Helical CT without contrast in choledocholithiasis diagnosis

The goal of this study was to determine the diagnostic value of the helical CT without contrast in suspected cases of choledocholithiasis, comparing this test with endoscopic retrograde cholangiopancreatography (ERCP). Forty patients with possible choledocholithiasis were studied prospectively. There were 23 women and 17 men, ranging in age from 24 to 91 years. Helical CT was performed immediately before ERCP (time interval between the two procedures was less than 1 h). A biliary area previously selected was studied with a technique of pitch 1 and slice thickness of 3.2 mm. Average time was 30 s. Reconstruction with different increments and windows were made. Stone presence was evaluated in bile duct and Vater's ampulla. Biliary dilation was evaluated too. Endoscopic retrograde cholangiopancreatography found stones in 19 patients and absence of stones in 20. One case was failed, but stones in bile duct were demonstrated during intraoperative cholangiography. Helical CT demonstrated stones in 15 of the 19 patients with positive ERCP. There were no false positives with CT. Patients without stones in ERCP were also negative in CT. The patient having the failed ERCP was considered positive in CT. The CT sensitivity was 80 % and specificity was 100 %, with an accuracy of 90 %. Helical CT without contrast has sensitivity and specificity good enough to be used as a screening technique in patients with suspected choledocholithiasis. Received: 15 February 2000/Revised: 3 July 2000/Accepted: 5 July 2000     

Helical CT cholangiography with oral cholecystographic contrast material

Twenty asymptomatic volunteers underwent helical computed tomographic (CT) cholangiography 10-12 hours after ingesting iopanoic acid. Three observers assessed the images for the extent of bile duct visualization and image quality. The common bile duct and common hepatic duct were adequately visualized in 19 (95%) subjects. Helical CT cholangiography with oral cholecystographic contrast material is feasible and deserves further clinical studies.     

CT angiography with gadolinium-based contrast media

RATIONALE AND OBJECTIVES: To evaluate the potential use of gadolinium (Gd)-based contrast media, especially that of Gadovist, a 1-molar Gd medium, in computed tomography (CT) and compare our findings with standard iodinated contrast media. MATERIAL AND METHODS: Using a live rabbit and an acrylic CT body phantom for comparative CT imaging of Gd- and I-based media. The images were acquired at 80, 100, and 120 kVp, using fixed standard beam filtration. The phantom study used serial dilutions of the Magnevist and Ultravist 300 (2.4-molar I), whereas the animal study used different volumes of Gadovist, Magnevist (0.5 molar Gd), and Ultravist administered intravenously. RESULTS: At 80 kVp for the same injection volumes of Gadovist and Ultravist, the image contrast enhancement of the aorta with Gadovist was 40% lower than that of Ultravist. In the phantom studies, however, for the same kVp settings the CT image contrast was up to fourfold higher for Gd compared with iodine when comparing the same molar concentrations of the two elements in the solutions. CONCLUSION: These results indicate a potential of Gd-based media for clinical CT angiography and provide incentive for further investigation of this subject.     

CT of melanoma liver metastases: is the examination without contrast media superfluous?

The current method of evaluating hypervascular liver metastases with CT includes both contrast enhanced and unenhanced studies. The necessity of performing both examinations for the detection of liver metastases in the workup of malignant melanoma has not been specifically addressed. This study evaluates potential additional information derived from an unenhanced examination of the liver. We studied 55 patients with malignant melanoma who had both contrast enhanced and unenhanced CT examinations performed during the workup and staging of their disease. Sixteen patients had 89 measurable liver lesions seen on enhanced CT. Three patients had liver lesions that were too numerous to accurately measure. Unenhanced CT demonstrated only 62% of the measurable lesions. All liver lesions seen on the unenhanced images were identified on the enhanced studies. Only one metastasis was found to be comparatively smaller on the enhanced examinations. The unenhanced examinations detected no additional lesions. It is reasonable to perform only an enhanced examination during the workup and staging of malignant melanoma liver metastases.     

