Enhanced radiation damage caused by iodinated contrast agents during CT examination

ObjectiveTo access the effect of iodinate contrast agent (ICA) on DNA double-stand breaks (DSBs) in human peripheral blood lymphocytes during computed tomography (CT) examinations.Materials and methodsThis present study was approved by the institutional ethics committee; written informed patient consent was obtained from 70 patients. A total of 48 patients underwent computed tomography urography (CTU), in which only one time CT scanning was examined after injecting ICA, and 22 patients received unenhanced whole abdominal CT, among them 10 patients were selected to get ICA injection immediately after irradiation. Blood samples were taken from all patients prior to and immediately after CT scan, as well as 8 min after the injection of ICA. The lymphocytes in these blood samples were separated by using density-gradient centrifugation, fixed and immunostained with γH2AX antibody. The average number of phosphorylated histone H2AX (γH2AX) foci per lymphocyte was counted under a fluorescence microscopy. Differences in the number of γH2AX-foci were statistically analyzed using independent sample t test and one way ANOVA.ResultThe three patient groups had no significant differences in the baseline foci numbers(P > 0.05). The γH2AX-focus levels increased in both groups after CT scan. Patients who underwent CTU examinations had a greater DSBs level (mean ± standard error of mean, 0.945 ± 0.184 foci per cell) than those who received unenhanced whole abdominal CT scan (mean ± standard error of mean, 0.700 ± 0.112 foci per cell), increasing by about 37.9%; The ICA injected before CT scan itself had an effect on the DSBs, which increased DSBs level by approximately 90.3% (0.059 ± 0.018 v s 0.031 ± 0.025, P < 0.05), but no significant difference was found if added after irradiation, increasing DSBs level only by 3.2% approximately (0.711 ± 0.091 v s 0.689 ± 0.108, P = 0.499).ConclusionThe iodinated contrast agent itself can lead to an increase in the level of DSBs as assessed with γH2AX foci formation, and the application of ICA can amplify DNA damage induced by diagnostic x-ray procedures such as whole abdominal CT.     

CT血管成像静脉注射碘对比剂的原则和策略

随着CT技术的迅速进展,CT已经成为医学影像检查中非常重要的组成部分,而静脉注射对比剂增强的CT检查,尤其是CTA的普及更是增加了静脉注射碘对比剂的应用.在很多医疗机构,CTA已基本代替了常规DSA检查,成为血管性病变诊断首选的影像检查手段,甚至被认为可作为影像诊断的金标准[1].然而在临床实践中,新的CT设备也带来了新的问题和挑战.虽然当前CT快速的扫描能力使进行对比增强CT扫描时常可以获得足够诊断的图像质量,但在非常短的扫描时间内确保得到靶部位最大程度的强化却成为一个很大的临床问题,这对精确确定靶部位扫描延迟时间提出了更高要求.笔者综述当前CT静脉注射碘对比剂的一些原则和策略.     

Rapid CT diagnosis of acute appendicitis with IV contrast material

The purpose of this study was to determine the sensitivity and specificity of computed tomography (CT) without administration of oral contrast in confirming suspected acute appendicitis. One hundred seventy-three patient studies were retrieved by a computer-generated search for the word “appendicitis” in radiology reports. Patients presenting to the emergency department over an 8-month period were examined for acute abdominal pain or suspected acute appendicitis. IV-contrast-enhanced CT scans of the abdomen and pelvis were obtained without oral or rectal contrast. Criteria for diagnosis of acute appendicitis included a dilated appendix (>6 mm), periappendiceal inflammation, or abscess. Final diagnoses were established with surgical/clinical follow-up, histopathological analysis or both. The standard time (1 h) for the administration of oral contrast prior to the CT scan was eliminated. Fifty-nine CT diagnoses were made of acute appendicitis, 56 of which were histologically verified and three of which resulted in another diagnosis. One hundred fourteen CT diagnoses were negative for appendicitis. This corresponds to a sensitivity of 100% and specificity of 97%, a positive predictive value of 95%, and a negative predictive value of 100%. CT with IV contrast is sensitive and specific for the confirmation or exclusion of acute appendicitis. By eliminating the time required to administer oral contrast, the diagnosis might be made more rapidly.     

Upper-extremity venography: CO2 versus iodinated contrast material

PURPOSE: To determine prospectively the diagnostic performance of CO(2) venography, by using conventional venography with iodinated contrast material as the reference standard, for the preoperative evaluation of upper-limb and central veins before creation of fistulas for hemodialysis access. MATERIALS AND METHODS: The study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-two patients underwent comparative CO(2) and conventional venography of upper-extremity and central veins. Two independent observers evaluated the opacification of the veins and grade of stenosis, if present. Interobserver agreements were estimated with the Cohen kappa coefficient. Calculations of sensitivity, specificity, and accuracy were used for intertechnique observations. RESULTS: For CO(2) venography, global interobserver agreement was good, with a kappa value of 0.90 (range, 0.71-1.00; 95% confidence interval: 0.84, 0.95). A kappa value of 0.96 (range, 0.86-1.00; 95% confidence interval: 0.93, 0.99) was calculated for global interobserver agreement for conventional venography. The sensitivity, specificity, and accuracy of CO(2) venography for all vein segments were 97%, 85%, and 95%, respectively. CONCLUSION: CO(2) venography had a sensitivity of 97% and a specificity of 85% in the assessment of upper-limb and central vein patency and stenosis, with conventional venography used as the reference standard.     

