: The objective of our study was to determine if the detection by Doppler sonography of blood flow in portal vein thrombi occurring in patients with cirrhosis could be used to distinguish benign from malignant portal vein thrombi. SUBJECTS AND METHODS: Color and duplex Doppler sonographic examinations were performed in 47 patients with proven cirrhosis and portal vein thrombi. The examinations were directed at the detection of continuous or pulsatile flow within the portal vein thrombi. The nature of the portal vein thrombi was proven histologically in 27 patients and by CT findings and clinical history in 20 patients. The frequency, type, and direction of portal vein thrombus flow was evaluated to determine if there was any correlation with the benign or malignant nature of the portal vein thrombi. RESULTS: Of the 47 patients, 26 had malignant portal vein thrombi and 21 had benign portal vein thrombi. Blood flow was detected in 22 of the malignant and in 15 of the benign portal vein thrombi. The blood flow was pulsatile in 16 malignant and three benign portal vein thrombi and continuous in six malignant and 12 benign portal vein thrombi. The direction of the pulsatile flow in the malignant portal vein thrombi was predominantly (13/16) hepatofugal. All continuous flow in both benign and malignant portal vein thrombi was hepatopetal. The detection of pulsatile flow in portal vein thrombi yielded a 62% sensitivity and 95% specificity for the diagnosis of malignant portal vein thrombus. CONCLUSION: The detection by Doppler sonography of pulsatile flow in portal vein thrombi occurring in patients with cirrhosis is a moderately sensitive but highly specific sign for the diagnosis of malignant portal vein thrombus. However, continuous flow can be detected in benign and malignant portal vein thrombus and is thus not useful in differentiating between the two.

Adult↗
PubMed1994

The effect of storage on the computed tomography attenuation of gallstones.

RATIONALE AND OBJECTIVES: The effect of storage in five media on the computed tomography (CT) attenuation of gallstones, which might be important to future in vitro studies involving gallstones and their CT characteristics, was determined. METHODS: Gallstones were obtained in bile from cholecystectomy specimens. To establish a range of normal variability in the attenuation measurements of gallstones, 24 stones were scanned three times within a 5-minute interval, with a comparison of the attenuation measurements of individual stones. To determine the effect of storage, five stones from the same gallbladder underwent CT within 48 hours of surgical retrieval and were then placed in native bile, sterile normal saline, sterile water, air, or formalin. The stones were rescanned after 1 week and 4 weeks in storage. Ten sets of five stones were evaluated with a comparison of the attenuation measurements of individual stones. RESULTS: There was an average difference of 10.2 Hounsfield Units (HU) and a maximum difference of 35 HU between the three attenuation measurements of the 24 stones that did not undergo storage. With storage, native bile was the only media where none of the 10 stones varied in attenuation by more than 35 HU. Air and saline had the greatest effect on the attenuation of stones with statistically significant differences after 4 weeks in storage (P < .02). Six of the stones stored in air and three stored in saline decreased in attenuation by more than 35 HU, with maximal decreases of 137 and 79 HU, respectively. Although not statistically significant, two stones in water and one stored in formalin showed more than 35 HU of attenuation change, varying by up to 69 and 47 HU, respectively. CONCLUSIONS: Storage may affect the CT attenuation of gallstones and needs to be considered in any in vitro experiment involving gallstone sand CT correlation. Native bile is the only medium where no stones varied in attenuation more than can be accounted for by normal measurement variation, and thus, is the storage medium of choice.

Air↗
PubMed1994

Hepatic CT enhancement: comparison of ionic and nonionic contrast agents in the same patients.

