Biomedical subjects

I Shariat Razavi

Publications and source records attributed to I Shariat Razavi.

6 recordsLinked to original sources

PubMed1997

[Turbo STIR sequence: optimization and comparison with conventional STIR sequence in bone diseases].

INTRODUCTION: The most common fat-suppressed sequence used to study skeletal conditions is the STIR sequence which has shown high sensitivity in the detection of skeletal lesions and whose main drawback is its long acquisition time. Currently, Turbo-STIR (T-STIR) sequences can shorten the acquisition time. The purpose of this study was therefore to compare the conventional STIR sequence with the new T-STIR sequence in the study of skeletal conditions to compare their diagnostic yield. MATERIAL AND METHODS: Twenty patients with different types of skeletal lesions were examined. MR examinations were performed with a Philips Gyroscan S15/ACS II unit (1.5 T). All the patients underwent a STIR sequence (TR/TE = 1500/20, TI = 180 ms, matrix = 204 x 256, NEX = 2, slice thickness = 5 mm, acquisition time = 9 min 24 s) and a T-STIR sequence (TR/TE = 1500/20, TI = 180 ms, matrix = 204 x 256, NEX = 2, slice thickness = 5 mm, TFL = 3, acquisition time = 3 min 33 s). The images were evaluated by measuring both quantitative parameters--percent contrast (%C), contrast to noise ratio (C/N), signal to noise ratio (S/N)--and qualitative parameters--lesion conspicuity, margins and extension, motion artifacts, image quality. RESULTS: The only statistically significant difference between the two sequences was image quality, which was superior in the conventional STIR sequence (p < .05). No statistically significant difference was demonstrated with the quantitative evaluation. DISCUSSION: In this study, T-STIR sequences were performed with low-high acquisition profile to acquire an actual echo time of 20 ms which permits to obtain optimal S/N with good spatial resolution. Therefore, T-STIR sequences with low-high acquisition profile provides better results than T-STIR sequences with linear acquisition profile which permits to obtain an actual echo time of 40 ms. CONCLUSION: This work shows that T-STIR sequences can replace conventional STIR sequences in the study of skeletal conditions reducing the acquisition time by 60%. This result can be obtained only by an accurate optimization of acquisition parameters.

Adolescent↗

PubMed1997

[A comparison between an ionic paramagnetic contrast agent (Gd-DTPA) and a nonionic one (Gd-DTPA-BMA) in functional kidney evaluation with magnetic resonance].

INTRODUCTION: The combination of TGE sequences with bolus injection of paramagnetic contrast agents permits to study renal function and perfusion. We studied renal function with both an ionic (Gd-DTPA) and a nonionic paramagnetic contrast agent (Gd-DTPA-BMA) to compare their kinetics in normal kidneys. MATERIAL AND METHODS: Twenty MR examinations were performed on 20 subjects with normal renal function. Ten subjects were examined after i.v. injection of Gd-DTPA and the other ten subjects after i.v. injection of Gd-DTPA-BMA. MR examinations were performed on a Philips ACS II unit (1.5 T). Two sequences were acquired in all cases; an SE coronal T1-weighted sequence (TR/TE = 600/19 ms) and a TGE coronal T1-weighted sequence (TR/TE = 12/5 ms, flip angle = 25 degrees) performed after bolus injection of the contrast agent at 0.1 mmol/kg. Signal intensity time curves were obtained in all the cases. The signal intensity of the cortex, corticomedullary junction, medulla and the pyelocaliceal system of each kidney was measured using a region of interest (ROI). Signal intensity curves were analyzed considering some quantitative parameters such as the area under the curve (AUC), the peak (P) and the time to peak (T-P). RESULTS: In the subjects with normal renal function, four phases were demonstrated after the i.v. injection of either Gd-DTPA or Gd-DTPA-BMA, namely the cortical phase, the cortico-medullary junction phase, the medullary phase and the pyelocaliceal system phase. No statistically significant differences between the two agents were demonstrated in signal intensity time curves and quantitative parameters. CONCLUSIONS: Gd-DTPA and Gd-DTPA-BMA showed the same efficacy in renal function studies.

Analysis of Variance↗

PubMed1995

[Tridimensional reconstructions of intra- and extracranial arteries using computerized tomography].

Three-dimensional Computed Tomographic Angiography (3D CTA) is a new imaging technique for vascular structures. This study was aimed at investigating the diagnostic role of 3D CTA in the intracranial and extracranial arteries. Fifteen patients with intracranial artery disease (thirteen with aneurysms and two with arteriovenous malformations) and fifteen patients with stenosis of the common, internal or external carotid arteries underwent 3D CTA. All patients had been examined with intraarterial angiography. The CT examinations were performed with dynamic scanning during intravenous contrast agent administration. Three-millimeter thick contiguous slices were obtained in the cervical region and 1.5-mm contiguous slices in the intracranial region. CT findings were processed to produce 3D views on an independent workstation. 3D CTA results were compared with those of intraarterial DSA in all cases. Agreement was found in 13 of 15 cases of intracranial vascular abnormalities, and in 26 of the 30 carotid arteries in classifying the severity of the stenosis. The 3D views, which exhibit an excellent image quality, seem to be comparable to angiography in the intracranial and extracranial arteries. The main advantages of this technique are: 1) its low invasivity since only an intravenous contrast agent injection is required; 2) its easy and fast acquisition (2-3 minutes are needed if a non-spiral CT unit is used and less than one minute with spiral CT); 3) good demonstration of the calcified plaques which can be also removed with the softwares available at the workstation, to show the overall vessel lumen; 4) thanks to its simplicity the examination can also be performed in emergency (i.e. in patients with subarachnoid hemorrhage, if plain CT is positive for subarachnoid bleeding). Its main limitations are: 1) the need of an adequate concentration of contrast agent in the vessels; 2) artifacts due to calcified and bone structures; 3) no information about vessel inflow; 4) limited discrimination between arteries and veins in some areas (cavernous sinus); 5) limited field of view compared to angiography.

