Biomedical subjects

J L Chezmar

Publications and source records attributed to J L Chezmar.

51 records · Page 3Linked to original sources

PubMed1989

Hepatic tumors: comparison of CT during arterial portography, delayed CT, and MR imaging for preoperative evaluation.

Forty-three patients with known primary or secondary neoplastic involvement of the liver underwent evaluation to determine the number, size, and location of focal lesions before possible tumor resection. Imaging studies included computed tomography (CT) during arterial portography (CTAP), delayed CT, and magnetic resonance (MR) imaging at various pulse sequences. Results of radiologic studies were compared with surgical and pathologic findings. In the combined group of surgical and nonsurgical patients, CTAP was significantly more sensitive (85%) than all other techniques except 1.5-T T2-weighted spin-echo imaging (64%). Combining the information from all MR pulse sequences yielded a cumulative sensitivity of 68%. Combining the information from two modalities yielded sensitivity of 96% for CTAP plus MR imaging, 85% for CTAP plus delayed CT, and 77% for delayed CT plus MR imaging. The authors conclude that when it is vital to know the precise number, size, and location of focal hepatic lesions before tumor resection, CTAP has the highest sensitivity, but MR imaging is an important adjuvant.

Adult↗

PubMed1989

Contrast-enhanced CT of the liver and spleen: comparison of ionic and nonionic contrast agents.

We conducted a randomized, blinded, prospective study evaluating hepatic parenchymal density changes during dynamic bolus CT (180 ml of contrast material given IV) and delayed CT (5 hr after 60 g of iodine) in order to compare the enhancement characteristics of an ionic contrast agent (iothalamate-60) and two nonionic agents (iohexol-300 and iopamidol-300). A total of 75 patients with known or suspected cancer were studied (25 patients per contrast agent). After a baseline unenhanced CT scan was obtained, dynamic bolus and delayed CT scans were obtained for all patients with one of the three contrast agents. The density of the liver and spleen was measured in Hounsfield units (H) for unenhanced CT, dynamic bolus CT, and delayed CT. The average percentage of enhancement was calculated as follows: postcontrast density minus precontrast density was divided by precontrast density and then multiplied by 100. For dynamic bolus CT, the average percentage of enhancement of the liver was 105% when iohexol-300 was used, 98% when iopamidol-300 was used, and 83% when iothalamate-60 was used. No significant difference was seen between the postcontrast enhancement of the three contrast agents on dynamic bolus CT scans (p greater than .05). For delayed CT, the average percentage of enhancement of the liver was 34% when iothalamate-60 was used, 28% when iopamidol-300 was used, and 16% when iohexol-300 was used. Both iothalamate-60 and iopamidol-300 showed superior enhancement on delayed CT, compared with iohexol-300 (p = .0001). We conclude that for dynamic bolus CT, all three contrast agents are similar, with no statistically significant differences in postcontrast enhancement of the liver. For delayed CT, however, hepatic enhancement with iothalamate-60 and iopamidol-300 is statistically superior to that with iohexol-300.

Adult↗

PubMed1989

Portal venous gas after hepatic transplantation: sonographic detection and clinical significance.

In seven (18%) of 39 liver transplantation patients, serial Doppler sonographic examinations performed in the first 2 weeks after the transplantation showed transient, highly echogenic nonshadowing particles moving within the portal vein, believed to be portal venous air. This finding was associated with sepsis in one patient, a positive stool culture for Clostridium difficile in another, and postoperative ileus in a third patient. A fourth patient had primary graft failure and required a second transplant. No potential cause was found in the other three patients. None of the patients had bowel infarction or necrosis. The finding was not associated with transplant rejection or graft infection. We conclude that the sonographic finding of portal venous gas is common in the first 2 weeks after hepatic transplantation and may not have grave prognostic significance.

Adolescent↗

PubMed1989

Magnetic resonance imaging of the kidneys and adrenal glands.

