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J Gaa

Publications and source records attributed to J Gaa.

At least 73 records · Page 4Linked to original sources
PubMed1995

Breath-hold 3D STAR MR angiography of the renal arteries using segmented echo planar imaging.

Three-dimensional (3D), cardiac triggered renal MR angiograms were acquired with excellent background suppression within a single breath-hold of 18 to 30 s using signal targeting with alternating radiofrequency (STAR), a subtraction time-of-flight MR angiography technique, and a 3D scheme combining echo planar imaging (EPI) readouts and k-space segmentation. The 3D STAR sequence was evaluated on 17 healthy individuals, 3 potential renal donors, and 2 patients with suspected renovascular hypertension. An inversion tag through the aorta was applied to produce the vascular contrast. After a suitable inflow time, 16 to 64 sections were encoded. An additional presaturation pulse applied over the imaging volume prior to tagging permitted improved background suppression by reducing signal variations from involuntary motion and changes in the cardiac period during breath-holding. Intrarenal branches were observed consistently in all healthy individuals. Longer inflow times provided better depiction of the intrarenal vessels while shorter delays delineated the proximal renal branches with better signal-to-noise ratio. Breath-hold and diastolic data collection reduced both blurring and flow related dephasing. Our results demonstrate excellent visualization of the renal arteries to the level of intrarenal branch vessels using the proposed technique.

Adult↗
PubMed1995

Spiral CT angiography of abdominal aortic aneurysms.

Spiral computed tomographic (CT) angiography involves a timed intravenous injection of contrast material, rapid data acquisition, reconstruction at narrow intervals, image editing, and maximum intensity projection image processing. Spiral CT angiography of the abdominal aorta was performed in 28 patients for preoperative aneurysm assessment. The results were unsatisfactory in only two patients; 54 main and 12 accessory renal arteries and 26 aortic aneurysms were seen. In 17 of the 26 patients with aneurysms, there was surgical confirmation of the CT angiographic findings regarding size, suprarenal extension, and distal extent of the aneurysms, with no additional renal arteries detected. With this technique, the relationship of an aneurysm to renal, superior mesenteric, and inferior mesenteric arteries can be assessed. CT angiography also depicts the proximal extent of an aneurysm, which is the single most crucial piece of preoperative information; an associated renal artery stenosis or occlusion; or an accessory renal artery. CT angiography can be performed as an outpatient procedure before vascular surgery with fewer risks, with lower radiation dose, and at one-third the cost of conventional angiography.

Aged↗
PubMed1995

Brain lesions in patients with multiple sclerosis: detection with echo-planar imaging.

PURPOSE: To evaluate the detection of brain lesions with echo-planar imaging relative to conventional spin-echo (SE) imaging. MATERIALS AND METHODS: In 17 patients (three men, 14 women; mean age, 31 years) with multiple sclerosis, the following were compared: single-shot proton-density- and T2-weighted and thin-section T2-weighted echo-planar, proton-density- and T2-weighted multishot echo-planar, and conventional SE sequences. Quantitative and qualitative criteria as well as lesion detectability were evaluated. The proton-density-weighted SE sequence was used as the standard of reference. RESULTS: Multishot sequences were superior to single-shot sequences in image quality and lesion detectability. With the multishot proton-density-weighted sequence, 53 of 54 large lesions and 23 of 30 small lesions were detected; with the single-shot proton-density-weighted sequence, 38 of 54 large lesions and five of 30 small lesions were detected. CONCLUSION: With multishot echo-planar sequences, detectability of large lesions is similar to that with conventional SE imaging. Susceptibility artifact is diminished in comparison to single-shot echo-planar sequences.

Adult↗
PubMed1994

Signal targeting with alternating radiofrequency (STAR) sequences: application to MR angiography.

We describe a time of flight subtraction method for cine MR angiography that provides nearly perfect suppression of background signal intensity with excellent flow contrast. The method consists of a preparation phase, during which the longitudinal magnetization of the target tissue is inverted on alternate acquisitions and the background tissue is presaturated, followed by a readout phase using a cine segmented turboFLASH sequence with a shared echo modification to improve temporal resolution. With appropriate alternation of the phases of the radiofrequency excitation pulses, there is cancellation of the background signal intensity but flow signal is optimized. By using a thick section (up to 25 mm), substantial portions of the vascular territory are encompassed in a single plane. This permits rapid, dynamic assessment of flow patterns in areas such as the circle of Willis, carotid bifurcation, or renal arteries. Applications of the method for bright and dark blood cine MR angiography are demonstrated.

Aorta, Abdominal↗
PubMed1994

In vivo measurement of water diffusion in the human heart.

Existing magnetic resonance methods for diffusion imaging, including echo planar, are ineffective in the beating heart due to motion-induced signal attenuation. To overcome this problem, we used a diffusion-weighted stimulated echo-echo planar magnetic resonance imaging sequence. The two lobes of the diffusion-sensitizing gradient were synchronized to the same point in successive cardiac cycles in order to fix the cardiac position and avoid bulk motion effects. The apparent diffusion coefficients (ADCs) of the interventricular septum in 12 healthy subjects for diffusion gradients along the x-, y-, and z-directions were 1.40 +/- 0.27, 1.48 +/- 0.35, and 1.78 +/- 0.27 x 10(-3) mm2/s. The ADCs of the interventricular septum in a second group of 15 healthy subjects for diffusion gradients along the short axis, horizontal and vertical long axes were 0.92 +/- 0.15, 1.50 +/- 0.15, and 1.10 +/- 0.24 x 10(-3) mm2/s. Because the ADCs were less than the measured values for skeletal muscle and their standard deviations were low, it seems unlikely that bulk motion effects made the dominant contribution to the measured myocardial ADC for the interventricular septum, although motion and/or susceptibility artifacts frequently degraded measurements in the free wall of the left ventricle. Additional evidence that ADC was not predominantly determined by wall motion was obtained in a third group of patients with various cardiac abnormalities, in whom there was only a weak correlation between ADC and ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Oxygenation of mammary tumors as evaluated by ultrasound-guided computerized-pO2-histography.