PURPOSE: The authors prospectively compared the effects of ionic and nonionic contrast agents on hepatic enhancement at computed tomography (CT) in the same patient population. MATERIALS AND METHODS: Forty-six patients underwent abdominal CT with either ionic or nonionic contrast agents. At 6-month follow-up, the alternative agent was used. Pre- and postcontrast attenuation values of liver and vessels were obtained; enhancement and postinjection time of each image were recorded. The area under a computer-generated enhancement-time curve was calculated as a means of measuring enhancement over time. Mean liver enhancement with ionic and nonionic contrast agents was compared. RESULTS: Mean hepatic enhancement with ionic contrast material was greater than with nonionic contrast material at all time intervals through 90 seconds after injection. The difference was statistically significant from 61 to 70 seconds. Mean peak liver enhancement for ionic and nonionic contrast agents was nearly identical (59 and 58 HU, respectively), but mean time to peak hepatic enhancement with nonionic contrast agent was greater by 10 seconds. CONCLUSION: These results indicate that ionic contrast agent may effect greater liver tumor conspicuity.

Female↗
PubMed1994

Sequential viewing of abdominal CT images at varying rates.

PURPOSE: To evaluate radiologists' ability to detect abdominal masses during sequential viewing of series of computed tomographic (CT) scans at varying rates. MATERIALS AND METHODS: Receiver operating characteristic (ROC) analysis was used to assess the ability of five experienced radiologists to determine the presence or absence of subtle abdominal masses in 29 cases (15 positive, 14 negative) while viewing CT scans sequentially at different rates (0.5, 1, 2, 4, 7, and 21 images per second) and also at reader-selectable rates. RESULTS: Even at extremely fast viewing rates (21 images per second), radiologists performed significantly better (P < .05) than would be expected by chance alone (average area Az under the ROC curve = 0.73 vs 0.5). As the viewing rate decreased, their performance increased. The reader-selectable mode was better than any fixed-rate cine mode (average Az = 0.93). CONCLUSION: Fixed-rate sequential viewing of CT images for the primary diagnosis of subtle abdominal masses should be restricted to no more than one or two images per second, but the reader-selectable viewing mode is preferable to any fixed-rate cine mode.

Humans↗
PubMed1994

Hepatic artery stenosis and thrombosis in transplant recipients: Doppler diagnosis with resistive index and systolic acceleration time.

PURPOSE: To assess the value of resistive index (RI) and systolic acceleration time (SAT) for diagnosis of stenoses and thromboses of the hepatic artery in liver transplant recipients. MATERIALS AND METHODS: Doppler sonograms and angiograms in 125 liver transplant recipients were correlated and analyzed for any statistically significant difference in the RI or SAT of patients with and without arterial stenosis or thrombosis. Sensitivity and specificity were calculated for RI, SAT, peak arterial systolic velocity, and absence of arterial flow. RESULTS: Forty-seven patients had a marked stenosis; 16 had thrombosis. There was a statistically significant difference (P < .05) in the RI and SAT of patients with stenosis or thrombosis versus those with normal arteries but not in patients with stenosis versus thrombosis. RI and SAT parameters allowed detection of abnormalities not found with peak velocity and no-flow parameters. Combined parameters produced 97% sensitivity and 64% specificity for marked arterial disease. CONCLUSION: Doppler spectral wave form analysis provides excellent screening for detection of hepatic allograft arterial stenosis or thrombosis.

Adolescent↗
PubMed1994

Hepatic CT enhancement. Part I. Alterations in the volume of contrast material within the same patients.

PURPOSE: To evaluate the effects of alterations in the volume of contrast material on liver enhancement. MATERIALS AND METHODS: Thirty patients underwent repeat computed tomographic (CT) examinations within 6 months, the first with either 100, 150, or 180 mL of nonionic contrast material (2 mL/sec). In the second, only volume was altered. Liver attenuation was measured before and after contrast material administration, and enhancement was calculated for each image. Comparisons were made only within the same patients. RESULTS: Mean liver enhancement was greater with 150 mL compared with 100 mL beyond 55 seconds after injection. Mean peak enhancement was greater by 21 HU with 150 mL; mean time to peak enhancement was longer by 14 seconds. Mean liver enhancement was greater with 180 mL compared with 150 mL at all intervals beyond 80 seconds. Mean peak enhancement was greater by 22 HU; mean time to peak liver enhancement was longer by 24 seconds. CONCLUSION: Alterations in contrast material volume have substantial impact on liver enhancement and potentially tumor conspicuity. The optimal window of time for liver imaging after contrast material injection varies with the volume administered.

