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Biomedical subjects

S Saini

Publications and source records attributed to S Saini.

At least 127 records · Page 7Linked to original sources
PubMed1994

Improving the efficiency and service of computed tomographic scanning.

RATIONALE AND OBJECTIVES: This study quantified the impact on service and costs of operational changes in CT. METHODS: Operational and financial analyses were performed in 1988 and 1991 after process flow and management changes were made. RESULTS: The backlog decreased from about 6 weeks to 1 week. The cost per scan decreased 25%. Volume increased 50%. Two technologists were assigned per scanner doing some steps of the process in parallel rather than sequentially. Decreasing throughput time accounted for three fifths of the cost decrease. The reduction in number of scanners and hours of operation, change in radiologists' practice patterns, coordination of scheduling, CT priority for escort personnel, and personnel changes accounted for two fifths of the cost decrease. CONCLUSIONS: It is possible to simultaneously decrease costs and improve the quality of service by careful operations analysis and management. Operational changes had synergistic effects that allowed more improvement than might be anticipated. Advisable management changes may be counterintuitive.

Appointments and Schedules↗
PubMed1994

State-of-the-art MR imaging of the adrenal gland.

The authors discuss the appearances of adrenal diseases characterizable with magnetic resonance (MR) imaging (pheochromocytomas, hemorrhage, cysts, adenomas, myelolipomas, and metastases), new imaging techniques, and differentiation of benign from malignant lesions. Most pheochromocytomas appear markedly hyperintense relative to the liver on T2-weighted images. However, this appearance is not specific, since adrenal metastases and adenomas may have similar features. Occasionally, pheochromocytomas may be iso- or hypointense to the liver on T2-weighted images. One of the new techniques for MR imaging of the adrenal gland, fat suppression, reduces cardiac and respiratory motion-induced artifacts, accentuates small differences in tissue contrast, and eliminates chemical shift artifacts. These advantages far outweigh the disadvantages of inhomogeneity of fat suppression and the fewer sections obtained per acquisition. Differentiation of adrenal metastases from adrenal adenomas with MR imaging is problematic with the use of signal intensity ratios (33% overlap) or T2 calculations. The future of discriminating between adrenal metastases and adenomas may rest with chemical shift MR imaging, which uses in-phase and out-of-phase gradient-echo pulse sequences. This approach relies on the fact that adrenal adenomas contain fat whereas metastases do not. The reported accuracy of chemical shift imaging in differentiating adrenal adenomas from metastases is 96%-100%.

Adrenal Gland Diseases↗
PubMed1994

Focal liver lesions: characterization with nonenhanced and dynamic contrast material-enhanced MR imaging.

PURPOSE: To evaluate prospectively the diagnostic accuracy of non-enhanced and gadolinium-enhanced magnetic resonance (MR) imaging in characterization of hepatic lesions. MATERIALS AND METHODS: Fifty-five patients with benign and 52 patients with malignant focal liver lesions underwent examination at 1.5 T that comprised nonenhanced and dynamic contrast material-enhanced images. Four experienced radiologists independently read the different sets of images without and with knowledge of clinical history. RESULTS: Receiver operating characteristic analysis showed that dynamic contrast-enhanced MR imaging added information to nonenhanced MR studies and thereby improved distinction between benign and malignant lesions (P < .05). Knowledge of clinical data further improved lesion characterization with nonenhanced and combined nonenhanced and contrast-enhanced MR imaging (P < .05). CONCLUSION: Dynamic contrast-enhanced MR imaging is a useful adjunct for characterization of hepatic lesions. Knowledge of clinical history still has a decisive effect on interpretation of MR images of the liver.

Adult↗
PubMed1994

Antibiotic-induced diarrhea: specificity of abdominal CT for the diagnosis of Clostridium difficile disease.

