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.     

Dynamic CT of hepatic masses with intravenous and intraarterial contrast material

Seven patients with primary and metastatic hepatic tumors had dynamic computed tomographic scans obtained after an intravenous and an intrahepatic arterial bolus of contrast media. Four patients had hepatoma and three had hepatic metastasis from either a colonic, pancreatic, or leiomyosarcoma primary malignancy. Computed tomography was also performed after an intravenous drip infusion of contrast material. Time-density curves of the hepatic lesions after contrast administration were analyzed and compared. The results demonstrated that: (1) intrahepatic arterial delivery of contrast fluid resulted in the greatest contrast enhancement of lesions and detected more lesions than the intravenous bolus technique, which was superior to the drip infusion technique; (2) no consistent difference in the pattern of contrast enhancement was found between various hepatic lesions; (3) within multiple lesions of similar pathology in any one liver, a spectrum of contrast enhancement pattern was found; and (4) changes in contrast enhancement occurred rapidly and lesions changed from hypodense to isodense to hyperdense to isodense within 30--45 sec.     

Study of bolus geometry after intravenous contrast medium injection: dynamic and quantitative measurements (Chronogram) using an X-ray CT device

An X-ray computed tomographic (CT) scanner was used to measure and image transmission profiles of a single 8 mm thick object slice digitally with a high temporal (up to 20 ms), spatial (1.1 mm), and density (0.5%) resolution. This special digital radiography imaging mode is called a Chronogram. It produces a time-history of measured attenuation values but not a normal anatomical image. After intravenous bolus injection of contrast medium, bolus shape as a function of time and bolus passage times can be imaged. Absolute iodine concentrations in blood vessels and soft tissue can be evaluated at any time in all body regions. The Chronogram has the potential to quantify physiological parameters such as enhancement, passage times, and relative blood flow through pairs of arteries or symmetrically arranged organs and to measure absolute iodine concentrations. As a disadvantage, patient motion can prevent quantitative evaluation. This drawback can, however, be turned into an advantage in that all kinds of motion can be measured, for example, movement and pulsation of the heart.     

Optimization of cardiac MSCT contrast injection protocols: dependency of the main bolus contrast density on test bolus parameters and patients' body weight

RATIONALE AND OBJECTIVES: Our aim was to evaluate the correlation of test bolus (TB) curve parameters with main bolus (MB) contrast density for cardiac 16-slice computed tomography, and to correlate observed enhancement with patient body weight. MATERIALS AND METHODS: Sixty patients with known or suspected coronary artery disease were included in a prospective double-blind study. Contrast material containing 300 mg iodine/mL (Iomeprol 300; Imeron 300, Bracco Imaging SpA, Milan, Italy) and 400 mg iodine/mL (Iomeprol 400; Imeron 400) was injected at a rate of 1 g of iodine/second. Contrast densities (Hounsfield units) of the MB were determined in the left cardiac system. The peak density (PD) of maximum attenuation and the area under the curve (AUC) of the TB curve were calculated for each patient. The dependency of MB contrast attenuation on these parameters and on patient body weight was evaluated. RESULTS: Positive correlations (r = 0.52 and r = 0.56, respectively; P < .0001) were obtained between the PD and AUC of the TB curve with the mean density of the MB. Stronger correlations (r = 0.63 and r = 0.64, respectively; P < .0001) between PD and AUC of the TB curve and MB attenuation were found when patient body weight was included in the analysis. CONCLUSIONS: Strong correlation of the PD and AUC of the TB curve with the mean density of the MB is observed when patient body weight is considered. Contrast injection protocols may be optimized, and variations of MB contrast density in the left ventricle and main coronary arteries reduced, by taking these TB parameters and the weight of the patient into account.     

