Is intravenous contrast enhancement effective in improving CT diagnosis of hepatic disease?]

PURPOSE: The purpose of this study was to evaluate the effectiveness of contrast enhancement in the diagnosis of hepatic disease. MATERIALS AND METHODS: 2761 cases involving CT of the liver and abdomen were analyzed using logistic analysis. CT was either helical-CT (SDCT) or multi-detector CT (MDCT), with power injector. RESULTS: Contrast enhancement use was 92% in liver disease and 95% in tumor cases. A typical case involved a 66-year-old man given 2-4 ml/sec of contrast material using dual injection. CT imaging was done in the equilibrium stage. The use of contrast material was effective for the diagnosis of liver tumor except in the qualitative diagnosis of hepatocellular carcinoma with SDCT where the odds ratio was 0.084. CONCLUSION: Intravenous contrast enhancement was effective for the CT diagnosis of hepatic tumor. Dynamic CT was effective using MDCT, and dual injection of contrast material was also valid for SDCT. Multiphasic studies were needed for detecting liver tumors not only on MDCT but also on SDCT. CT imaging during the equilibrium phase alone is inadequate to document diagnosis of metastatic liver tumors. The addition of various phasic contrast materials during CT was effective in evaluating liver tumors that showed angiogenesis.     

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.     

CT attenuation of colorectal polypoid lesions: evaluation of contrast enhancement in CT colonography

The aim of this study was to calculate pre- and postcontrast CT attenuation values of benign colorectal polyp and carcinoma lesions detected by virtual colonoscopy, and to investigate whether contrast enhancement of these lesions can be potentially used for differentiation from residual fluid in the colon. Fifteen benign polyps and 21 colorectal carcinoma lesions detected by virtual colonoscopy in 18 patients were included in our study. All of the polyps and carcinoma lesions were confirmed by colonoscopic biopsy. Measurement of CT attenuation values was performed in precontrast (supine) and postcontrast (prone) scans for each polyp and carcinoma. The CT attenuation values of residual fluid in the colon was also measured from the same location before and after intravenous contrast administration. On unenhanced CT scan mean attenuation values of benign polyps and colorectal carcinomas were 32.4 and 42.6 HU, respectively. Following contrast enhancement, mean attenuation value increased to 78.9 HU for polyps and 90.7 HU for carcinomas. Increase in the CT attenuation values of these lesions was significant ( p <0.0001). Mean CT attenuation value of residual fluid before and after administration of IV contrast were 14.6 and 13.8 HU, respectively. The difference between CT attenuation value of residual fluid in the colon before and after contrast material was not significant ( p =0.29). Colorectal benign polyps and carcinomas demonstrate significant enhancement following contrast administration and use of intravenous contrast material during virtual colonoscopy may help in some cases in differentiating these solid lesions from residual colonic fluid that does not enhance. This paper was presented at RSNA 2001 meeting.     

Multi-slice CT contrast enhancement regimens

Historically, the development of progressively faster Computed Tomography (CT) technology has dictated a recurrent need to re-examine intravenous contrast agent enhancement regimens. The most recently introduced development, the very fast, multi-slice helical/spiral systems, have raised the same issue yet again. It is possible, exploiting the technology to its maximum potential as regards speed, to perform an examination many times faster (depending on the number of detector rings from 4 to 64) even than with earlier single slice spiral instruments. In order to optimise image quality, such maximal speed gains will not usually be sought but, nevertheless, imaging time will generally be substantially reduced. It is natural that the question of a possible need to modify contrast agent enhancement protocols designed for an earlier generation of slower machines should again be considered. Using as a basis known contrast agent pharmacokinetics and results of modelling techniques, the matter is tackled in this paper.     

Enhancement of cervical intraspinal tumors in MR imaging with intravenous gadolinium-DTPA

Intravenous Gd-diethylenetriamine pentaacetic acid (Gd-DTPA) was administered to 10 successive patients with cervical intraspinal tumors. Contrast enhancement was seen in each case. Gadolinium-DTPA was useful in outlining the tumoral masses, as well as in distinguishing intramedullary from extramedullary neoplasms.     

