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R K Zeman

Publications and source records attributed to R K Zeman.

142 records · Page 8Linked to original sources
PubMed1977

The value of bowel preparation in Ga-67 citrate scanning: concise communication.

In order to assess the value of bowel preparation in Ga-67 citrate scanning, we retrospectively analyzed 156 randomly selected 72-hr Ga-67 scans and compared the extent of bowel activity in two groups of patients: those receiving a vigorous 3-day bowel preparation and those receiving no preparation. The populations were studied with regard to age, sex, and bowel preparation. A three-way analysis of variance (prep X sex X age) revealed no influence of these parameters on the degree of colonic gallium activity. We conclude that bowel preparation as used at our institution did not seem to reduce colonic gallium content significantly (p greater than 0.10).

Abscess↗
PubMedDate not supplied

Imaging of the liver: a survey update of prevailing techniques for conventional CT scanning.

BACKGROUND: A survey of the Society of Computed Body Tomography/Magnetic Resonance (SCBT/MR) was performed to assess current techniques in liver CT scanning. METHODS: The study was designed as an update to a study performed in 1987. The survey was distributed to 67 members of the SCBT/MR at 35 institutions. RESULTS: Twenty-six institutions responded. As in 1987, none relied solely on noncontrast scans. In 1987, only 54% (12/22) of institutions performed contrast-enhanced scans as their primary technique compared with 73% (19/26) in 1993. Ionic contrast was used exclusively in the earlier study, whereas in the present study 58% used nonionic contrast in the majority of cases and 38% used nonionic contrast routinely. In 1987, 41% performed scans with a power injector compared with 85% in the present study. Enhanced scans were performed during the contrast bolus in 36% of institutions in 1987 compared with 76% in this study. No institution relied on noncontrast scans alone. In the previous study the delay between injection and scanning was variable (0-60 s), whereas in the present study 83% specified a delay of 21-45 s. CONCLUSION: Significant refinements in CT technique, wider use of power injectors, utilization of nonionic contrast, and a more critical approach to optimize liver imaging have created a significant impact on the practice of liver CT.

Angiography↗
PubMedDate not supplied

Cluster scanning in body CT.

Rapid, dynamic computed tomography (CT) is essential in scanning the body in order to maintain adequate contrast enhancement during the entire examination. In the case of the liver, this is most critical in order to complete scanning prior to the equilibrium phase when lesions are less conspicuous or may be missed entirely. This technical note describes the application of "cluster scanning" to conventional scanning in order to optimize body CT by decreasing the total exam time.

Humans↗
PubMedDate not supplied

PACS clinical experience at Georgetown University.

Georgetown University Hospital has been operating an image management and communications system (IMACS or PACS) for three-and-a-half years. This work was initially funded under the Army Medical Research and Development Command Digital Imaging Network Systems (DINS) project. The system was taken from a research system supporting only radiology tasks to one extended to clinical use, and has been used in clinical work for two-and-a-half years. This paper will summarize our PACS clinical experience and will describe the operational features implemented and those still necessary.

Computer Systems↗
PubMedDate not supplied

Computed tomographic cholangiography in a canine model of biliary obstruction.

The CT scanner was used to generate the time-density relationship for hepatic parenchyma following Iodipamide (Cholografin, E.R. Squibb Co., New York, N.Y.) infusion. The curves which resulted from the normal, acutely obstructed, and chronically obstructed biliary system are shown. The peak enhancement of parenchyma is seen to be blunted in acute obstruction prior to anatomic evidence of dilated ducts. This finding may be of value in the early diagnosis of obstructive jaundice.

Absorptiometry, Photon↗
PubMedDate not supplied

Computed tomography of acute renal failure secondary to rhabdomyolysis.

Two patients with rhabdomyolysis and renal failure were imaged with CT. The presence of a striate nephrogram, nephromegaly, and perinephric fluid has not previously been described on CT. Although nonspecific, these findings suggest the diagnosis of acute tubular blockade, and, once identified, administration of additional urographic contrast medium should be avoided.