Neurotoxicity of nonionic iodinated water-soluble contrast media in myelography: experimental study

The neurotoxicity of four contrast media--iotrol, iopamidol, metrizamide, and ioglunide--was studied by subarachnoid injection in 14 rabbits implanted with four cerebral electrodes. Thirty-four recordings and quantitative analyses were carried out of spontaneous electrical brain activity, seizure activity, and visual- and somatosensory-evoked potentials. The quantitative study of the electroencephalograms showed differences among the four products. All four of the contrast media induced a general slowing of the electroencephalographic activity and, 30 min after injection, slow waves and a shift of the spectrum energy toward the slow frequencies (0.5-3.5 Hz). The slowing of the recording was the least marked with iotrol and recovery of a normal recording was also quickest with iotrol. The quantitative study of electrical seizures and paroxysms revealed higher seizure activity with ioglunide and iopamidol. The study of the evoked potentials does not permit any distinction among the four contrast agents. Metrizamide induced the fewest seizures, but, considering the slow waves and the seizures, iotrol appears to be the least neurotoxic.     

Peritoneal reaction resulting from iodinated contrast material: comparative study

A consensus does not exist as to the optimal contrast agent for hysterosalpingography. This study was undertaken to evaluate the early and delayed inflammatory responses of the peritoneal surfaces to various types of iodinated contrast media. Guinea pigs received intraperitoneal injections of lactated Ringer solution, iothalamate meglumine, diatrizoate sodium, ioxilan, or ethiodized oil. The inflammatory response of the peritoneal surfaces was assessed at 1,7, and 30 days. Five animals were studied at each time point for each agent. No animals that received Ringer lactate or iothalamate meglumine had inflammation at any time. Ioxilan produced inflammation in two of five animals at 7 days and no inflammation at 1 or 30 days. Ethiodized oil produced no inflammation at 1 day; however, three animals had inflammation at 7 days, and all five had inflammation at 30 days. The 30-day group showed striking inflammatory response with granulomatous features. The authors recommend the continued use of meglumine-based water-soluble ionic contrast material for hysterosalpingography.     

IV contrast material for abdominal CT: comparison of three methods of administration

Despite a decade of experience, there is still no consensus as to the optimal IV contrast regimen for use in combined abdominal and pelvic CT scanning. In order to determine which regimen is most effective, 90 patients undergoing CT were prospectively randomized into one of three groups, depending on the method by which IV contrast material was administered: (1) a single bolus (150 ml or 175 ml, depending on the patient's weight) started when scans were made at the level of the dome of the diaphragm; (2) a split bolus delivered by means of a power injector, with the first bolus (100 or 125 ml) given when scans were made at the level of the dome of the diaphragm and the second bolus (50 ml) given when scans were made at the level of the iliac crest; (3) an initial hand-delivered bolus (100 or 125 ml) given when scans were made at the level of diaphragm, followed by rapid IV drip infusion of 50 ml throughout the remainder of the study. Quantitative comparison of pre- and postcontrast scans was performed at two levels: at the mid-liver to assess hepatic enhancement and 1 cm above the sacrosciatic notch to assess pelvic vascular enhancement. The single bolus provided better mean liver enhancement (46 H) than did either the split-bolus (36 H) or the bolus-drip (32 H) method (p less than .05). The last two methods achieved a sufficient aortocaval difference (greater than 10 H) to allow for evaluation of the liver in the nonequilibrium phase of contrast enhancement in which lesion detection is thought to be optimal. Mean enhancement of pelvic vessels was significantly better with the split bolus (arterial enhancement of 56 H, venous enhancement of 47 H) than with the single bolus (34 H, 31 H) or bolus-drip infusion (38 H, 35 H) (p less than .05). We conclude that the split-bolus method is optimal for routine combined abdominal and pelvic CT scanning. The bolus-drip method is the least effective method for administering the contrast material.     

Peripheral blood eosinophilia associated with gastrointestinal administration of iodinated contrast media

OBJECTIVE: This study was designed to assess whether gastrointestinal administration of iodinated contrast media results in peripheral blood eosinophilia. MATERIALS AND METHODS: We studied 110 patients in a retrospective review. Diatrizoate meglumine and diatrizoate sodium for abdominal CT were administered to 98 of these patients; 22 of the 98 had also been given the same contrast medium administered by enema. The remaining 12 patients were given diatrizoate sodium for gastrointestinal fluoroscopy. A control group of 65 patients underwent single-contrast barium upper gastrointestinal or enema examinations. WBC and eosinophil counts were determined approximately 24 hr before the examination and every 24 hr thereafter, through the ninth day. RESULTS: Eosinophilia was detected in 17 (15.5%) of 110 patients after gastrointestinal administration of iodinated contrast media. The prevalence of eosinophilia after administration of iodinated contrast media was statistically significantly different compared with that in the control group, in which none of the 65 patients had eosinophilia (p < 0.001). Eosinophilia was detected 48 hr after application of iodinated contrast agents and lasted through the sixth day, with a peak on the fifth day. The prevalence of eosinophilia was independent of route of application, dose, or type of iodinated contrast medium. Eosinophilia in all cases was clinically asymptomatic. CONCLUSION: Eosinophilia that is caused by gastrointestinal administration of iodinated contrast media is a transient, clinically silent phenomenon. It may lead to unnecessary workup for known conditions associated with eosinophilia.