A simple renal cyst will have low signal intensity on T1-weighted SE images with short TE and short TR because of the long T1 values of the cyst fluid. With increasing TE and TR, cysts demonstrate increased signal intensity due to the long T2 values of the cyst fluid. On T1-weighted images a complicated cyst will have higher signal intensity than a simple cyst; it may not be possible to differentiate these complicated cysts from solid masses. MRI seems to be useful in identifying simple cyst fluid and, therefore, has potential in characterization of cystic lesions considered complex by CT or ultrasound. Unfortunately, imaging techniques have not yet been optimized, diagnostic criteria are somewhat vague, and accuracy has not been established in a representative patient population. Solid masses often can be identified and differentiated from simple, uncomplicated cysts on MR images. The inability to differentiate among various types of solid tumors or to separate these from complicated cysts or inflammatory masses remains a limitation. Most lesions are more readily seen on contrast-enhanced CT than on MR images and therefore the role of MRI in the detection and diagnosis of renal cell carcinoma remains limited. Although the high detection rate of renal cell carcinoma is encouraging, CT is still more sensitive than MR in demonstrating solid lesions less than 3 cm in diameter. MRI cannot be used as a screening modality for renal tumors. MRI seems quite helpful in the staging of renal cell carcinoma. Macroscopic extension into the perinephric fat, tumor extension into the renal vein and the inferior vena cava, and macroscopic metastases to other organs are readily seen. Furthermore, differentiation between enlarged nodes and vessels is possible with MRI. Some authors recommended the use of MRI to stage renal cell carcinoma in patients with known contraindication to contrast, prior suboptimal bolus contrast enhanced CT scan, and equivocal CT findings. MRI can replace the inferior vena cavagram in the staging work-up and MR may be superior to CT for planning the surgical approach in Stage IIIA lesions by determining the upper extent of tumor thrombus within the inferior vena cava or the right atrium.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Gland Diseases↗

PubMed1988

Focal hepatic lesions: detection by dynamic and delayed computed tomography versus short TE/TR spin echo and fast field echo magnetic resonance imaging.

Eighteen patients with focal hepatic lesions were evaluated with two computed tomographic (CT) techniques including dynamic sequential bolus contrast CT and delayed contrast CT, and 3 magnetic resonance (MR) techniques including a spin echo pulse sequence with TE/TR of 21/310 msec and 2 fast field echo sequences using a TE/TR of 15/300 msec and 80 degrees flip angle (T1-weighted) and TE/TR of 15/500 msec and 10-20 degrees flip angle (T2-weighted). We concluded that CT, using delayed contrast and dynamic sequential bolus contrast techniques, was consistently superior to the 3 MR pulse sequences used on our imagers in terms of number of lesions detected, lesion-to-liver contrast, and quality of scan.

Adult↗

PubMed1988

Incidence of cholelithiasis among patients with cirrhosis and portal hypertension.

One hundred and two patients with cirrhosis and portal hypertension were evaluated sonographically to determine the presence or absence of cholelithiasis. The gallbladder was visualized in 80 of 102 patients. Cholelithiasis was present in 43 of 80 cases (54%). All 22 patients in whom the gallbladder was not seen sonographically had had a previous cholecystectomy. Five of them were operated on prior to development of cirrhosis with portal hypertension, but 14 of the remaining 17 (82%) had evidence of cholelithiasis at pathology. Hence, there was an overall incidence of cholelithiasis of 59% among out 97 patients. This study as well as previous autopsy data indicate an increased incidence of cholelithiasis in patients with cirrhosis, irrespective of etiology or sex. The incidence of cholelithiasis in this study, however, was approximately twice that previously reported in cirrhotics at autopsy. Furthermore, patients with portosystemic shunts showed a significantly higher incidence of cholelithiasis compared to patients who were not shunted (68% vs 49%, p = 0.028). We believe the severity and duration of cirrhosis in our patient population, all with documented portal hypertension, may be the cause of this increased incidence.

Adolescent↗

PubMed1988

Delayed magnetic resonance hepatic imaging with gadolinium-DTPA.

Magnetic resonance imaging of the liver was performed on 11 rabbits (3-5 kg) before and at 4, 5 and 6 hours after the intravenous administration of 0.3 mM/kg Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) to determine if hepatocytes exhibit delayed excretion of Gd-DTPA, similar to the delayed hepatic excretion of iodinated contrast agents. Imaging was performed at 0.5 Tesla in the axial plane using a spin echo sequence of TR/TE, 250/20 milliseconds. Precontrast and postcontrast intensity changes for liver and muscle were standardized and compared over time. The average percent of postcontrast enhancement for liver and muscle, respectively was: 30.6 +/- 9.5% and 17.3 +/- 17.0% immediately postcontrast; 9.7 +/- 13.6% and 1.6 +/- 13.8% at 4 hours; 9.6 +/- 7.8% and 4.3 +/- 13.2% at 5 hours; and 11.0 +/- 7.8% and 4.1 +/- 11.7% at 6 hours. We conclude that there is not significant hepatocyte excretion of Gd-DTPA at 4 to 6 hours postcontrast injection in rabbits and that this may not be an advantageous paramagnetic contrast strategy for focal hepatic lesion detection.

