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Biomedical subjects

J L Chezmar

Publications and source records attributed to J L Chezmar.

At least 37 records · Page 2Linked to original sources
PubMed1992

Fast spin-echo imaging of the abdomen during breath-holding: an alternative to RASE and other fast imaging techniques.

We have developed a rapidly acquired T1-weighted spin-echo pulse sequence that uses gradient echo-like parameters of TR 70 ms, TE 10 ms, NEX-1 (SE 70/10/1) with large pulse angles, and presaturation. This sequence yields two images of the abdomen during a comfortable breath-hold of 9 s. Preliminary phantom studies with this sequence demonstrated that peak signal-to-noise ratios occurred at pulse angles of 120 degrees and 135 degrees. Compared to this rapidly acquired sequence, a conventional T1-weighted spin-echo sequence of TR 140 ms, TE 10 ms, NEX-4 demonstrated 2.8 times the signal-to-noise ratio, 2.6 times the liver-spleen contrast-to-noise ratio but only 1.6 times the contrast-to-artifact ratio. When normalized for the imaging time, however, there was little difference in the signal-to-noise and contrast-to-noise ratios, although the SE 70/10/1 demonstrated 2.0 times the contrast-to-artifact ratio. We conclude that for abdominal imaging the SE 70/10/1 is an excellent alternative to RASE and other fast imaging techniques, and, although there are inherently low signal-to-noise ratios, it may be particularly useful when coupled with a paramagnetic contrast agent.

Abdomen↗
PubMed1992

CT during arterial portography: diagnostic pitfalls.

Computed tomography (CT) during arterial portography (CTAP) is an important technique for evaluating the liver before hepatic tumor resection. With this technique, most tumors are of low attenuation compared with that of enhancing parenchyma. At times, low-attenuation lesions are encountered that represent perfusion abnormalities rather than tumor deposits. These perfusion abnormalities can be categorized as (a) those resulting from improper technique; (b) those extending from hilum to capsule (straight-line sign), with or without an obstructing mass; (c) perihilar and periligamentous abnormalities; (d) subcapsular defects (linear or wedge shaped); and (e) those seen with cirrhosis or regenerating nodules. Adjuvant use of delayed CT, magnetic resonance imaging, and intraoperative ultrasound aids in characterization of these nontumorous defects, thereby improving specificity. The authors conclude that when potential candidates are evaluated for hepatic tumor resection, knowledge of the existence of the various diagnostic pitfalls of CTAP and their imaging characteristics is imperative to avoid inadvertent false results.

Angiography, Digital Subtraction↗
PubMed1992

Peritoneal carcinomatosis: preoperative CT with intraperitoneal contrast material.

Thirty-five abdominal computed tomographic (CT) scans of 27 patients with peritoneal metastases from a mucin-producing tumor of the appendix, colon, small bowel, or ovary were retrospectively reviewed. Fifteen scans were obtained of 15 patients after CT with intraperitoneal infusion of contrast material (IP), and 20 scans were obtained of 16 patients with CT without IP. Subsequent exploratory laparotomy revealed that all 27 patients had multi-focal spread of peritoneal metastases. The sensitivity of CTIP and CT without IP for detection of peritoneal metastases at all sites of involvement was 61% and 59%, respectively. For CTIP, the highest sensitivity was in the right subphrenic space (88%), splenic hilum (86%), and left subphrenic space (83%). For CT without IP, the highest sensitivity was noted in the splenic hilum (100%), left subphrenic space (75%), and left paracolic gutter (75%). CTIP and CT without IP had low sensitivity for detection of disease in the greater omentum (50% each) and small-bowel mesentery (38% and 59%, respectively), two areas that had the highest frequency of metastases.

Appendiceal Neoplasms↗
PubMed1992

The frequency and significance of small (less than or equal to 15 mm) hepatic lesions detected by CT.

