Contrast enhancement of brain tumors and irradiated normal brain: a comparison of Iohexol and Iothalamate

Summary The nonionic contrast agent iohexol was compared with the ionic agent iothalamate for contrast enhancement of brain tumors and radiation brain damage in dogs. Tissue enhancement during infusion of contrast and 5, 10, 15 and 30 min later was measured using quantitative computed tomography. Blood iodine was measured using x-ray fluorescence. Peak contrast enhancement occurred during infusion in tumors and after 5 min in irradiated normal brain for both contrast agents. Absolute uptake of contrast in each lesion was the same for both agents when normalized to total grams of iodine administered. Blood iodine levels were slightly but not significantly higher using iohexol. The reduced osmotic load and similar contrast enhancement of lesions suggest that the nonionic contrast medium iohexol may be a useful agent for routine CT of the brain.     

Dynamic perfusion CT parameters and delayed contrast washout CT in characterization of adrenal tumors: A comparative study

Purpose

The study aims to compare the accuracy of washout and perfusion CT techniques in diagnosis of adrenal tumors.

Postoperative contrast enhancement in brain tumors and intracerebral hematomas: CT study

Postcontrast cerebral CT was performed sequentially on days 3, 7, and 14 after surgery in 34 patients [11 with gliomas; 6 with metastatic tumors, and 17 with intracerebral hematomas (ICH)]. The purpose of this study was to investigate the natural course and mechanisms of postoperative contrast enhancement (CE) of the brain around the removed lesions. Contrast enhancement was noted on days 3-14 in 10 patients in whom the gliomas were partially or subtotally removed. The intensity of CE appeared to increase with time. Among the six patients in whom the metastatic tumors were totally removed, four showed no CE until day 14 after surgery. Contrast enhancement appeared on day 3 in one and on day 14 in another. In 12 patients with ICH, which had been evacuated during the first 5 days after hemorrhage, CE was not noted on day 3 but began to appear on day 7, and intensified on day 14 after surgery. Contrast enhancement was demonstrated on day 3 in four of the five patients in whom the ICH was removed later than 10 days after the hemorrhage. No CE was observed on days 3 through 14 in the one patient in whom the hematoma capsule was totally removed. The present study suggests that CE noted on day 3 after removal of gliomas and metastatic tumors seems to be caused by extravasation of contrast medium within the residual tumor, which is devoid of blood-brain barrier. Contrast enhancement noted in ICH cases and intensifying CE noted in tumors 7 days after surgery seems likely to be caused by neovascularization in the postoperative brain.     

Contrast medium pooling in cystic renal carcinoma: CT findings

This case report describes a serendipitously diagnosed renal carcinoma in a transplant donor. Computed tomography was instrumental in establishing the true nature of this mass based on its ability to demonstrate pooling of contrast material and staining of discrete septae on dynamic postcontrast scans.     

Neonatal brain tumors: CT and MR findings

Twelve neonatal brain tumors, presenting within 60 days of birth, constituted 3.3% of pediatric brain tumors. Three-fourths were supratentorial. Two-thirds were benign. Forty-two percent were choroid plexus papilloma. Twenty-five percent were teratoma. Eight percent each were hypothalamic glioma, gliosarcoma, medulloblastoma, and primitive neuroectodermal tumor. Clinical symptoms were nonspecific. Signs of herniation were absent in all 12 patients. Forty-two percent of these patients died 1 day to 8 months after diagnosis. Ultrasound, CT, and magnetic resonance have all proved useful for displaying these lesions suitably for surgery.     