Adult↗
PubMed1994

Hepatic CT enhancement. Part II. Alterations in contrast material volume and rate of injection within the same patients.

PURPOSE: To evaluate the effects of alterations in contrast material volume and injection rate on liver computed tomographic (CT) enhancement within the same patients. MATERIALS AND METHODS: Forty patients underwent repeat CT within 6 months, one with 150 mL of nonionic contrast material at 2 mL/sec, the other with 150 mL (n = 8, group A), 100 mL (n = 14, group B), or 180 mL (n = 18, group C) at 3 mL/sec. Comparisons were made only within the same patients. RESULTS: In group A, mean liver enhancement was greater with the higher rate (3 mL/sec) up to 130 seconds after injection, mean peak liver enhancement was greater by 10 HU, and mean time to peak enhancement was shorter by 15 seconds. In group B, mean peak enhancement was greater with 150 mL by 9 HU, and mean time to peak enhancement was longer by 27 seconds. In group C, peak enhancement and time to peak liver enhancement were greater. CONCLUSION: Contrast material volume and injection rate have interdependent effects on liver enhancement and potentially tumor conspicuity. Higher rates compensate partially for lower volume, but enhancement is still reduced. The optimal window of time for imaging after injection varies with injection technique.

Adult↗
PubMed1994

Malignancies in patients with cirrhosis: CT sensitivity and specificity in 200 consecutive transplant patients.

PURPOSE: To determine the sensitivity and specificity of computed tomography (CT) as a screening tool in patients with cirrhosis. MATERIALS AND METHODS: CT examinations were performed before liver transplantation in 200 consecutive patients with cirrhosis. Scans were prospectively reviewed and compared with pathologic findings in the fresh serially sectioned whole livers. RESULTS: Pathologic evaluation revealed hepatocellular carcinoma in 35 patients and cholangiocarcinoma in five. Malignancy was clinically suspected in 18 patients prior to imaging. CT depicted tumor in 25 patients; tumor was identified only at pathologic study in 14 patients. Sensitivity of unenhanced and enhanced CT in detection of malignancy was 63% and 68%, respectively, and specificity was 63% and 81%, respectively. Cysts and hemangiomas were found in only 10 and five patients, respectively. CONCLUSION: CT is insensitive for detection of neoplasms in the cirrhotic liver. Unsuspected malignant neoplasms are encountered more frequently than cysts or hemangiomas. Sensitivity of unenhanced CT for tumor detection is similar to that of enhanced CT; unenhanced CT, however, is less specific for malignancy.

Bile Duct Neoplasms↗
PubMed1994

Optimizing CT portography: a prospective comparison of injection into the splenic versus superior mesenteric artery.

PURPOSE: To evaluate whether computed tomographic arterial portography (CTAP) is best performed with injections in the superior mesenteric artery (SMA) or the splenic artery. MATERIALS AND METHODS: Seventy-one studies were performed with injection into the SMA (n = 37) or splenic artery (n = 34) of 150 mL of contrast material at 1.5 mL/sec and 20-second delay for both groups. Images were reviewed for location and type of nontumoral perfusion abnormalities. The degree of liver parenchymal enhancement with each technique was compared. RESULTS: Fewer nontumoral perfusion defects were seen with splenic artery (65%) versus SMA (78%) injection. Visual differences in contrast enhancement with greater attenuation in dependent portions of the liver were seen with greater frequency with SMA (41%) than with splenic artery (24%) injection. Contrast enhancement that obscured detail in the right lobe was seen only with SMA injections (16%). Greater parenchymal enhancement (up to 18 HU) at all time intervals was seen with splenic artery injection. CONCLUSION: Because of greater parenchymal enhancement and fewer nontumoral perfusion abnormalities, splenic artery catheterization is the preferred technique for CTAP.

Catheterization, Peripheral↗
PubMed1994

A carbamate insecticide: a case study of aldicarb.