The purpose of our study was to determine the frequency of detection of small hepatic lesions (less than or equal to 15 mm) in outpatients who had abdominal CT and to assess the significance of these lesions in the presence or absence of known malignant tumors. Contrast-enhanced abdominal CT scans in 1454 patients were reviewed. In 254 patients (17%), hepatic lesions 15 mm or smaller were detected. In 51% of these patients, lesions were judged benign on the basis of other imaging studies, biopsy results, or stability for at least 6 months as shown by CT. Lesions were judged malignant on the basis of progression seen on radiologic studies or biopsy in 22%. The other 27% of the patients had lesions that could not be classified. The majority of patients with small hepatic lesions (82%) were known to have a malignant tumor; in 51% of these patients, lesions were diagnosed as benign. No patient without a known malignant tumor had a small hepatic lesion that was determined to be malignant. Multiple small lesions were more likely to represent malignant disease than were single small lesions. We conclude that small hepatic lesions are common (seen in 17% of our patients), and that there is a high probability that hepatic lesions smaller than 15 mm are benign, even in patients known to have an extrahepatic malignant tumor.

Humans↗
PubMed1992

Persistence of portosystemic collaterals and splenomegaly on CT after orthotopic liver transplantation.

OBJECTIVE: The appearances of portosystemic collaterals and splenomegaly on CT before and after liver transplantation were evaluated. MATERIALS AND METHODS: The records of 54 patients undergoing liver transplantation during a 2.5-year period were reviewed retrospectively. Twenty-five of these patients, in whom both a preoperative abdominal CT scan and a follow-up CT scan at least 1 year after transplantation had been obtained, were clinically well and had had no significant episodes of rejection, severe recurrent hepatitis, or other complication at the time of study. A total of 94 abdominal CT scans in these patients were reviewed to assess changes in portosystemic collaterals and splenic volume. RESULTS: At 6 months after transplantation, portosystemic collaterals at one or more sites were seen in 14 (74%) of the 19 patients scanned at this time in whom collaterals had been seen on CT preoperatively. At 1 year after transplantation, splenic hilar collaterals persisted in 64% of patients, splenocolic ligament collaterals in 50%, retroperitoneal collaterals in 38%, and peripancreatic collaterals in 38% of patients with preoperative varices at these sites who were examined with CT at this interval. Splenic hilar, coronary, and retroperitoneal collaterals were found to persist for up to 4 years after transplantation in the single patient examined at that time. Splenic volume decreased in 94% of patients examined after transplantation, with a mean reduction of 60 +/- 19%. However, the spleen remained significantly enlarged in 56% of patients. CONCLUSION: We conclude that portosystemic collaterals and splenomegaly frequently persist after liver transplantation, but that this finding need not indicate recurrence of hepatic disease or other posttransplantation complications.

Adult↗
PubMed1991

Magnetic resonance imaging of the pancreas with gadolinium-DTPA.

Gadolinium (Gd)-DTPA was evaluated as a contrast agent for magnetic resonance (MR) imaging of the pancreas at 1.5T. Twenty-five patients were imaged with identical gradient-echo (GE) (TR 47, TE 13, 80 degree pulse angle) and spin-echo (SE) (TR 300, TE 15) MR sequences prior to and following an intravenous bolus of 0.1 mmol/kg Gd-DTPA. Marked pancreatic enhancement was demonstrated on dynamic sequential breath-hold GE images obtained immediately following the Gd-DTPA bolus (116% mean enhancement over pre-Gd-DTPA images). Enhancement decreased but persisted on the SE images obtained approximately 5 and 15 min following the Gd-DTPA bolus (65 and 60% mean enhancement, respectively). Five of the patients had a pancreatic mass. In these five patients, the enhancement of pancreatic tissue resulted in improved conspicuity of the mass. These initial results suggest that pancreatic enhancement occurs following an intravenous bolus of Gd-DTPA and has the potential to improve MR visualization of pancreatic masses.

Adenocarcinoma↗
PubMed1991

Hepatic dynamic sequential CT: section enhancement profiles with a bolus of ionic and nonionic contrast agents.

The enhancement characteristics in different portions of the liver during dynamic sequential bolus computed tomography (CT) with iodinated contrast material (DSBCT) were prospectively evaluated in 75 patients by using iothalamate meglumine, iopamidol, and iohexol (25 patients received each agent). After baseline noncontrast CT was performed, DSBCT was performed with a 180-mL intravenous bolus administered at 2 mL/sec. Scanning was started 25 seconds after the bolus was initiated, by using a 3-second scan time and rapid cephalocaudal table incrementation, yielding contiguous 8-mm-thick sections at a rate of nine sections per minute. On postcontrast images, peak enhancement was 115% for iopamidol and 117% for iohexol, both of which were superior to iothalamate meglumine at 95% (P less than .05). After peaking, enhancement then decreased for all three contrast agents, although the decline was more precipitous for iothalamate meglumine. Enhancement on the more caudal sections with both iopamidol and iohexol was superior to that with iothalamate meglumine (P less than .05). The data suggest that the enhancement characteristics for the two nonionic agents may be more optimal for detection of focal hepatic lesions than the ionic agent.