Computed tomography of virally induced canine brain tumors: a preliminary report

Seven neonatal dogs were inoculated intracerebrally with Avian Sarcoma Virus (ASV) and studied by computed tomography (CT) for intracranial tumors. The tumor yield was five anaplastic astrocytomas and two sarcomas, with an average latency of 57 days. Computed tomography accurately detected all tumors over 5 mm in diameter and predicted the size of the tumors within 3 mm. The intensity of contrast enhancement was directly related to the dose of Conray-60. The area of enhancement on the CT scan correlated precisely with tumor permeability as determined histologically with horseradish peroxidase (HRP). Edema seen in CT scans correlated well with edema present in histological sections. Peritumoral edema was impermeable to both Conray-60 and HRP. The ASV-induced canine brain tumor model appears well suited for future CT studies.     

Normal brain iodine-125 radiation damage: effect of dose and irradiated volume in a canine model

High-activity iodine-125 sources in plastic catheters were surgically placed in the cerebral white matter of healthy beagle dogs and later removed. Reference doses, calculated at a point 0.75 mm from the source, ranged from 10 to 40 Gy. Necrosis, vascular-related damage, and edema were quantified by computed tomography. Volumetric analyses were used to derive the relationship of dose and dose rate to necrosis and contrast enhancement. The extent of necrosis was related to irradiated volume; a minimum effective dose averaging 180-200 Gy was required to induce this type of damage. Contrast enhancement was less dependent on irradiated volume or total dose. The extent of radiation-induced edema was directly related to the volumes of necrosis plus contrast enhancement. Noninvasive serial studies in a well-characterized in vivo model can address specific clinically related questions on damage to normal tissue after interstitial irradiation.     

Contrast enhancement of hepatic tumors in CT: comparison between bolus and infusion techniques

Pre- and postcontrast CT scans of 125 nonselected patients with histologically verified hepatic neoplasms were analyzed. Sixty patients received an intravenous bolus injection of 50-100 ml diatrizoate 60% in 10-20 sec, and 65 patients an intravenous infusion of 300 ml diatrizoate 30% in 5-10 min. Compared to the precontrast examination, a significant improvement in the visualization of hepatic tumors was obtained with both contrast administration methods when the patients were examined before the equilibrium phase (difference in blood iodine concentration between aorta and inferior vena cava of less than 10 H) is reached. The equilibrium phase is reached 2 min after a contrast material bolus and with termination of an infusion. Scanning in the equilibrium phase does not significantly improve visualization of hepatic tumors when compared to the precontrast examination and carries a considerable risk of partial to complete tumor concealment. For similar reasons, concealment of hepatic tumors might also result when intravenous contrast material is used for another radiographic study preceding the CT examination.     

Attenuation changes of the normal and ischemic canine kidney. Dynamic CT scanning after intravenous contrast medium bolus

The potential of CT scanning to explore total and regional renal blood flow was evaluated in a dog model with unilateral renal artery stenosis (n = 7, reduction of renal blood flow: 32-75% of base line flow). Attenuation versus time curves were generated for the renal cortex and medulla, as well as for the aorta and renal vein. A fast CT scanner was used which allowed for up to 24 scans/minute at the same level (slice thickness: 10 mm). A total of 10 ml contrast medium was injected into a peripheral vein for each scan series taken. During baseline conditions, the curve of the renal cortex and medulla demonstrated 2 peaks. The first peak was mainly related to early vascular enhancement, whereas the second peak corresponded mainly to the appearance of contrast medium in the distal convolutes and collecting ducts. Ischemia of the kidney resulted in a reduction of the first peak and a flattening of the leading edge slope. Transport of contrast medium through the extravascular compartments of the kidney was delayed during ischemia. Relative renal blood flow was obtained from the CT data by dividing peak enhancement by rise-time as assessed from the cortical curve. All measurements were related to baseline flow and validated by flow measurements using radioactive labeled microspheres (n = 5). Correlation was found to be r = 0.97.     

Perfusion CT imaging of brain tumors: an overview

Perfusion imaging of brain tumors has been performed by using various tracer and nontracer modalities and can provide additional physiologic and hemodynamic information, which is not available with routine morphologic imaging. Tumor vascular perfusion parameters obtained by using CT or MR perfusion have been used for tumor grading, prognosis, and treatment response in addition to differentiating treatment/radiation effects and non-neoplastic lesions from neoplasms. This article is an overview of the utility of PCT for assessment of brain tumors and describes the technique, its advantages, and limitations.     

