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J Gaa

Publications and source records attributed to J Gaa.

At least 55 records · Page 3Linked to original sources
PubMed1998

[Ultrafast contrast-enhanced 3D MR angiography in the preoperative diagnosis of liver tumors].

PURPOSE: To evaluate the accuracy of 3D-MRA in preoperative staging in correlation to intraoperative and histological results. METHODS: In 30 patients with focal liver lesions axial and coronal MR sequences (T1w-Flash 2D, T2w-TSE unenhanced. T1w-Flash 2D, TRUE FISP contrast-enhanced) as well as coronal breath-hold MRA were performed. The technical parameters of the MRA were as follows; TR/TE 5/2 ms, flip angle 40 degrees, 32-40 partitions with an effective slice thickness of 2-3 mm, acquisition time 26 s, matrix 128 x 256, FOV 320 x 320 to 400 x 400. RESULTS: In 23/30 patients liver resection was performed. Correct prediction of segmental localization was achieved in preoperative MRI of 22 patients (98%). The presumed histology was correct in 20/23 cases (87%). The evaluation of the hepatic vascular structures was correctly predicted in all cases. By use of multiplanar reconstructions and single image view of the 3D data base of MRA, additional information could be obtained in 13 patients. CONCLUSIONS: Breath-hold 3D-MRA gives certain information on localization and relation of vascular structures to focal hepatic lesions. In presentation of portal venous structures MRA is superior to conventional angiography.

Adult↗
PubMed1998

[Stereo display of MR angiograms].

PURPOSE: To provide methods for stereoscopic visual demonstration from 3D reconstructed MR angiographic images. METHODS: Stereoscopic viewing can be obtained with pairs of images that are displayed at angles of 15 degrees. Optical devices as stereoscopic binoculars or minor stereoscopes facilitate stereoscopic viewing. The possibility of stereoscopic projections for a larger auditorium is mentioned. RESULTS: Using three clinical examples the advantages of stereoscopic display of MR angiograms are demonstrated. CONCLUSIONS: MR angiography allows stereoscopic viewing with simple methods, like CT- and conventional rotation angiography. This principle, which has been known for 100 years, may thus acquire a new significance.

Adult↗
PubMed1998

[Magnetic resonance tomography in diagnosis of vascular infiltration in malignant pancreas tumors].

This study was undertaken to evaluate the accuracy of magnetic resonance angiography (MRA) in assessing venous or arterial infiltration in pancreatic cancer. In 90 patients MRA showed a sensitivity of 81.1%, a specificity of 90.2% and an accuracy of 85.9% in predicting venous infiltration and a sensitivity of 81.8%, a specificity of 90.7% and an accuracy of 88.1% in predicting arterial infiltration. From these data we conclude that MRA is an accurate method for detecting vascular infiltration in pancreatic cancer.

Arteries↗
PubMed1997

Ultrafast magnetic resonance imaging improves the staging of pancreatic tumors.

