Value of high contrast medium dose in brain CT

Systemic, Pulmonary and Renal Haemodynamic Effects of Large Intravenous Doses of High and Low Osmolar Contrast Media; An Investigation in the Pig of Ratio 1.5 and Ratio 3 Media

The central, peripheral and renal haemodynamic effects of intravenous infusion (1 ml/s) of large doses (4 ml/kg body weight) of non-ionic (iohexol) and ionic (metrizoate and ioxaglate) contrast media were studied in 24 anaesthetized pigs. All contrast media showed marked haemodynamic effects with an increase of mean right atrial pressure, mean pulmonary arterial pressure, mean pulmonary occlusion pressure, cardiac output and stroke volume. The response of the pulmonary circulation to contrast media was a fall rather than a rise in pulmonary vascular resistance. No significant changes were detected in the renal circulation after infusion of contrast media.

Opening of the Blood-Brain Barrier by Intravenous Contrast Media in Euvolemic and Dehydrated Rabbits

It has been suggested that intravenous injections of hypertonic contrast media when used in computed tomography and digital subtraction angiography might raise plasma osmolality sufficiently to open the blood-brain barrier (BBB). The current investigation establishes the threshold of plasma osmolality that causes the the opening of the BBB in euvolemic and dehydrated rabbits. Euvolemic rabbits were allowed food and water ad libitum. Dehydrated rabbits received 4.0 mg/kg of furosemide intramuscularly and were deprived of water for 72 hours. Meglumine/sodium diatrizoate 76 per cent (n=28) or mannitol 20 per cent (n= 12) was administrated intravenously, at a rate of 25 mmol/kg body weight/hour for 2, 3 or 4 hours. Plasma osmolality, blood iodine concentration, blood pressure, heart rate and hematocrit were assessed at regular intervals. Evans blue and 99Tcm-DTPA were used simultaneously as tracers for BBB opening. Rating of BBB opening with 99Tcm-DTPA correlated well with Evans blue staining (r=0.863, p<0.001; n=42). BBB opening was related to plasma osmolality and was similar for both contrast media and mannitol. Widespread BBB opening occurred above 400 mmol/kg while focal BBB opening occurred above 370 mmol/kg. Dehydration per se increased plasma osmolality but did not reduce the threshold for BBB opening.

Quantitative contrast media dose evaluation for cranial computed tomography

The goal of this study was to quantitatively evaluate the CT enhancement characteristics of selected intracranial blood vessels using four different volumes of a contrast medium under otherwise identical conditions in order to help determine a cost-effective dose. In a double blind, prospective manner, 100 patients referred for contrast-enhanced cranial CT were randomly assigned to receive one of four different volumes (50, 75, 100 or 120 ml) of ioversol 320 mg I/ml which was subsequently administered intravenously at a rate of 1 ml/s via a power injector. Unenhanced images were also obtained. Scanning times, slice thickness and other parameters were identical in all patients. Scanning was initiated immediately following delivery of the full volume of contrast. Region of interest Hounsfield unit measurements were acquired in a standardized manner using a 1 mm diameter circle on the pre- and post-contrast scans of the supraclinoid left internal carotid artery (LICA), supraclinoid right internal carotid artery (RICA), basilar artery (BA), and torcular region (TR). The mean enhancement value (in Hounsfield units) for the 50 ml, 75 ml, 100 ml and 120 ml dose groups respectively were as follows for each vessel: LICA 29.9, 41.5, 63.9, 64.6; RICA 30.1, 39.4, 62.6, 65.1; BA 30.0, 41.7, 66.0, 71.9; TR 31.7, 46.8, 68.9, 74.3. There was no statistically significant (p > 0.05) difference in enhancement in any of the four vessels when the 120 ml volume was delivered compared to the 100 ml volume. However, there was a statistically significant (p < 0.05) improvement in enhancement in all four vessels when 100 ml of contrast was administered compared to 75 ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Triple-dose versus single-dose gadoteridol in multiple sclerosis patients

Nine patients with multiple sclerosis underwent brain magnetic resonance imaging (MRI) to evaluate the contrast enhancement of individual lesions after a single dose and a triple dose of gadolinium. A single dose (0.1 mmol/kg) of gadoteridol was administered and after a delay, axial T1-weighted images were obtained. After an additional 0.2-mmol/kg dose, the same T1-weighted sequence was repeated. An unblinded reader simultaneously viewed the images from both doses, and utilizing a computer console to rule out flow artifacts, created a gold standard of "definite" enhancing lesions. Using this system, he determined that there was a total of 12 definite enhancing lesions among the patients. This reader also evaluated lesion conspicuity. The contrast-noise ratio was calculated for each lesion. A second reader, blinded to the dose used, then evaluated the number of enhancing lesions at both doses. The unblinded reader noted increased lesions at both doses. The unblinded reader noted increased lesion conspicuity after the triple dose. Contrast-noise ratios were significantly (p < 0.001) higher after the triple dose (mean, 9.19) than after the single dose (mean, 2.97). The blinded reader detected 11 of the 12 definite lesions on MRIs after the triple dose (sensitivity, 92%) but saw only 6 on MRIs after the single dose (sensitivity, 50%). The difference was significant (p < 0.001). Subjective analysis of the films revealed an increase in "ghosting artifacts" at the high dose. Administration of triple-dose gadolinium provides increased lesion conspicuity and an improved lesion detection rate when compared to single-dose gadolinium in patients with multiple sclerosis.

High-dose contrast-enhanced computed tomography (CECT) with iopamidol in the detection of cerebral metastases. Tolerance of the contrast agent

Intravenously administered iodinated contrast media have been demonstrated, since early experience with computed tomography of the brain, to improve clinical value of the procedure for detecting intracranial lesions. There is no universal agreement about the amount and the method of administration of the contrast medium. Many authors maintain that the use of large doses gives better results for the diagnosis of tumors and metastases. The purpose of this paper is to evaluate the tolerance of iopamidol administered by rapid intravenous infusion in a large number of patients undergoing contrast enhanced computed tomography to detect brain metastases. The authors examined 969 consecutive adult patients suffering from lung cancer, brain metastases have been detected in 17% of cases. Adverse reactions to contrast media occurred in 3 patients. Non ionic contrast media are recommended in this diagnostic procedure.