PURPOSE: To evaluate the specificity of abdominal computed tomography (CT) in the diagnosis of Clostridium difficile disease. MATERIALS AND METHODS: The authors retrospectively reviewed CT scans of 64 patients with C difficile disease and 30 control subjects with diarrhea and negative findings for C difficile disease at stool tests. RESULTS: Colon wall thickening (range, 4-22 mm; mean, 11.7 mm; median, 11 mm) was seen in 39 patients (61%) with C difficile disease. Other findings included focal colon wall thickening (n = 28) and pancolonic thickening (n = 11). Two patients had only right-sided and transverse colon involvement. CT-specific diagnostic features of C difficile disease, such as nodular haustral thickening or the accordion pattern, were present in 17% of patients. No colonic abnormality was detected in 25 patients (39%). Seven of the 30 (23%) control subjects had colon wall thickening. Six of those seven subjects were subsequently determined to have ischemic colitis. The sensitivity of CT in the detection of colon abnormalities in patients with C difficile disease was 85%, and the specificity was 48%. CONCLUSION: Specific CT features of C difficile disease are uncommon. A considerable number of patients (39%) with C difficile disease have normal abdominal CT scans.

Adult↗
PubMed1994

Hepatic hemangiomas and malignant tumors: improved differentiation with heavily T2-weighted conventional spin-echo MR imaging.

PURPOSE: To determine whether hemangiomas and malignant tumors can be better differentiated at 1.5-T magnetic resonance imaging with use of more heavily T2-weighted conventional spin-echo sequences. MATERIALS AND METHODS: Eighty-three patients with focal liver lesions (50 malignant tumors, 24 hemangiomas, nine cysts) larger than 1 cm were studied with a 3,000/80, 160 sequence (repetition time msec/echo time [TE] msec). T2 relaxation times and lesion/liver signal intensity ratios at TEs of 80 and 160 msec were measured. Receiver operating characteristic (ROC) analyses of expert readers and quantitative measures were performed. RESULTS: T2 relaxation times demonstrated the best performance in distinguishing hemangiomas from malignant tumors (area under ROC curve = .99 +/- .01). Mean T2 times were 76 msec +/- 11 for malignant tumors, 142 msec +/- 40 for hemangiomas, and 341 msec +/- 38 for cysts. A cutoff T2 value of 112 msec allowed discrimination between hemangiomas and malignant tumors with a 97% accuracy, 100% sensitivity, and 92% specificity. CONCLUSION: Hemangiomas and malignant tumors are better differentiated with use of T2 relaxation times obtained with a more heavily T2-weighted sequence.

Cysts↗
PubMed1994

Hepatic metastases and cavernous hemangiomas: distinction with standard- and triple-dose gadoteridol-enhanced MR imaging.

PURPOSE: To determine if hepatic metastases can be distinguished from cavernous hemangiomas by pattern analysis of magnetic resonance (MR) images obtained prior to and following administration of gadoteridol at standard (0.1 mmol/kg) and triple (0.3 mmol/kg) doses. MATERIALS AND METHODS: Ninety-five patients with proved hepatic metastases (n = 71) or cavernous hemangiomas (n = 24) underwent MR imaging at 16 different institutions. T2-weighted spin-echo and T1-weighted images were obtained before and after gadoteridol administration. Two independent blinded reviewers rated individual features of benignancy versus malignancy on a five-point confidence scale. RESULTS: The most useful diagnostic features, with 100% specificity, were nodular enhancement for hemangiomas and rim enhancement for metastases. Confident (definitely benign or definitely malignant) diagnoses were rendered in 80 of 95 cases (84%), with an accuracy of a confident diagnosis of 96%. CONCLUSION: The pattern of enhancement on T1-weighted images is highly accurate for distinction between hemangiomas and metastases in images obtained with both doses.

Contrast Media↗
PubMed1994

T2-weighted MR imaging of the upper part of the abdomen: should fat suppression be used routinely?