Contrast medium injection on CT during hepatic arteriography: comparison of two protocols

To assess the optimum method of contrast medium injection on CT during hepatic arteriography (CTHA), we performed this procedure in 37 patients using two consecutive protocols (A and B) employing different concentrations of iodine (iohexol at 140 mgI/ml and 300-350 mgI/ml), flow rates (2 ml/sec and 1 ml/sec), and contrast medium volumes (60 ml and 30 ml). Mean parenchymal enhancement of the right lobe and left lateral segment were measured and compared. Enhancement varied significantly more with protocol B, especially in the left lateral segment. These results suggest that a low iodine concentration and high injection rate are suitable for CTHA, to avoid nonuniform parenchymal enhancement.     

Excessive accumulation of normal retroperitoneal fat mimicking a neoplasm: urographic/CT correlations

Computed tomography (CT) was performed on four patients in whom excretory urograms revealed marked displacement of the kidneys and/or ureters. CT in each case was remarkable for the presence of excessive accumulation of normal retroperitoneal fat and failed to document the existence of a retroperitoneal neoplasm, lymphadenopathy, or other pathological mass.     

Excessive accumulation of normal retroperitoneal fat mimicking a neoplasm: Urographic/CT correlations

Computed tomography (CT) was performed on four patients in whom excretory urograms revealed marked displacement of the kidneys and/or ureters. CT in each case was remarkable for the presence of excessive accumulation of normal retroperitoneal fat and failed to document the existence of a retroperitoneal neoplasm, lymphadenopathy, or other pathological mass.     

PET study of methionine accumulation in glioma and normal brain tissue: competition with branched chain amino acids

Five patients with glioma were examined with positron emission tomography using ([11C]methyl)-L-methionine. The study was repeated while the patient was being infused with branched chain amino acids (BCAA), 250 mumol/min. The accumulation rates of methionine in tumor tissue and in normal brain tissue were compared without and with the infusion of amino acids. Both tumor tissue and normal brain tissue showed a reduction in the methionine accumulation by 35% while the patient received the infusion. In one patient with a severe blood-tissue barrier disruption the tumor accumulation rate was unaffected. It is concluded that in gliomas without severe blood-tissue barrier disruption, the accumulation of methionine is governed by processes exhibiting similar properties regarding competition with BCAA as in normal brain tissue.     

Contrast medium precipitation in the stomach between contiguous plain and contrast CT scans

Precipitation of diluted Gastrografin (meglumine sodium amidotrizoate) occurred in the stomach during computed tomography (CT) examination in a 43-year-old man with fasting. Precipitation was not observed on the initial plain CT scan, but was demonstrated on the contrast-enhanced CT scan following the plain CT. Hyperacidity in the stomach might be promoted during CT examination and cause precipitation between scans.     

CT of the normal brain in preterm infants

Twenty-two normal preterm and 10 full-term infants were studied by cranial computed tomography. The study included correlation of the gestational age and birth weight to the ventricular size, brain size, and the area of the sylvian fissure. The most relevant parameters were the bifrontal diameter, bifrontal index, and the transverse diameter of the brain. The incidence of visualization of the sylvian fissure diminished with gestational age. Density measurements revealed the high cortical sections had a higher average density than the whole brain sections. The parietooccipital region showed an increasing average attenuation during the preterm period until term.     

The CT scan appearance of the brain in the normal elderly population: A correlative study

Summary Atrophy of the brain as depicted on CT scan was correlated with social and psychological testing in 100 selected volunteers with no known neurologic or psychiatric impairment. The data indicated cognitive impairment based on psychometric test results in those with atrophy, independent of its severity. No organic or biochemical changes could be found that could explain these findings. Repeat examinations at 1-year intervals are planned to evaluate the evolution of these findings.