Animals↗

PubMed1988

Adrenal masses: characterization with T1-weighted MR imaging.

The ability of a T1-weighted spin-echo magnetic resonance (MR) sequence to allow differentiation of benign from malignant adrenal masses at 0.5 T was investigated in 28 patients with 35 adrenal masses. All nine lesions with an adrenal mass-liver signal intensity ratio of 0.71 or less were metastases, and all 15 with a ratio of 0.78 or more were adenomas. Eleven masses (31%)--including six adenomas, three metastases, a pheochromocytoma, and a neuroblastoma--had ratios between these values. Nine of ten masses with adrenal mass-fat intensity ratios of 0.35 or less were metastases, and all 12 with ratios of 0.42 or more were benign. Eleven masses (31%), four malignant and one benign, had ratios between these values. The ratios for two masses could not be calculated due to lack of fat. The specificity of T1-weighted MR imaging in differentiating benign from malignant adrenal masses appears similar to that reported for T2-weighted imaging. However, significant overlap occurred, as has also been reported for T2-weighted imaging. While both imaging sequences may help distinguish benign from malignant adrenal masses in some cases, biopsy is still necessary when an accurate histologic diagnosis is essential.

Adenoma↗

PubMed1988

Liver and abdominal screening in patients with cancer: CT versus MR imaging.

A prospective multiinstitutional study was performed to compare the ability of dynamic sequential contrast material-enhanced computed tomography (CT), delayed contrast material-enhanced CT, and two T1-weighted magnetic resonance (MR) sequences (spin echo and inversion recovery) to demonstrate metastatic disease in the liver and abdomen in patients with cancer. All four techniques had comparable rates of hepatic lesion detection when compared individually or when the combined CT techniques were compared with the combined MR techniques. The sensitivity to hepatic disease was 96% (27 of 28 patients) for the combined MR techniques versus 93% (26 of 28 patients) for the combined CT techniques. However, CT was statistically superior in the detection of extrahepatic disease, with significant extrahepatic findings demonstrated by CT in only 12 of 59 patients (20%). For this reason, the authors continue to recommend CT in the initial screening of patients with cancer for upper abdominal metastatic disease.

Abdominal Neoplasms↗

PubMed1987

Renal allograft rejection: evaluation by Doppler US and MR imaging.

A prospective study compared the efficacy of Doppler ultrasonography (US) and magnetic resonance (MR) imaging in evaluating 38 renal allografts, with specific attention to transplant rejection. Forty-three Doppler US and 42 MR examinations were performed and interpreted. Histologic correlation was obtained from 22 biopsy or nephrectomy specimens. Clinical correlation or a response to instituted therapy was used as confirmation in the remaining allografts. Accuracy in identifying cyclosporine toxicity or acute tubular necrosis could not be evaluated because there were few such cases, with concomitant rejection in most. The ability to predict and identify presence or absence of rejection was not affected by different serum creatinine values. Doppler US was significantly superior to MR imaging in identifying allograft rejection, demonstrating a higher sensitivity (95% vs. 70%), specificity (95% vs. 73%), and accuracy (95% vs. 71%). Because of its low cost and accessibility, Doppler US should become the primary modality for renal transplant screening.

Adult↗

PubMed1987

Comparison of pulsed Doppler sonography and angiography in patients with portal hypertension.

Pulsed Doppler sonography and liver panangiography were performed in 43 patients with cirrhosis. Fourteen patients were evaluated preoperatively, and 28 patients were evaluated after a variceal decompressive shunt. One patient was studied before and after undergoing a shunt. The direction of portal blood flow by Doppler sonography was compared with both the grading pattern and direction of flow by angiography. When portal blood flow was determined to be antegrade by Doppler sonography, angiography showed antegrade flow in 84% (grade I, II, or III portal venous pattern). Six percent had retrograde flow (grade IV), and 10% had portal vein thrombosis. When the portal blood flow was determined to be retrograde by Doppler sonography, angiography showed retrograde flow (grade IV portal venous pattern) in 80% and antegrade flow (grade I, II, or III) in 20%. When an inadequate Doppler tracing was obtained from the portal vein, angiography showed either grade I, II, or III in 38%; grade IV in 50%, and portal vein thrombosis in 13%. There was poor correlation between the calculated mean flow rates, as determined by Doppler sonography, and the angiographic grade. We conclude that pulsed Doppler sonography is accurate in determining the direction of portal flow when an adequate tracing is obtained (36 of 44 studies). When an inadequate tracing is obtained, retrograde portal flow or portal vein thrombosis is likely.