Evaluation of various methods of intravenous contrast enhancement for thoraco-abdominal spiral CT scanning in trauma patients

The purpose of this study was to determine the optimal contrast concentration, volume, and injection rate for helical CT imaging of trauma patients requiring evaluation of the chest, abdomen, and pelvis. Two hundred forty patients were randomized into six different regimen groups for administration of iohexol nonionic intravenous contrast medium, each regimen containing 36 g iodine, with various injection rates, volumes, and concentrations of intravenous contrast enhancement. Parenchymal and vascular enhancement was objectively measured by obtaining pre- and post-contrast attenuation values of the thoracic and abdominal aorta, liver, and spleen, as well as post-contrast attenuation values of vascular enhancement of the portal vein and iliac artery. The contrast-enhanced images were subjectively reviewed by four radiologists blinded to the contrast administration techniques and objective evaluation results. It was found that while our ability to evaluate the abdominal organs was essentially equivalent with all six contrast administration regimens, our ability to evaluate the thoracic aorta was significantly better using 150 ml iohexol (Omnipaque 240) at 3 ml/s than with the other methods. Therefore, we recommend the use of 150 ml iohexol (Omnipaque 240) at 3 ml/s for combined chest and abdominal studies in patients with blunt trauma.     

CT contrast enhancement in cerebral infarction.

Computed tomography was used to study 100 patients with ischemic cerebral infarcts. All cases were documented by autopsy, radionuclide imaging, cerebral angiography, or clinical course. Vascular distribution of infarcts was varied and included infarcts of cerebral hemispheres, basal ganglia, and cerebellum. Distinct patterns of enhancement are seen following administration of intravenous contrast material: predominantly peripheral, central, homogeneous, or heterogeneous. Enhancement of the infarcted area usually occurs 1-4 weeks after the onset of clinical symptoms, but was seen as early as the first day or as late as several months after the onset of symptoms. Infarcts showing contrast enhancement may or may not revert to a nonenhanced pattern on follow-up examination for several months. Lesions demonstrating contrast enhancement in cerebrovascular disease may at times be indistinguishable from tumor. Contrast enhancement was the only manifestation of infarction in some instances, and an infarcted area may be completely missed if a postcontrast examination is not performed.     

Hepatic tumors: signal enhancement at Doppler US after intravenous injection of a contrast agent

Experiments were carried out to detect and establish the origin of Doppler and echo signal enhancement in small vessels of the systemic circulation and of tumors after intravenous injection of a contrast agent. Eight woodchucks (Marmota monax) were studied; each woodchuck had naturally occurring hepatocellular carcinoma. Injections of 0.1-4.0 mL of air-filled human serum albumin microspheres were administered into a hind limb or jugular vein. Ultrasound (US) examination included transabdominal duplex scanning, color Doppler imaging, placement of a Doppler transducer on the exposed tumor, and surgical implantation of pulsed Doppler cuffs. Doppler signals were assessed by recording color Doppler images and results of spectral analysis. While subjective echo level was unaffected within the tumors, dramatic Doppler signal enhancement was recorded in both normal and tumor vessels. At optimum dose levels, a signal gain of approximately 10 dB was recorded from the tumor. Analysis showed that the echo enhancement was due to the presence of the contrast agent in branches of the hepatic artery. These results suggest that tumor detection may be enhanced by intravenous administration of a US contrast agent.     

Dynamic imaging of contrast enhancement in brain tumors

Gadolinium-DTPA has been shown to be a good probe for demonstrating defects in the blood-brain barrier, but it has a rapid rate of elimination so that peak circulating levels are short-lived. In this study ultrafast echo-planar imaging has been used in combination with a bolus injection of gadolinium-DTPA to evaluate perfusion within brain tumors and to assess the degree of disruption of the blood-brain barrier. The temporal profile of enhancement may allow discrimination between different tumor types.     