正常肝脏与肝硬化螺旋CT扫描时对比剂最优化使用方法的研究

目的 研究正常肝脏与肝硬化肝脏在螺旋CT增强多期扫描中最佳对比剂剂量、注射流率及各组织强化达到峰值的时间。方法 正常肝脏、肝硬化肝脏各60例，按完全随机设计法各分成6组，分别以不同的注射剂量及流率在肘静脉注射非离子型对比剂，并在同一层面作连续多层扫描。最后测量各组织CT值，建立统计表并相互比较。结果 正常肝脏当注射剂量为1.5ml/kg时，3种不同的注射流率除主动脉强化峰值两两比较统计学上差异均有显著性意义外（P＜0．05），门静脉、肝实质差异均无显著性意义（P＞0．05）；当注射流率为2.5ml/s时，不同的剂量强化峰值主动脉、门静脉、肝实质差异均有显著性意义（P＜0．05）。肝硬化组：当注射剂量为2.0ml/kg时，3种不同的注射流率时肝实质在2.5ml/s与3.0ml/s时强化峰值差异有显著性意义（P＜0．05）。当注射流率为3.0ml/s时，不同的剂量肝实质强化峰值差异有显著性意义（P＜0．05）。结论 正常肝脏与肝硬化肝脏的螺旋CT增强扫描的最佳剂量、注射流率应分别为1.5ml/kg、2.5ml/s和2.0ml/kg、3.0ml/s。其主动脉、门静脉及肝实质达到峰值的时间分别为：28s、52s、73s和31s、68s、77s。     

Three-dimensional imaging of liver tumors using helical CT during intravenous injection of contrast medium.

PURPOSE: The goal of this work was to determine whether 3D reconstruction of images from CT during intravenous injection of contrast medium, performed in tandem with advanced rendering algorithms, could accurately depict major anatomic structures and hepatic tumors. METHOD: Thirty-one patients (22 with hepatocellular carcinoma, 8 with metastatic lesions, and 1 with intrahepatic cholangiocarcinoma) underwent CT imaging. Twenty-three of the 31 patients underwent needle biopsy or surgery, yielding a histologic diagnosis. The remaining eight patients were diagnosed from imaging findings and laboratory data. We compared the ability of maximum intensity projection (MIP) and volume-rendered technique (VRT) images to depict the hepatic veins and intrahepatic portal veins. RESULTS: Both MIP and VRT depicted the course of vessels up to the second or third branches. The techniques did not significantly differ. In this regard, in most cases, visualization of the liver surface and tumor was excellent with VRT images. CONCLUSION: Volume-rendered 3D-CT images during intravenous injection without the MIP technique produced 3D images of high quality with excellent visualization of tumors and their relationships to vital structures.     

Attenuation changes of the ventricular CSF after intravenous injection of contrast material

Summary The CT attenuation change of the intraventricular CSF after i. v. administration of contrast material has been studied in 20 patients. A very small increase of attenuation was observed in the entire material. The method does not seem to be appropriate at present for the study of small attenuation changes in the CSF reflecting the passage of contrast material.     

CTF-guided puncture of an unenhanced isodense liver lesion during continuous intravenous injection of contrast medium

CT fluoroscopy (CTF) facilitates guidance of percutaneous biopsies and other interventional procedures. We wished to demonstrate the usefulness of CTF for the puncture of an unenhanced isodense liver lesion during continuous injection of intravenous contrast medium. We performed CTF-guided puncture of a 2-cm lesion in the liver of a patient suffering from lung cancer. CTF enables puncture of liver foci even if they are unenhanced and isodense with the surrounding parenchyma.     

Preheated contrast media: the advantage of intravenous injection

A study was performed to evaluate the effectiveness of intravenous injections with preheated contrast as opposed to room temperature contrast. Methods of preheating contrast are described as well as the accompanying complications and treatments of side effects. This article explains why preheated contrast media is a recommended procedure.     

Multi-detector row helical CT of the liver: quantitative assessment of iodine concentration of intravenous contrast material on multiphasic CT--a prospective randomized study

PURPOSE: The purpose of this study was to assess the quantitative effects of contrast material concentration on hepatic parenchymal and vascular enhancement in multiphasic computed tomography (CT), using multi-detector row helical CT. MATERIALS AND METHODS: We designed a prospective randomized study to test two different concentrations of contrast material on five phasic scans of the liver. One hundred patients were randomly assigned to two groups: an iodine concentration of 300 mg/mL in group A and 370 mg/mL in group B. All patients received a fixed volume of 100 mL at a 4 mL/sec injection rate. Enhancement values for the hepatic parenchyma and aorta at three levels (upper, middle, and lower level of the liver), and values for portal and hepatic veins were statistically compared between the two groups. RESULTS: Hepatic parenchymal enhancement values at all levels of the liver in portal phase (PP) and equilibrium phase (EP) were significantly higher in group B than in group A (p<0.01). Aortic enhancement values at two levels of the liver (middle and lower) in early hepatic arterial phase (EAP) were significantly higher in group B than in group A (p<0.05), however, there was no significant difference between groups A and B in aortic enhancement during the delayed hepatic arterial phase (DAP). Portal and hepatic venous enhancement values in PP and EP were significantly higher in group B than in group A (p<0.01). CONCLUSION: On multiphasic dynamic CT, the use of a higher iodine concentration of contrast material results in higher hepatic parenchymal enhancement and aortic enhancement, as well as higher portal and hepatic venous enhancement.     