Using a saline chaser to decrease contrast media in abdominal CT

OBJECTIVE: The purpose of this study was to compare hepatic tumor conspicuity on CT after injection of either 150 mL of contrast material or 100 mL of contrast material plus a 50-mL saline chaser. SUBJECTS AND METHODS: We evaluated 86 hypoattenuating liver metastases in 26 patients. Patients underwent CT in two sessions separated by a mean of 85 days: one time with 150 mL of contrast material and the other time with 100 mL of contrast material followed by a 50-mL saline chaser. The order of the sessions was randomized. Contrast material was administered via power injector and matched for injection rate and delay time. Attenuation values were obtained from normal liver tissue and metastases and from the spleen, kidney, aorta, and inferior vena cava. RESULTS: The 150 mL dose of contrast material caused slightly greater liver and tumor attenuation than 100 mL of contrast material with a chaser (mean hepatic attenuation, 95.6 vs 89.8 H, respectively; p < 0.03, paired t test; mean tumor attenuation, 53.2 vs 49.1 H, respectively; r = 0.71, p = 0.09). The difference in conspicuity of liver lesions was slightly greater with 150 mL than with 100 mL with a chaser (46.8 H vs 44.2 H; r = 0.46, p = 0.08, paired t test), but was of doubtful clinical significance (2.6 H). Kidney, spleen, and vascular structures enhanced more with 150 mL than with 100 mL and a chaser. CONCLUSION: Using 100 mL of contrast material and a saline chaser did not result in a meaningful difference in liver parenchyma attenuation or lesion conspicuity compared with using 150 mL of contrast medium alone. Routine use of a chaser for abdominal CT may yield cost savings and a decreased risk of contrast nephropathy.     

Low contrast media volume in pre-TAVI CT examinations

Purpose

To evaluate image quality using reduced contrast media (CM) volume in pre-TAVI assessment.

Methods

Forty-seven consecutive patients referred for pre-TAVI examination were evaluated. Patients were divided into two groups: group 1 BMI?<?28 kg/m² (n?=?29); and group 2 BMI?>?28 kg/m² (n?=?18). Patients received a combined scan protocol: retrospective ECG-gated helical CTA of the aortic root (80kVp) followed by a high-pitch spiral CTA (group 1: 70 kV; group 2: 80 kVp) from aortic arch to femoral arteries. All patients received one bolus of CM (300 mgI/ml): group 1: volume?=?40 ml; flow rate?=?3 ml/s, group 2: volume?=?53 ml; flow rate?=?4 ml/s. Attenuation values (HU) and contrast-to-noise ratio (CNR) were measured at the levels of the aortic root (helical) and peripheral arteries (high-pitch). Diagnostic image quality was considered sufficient at attenuation values > 250HU and CNR > 10.

Results

Diagnostic image quality for TAVI measurements was obtained in 46 patients. Mean attenuation values and CNR (HU?±?SD) at the aortic root (helical) were: group 1: 381?±?65HU and 13?±?8; group 2: 442?±?68HU and 10?±?5. At the peripheral arteries (high-pitch), mean values were: group 1: 430?±?117HU and 11?±?6; group 2: 389?±?102HU and 13?±?6.

Conclusion

CM volume can be substantially reduced using low kVp protocols, while maintaining sufficient image quality for the evaluation of aortic root and peripheral access sites.

Key points

? Image quality could be maintained using low kVp scan protocols. ? Low kVp protocols reduce contrast media volume by 34–67 %. ? Less contrast media volume lowers the risk of contrast-induced nephropathy.

     

Porphyrins as contrast media.

The interest in tissue distribution of variously labeled or otherwise detectable natural and synthetic porphyrins and porphyrin derivatives dates back well over 60 years. Although a considerable interest in fluorescent tumor localization and therapy dominates the history of porphyrin biodistribution studies, many investigators have evaluated the diagnostic and therapeutic characteristics of porphyrins with radioactive, radiopaque, and paramagnetic qualities. In this paper, a review of the use of porphyrins as nuclear medicine, X-ray, and NMR contrast agents is presented.     

Glass fragments and other particles contaminating contrast media.