Acute Kidney Injury↗
PubMedDate not supplied

Pancreatic pseudotumor in pancreas divisum: CT characteristics.

We report a case in which a focally spared area of pancreatic tissue in a gland otherwise replaced by fat created a "pseudomass" mimicking neoplasm on sonography and CT. The "pseudomass" appearance was related to the anomalous ductal anatomy in pancreas divisum. The spared area of pancreas creating a "pseudomass" was drained by the dorsal duct and the remainder of the pancreas that had undergone relative fatty replacement was drained by the ventral duct.

Adult↗
PubMedDate not supplied

Dynamic CT vs 0.5 T MR imaging in the detection of surgically proven hepatic metastases.

Seventeen patients with 52 surgically proven hepatic metastases were studied preoperatively with dynamic CT and 0.5 T magnetic resonance (MR). Dynamic CT detected 38 metastases (73%), and the combination of short echo time (T1-weighted) and T2-weighted pulse sequences detected 46 lesions (88%). Magnetic resonance was also superior at assessing potential resectability. This study suggests that MR excels in detecting and anatomically localizing individual hepatic metastases.

Humans↗
PubMedDate not supplied

The optimal temporal window for CT of the liver using a time-density analysis: implications for helical (spiral) CT.

OBJECTIVE: Scanning protocols for conventional CT of the liver have been proposed. Current availability of helical CT with a four- to sixfold decrease in scan time requires significant adjustments in these protocols. The present study assesses the implications of time-density curves on the performance of helical liver CT. MATERIALS AND METHODS: Twenty patients without liver lesions were studied for time-density analysis of the aorta, inferior vena cava (ICV), portal vein, and liver. Scans were performed at the level of the portal vein at baseline and every 15 s for 3 min following uniphasic administration of 150 ml (300 mg I/ml) nonionic contrast agent. Regions of interest were used to measure three areas in each anatomic structure over time. Median and mean peak enhancement times were calculated for all 20 patients. Cubic spline interpretation was employed to determine the point of equilibrium. RESULTS: Results demonstrated the following average maximum enhancement values and times for peak enhancement: aorta: 227 HU (75 s); liver: 123 HU (105 s); portal vein: 187 HU (90 s); IVC: 142 HU (90 s). Hepatic enhancement achieved 67 HU over baseline. Peak portal enhancement occurred 15 s prior to liver enhancement (p = 0.001). Aortic and hepatic curves became parallel (onset of equilibrium) at a median time of 120 s. CONCLUSION: Helical scanning requires a longer delay (70-80 s) than used for conventional CT. Upon application of these principles, scan initiation occurs higher on the liver enhancement curve, improving liver enhancement without impinging on equilibrium.

Aorta, Abdominal↗
PubMedDate not supplied

A phantom study: evaluation of renal artery stenosis using helical CT and 3D reconstructions.

PURPOSE: We studied which set of CT parameters and modeling parameters yielded accurate measurements of three graded artificial renal artery stenoses. METHOD: An acrylic phantom resembling the abdominal aorta and renal arteries was constructed. Stenotic segments had diameters of 1.8, 3.2, and 4.8 mm; nonstenotic segment diameter was 6.3 mm. Helical scans were done using 1 and 3 mm collimation at pitches of 1, 1.5, and 2. 3D renderings were produced and measured. Multifactorial and regression tree analysis were used to determine the accuracy of the 3D renderings. Mean squared error (MSE) was used to compare true diameter with measured diameter. RESULTS: Collimation of 1 mm produced an MSE of 0.55 versus an MSE of 1.35 for 3 mm collimation. Stenosis grade was the next most important parameter in the 1 mm subgroup and viewing direction in the 3 mm collimation subgroup. In the 1 mm subgroup, high and mid grade stenoses had an MSE of 0.52 versus low grade stenosis that had an MSE of 0.61. Pitch was a fourth-order effect. CONCLUSION: Collimation of 1 mm combined with a pitch ratio as high as 2:1 is superior to 3 mm collimation. Shaded surface modeling was the single best choice for rendering 3D data. Stenosis grade interacted strongly with user-controllable parameters.

Analysis of Variance↗