OBJECTIVE: This prospective study was undertaken to evaluate the accuracy of a noninvasive "all-in-one" staging method in predicting surgical resectability in patients with pancreatic or periampullary tumors. SUMMARY BACKGROUND DATA: Despite progress in imaging techniques, accurate staging and correct prediction of resectability remains one of the chief problems in the management of pancreatic tumors. Staging algorithms designed to separate operable from inoperable patients to save the latter an unnecessary laparotomy are becoming increasingly complex, expensive, time-consuming, invasive, and not without risks for the patient. METHODS: Between August 1996 and February 1997, 58 consecutive patients referred for operation of a pancreatic or periampullary tumor were examined clinically and by 5 staging methods: 1) percutaneous ultrasonography (US); 2) ultrafast magnetic resonance imaging (UMRI); 3) dual-phase helical computed tomography (CT); 4) selective visceral angiography; and 5) endoscopic cholangiopancreatography (ERCP). The assessment of resectability by each procedure was verified by surgical exploration and histologic examination. RESULTS: The study comprised 40 male and 18 female patients with a median age of 63 years. Thirty-five lesions were located in the pancreatic head (60%), 11 in the body (19%), and 1 in the tail of the gland (2%); there were 9 tumors of the ampulla (16%) and 2 of the distal common duct (3%). All five staging methods were completed in 36 patients. For reasons ranging from metallic implants to contrast medium allergy or because investigations already had been performed elsewhere, US was completed in 57 (98%), UMRI in 54 (93%), CT in 49 (84%), angiography in 48 (83%), and ERCP in 49 (84%) of these 58 patients. Signs of unresectability found were vascular involvement in 22 (38%), extrapancreatic tumor spread in 16 (26%), liver metastases in 10 (17%), lymph node involvement in 6 (10%), and peritoneal nodules in only 2 patients (3%). These findings were collated with those of surgical exploration in 47 patients (81 %) and percutaneous biopsy in 5 (9%); such invasive verification was deemed unnecessary and therefore unethical in 6 clearly inoperable patients (10%). In assessing the four main signs of unresectability (extrapancreatic tumor spread, liver metastases, lymph node involvement, and vascular invasion), the overall accuracy of UMRI was 95.7%, 93.5%, 80.4%, as compared to 85.1%, 87.2%, 76.6% for US and 74.4%, 87.2%, 69.2% for CT. In assessing vascular invasion, the sensitivity, specificity, and overall accuracy of angiography were 42.9%, 100%, and 68.8%, respectively. There were 3 complications (12.5%) after 24 resections, 5 in 17 palliative procedures, and none after 6 explorations only. The hospital stay was 14 days after resection, 13 after palliative bypass, and 6 after exploration alone. There was no operative or hospital mortality in these 58 cases. CONCLUSIONS: Although it is by no means 100% accurate, UMRI is equal or even superior to all other staging methods. It probably will replace most of these, because it provides an "all-in-one" investigation avoiding endoscopy, vascular cannulation, allergic reactions, and x-radiation. But because even UMRI is not perfect, the final verdict on resectability of a tumor still will depend on surgical exploration in some cases.

Adult↗
PubMed1997

[Ultra-rapid magnetic resonance tomography: a quantum leap in preoperative hepatobiliary diagnosis?].

The recent improvements in magnetic resonance (MR) imaging using the new ultrafast echo-planar technique for diagnosis of hepatobiliary lesions are outstanding. Besides the detection and preoperative evaluation of benign and malignant hepatobiliary tumors, angiography and cholangiography can be simultaneously performed using the techniques of MR angiography or MR cholangiography. Looking ahead, further advantages such as three-dimensional image reconstruction, no X-ray exposure, and short examination time, this MR technique will become the preferred diagnostic procedure for evaluating hepatobiliary lesions.

Bile Duct Neoplasms↗
PubMed1996

Pulmonary perfusion: qualitative assessment with dynamic contrast-enhanced MRI using ultra-short TE and inversion recovery turbo FLASH.

The accurate assessment of pulmonary perfusion is especially important in the evaluation of patients with suspected pulmonary embolism, a common and potentially lethal disorder that can be treated by aggressive anticoagulation. In this study, we demonstrate for the first time the use of MR to image pulmonary perfusion in humans by using dynamic imaging after contrast administration. The technique, which uses an inversion recovery turbo FLASH sequence with ultrashort TE (1.4 ms) and 1-s temporal resolution, was tested in a series of eight healthy subjects and in a porcine model of pulmonary embolism. After the administration of gadopentetate dimeglumine in humans and animal models, there was serial enhancement of the systemic veins, right atrium, right ventricle, and pulmonary arteries. The pulmonary arterial tree was visualized beyond the segmental branches, followed by a gradual diffuse increase in signal intensity of the lung parenchyma over a period of 4.0-7.0 s. Pulmonary circulation times ranged from 3.0-3.4 s. Whereas a high dose (20 or 40 ml) of contrast agent tended to produce the most intense parenchymal enhancement, a low dose (5 ml) was best for showing recirculation. In the animal model, a perfusion defect due to a pulmonary embolus was clearly shown and confirmed by cine angiography. It is concluded that MRI of lung perfusion is feasible. With further development, perfusion MRI could eventually have a significant clinical role in the diagnostic evaluation of pulmonary embolism.