Carotid Arteries↗

PubMed1994

[Anatomic characteristics of pelvic fascia and ligaments in computerized tomography].

The pelvic fascia consists of two layers, the parietal and the visceral layers I whose appendages represented by various septa and ligaments subdivide the pelvis in intra- and extraperitoneal spaces. These structures are extremely thin but can be demonstrated thanks to the high-quality images obtained with the latest CT scanners and to the good natural contrast of pelvic fat. To assess the visibility of the anatomic features of these structures, 50 patients with no pelvic conditions which could affect the thickness of the pelvic fasciae and ligaments were examined with CT. The pelvic visceral fascia was clearly demonstrated in 60% of cases, the rectovesical and rectovaginal septa and the medial umbilical ligaments were demonstrated in 100% and 92% of cases, respectively. The umbilico-prevesical fascia and the lateral umbilical ligaments were poorly demonstrated. The depiction of these structures improves the knowledge of pelvic anatomy and yields major pieces of information to better understand several pelvic conditions.

Adult↗

PubMed1994

[Pelvic fascia, ligaments, and spaces in neoplastic disease in computerized tomography].

The fasciae and ligaments which are visible on CT images as extremely thin structures in normal conditions tend to appear thicker in such abnormal conditions as pelvic neoplasms and are therefore easily demonstrated on axial scans. To assess the CT patterns and the meaning of fascial thickening, the CT images of 40 patients with pelvic tumors (25 rectal, 7 uterine, 6 ovarian and 2 bladder lesions) were examined. Ten cases of peritoneal carcinomatosis with ascitis were also studied. The umbilico-prevesical fascia was demonstrated in 60% of cases, while the medial umbilical ligaments, the pelvic visceral fascia and the rectovesical and rectovaginal septa were detected in 90, 96 and 100% of cases, respectively. Fascial thickening is not a specific sign of neoplastic disease since it can be due to neoplastic infiltration or be the response to an irritative stimulus. Moreover, fascial thickening can be observed also in inflammatory conditions of the pelvis and following major traumas. Thickened fasciae and ligaments make the demonstration of paravesical, intra- and extraperitoneal spaces easier, which is useful to distinguish both etiology and site of pelvic fluid collections. All these pieces of information lead to better understanding pelvic abnormalities.

Adult↗

PubMedDate not supplied

[Morpho-functional study of the kidney in patients with kidney disease and liver disease with magnetic resonance].

INTRODUCTION: We studied renal function and perfusion after the i.v. injection of Gd-DTPA-BMA, a nonionic paramagnetic contrast agent, to assess renal morphology and function in normal subjects, in renal insufficiency patients and in patients with hepatic failure and normal renal function. The latter were chosen because some patients with advanced hepatic failure may suffer from the hepatorenal syndrome, characterized by severe vasoconstriction in the renal cortical vessels. We investigated if dynamic MRI can detect early renal perfusion abnormalities in the patients who will eventually develop this syndrome. MATERIAL AND METHODS: Thirty MR examinations were carried out on 30 subjects after the i.v. injection of Gd-DTPA-BMA. Our series consisted of: 10 normal subjects; 10 renal insufficiency patients; 10 patients with hepatic failure and normal renal function. MR examinations were performed on a Philips ACS II scanner operating at 1.5 T. Two sequences were carried out in all cases: T1-weighted SE and T1-weighted TGE sequences after the bolus injection of .1 mmol/kg contrast agent. Renal longitudinal diameter and parenchymal thickness were measured in all cases and signal intensity time curves were always made. The signal intensity of the cortex, corticomedullary junction, medulla and pyelocaliceal system of each kidney was measured using a region of interest (ROI). The signal intensity curves were made considering quantitative parameters, including the area below the curve (ASC), the peak (P) and the time to peak (T-P). RESULTS: Longitudinal diameter and parenchymal thickness values were significantly lower in renal insufficiency patients than in normal subjects. Four phases were demonstrated after i.v. contrast agent injection in normal subjects, namely A) the cortical phase, B) the corticomedullary junction phase, C) the medullary phase, D) the pyelocaliceal phase. No signal intensity decrease in the medullary and pyelocaliceal curves was observed in renal insufficiency patients. Signal intensity curves values were lower in hepatic failure patients than in those with normal renal function. Hepatic failure patients could be divided into two groups: 5 patients had low P and ASC values and 4 had normal P and ASC values. The patients with lower P and ASC values developed the hepatorenal syndrome within a few months of the MR examination. DISCUSSION: Signal intensity decreased in the pyelocaliceal system phase in normal subjects because of the high paramagnetic contrast agent concentration. The lack of signal intensity decrease in renal insufficiency patients was caused by the reduced capability of concentrating Gd-DTPA-BMA. Lower signal intensity values in hepatic failure patients may be considered an early sign of the hepatorenal syndrome.

Adult↗