OBJECTIVE: Fat suppression has shown promise in improving the quality of T2-weighted spin-echo MR images of the upper part of the abdomen. The purpose of this study was to determine whether fat-suppressed images should be routinely used in lieu of conventional images. Accordingly, we prospectively compared the two techniques in a series of patients with both normal and abnormal findings in the upper part of the abdomen. MATERIALS AND METHODS: Conventional and fat-suppressed T2-weighted spin-echo images (3000/80,160 [TR/TE]) were obtained in 45 consecutive patients referred for MR imaging of the upper part of the abdomen. Thirty-three patients had abnormal findings, and 22 of those 33 patients had histologic or follow-up confirmation of the diagnosis (14 with metastasis, one with hepatoma, four with hemangiomas, and three with cysts). Signal intensities (hepatic lesions, liver, spleen) and noise were measured to calculate signal-to-noise ratios and contrast-to-noise ratios. Qualitative comparison (liver, hepatic lesions, porta hepatis, spleen, pancreas, bowel, kidneys, adrenal glands, noise), evaluation of the number of hepatic lesions, and characterization of hepatic lesions were done by independent observers. RESULTS: Compared with conventional images, fat-suppressed images had higher signal-to-noise ratios (lesions, liver, spleen) and contrast-to-noise ratios (lesion-liver and spleen-liver) (p < .005). In qualitative comparison, three of three radiologists preferred fat-suppressed over conventional images for depiction of hepatic lesions and all upper abdominal organs except the liver, for which no clear preference was shown for either technique. Detection rates for hepatic lesions were similar with both types of images (observer 1: 112 lesions on fat-suppressed vs 118 on conventional images, observer 2: 142 vs 135), as was the characterization of hepatic lesions (91% accuracy on fat-suppressed images and 84% accuracy on conventional images, for 22 proved lesions and two observers). CONCLUSION: Fat-suppressed T2-weighted spin-echo MR images were better than non-fat-suppressed images for evaluation of the upper part of the abdomen. These results suggest that fat suppression should be routinely used in T2-weighted MR imaging of the upper part of the abdomen.

Abdomen↗
PubMed1994

MR imaging of the liver at 1.5 T: value of signal averaging in suppressing motion artifacts.

OBJECTIVE: Prior reports have suggested that signal averaging is not as effective as phase reordering for suppressing motion-related artifacts on T1-weighted spin-echo MR imaging of the liver at high field strengths. We hypothesized that with shorter TEs, signal averaging could be effective, and therefore undertook this study to compare signal averaging with phase reordering at 1.5T. SUBJECTS AND METHODS: Thirty consecutive patients underwent MR imaging of the liver at 1.5 T with two T1-weighted spin-echo pulse sequences. In one sequence we used signal averaging and in the other we used phase reordering as the primary motion suppression techniques. For each patient, the order in which these sequences were performed was randomized; TR (400-500 msec), TE (11-12 msec), and field of view (32-34 cm) remained constant. Images were analyzed quantitatively for liver signal-to-noise ratio (SNR), liver-spleen contrast-to-noise ratio (CNR), and liver-lesion CNR (in 16 patients with focal liver lesions), as well as qualitatively (three observers, blinded to technique) for overall image quality. RESULTS: Signal averaging resulted in images with significantly greater liver SNR, liver-spleen CNR, and liver-lesion CNR than did phase reordering (p = .0001, .002, and .02, respectively). All observers showed a preference for the signal-averaged images. For one observer, this preference was statistically significant; for the others, it was not. CONCLUSION: Signal averaging can be an effective means of suppressing motion-related artifacts on T1-weighted MR images of the liver obtained at 1.5 T.

Artifacts↗
PubMed1994

Echoplanar MR imaging of the liver in patients with focal hepatic lesions: quantitative analysis of images made with various pulse sequences.

OBJECTIVE: We undertook this study to evaluate pulse-sequence performance in terms of liver signal-to-noise ratio (SNR) and lesion-liver contrast-to-noise ratio (CNR) on T1- and T2-weighted echoplanar MR imaging. SUBJECTS AND METHODS: Forty-nine patients referred for MR imaging of the liver were examined at 1.5 T with echoplanar MR imaging using spin-echo, inversion-recovery, and gradient-echo pulse sequences. T2-weighted spin-echo (TE = 25, 50, 100, and 150 msec), T1-weighted inversion-recovery (T1 = 100, 380, 600, and 800 msec), and T2*-weighted gradient-echo (TE = 20 msec) images were acquired after one excitation (TR = infinite), using a 128 x 128 data matrix. T2-weighted spin-echo (TE = 20, 50, 100, and 150 msec) images were also obtained with two excitations (TR = 6 sec), resulting in a 128 x 256 data matrix. Signal intensity measurements were made to calculate liver SNR and lesion-liver CNR. RESULTS: Single-excitation, T2-weighted, spin-echo images at a minimum TE of 25 msec provided the highest liver SNR (p < .05). Single-excitation, T2-weighted, spin-echo images at TEs of 50 and 100 msec, and T1-weighted inversion-recovery images at Tls of 100 and 380 msec provided the highest lesion-liver CNR (p < .05). However, the latter two pulse sequences had considerably inferior liver SNR (p < .05). CONCLUSION: Single-excitation, T2-weighted, spin-echo images provide both superior liver SNR and superior lesion-liver CNR. These results can be used to guide technique selection when echoplanar MR imaging is used to examine the liver.