Animals↗
PubMed1996

Noninvasive perfusion imaging of human brain tumors with EPISTAR.

A total of 17 patients with histologically proven diagnoses of low-grade astrocytoma (n = 4), high-grade astrocytoma (n = 8), lymphoma (n = 3), and meningioma (n = 2) were examined by using EPISTAR MR imaging. Meningiomas had the highest EPISTAR tumor/white matter contrast and low-grade astrocytomas and lymphomas the lowest. High-grade astrocytomas demonstrated elevated EPISTAR signal with marked regional heterogeneity. There was agreement between tumor vascularity by SPECT and EPISTAR in the five cases where both were done. Our results show that tumor vascularity can be assessed qualitatively by using EPISTAR without the need for contrast medium injection.

Adult↗
PubMed1996

Breath-hold MR imaging of focal liver lesions: comparison of fast and ultrasound techniques.

The performance of breath-hold MR imaging using two T2-weighted hybrid sequences (TSE, TGSE), two T2-weighted single-shot sequences (HASTE, EPI-SE), and one T1-weighted gradient-echo sequence (FLASH) was compared with a standard conventional T2-weighted SE sequence in 20 patients with focal liver lesions. Liver signal-to-noise ratio was highest for the FLASH sequence (54.3 +/- 8.3) and the HASTE (41.1 +/- 12.5) sequence, whereas the highest spleen-liver contrast-to-noise ratio was obtained by the TSE sequence (38.9 +/- 20.7). Lesion-liver CNR was highest with the TSE sequence (63.9 +/- 21.4). With both TSE and HASTE significantly (p < 0.01) more lesions were detected as compared with SE and EPI-SE sequences. Our results indicate that breath-hold TSE and HASTE sequences will eventually replace conventional T2-weighted SE techniques, due to their insensitivity to motion artifacts, superior lesion detectability and inherently short acquisition times.

Adult↗
PubMed1996

Gonadal vein recruitment in renal cell carcinoma: incidence, pathogenesis and clinical significance.

OBJECTIVE: Gonadal vein recruitment by collateral veins in patients with renal cell carcinoma is not routinely searched for during abdominal computed tomography. We performed a retrospective view to determine the incidence of gonadal vein recruitment for collateral venous drainage in patients with renal cell carcinoma and we discuss its potential importance. PATIENTS AND METHODS: Abdominal CT examinations were available for 58 of 95 patients with renal cell carcinoma identified during a 3-year-period. The presence of collateral veins and recruitment of the ipsilateral gonadal vein was recorded and correlated with the estimated blood loss at surgery. RESULTS: Eighteen of 58 tumours were small (less than 5 cm). Multiple (greater than three) collateral renal capsular veins were noted in 26 of 58 patients and few (less than three) were noted in 11. Recruitment of the gonadal vein (range 4-18 mm, mean 8 mm) was seen in 18 of 58 patients (31%) who all had multiple collaterals. Gonadal vein recruitment was only seen in patients with tumours greater than 5 cm. Mean estimated blood loss at surgery was significantly different (P < 0.01) in 18 of 58 patients (mean, 1078 ml) with gonadal vein recruitment compared to 40 of 58 patients (mean 304 ml) without distinct visualization of the gonadal vein and compared to 22 of 40 patients with large tumours (mean 368 ml). CONCLUSION: Gonadal vein recruitment signifies well-developed arteriovenous shunting and high flow collateral venous drainage pathways and may be used as an index of tumour vascularity. This finding may have clinical potential in triaging patients toward pre-operative renal embolization.

Adult↗
PubMed1996

Liver masses: replacement of conventional T2-weighted spin-echo MR imaging with breath-hold MR imaging.