Adult↗
PubMed1991

Liver transplant biopsies with a biopsy gun.

The authors evaluated the safety and efficacy of a biopsy gun for performance of image-guided percutaneous biopsy of hepatic allografts in liver transplant recipients. Two hundred fifty-two liver biopsies were performed in 58 transplant recipients over a 27-month period by using this instrument with an 18-gauge needle. Major complications occurred in two of the 252 biopsies (0.8%): One hemopneumothorax necessitated drainage with a chest tube, and one hemorrhage necessitated transfusion. No patient required surgical exploration because of a complication of the biopsy. Specimens were adequate for accurate histopathologic diagnosis in 248 of 252 procedures (98.4%). The authors conclude that image-guided percutaneous biopsy of hepatic allografts with use of the biopsy gun is a safe and accurate method of obtaining hepatic tissue from liver transplant recipients for histopathologic analysis.

Adolescent↗
PubMed1991

Biliary lithotripsy versus cholecystectomy: a cost-utility analysis.

Evaluating the economic impact of medical procedures is of increasing importance in the American health care system, and this is especially true in the case of new medical technologies. Both the cost and the outcome of a treatment, and its alternatives must be evaluated. A cost-utility analysis was performed to compare cholecystectomy with biliary lithotripsy accompanied by bile acid therapy. Using a Markov approach, a model was designed to project expected cost and quality-adjusted survival over a 5-year period in patients with solitary stones of less than or equal to 20 mm in diameter. The viewpoint of the analysis was chosen to be that of the general society, since it can be considered as a consensus of all interest groups. Direct costs were obtained from hospitals in Atlanta, Georgia; indirect costs are based on average United States earnings. Utility was estimated using a model that combines different scales of well-being with an underlying etiology. The findings indicate that from society's point of view for all patients meeting lithotripsy inclusion criteria, based on this cost-utility analysis, biliary lithotripsy would be the procedure of choice.

Adult↗
PubMed1991

Manganese dipyridoxyl diphosphate. Effect of dose, time, and pulse sequence on hepatic enhancement in rats.

We used an animal model to investigate the hepatic enhancement characteristics of manganese dipyridoxyl diphosphate (MnDPDP) related to time, dose, and pulse sequence. The contrast doses selected were in the human tolerance range. Using an SE 300/15 pulse sequence, maximum mean hepatic enhancement of 45% (8 mumols/kg) and 58% (12 mumols/kg) over baseline was seen during a plateau maintained between 5 and 50 minutes postinjection in the 8 mumols/kg group, and between 10 and 90 minutes in the 12 mumols/kg group. This plateau was followed by a very gradual decline in hepatic enhancement. Using either 4 or 8 mumols/kg, there was a significant increase in postcontrast hepatic intensity on all relatively T1-weighted pulse sequences (spin echo [SE] 300/15, inversion recovery [IR] 1400/20/400, gradient echo [GE] 47/13/80 degrees, and GE 60/20/30 degrees) except GE 47/13/80 degrees at 4 mumols/kg. At 8 mumols/kg there was superior enhancement, with IR 1400/20/400 and SE 300/15, but at 4 mumols/kg there was no consistently superior sequence. None of the relatively T2-weighted pulse sequences (SE 2000/50, SE 2000/100, or GE 100/30/20 degrees) demonstrated a significant change in hepatic intensity using either dose of contrast. The data suggest that the best combination of dose, pulse sequence, and time for hepatic imaging with MnDPDP is 8 mumols/kg using heavily T1-weighted sequences 5 to 60 minutes following contrast administration.

Animals↗
PubMed1991

Magnetic resonance imaging of the liver. Technique.