Angiography↗

PubMed1987

Mesoatrial shunt for the treatment of Budd-Chiari syndrome: radiologic evaluation in eight patients.

The construction of a mesoatrial shunt for portal decompression is one of the surgical procedures used for the treatment of Budd-Chiari syndrome. The results of the imaging procedures performed in eight patients treated in this fashion were retrospectively analyzed. All of the patients had angiography; seven had MR imaging and two had Doppler sonography. The demonstration of shunt patency, stenosis, or occlusion by MR and Doppler sonography was confirmed by angiography in all cases. We conclude that MR imaging may serve as an accurate screening method to assess shunt patency and to determine which patients require angiography to obtain hemodynamic data. Doppler sonography may also be a useful screening method, but additional data must be obtained to assess its role in evaluation of shunt patency.

Adult↗

PubMedDate not supplied

"Keyhole" method for accelerating imaging of contrast agent uptake.

Magnetic resonance (MR) imaging methods with good spatial and contrast resolution are often too slow to follow the uptake of contrast agents with the desired temporal resolution. Imaging can be accelerated by skipping the acquisition of data normally taken with strong phase-encoding gradients, restricting acquisition to weak-gradient data only. If the usual procedure of substituting zeroes for the missing data is followed, blurring results. Substituting instead reference data taken before or well after contrast agent injection reduces this problem. Volunteer and patient images obtained by using such reference data show that imaging can be usefully accelerated severalfold. Cortical and medullary regions of interest and whole kidney regions were studied, and both gradient- and spin-echo images are shown. The method is believed to be compatible with other acceleration methods such as half-Fourier reconstruction and reading of more than one line of k space per excitation.

Contrast Media↗

PubMedDate not supplied

Are hepatic and muscle T2 values different at 0.5 and 1.5 Tesla?

In an effort to determine whether T2 values of liver and muscle change with increasing field strength, 144 abdominal MR examinations were retrospectively evaluated. These patients were evaluated with a dual echo T2-weighted spin-echo sequence. Eighty-two of the examinations were performed at 0.5 Tesla and 72 at 1.5 Tesla (T). Eleven of the patients were evaluated with both MR systems with the same sequences. T2 values were also obtained from a Fe NH4(SO4)2 12H2O phantom. The T2 values of liver decreased from 57.8 +/- 11.3 at 0.5 T to 43.7 +/- 8.3 at 1.5 T. The T2 values of muscle decreased from 44.2 +/- 9 at 0.5 T to 35.4 +/- 7.2 at 1.5 T. Patients who were examined on both systems also demonstrated a decrease in both liver and muscle T2 values. For concentrations in the range of hepatic T2's, the phantom demonstrated a decrease in T2 values from 0.5 to 1.5 T ranging from 20.3 to 23.4%. All the T2 changes were statistically significant (p less than .05). The findings suggest that T2 values may depend on field strength, or may vary due to other hardware-related differences.

Evaluation Studies as Topic↗

PubMedDate not supplied

CT angiography and CT arterial portography in evaluation of hepatic adenomas.

OBJECTIVE: Our goal was to evaluate the contribution of CT arterial portography (CTAP) and CT angiography to accurate determination of disease extent in patients with known hepatic adenomas. MATERIALS AND METHODS: Imaging results were reviewed in three women with known hepatic adenomas, all of whom had percutaneous biopsy to confirm the diagnosis. Results of CTAP studies in all patients as well as results of CT arteriography in one patient were compared with routine dynamic CT studies in all three and with MRI studies in two. RESULTS: The CTAP and CT arteriography demonstrated multiple additional lesions in all patients as compared with routine dynamic CT and MRI studies. In one of the patients who was found to have hepatic adenomatosis, the degree of tumor involvement changed the operative procedure from partial hepatectomy to liver transplantation. CONCLUSION: In patients with known hepatic adenomas who require surgery, CTAP provides more accurate preoperative staging of extent of liver replacement with tumor.

Adenoma↗