Effects of nonionic intravenous contrast agents at PET/CT imaging: phantom and canine studies

PURPOSE: To investigate the effects of intravenous contrast agents on quantitative values obtained with a combined positron emission tomographic (PET) and computed tomographic (CT) scanner by using several phantoms and a dog. MATERIALS AND METHODS: Fluorine 18 fluorodeoxyglucose (FDG) was mixed with different concentrations of contrast agent with the same syringe (phantom 1), and the phantom was scanned. After image reconstruction with various attenuation maps, radioactivity concentrations were compared. Then, FDG solutions with (phantom 2) or surrounded by (phantom 3) various concentrations of contrast agent were scanned repeatedly, and radioactivity concentration was compared. Finally, PET and CT with and without contrast agent were performed in a dog. PET images were reconstructed by using different attenuation maps, and radioactivity concentrations were compared. The radioactivity concentration on germanium 68 (68Ge)-based corrected images was regarded as standard, and percentage bias, defined as difference divided by measured activity of 68Ge-based corrected images, was assessed. The relationship between the concentration of contrast agent and the percentage bias was assessed with the Pearson coefficient r, and the significance of correlations was evaluated with the Fisher z test. RESULTS: All phantom studies demonstrated that presence of a contrast agent resulted in overestimation of emission data. CT numbers showed a strong positive correlation with the percentage bias in phantoms 2 (r = 0.999) and 3 (r = 0.987); the maximum percentage bias at 1,360 HU reached approximately 45%. These effects were independent of FDG concentration. In a canine model, presence of a contrast agent also increased emission activity, but the percentage bias was less than 15% in the liver and smaller in all other organs except the kidney (26%). CONCLUSION: High concentrations of a contrast agent caused considerable overestimation of apparent tracer activity in phantom studies; however, the emission bias was relatively modest in vivo, except in areas with very high contrast agent concentrations.     

Contrast-enhanced spiral CT of the head and neck: comparison of contrast material injection rates.

BACKGROUND AND PURPOSE: Contrast-enhanced spiral CT studies of the head and neck are performed frequently using contrast material volumes of approximately 30 g iodine and a scan delay of 30-45 seconds. Because little is known about the effects of contrast material injection rates on tissue enhancement, this was prospectively investigated in our study. METHODS: Ninety-seven patients underwent spiral CT of the head and neck. Each patient was assigned randomly to one of four groups who received 100 mL of nonionic contrast material (300 mg I/mL) at different monophasic injection flow rates with 1.5, 2, 3, and 4 mL/s. Scanning started after a constant delay of 35 seconds. The attenuation of the carotid artery, jugular vein, and sternocleidomastoid muscle was measured over time and the attenuation of the submandibular and thyroid gland was evaluated. Vascular attenuation of at least 150 HU was considered to be sufficient. RESULTS: The mean scan time was 33+/-5 seconds. The study, using an injection rate of 2 mL/s, showed the longest time of sufficient overall (arterial and venous) vessel attenuation (27+/-4 seconds, P< or =.008). The injection flow rate did not influence significantly muscular attenuation (mean enhancement during scan time: 9+/-7 HU). The 1.5 mL/s protocol showed the lowest attenuation values of the submandibular gland (81+/-12 HU) and the highest attenuation values of the thyroid gland (164+/-22 HU), but the attenuation of the thyroid gland was not statistically different from that revealed by the 2 mL/s protocol. CONCLUSION: Using 100 mL of intravenous contrast material with 300 mg I/mL for spiral CT studies of the entire head and neck, the optimal injection flow is 2 mL/s, whereas lower flow rates resulted in insufficient venous enhancement.