Image quality and the ability to detect disease in the liver with magnetic resonance (MR) imaging are critically dependent on the pulse sequences used and on the reduction of motion artifact. Selection of appropriate pulse sequences depends on a number of factors including magnetic field strength, equipment manufacturer, and availability of pulse sequences and motion artifact reduction techniques on the individual equipment used. This article summarizes some of the current methods available for reducing motion artifacts, discusses selection of imaging parameters for maximizing hepatic lesion detection, and reviews research on the use of contrast agents for MR imaging of the liver.

Artifacts↗
PubMed1990

Hepatic iron overload: diagnosis and quantification by noninvasive imaging.

The diagnostic efficacy of magnetic resonance (MR) and computed tomography (CT) for detection and quantification of hepatic iron was assessed in a series of patients under investigation for clinical or biochemical evidence of hepatic iron overload. Thirty patients underwent MR imaging (SE 30,60/1000 or SE 30,60/2000) at 0.5 Tesla with calculation of hepatic T2 and liver to paraspinous muscle signal intensity ratios. Twenty-nine patients also had measurement of hepatic attenuation on noncontrast CT images. Results of these imaging studies were correlated in all patients with quantitative iron determination from liver biopsy specimens. The best predictor of liver iron among parameters studied was the ratio of the signal intensities of liver and paraspinous muscle (L/M) on a SE 60/1000 sequence. Both MR using L/M ratios and CT were sensitive methods for detection of severe degrees of hepatic iron overload with 100% of patients with hepatic iron on biopsy greater than 600 micrograms/100 mg liver dry weight detected on the basis of L/M less than 0.6 or CT attenuation greater than 70 Hounsfield units (HU). The MR parameter, however, was more specific than CT (100 vs 50%) and showed a higher degree of correlation with quantitated hepatic iron from biopsy. T2 measurements showed poor correlation with hepatic iron, due to difficulty in obtaining precise T2 measurements in vivo when the signal intensity is low. None of the parameters utilized was sensitive for detecting mild or moderate degrees of hepatic iron overload. We conclude that MR and CT are sensitive techniques for noninvasive detection of severe hepatic iron overload, with MR providing greater specificity than CT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Preoperative localization of focal liver lesions to specific liver segments: utility of CT during arterial portography.

The authors retrospectively studied 36 hepatic masses in 20 patients who underwent computed tomography during arterial portography (CTAP) and subsequent hepatic tumor resection. The authors used the right main and left main portal veins as landmarks for the transverse scissura, along with the hepatic veins, the gallbladder fossa, and the umbilical fissure to blindly predict the segmental location of each tumor confirmed at surgery. The right main and left main portal veins were found to be consistently near the middle sections through the liver. CTAP findings and surgical descriptions agreed on the primary segmental location of 33 of 36 focal lesions (92%) but disagreed on the extent of 11 of 36 lesions (31%). Further review of the CTAP scans of the 11 lesions revealed that the extent of the lesion was more correctly described at surgery in six masses and at CTAP in four masses; in one lesion, opposite margins of the same mass were correctly described at both surgery and CTAP. Since it may be difficult or impossible to localize deep hepatic lesions intraoperatively by means of palpation or inspection, CTAP is a helpful preoperative tool for determining the segmental location of lesions and for planning the surgical approach.

Adult↗
PubMed1990

A segmental approach to computerized tomographic portography for hepatic resection.

Surgical treatment has proved to be of benefit to patients with primary and metastatic tumors of the liver. However, the ability to localize tumors preoperatively to particular segments within the liver has not been emphasized. The large size of this organ and its complex vascular structure have not allowed the surgeon either to determine accurately the hepatic segment occupied by the tumor or to identify major vascular structures adjacent to the tumor. We have expanded the use of a new roentgenologic technique to determine preoperatively with more clear definition the segmental anatomy of the liver. Computerized tomographic portography (CT-P) images hepatic veins and the segmental branches of portal vein and identifies the anatomic location of tumor nodules. To read the roentgenograms, one first identifies the middle CT-P slice that will cut the transverse scissura. Slices cephalad to the transverse scissura are through segments 7, 8, 4a and 2 in a clockwise order; slices caudad to the transverse scissura are through 6, 5, 4b and 3. Selected CT-P cuts from a series of patients show the typical CT-P configuration of the hepatic vasculature anatomy and the structures that can be identified roentgenologically. The CT-P provides valuable information not previously available preoperatively to the surgeon operating upon the liver.

Contrast Media↗