Echo-Planar Imaging↗
PubMed1994

[Progress in magnetic resonance tomography of the liver: value of ultra-rapid imaging and liver-specific contrast media].

Ongoing technical improvements in magnetic resonance imaging (MRI) and the development of liver-specific contrast agents are likely to have an impact on the clinical assessment of liver disease. Technical progress towards methods of motion-free MRI and concepts of liver-specific contrast agents are presented. The potential impact of these developments on clinical medicine is discussed.

Animals↗
PubMed1993

[The clinical use of echoplanar MR tomography in the detection of focal liver lesions. The results of a quantitative study].

The purpose of the present study was to investigate the clinical application of echoplanar MR imaging compared to conventional MR imaging in the detection of focal liver lesions. A total of three conventional and 12 echoplanar pulse sequences were acquired in 35 patients with focal liver lesions. Motion artifacts were eliminated because of short acquisition times of 32 ms subsequently improving signal-to-noise. A single-shot spin-echo technique with a TE of 26 ms provided the highest liver signal-to-noise ratio (p < 0.05) of all sequences acquired. Contrast-to-noise ratios for a single-shot SE technique with echo times of 50-100 ms were as high as 10-40.

Cysts↗
PubMed1993

Evaluation of the fluorescence actin staining test for detection of enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) strains designated on the basis of their serotypes are epidemiologically associated with diarrhea. They adhere to the intestinal mucosa, producing the characteristic attaching and effacing (AE) lesion in an in vitro organ culture system. EPEC manifest localized adherence (LA) in the HEp-2 cell assay, and this is commonly used for clinical diagnosis. Recently, the fluorescence actin staining (FAS) test was proposed for the identification of E. coli causing the AE lesion. We therefore compared the FAS test with the HEp-2 cell assay and the EPEC adherence factor (EAF) probe assay for the detection of EPEC strains. Among 240 stool samples from children with diarrhea examined, 176 yielded E. coli and 14 of these strains showed the LA pattern in the HEp-2 cell assay; 11 of these were positive by both the EAF and the FAS tests. By using the HEp-2 cell assay as the "gold standard," the FAS test gave a sensitivity of 78.5% and a specificity of 100%. The three localized adherent FAS-negative strains tested subsequently were positive by the enteroaggregative E. coli DNA Probe and failed to produce the AE lesions characteristic of EPEC. When these strains were not considered, the sensitivity of the FAS test for detecting isolates that manifest LA was 100%. Against the EAF probe, the sensitivity and specificity of the FAS test were 91.6 and 100%, respectively. The FAS test avoids infrequent but nevertheless important phenotypic misclassifications in the HEp-2 cell assay, and it may therefore serve as a confirmatory test for EPEC.

Actins↗
PubMed1993

Percutaneous management of hilar biliary malignancies with metallic endoprostheses: results, technical problems, and causes of failure.

Malignant obstruction at the biliary hilum is a challenging problem for percutaneous management because of the anatomy of the biliary hilum, which facilitates spread of tumor into multiple biliary radicles. Metallic self-expanding stents were used in 22 patients with hilar malignancies. Sixteen patients had focal common hepatic duct strictures, and six had multisegmental disease. Stents were placed in the biliary system with a single transhepatic approach in 16 patients with common hepatic duct strictures; stent placement in the right and left biliary ducts was performed with a bilateral transhepatic approach in five patients and with a single transhepatic approach in one patient. Metal stent occlusion occurred in six patients (27%) at a mean of 2.5 months after initial insertion. Stent occlusion was due to inspissated debris in two of these patients and to tumor overgrowth in four. The key to successful long-term treatment is to "overstent" to ensure adequate purchase above hilar tumors and insertion in a balanced position. Thus, the prevalence of tumor overgrowth is decreased.