The average pO2 in breast carcinomas in situ is significantly lower than that in the normal breast tissue. The mean pO2 value for benign breast tumors is significantly higher than that of the breast cancers but lies significantly lower than the corresponding normal breast. No significant differences are found in the mean pO2 values when comparing cancers of different stages and histology. A decrease in the mean pO2 value is measured from the periphery to the center of the breast tumors investigated. The average pO2 values for pre- and postmenopausal patients differ significantly. The described method provides a reliable assessment of tissue pO2 in situ with a minimum of discomfort. Due to extensive inter tumor heterogeneity, prediction of pO2 values for tumors of same stage and same histology is not possible, so that measurement of individual tumor is mandatory for determining therapy response.

Adenofibroma↗
PubMed1994

Case report: haemorrhagic hepatic adenoma--MR features.

Hepatic adenomas are incidentally detected with increasing frequency after imaging the abdomen for unrelated pathology. We report the CT and MR features of an asymptomatic hepatic adenoma with evidence of subclinical intratumoral haemorrhage.

Adenoma↗
PubMed1994

Gallstones in critically ill patients with acute calculous cholecystitis treated by percutaneous cholecystostomy: nonsurgical therapeutic options.

OBJECTIVE: Patients with acute calculous cholecystitis require removal of gallstones (generally cholecystectomy), as acute cholecystitis is likely to recur if gallstones are left in situ. The purpose of this study was to assess the role of nonsurgical techniques for treating gallstones in critically ill patients with acute calculous cholecystitis managed by percutaneous cholecystostomy. MATERIALS AND METHODS: Twenty-six critically ill patients with complex medical and surgical problems who were in intensive care units underwent emergent percutaneous cholecystostomy for acute calculous cholecystitis. Seven of the 26 patients subsequently died of multiple organ failure. Curative gallstone therapies were tried in the surviving 19 patients, seven of whom underwent elective surgical cholecystectomy. Nonsurgical management was attempted in 12 of 19 patients, including six with terminal disease who were treated with long-term gallbladder drainage, three who were treated with methyl tert-butyl ether for stone dissolution, two who had percutaneous cholecystolithotomy, and one who had a gallbladder stone that had passed into the common bile duct and was retrieved endoscopically. RESULTS: Long-term gallbladder drainage was successful in all six patients with terminal disease in whom it was attempted; they experienced no further episodes of cholecystitis. In four of the other six patients treated with nonsurgical therapies (percutaneous cholecystolithotomy, stone dissolution with methyl tert-butyl ether, and endoscopic removal), gallstones were successfully removed and no further therapy was required. Percutaneous therapies failed in two patients, who then had cholecystectomy. CONCLUSION: Nonsurgical gallstone therapies should be attempted in high-risk patients with acute calculous cholecystitis. Some patients may benefit from long-term catheter drainage of the gallbladder.

Acute Disease↗
PubMed1993

[Computed tomography in a case of pseudomembranous colitis].

Pseudomembranous colitis (PMC) is an infectious colitis usually occurring as a complication of antibiotic therapy. The computed tomography (CT) findings of 10 patients with PMC are reviewed. All patients demonstrated an abnormal large bowel wall with an average thickness of 13 mm (range 7-31 mm). Additional, but less frequent findings included mesenteric inflammation, ascites, pleural effusions, and dilatation of the large or small bowel. Pancolonic involvement was seen in 7 cases, while three patients had focal colitis. Although the CT appearance of PMC is not specific, the diagnosis may be suggested in the proper clinical setting.

Adult↗
PubMed1993

Clinical assessment of an interventional CT table.

A computed tomographic (CT) system was modified to enable fluoroscopy during interventional CT procedures. Five patients with infradiaphragmatic abscesses underwent drainage by means of fluoroscopic CT guidance with a mean procedural time of 12 minutes. The addition of fluoroscopy facilitates avoidance of the diaphragm and injection of contrast material, makes catheter exchange easy, and minimizes procedural time.

Abdomen↗
PubMed1991

[Outpatient transbrachial arterial DSA using a 4F catheter for the clarification of extracranial vascular processes].

Experience with intravenous digital subtraction angiography (DSA) has proven disappointing in the outpatient evaluation of cerebrovascular disease. Variations in cardiac output, vessel superimposition, patient motion and poor vascular opacification frequently combine to produce nondiagnostic examinations. To assess the safety of nonselective intra-arterial DSA performed from a brachial artery approach, the complications of 103 examinations, most of which (85%) were performed on outpatients, were prospectively studied. The injection of contrast material into the aorta was made through a 4F multiple side-hole pigtail catheter, inserted percutaneously from the brachial artery. Images were good or excellent in nearly all cases. No permanent neurovascular complications or local artery complications such as thrombosis requiring surgery were encountered and only a few minor complications occurred. We believe that transbrachial intraarterial DSA is a safe, simple and well-tolerated out-patient procedure that can yield reliable, definitive, and complete cerebrovascular studies in nearly all patients referred for the examination.

Adult↗