增强MRI时间-信号增强率曲线对肾上腺肿瘤的鉴别价值

目的 :以肿瘤的时间 信号增强率曲线作为诊断标准 ,进一步证实Gd DTPA动态增强MRI检查技术对肾上腺肿瘤的鉴别诊断价值。方法 :3 6例共 41个肾上腺肿瘤 ,腺瘤 19例共 19个 ,非腺瘤 17例共 2 2个。所有肿瘤均先行常规SE序列T1 W和T2 W成像 ,选定肿瘤中心层面定位后 ,再利用屏气快速多层面破坏性梯度回波序列 (FMPSPGR)行轴位扫描 ,先平扫 ,再以同样条件行MRI动态增强检查 ,即静注Gd DTPA ,自注药后 0 .5min开始扫描 ,之后分别在 60min内共 17个时间点 ,以同等条件延时扫描 ,观察病变的增强程度 ,并分别测量其实质部分的信号值。计算肿瘤的信号比、最大信号增加比、增强率 ,再根据随时间延时肿瘤增强率的变化绘制曲线 ,比较肾上腺肿瘤间的时间 信号增强率曲线有无差异 ,并明确其对肾上腺肿瘤的鉴别诊断价值。结果 :Ⅰ型时间 信号增强率曲线具有高度特异性 ,只有大多数神经源性肿瘤符合此增强特点 ,对区分腺瘤与其它类型的非腺瘤无诊断价值 ;以Ⅲ型或Ⅳ型曲线为标准诊断恶性肿瘤的准确率均不高 ,有 5 0 %的恶性肿瘤无法确诊 ;而以Ⅱ型时间 信号增强率曲线为标准较前 3种曲线更有助于肾上腺肿瘤的鉴别诊断 ,即以早期增强 ,延时 9min内肿瘤增强率下降程度超过肿瘤最大增强率的 5 0 %为诊断腺瘤的标准 ,敏     

Comparison of diatrizoate, iopamidol, and ioxaglate for the contrast enhancement of experimental hepatic tumors in CT

The accumulation of diatrizoate and two new low osmolality contrast agents, iopamidol and ioxaglate, was investigated in three experimental tumors (a well differentiated mammary adenocarcinoma, a poorly differentiated colon carcinoma, and a hepatoma) in the rat. All three tumors were implanted into the liver 12 to 14 days prior to intravenous injection of the contrast agents in a dose of 300 mg iodine per kg. Iodine concentrations were determined in blood, liver, and tumors at 1, 5, 10, and 30 minutes using x-ray energy spectrometry. Ratios between tumor iodine and blood iodine concentrations increased more with time with diatrizoate than either iopamidol or ioxaglate and were at 30 minutes significantly greater for diatrizoate than the other two agents. This suggests that the contrast medium efflux from the vascular compartment into the extravascular compartment of all tumors is greater for diatrizoate than either iopamidol or ioxaglate. Although it is known from clinical experience that the differential enhancement between hypodense hepatic tumors and liver parenchyma decreases rapidly with time after contrast administration, this investigation suggests that the substitution of diatrizoate by either iopamidol or ioxaglate should not affect appreciably the contrast enhancement in this condition in dynamic CT completed within the first minutes after contrast administration. In a later phase, after contrast administration, however, both iopamidol and ioxaglate should conceal hypodense hepatic tumors less than diatrizoate.     

Periportal contrast enhancement on CT scans of the liver

Periportal contrast enhancement relative to adjacent liver and portal blood has been reported on CT scans in cases of schistosomiasis and hepatic Kaposi sarcoma in AIDS patients. We observed this phenomenon in 10 (8%) of 130 consecutive, contrast-enhanced, nondynamic CT examinations of the abdomen. Thus, the occurrence is more common and less specific than previously reported. Seven of the 10 patients in our series were receiving chemotherapy for malignant disease, and three had abdominal pain with no definitive diagnosis. In four of the 10 patients, corresponding areas of periportal low attenuation or radiolucency were observed on initial dynamically enhanced scans. Periportal enhancement may be related to late diffusion of contrast material into periportal areas that were initially radiolucent. Such diffusion may occur because of endothelial insult. Periportal contrast enhancement appears to be a nonspecific finding on nondynamic contrast-enhanced CT scans of the abdomen. Periportal enhancement is important to recognize because it can mimic the appearance of portal vein thrombosis and may also be used to differentiate intrahepatic biliary dilatation from periportal radiolucency.