Bile Duct Neoplasms↗
PubMed1993

MR angiography of the portal and hepatic venous systems: preliminary experience with echoplanar imaging.

OBJECTIVE: The purpose of this study was to evaluate the ability of echoplanar MR angiography to depict the major hepatic and portal venous structures. SUBJECTS AND METHODS: Echoplanar and conventional MR angiographic examinations were performed in 10 subjects (seven healthy volunteers, three patients with focal hepatic lesions). A gradient-recalled echo (GRE) time-of-flight technique (125/10 [TR/TE], 90 degrees flip angle) was used for echoplanar angiography. Eight complete single-excitation images were acquired at each level in 1.5 sec and then collapsed into a single maximal intensity projection. Conventional time-of-flight MR angiography (34/13, 30 degrees flip angle) also was performed. The vascular anatomy from the right atrium to the splenic vein was imaged (6-mm contiguous levels) in three 10.5-sec breath-holds with echoplanar imaging, as compared with seven 11.5-sec breath-holds with conventional MR angiography. Echoplanar and conventional images were compared quantitatively and qualitatively. RESULTS: Echoplanar imaging was 61% faster than conventional MR angiography. Vessel-to-liver signal-intensity ratios were significantly higher for echoplanar imaging (p < .0001), signal-to-noise ratios were significantly higher for conventional MR angiography (p < .0001), and contrast-to-noise ratios were comparable. Qualitatively, echoplanar imaging and conventional MR angiography provided similar anatomic information about the hepatic and portal veins. CONCLUSION: Angiograms of the hepatic and portal venous systems that are of diagnostic quality can be acquired much more quickly with echoplanar imaging than with conventional MR angiography.

Echo-Planar Imaging↗
PubMed1993

Value of T1 and T2 relaxation times from echoplanar MR imaging in the characterization of focal hepatic lesions.

OBJECTIVE: The purpose of this study was to determine the value of echoplanar imaging in characterizing focal hepatic lesions on the basis of image-derived T1 and T2 relaxation times. SUBJECTS AND METHODS: Forty-six proven hepatic lesions were analyzed: 24 solid (21 metastases, three primary liver tumors) and 22 nonsolid (11 hemangiomas and 11 cysts). Mean lesion size (maximal length) was 4.0 (+/- 3.2) cm, and 16 of 46 lesions were less than 2.0 cm. A commercially available 1.5-T echoplanar-equipped MR scanner was used to obtain fat-suppressed, single-excitation (TR essentially infinite) axial images with a slice thickness of 10 mm. T1-weighted inversion recovery images (TE = 25 msec; TI = 100, 380, 600, or 800 msec) were acquired for 28 of 46 lesions, and T2-weighted spin-echo images (TE = 25, 50, 100, 75 or 150 msec) were acquired for 45 of 46 lesions. For each acquisition (i.e., each different TI or TE), the entire liver was imaged in a single breath-hold of 12 sec or less. RESULTS: The mean T1 was 1004 (+/- 234) msec for solid lesions, 1337 (+/- 216) msec for hemangiomas, and 3143 (+/- 1392) msec for cysts. Although the mean T1 of solid and nonsolid lesions differed (p < .004), overlap precluded the use of T1 as a discriminatory index. Mean T2 times were 80 (+/- 18) msec for solid lesions, 178 (+/- 40) msec for hemangiomas, and 517 (+/- 429) msec for cysts. The mean T2 for hemangiomas is the longest reported to date. A T2 cutoff of 116 msec was 100% accurate for classifying lesions as solid or nonsolid and 93% accurate for characterizing them as benign or malignant. CONCLUSION: Our study suggests that echoplanar-derived T2 times (but not T1 times) are useful for characterizing focal hepatic lesions. An important use may be to characterize small lesions measuring less than 2.0 cm. The main advantages of echoplanar imaging are the absence of motion-induced volume averaging and phase artifacts, the ability to acquire purely T2-weighted images, and the use of multiple data points to calculate relaxation times.

Cysts↗