Aldicarb, the active ingredient in the insecticide TEMIK, was introduced to the agricultural community over 25 years ago. It has been registered worldwide to control a wide variety of insect, mite, and nematode pests in agriculture. The toxicological research database supporting the registration and use of aldicarb was generated over more than 25 years and contains more than 280 animal studies on 12 species of animals, 2 clinical human trials, and over 20 human monitoring studies. This database, which includes biochemical aspects (metabolism and mode-of-action studies), acute toxicity and special short-term toxicity studies, long-term toxicity studies, and epidemiological observations in humans, serves as the starting point for the evaluation of the risks associated with the acceptance of levels of aldicarb residues in food and drinking water and for the more direct occupational exposure. This article highlights the available toxicological data and reviews worldwide regulation of aldicarb. Included in these discussions is a brief description of the toxicological end point upon which regulatory decisions have been based, namely acetylcholinesterase depression. Aldicarb, the N-methylcarbamic acid ester of 2-methyl-2-(methylthio) propionaldehyde oxime, was the first of a limited group of insecticidal oxime N-methylcarbamates that have properties distinct from N-methylcarbamates which have a phenolic constituent, instead of the oxime moiety. Aldicarb is highly water-soluble (approximately 6000 ppm), nonvolatile, relatively stable under acidic conditions, and is easily degraded under alkaline conditions. These properties are important determinants of its systemic action in plants and of its problematic environmental behavior. Possible environmental hazards involving the chemical include groundwater contamination and (more recently) excessive terminal residues in certain foods.

Aldicarb↗
PubMed1994

Peribiliary cysts associated with severe liver disease: imaging-pathologic correlation.

OBJECTIVE: Prior pathology reports describe peribiliary cysts in patients who have severe liver disease. The purpose of this study was to determine whether these cysts could be identified on imaging studies, and to determine the range of imaging findings when identified. SUBJECTS AND METHODS: Imaging and pathologic findings were correlated in 12 patients in whom peribiliary cysts were found on gross inspection of the liver after autopsy (one) or liver transplantation. All patients had been examined with CT and sonography, three patients had undergone MR imaging, and one had had cholangiography. The liver was sectioned in the axial plane at 1-cm intervals, and the porta hepatis and the proximal extrahepatic bile ducts were examined macroscopically. Pathologic findings were recorded and compared with the patients' imaging findings and clinical course. RESULTS: CT showed the peribiliary cysts in the porta hepatis in 10 of 12 patients. These appeared as discrete cysts in four patients, a tubular structure paralleling the portal structures in four patients, and a string of cysts that simulated abnormal bile ducts in two patients. Sonography showed the cysts in four of 12 patients, as anechoic cystic structures in three and as a septated, tubular channel in one. MR showed the cysts in two of three patients, and T2-weighted images were better than T1-weighted images. The cysts appeared in a cluster in one patient, and as a tubular structure of high intensity on T2-weighted images that simulated a dilated bile duct in the other. Patients were asymptomatic in 11 of 12 cases. In one case, large cysts caused biliary obstruction, which was apparent on CT scans, sonograms, and cholangiograms. CONCLUSION: Peribiliary cysts associated with a variety of disorders can be detected with CT, sonography, and MR imaging. Recognition of the imaging appearance of these cysts may avoid the misdiagnosis of dilated bile ducts, cystic neoplasm, or abscess. Conversely, when seen on images, these cysts might suggest one of the underlying associated disorders.

Adult↗
PubMed1994

Understanding and optimizing use of contrast material for CT of the liver.

Improvements in CT technology have dramatically increased our ability to detect and diagnose liver abnormalities, particularly neoplastic disease. Because of the high prevalence of liver disease in patients referred for abdominal CT examinations, contrast administration and scanning techniques are usually optimized for detection of liver disease on abdominal CT scans. A wide variety of contrast techniques can be used to evaluate the liver, and it is important to understand both the rationale behind each technique and the impact on the quality of the examination when one deviates from these techniques. In addition, the timing of contrast administration and scan acquisition has become critical, and improper timing can cause lesions that are easily visualized to be obscured. This article reviews principles of lesion detection and the effects of various contrast techniques on lesion visualization.

Adenoma, Liver Cell↗