This was a randomized study conducted from April 2014 to 2015 at Chongqing City Chinese Medicine Hospital. The consecutive patients, who were scheduled to undergo a follow-up contrast-enhanced CT for the assessment of pain or the evaluation of suspected masses in organs, were prospectively enrolled in this study. In brief, nine variables were assigned as exclusion criteria: (1) a known history of hypersensitivity to iodine, (2) pregnancy, (3) lactation, (4) clinically unstable condition, (5) having received contrast media <7 days before the procedure, (6) cardiogenic shock, (7) known renal dysfunction, (8) pulmonary edema, (9) mechanical ventilator support. The subjects were randomized into two groups by the permuted block randomization method. Subjects allocated to the experimental arm underwent body computed tomography scanning using the contrast medium of iodixanol, whereas iohexol was used in the controlled arm of the trial.
The radiology nurse established the heparin lock intravenous line before injection. Both of the contrast material were pre-warmed to 37 °C prior for intravascular use. The regional difference in contrast agent wash-in and wash-out time constants were identified as the main mechanism of delayed contrast enhancement on scan images. The highest attenuation difference for idoixanol on delayed contrast-enhanced images was achieved 4 min post injection comparing to 3 min for iohexol. In this trial, 1000 individuals were injected 100 ml iohexol 300 mg I/ml, while the other 1000 participants received intravenously 100 ml iodixanol 300 mg I/ml. The whole participants were monitored through completion of injections and throughout the scanning. In addition, these patients were further interviewed at the end of the test immediately, at 1 h, as well as at 24 h, concerning any local or systemic syndrome. The radiology nurse recorded vital signs at the time of interview. Urine and blood specimens were also obtained at the aforementioned time. The CTDIvol was 13.82 mGy for the 80 kV scan protocol.
This analysis was performed on both venous blood samples and voided urine samples, which were collected in a blinded fashion and measured by auto-analyzer of the clinical laboratory in Chongqing City Chinese Medicine Hospital. Generally, blood samples included tests for potassium chloride, platelet count, alanine aminotransferase, white blood cells, eosinophils, lymphocytes, aspartate aminotransferase, hemoglobin, red blood cells, sodium, blood urea nitrogen, creatinine, basophils, hematocrit, lactate dehydrogenase, and neutrophils. Urine samples usually contain occult blood (red blood cells), glucose, pH, specific gravity, and protein.
Assessment of contrast enhancement on images
All participants were instructed to practice breath holding before scanning which was all performed on a second-generation 64-slice scanner. Three experienced CT radiologists, each with more than 5 years’ work experience was allocated in a group, to evaluate the images independently. Contrast quality grades should arrive at consensus for each diagnostic item by discussion. None radiologists had been involved in the patients recruiting. The radiologists were fully unaware of the original examination interpretation results and the specific contrast material injected. Contrast quality grades which is referenced as diagnostic images quality in this passage, which could be classified into three distinct grades as follows: Grade one is optimal, the one that provides optimal information to make a definitive decision. Grade two is the suboptimal choice, which provides less definitive information to make a suboptimal decision, which was also taken, if the images enhancement could not arrive at the optimal conditions in any aspect. Grade three is definitely not determinative, could not offer sufficient information to make the diagnosis. Results of this trial would be presented for all participants recruited in this research.
Contrast agent reactions
Based on the reaction severity according to the criteria, patients’ reactions to the contrast enhanced CT could be graded as mild, moderate, or severe (Pintassilgo Santos et al. 2009). Discomfort related to the injection was classified into three grades as follows: mild, moderate, or severe, with the definition of subjective feeling, which resulted from physiology and psychology. Mild contrast reactions including rash, emesis, peculiar taste, itching, did not require any treatment. Moderate events were of any aforementioned in more advanced degree and required close monitoring and immediate therapy. Serious reactions were regarded as life-threatening events and more robust solutions were further required. All incidents accompanied with the material injection were recorded in this institution. For each adverse event, both supervising CT radiologists and technologists involved, completed the incidents reports, which contain the personal characteristics, contrast medium as well as date of the scanning and the events descriptions. These reactions could be classified into either immediate or delayed event according to the events onset time. Immediate events were those that occur within 1 h and were reported by experimentalists nearby or patients. Delayed reactions were subsequent clinical symptoms up to 7 days from time of intravenous use. The patients or their companions reported these information to us voluntarily.
Quantitative variables were summarized by use of descriptive statistics, expressed as mean ± SD, while categorical variables were expressed as frequencies or percentages. Personal characteristics were compared between two contrast media by Student’s t test. Fisher’s exact test was used to evaluate the frequency of adverse events and discomfort. P values <0.05 were considered statistically significant difference. Statistical analysis was performed by spss version 18.0 for Mac.
This study was approved by local institutional review boards, and written informed consents were obtained from all patients before they were randomly assigned.