PURPOSE: To evaluate breath-hold magnetic resonance (MR) imaging with single-shot and multishot T2-weighted fast spin-echo (SE) and inversion-recovery (IR) SE echo-planar (EP) SE (IR-SE-EP) sequences compared with conventional T2-weighted SE imaging for detection of liver masses. MATERIALS AND METHODS: Imaging with all sequences was performed in 32 patients on a 1.5-T whole-body system. Images were compared on the basis of lesion-to-liver contrast-to-noise ratio (C/N), lesion conspicuity, and image quality. Image analysis was performed by two experienced radiologists in consensus. RESULTS: Lesion-to-liver C/Ns were highest on fat-suppressed-half-Fourier-single-shot-fast-SE images. For solid lesions, the lesion-to-liver C/Ns were highest with IR-fast-SE, which was significantly better (P < .05) than IR-SE-EP and conventional SE techniques and also produced the best image quality. Sensitivity with IR-fast-SE was 96%; with fat-suppressed-half-Fourier-single-shot-fast-SE, 92%; with fat-suppressed-fast-SE, 89%; with IR-SE-EP, 83%; and with conventional SE, 78%. CONCLUSION: T2-weighted breath-hold imaging, particularly IR-fast-SE imaging, was more sensitive for hepatic masses than conventional SE imaging, with a substantial reduction in acquisition time. Half-Fourier-single-shot-fast-SE imaging was especially useful in patients who were unable to hold their breath.

Adult↗
PubMed1996

Fetal anatomy revealed with fast MR sequences.

Although all the imaging studies in this pictorial essay were done for maternal rather than fetal indications, fetal anatomy was well visualized. However, when scans are undertaken for fetal indications, fetal motion in between scout views and imaging sequences may make specific image planes difficult to obtain. Of the different techniques described in this review, we preferred the HASTE technique and use it almost exclusively for scanning pregnant patients. The T2-weighting is ideal for delineating fetal organs. Also, the HASTE technique allows images to be obtained in 430 msec, limiting artifacts arising from maternal and fetal motion. MR imaging should play a more important role in evaluating equivocal sonographic cases as fast scanning techniques are more widely used. Obstetric MR imaging no longer will be limited by fetal motion artifacts. When complex anatomy requires definition in a complicated pregnant patient, MR imaging should be considered as a useful adjunct to sonography.

Female↗
PubMed1995

Acute human stroke studied by whole brain echo planar diffusion-weighted magnetic resonance imaging.

Our purpose was to use whole brain echo planar magnetic resonance imaging (MRI) to identify and characterize diffusion abnormalities in acute cerebral ischemia. We studied 40 patients as early as 3 hours after onset of signs and symptoms of cerebral ischemia. Diffusion-weighted imaging (DWI) of the entire brain could be completed in 3 seconds or, using seven different diffusion sensitivities (maximum b = 1,271 sec/mm2), in 48 seconds. Measurements and synthetic maps were made of apparent diffusion coefficients (ADC), a physiological parameter that characterizes the self-diffusion of water in tissue. Early ischemic lesions were identified with DWI as hyperintense regions of decreased ADC in all patients who subsequently developed infarction, before changes were evident on conventional MRI in cases studied earlier than 6 hours after onset of ischemic symptoms. Lesions as small as 4 mm in diameter were identified. The extent of lesions within white matter was best defined by controlling for the anisotropic effect of axonal orientation. The mean ADC (+/- SD) for control regions in the 36 patients was 9.15 (+/- 2.91) x 10(-4) mm2/sec. Mean ADC of ischemic regions was 56% of control values at 6 hours or less and stayed significantly reduced for 3 to 4 days after onset of ischemia. The relative ADC increased progressively over time to be pseudonormalized at 5 to 10 days and elevated in the chronic state, making the distinction of acute lesions adjacent to chronic infarcts readily apparent. DWI with echo planar imaging measures a unique physiological parameter that is sensitive to ischemic changes before conventional MRI. Its potential role in the quantitative study of human stroke pathophysiology and therapeutics is the subject of further investigation.

Adult↗