Microscopy of filtrates made from contrast media of routinely opened glass ampoules substantiates previous assumptions that small fragments of glass may enter into the ampoule and the medium with considerable frequency. Such glass fragments may cause embolic lesions on intraarterial injections of the medium; the lesions, however, are histologically non-specific consisting of proliferation of intima and small granulomas associated with dilated nephrons in a ray-like arrangement. A significant amount of plastic particles may be added to injectable fluids on usage of disposable syringes.     

Gd-DTPA as a contrast agent in CT

An evaluation was done of the effect of gadolinium diethylenetriaminepentaacetic acid (DTPA) on computed tomographic (CT) studies performed after magnetic resonance (MR) imaging. CT scans of two solutions of Gd-DTPA demonstrated substantial attenuation. In two patients who underwent CT after Gd-DTPA-enhanced MR imaging, the high attenuation of concentrated Gd-DTPA was seen in the urinary bladder and renal collecting system. However, in the concentration presently used in MR imaging, Gd-DTPA results in only minor enhancement of renal cortex.     

Venous air embolization as a complication of pressure injection of contrast media: CT findings

Pressurized contrast medium infusion for CT carries a risk of potentially fatal air embolization if improperly or carelessly administered. Two cases of intracardiac air embolization and three cases of subclavian venous air due to faulty contrast medium administration have been seen by the authors during a 2 year period.     

Marchiafava-Bignami disease: use of contrast media in CT and MRI

We report two cases of Marchiafava-Bignami disease studied by CT and MRI. Both patients displayed persistent confusion and a disconnection syndrome but had a favourable outcome. In both cases, CT with intravenous contrast medium revelaed enhancement of the corpus callosum in the early stage. MRI showed gadolinium uptake in both the genu and splenium of the corpus callosum in one case, 8 days after the onset. Three weeks after admission, cystic lesions appeared in the corpus callosum on MRI T1-weighted sagittal images in both cases. Contrast medium uptake may be useful in the diagnosis of Marchiafava-Bignami disease.     

Spiral computerized tomography without perfusion of contrast media as first line investigation in patients with renal colic

INTRODUCTION: We investigated the diagnostic accuracy of unenhanced helical CT in the detection of stones in patients with suspected renal colic from ureteral stones and compared CT findings with the results of plain abdominal film and US. MATERIAL AND METHODS: We reviewed the findings relative to 80 patients (age range 24-75) who came to our observation to the Emergency Department with acute flank pain. All patients had been examined with plain abdominal radiography, US and unenhanced helical CT. RESULTS: While abdominal radiography showed the presence of radiopaque stones in 38 patients only (47.5%), US demonstrated ureter dilatation in 72 patients and detected stones in 36 of them (45%). Helical CT performed best, depicting a stone in 72 patients (90%), with high sensitivity and specificity. Mean stone size was 3 mm, with 7 mm-1 mm range. The biggest stones were seen in 3 cases and the smallest ones in 34. In 8 patients with no signs of stones we found other extraurinary conditions, namely pancreatitis, diverticula, renal cancer. We also found a case of urinary tract infection. CONCLUSIONS: Thanks to its short execution time and accuracy, helical CT makes the examination of choice in patients with acute flank pain due to renal colic. It is also a most valuable tool in the differential diagnosis of other pathological causes of pain such as abdominal or pelvic masses and inflammatory conditions.     

Gadodiamide as an alternative contrast medium in cerebral angiography in a patient with sensitivity to iodinated contrast medium

The physical and pharmacological properties of gadolinium enable its chelates to be used as a contrast medium in digital subtraction angiography. We report the use of gadodiamide, a low-osmolar nonionic gadolinium chelate, for selective angiography in a patient with known sensitivity to iodinated contrast medium. No adverse effects were encountered during or after injection. Contrary to a single previous report of the use of these agents in cerebral angiography, contrast in the angiogram was not particularly good, especially in the distal circulation, but the angiogram was diagnostic. Received: 16 April 1999/Accepted: 14 June 1999     

双能量CT区分体内互补型对比剂的研究

摘要目的评估市售的应用于临床的双能量CT扫描设备区分活体内同时注射两种对比剂(增加X线衰减比率)的增强效果的可行性。材料与方法本研究获得动物保护及使用委员会的批准,并遵守国家卫生研究院实验动物保护及使用指南。