Selective use of low-osmolality contrast media in computed tomography

The aim of this study was to describe our experience and institutional savings with a selective use of low-osmolality contrast media (LOCM) in CT. From 1995 to 1998, a total of 19,834 contrast-enhanced CT examinations were performed at our institution. Contrast was injected with a power injector and large venous catheter, 20-G for 2- to 3-ml rate and 18-G for 3- to 5-ml rate. High-osmolality contrast media was used in 13,670 patients (71%). The LOCM was used in 5884 (29%) patients. Our guidelines for the use of LOCM included cardiac dysfunction, severe pulmonary impairment, history of allergy or prior moderate reaction to HOCM and severe debilitation. Prior to the injection of HOCM, 10 mg of metoclopramide (Primperan, Delagrange Quétigny, France) were administered to reduce nausea and vomiting. In the HOCM group there were 304 minor or mild adverse reactions (2.2%), and 10 severe adverse reactions (0.08%). In the LOCM there were 34 mild or moderate adverse reactions (0.59%) and 3 severe adverse reactions (0.05%). Significant differences in terms of mild adverse reactions were found between HOCM and LOCM (Fischer's test, p<0.001). No significant differences were found in terms of severe adverse reactions (p=0.27). After subtracting the cost of treating additional adverse reactions, the net differential cost between universal and selective use of LOCM was 565,285 Euro (US$601,067). This means a net increase of 41.4 Euro per patient or 414,000 Euro per 10,000 patients (US$438,840). Selective use of LOCM in CT is safe and effective and results in a substantial reduction in costs. Given at the 1999 RSNA Scientific Assembly.     

Contrast Media in Abdominal Computed Tomography: Optimization of Delivery Methods

Objective

To provide a systematic overview of the effects of various parameters on contrast enhancement within the same population, an animal experiment as well as a computer-aided simulation study was performed.

Materials and Methods

In an animal experiment, single-level dynamic CT through the liver was performed at 5-second intervals just after the injection of contrast medium for 3 minutes. Combinations of three different amounts (1, 2, 3 mL/kg), concentrations (150, 200, 300 mgI/mL), and injection rates (0.5, 1, 2 mL/sec) were used. The CT number of the aorta (A), portal vein (P) and liver (L) was measured in each image, and time-attenuation curves for A, P and L were thus obtained. The degree of maximum enhancement (Imax) and time to reach peak enhancement (Tmax) of A, P and L were determined, and times to equilibrium (Teq) were analyzed. In the computed-aided simulation model, a program based on the amount, flow, and diffusion coefficient of body fluid in various compartments of the human body was designed. The input variables were the concentrations, volumes and injection rates of the contrast media used. The program generated the time-attenuation curves of A, P and L, as well as liver-to-hepatocellular carcinoma (HCC) contrast curves. On each curve, we calculated and plotted the optimal temporal window (time period above the lower threshold, which in this experiment was 10 Hounsfield units), the total area under the curve above the lower threshold, and the area within the optimal range.

Results

A. Animal Experiment: At a given concentration and injection rate, an increased volume of contrast medium led to increases in Imax A, P and L. In addition, Tmax A, P, L and Teq were prolonged in parallel with increases in injection time The time-attenuation curve shifted upward and to the right. For a given volume and injection rate, an increased concentration of contrast medium increased the degree of aortic, portal and hepatic enhancement, though Tmax A, P and L remained the same. The time-attenuation curve shifted upward. For a given volume and concentration of contrast medium, changes in the injection rate had a prominent effect on aortic enhancement, and that of the portal vein and hepatic parenchyma also showed some increase, though the effect was less prominent. A increased in the rate of contrast injection led to shifting of the time enhancement curve to the left and upward. B. Computer Simulation: At a faster injection rate, there was minimal change in the degree of hepatic attenuation, though the duration of the optimal temporal window decreased. The area between 10 and 30 HU was greatest when contrast media was delivered at a rate of 2-3 mL/sec. Although the total area under the curve increased in proportion to the injection rate, most of this increase was above the upper threshould and thus the temporal window was narrow and the optimal area decreased.

Conclusion

Increases in volume, concentration and injection rate all resulted in improved arterial enhancement. If cost was disregarded, increasing the injection volume was the most reliable way of obtaining good quality enhancement. The optimal way of delivering a given amount of contrast medium can be calculated using a computer-based mathematical model.     

实验性脑脓肿CT与病理对照研究

明确脑脓肿脑炎期与包膜期ＣＴ分期标准。材料与方法,对１４只犬脑脓肿模在不同时间进行ＣＴ增强延迟扫描与病理研究,绘制并分析时间,密度曲线。结果脑炎期以“血管周围套”血管周围套”为镜下特征,包膜期表现为５个独特的组织学区带。结论通过ＣＴ增强延迟扫描表现和时间－密度曲线形态可区分脑炎期和包膜期脓肿。     

膝关节充气CT扫描影像学与临床意义的研究

目的：研究膝关节充气造影CT检查的诊断价值。材料和方法：对1例离休左膝关节标本，56例活体膝关节做充气造影CT检查。然后解剖离休膝关节并对有手术指征的48例56个膝关节进行手术探查、结果：初步确定了膝关节充气条件下的正常CT解剖及某些异常表现。结论：膝关节充气造影CT检查对滑膜皱赞综合征、滑股肿瘤、滑膜炎等许多洛膜病具有重要诊断价值。     

Evaluation of simethicone-coated cellulose as a negative oral contrast agent for abdominal CT

RATIONALE AND OBJECTIVES: Because of the increased clinical use of computed tomography (CT) for imaging the abdominal vasculature and urinary tract, there is a need for negative contrast agents. The authors undertook this study to assess the suitability of simethicone-coated cellulose (SCC), which is approved for use as an oral contrast agent in sonography, for use as a negative oral contrast agent in abdominal CT. MATERIALS AND METHODS: This prospective study involved 40 adult patients scheduled to undergo abdominal CT for the evaluation of hematuria. Prior to scanning, 20 subjects received 800 mL of SCC and 20 received 800 mL of water as an oral contrast agent. Imaging was performed with a multi-detector row helical scanner in two phases, according to the abdominal CT protocol used for hematuria evaluation at the authors' institution. The first, "early" phase began an average of 15 minutes after the ingestion of contrast material; the second, "late" phase began an average of 45 minutes after the ingestion of contrast material. Blinded analysis was performed by three abdominal radiologists separately, using a three-point scale (0 = poor, 1 = acceptable, 2 = excellent) to assess the effectiveness of SCC for marking the proximal, middle, and distal small bowel. Average scores for enhancement with SCC and with water were obtained and compared. Statistical analysis was performed with a Wilcoxon signed-rank test. RESULTS: SCC was assigned higher mean scores than water for enhancement in each segment of the bowel, both on early-phase images (0.8-1.35 for SCC vs 0.6-1.1 for water) and on late-phase images (1.1-1.4 vs 0.81-0.96). Bowel marking with SCC, particularly in the jejunum and ileum, also was rated better than that with water in a high percentage of patients. The differences between the scores for water and for SCC, however, were not statistically significant (P > .05). CONCLUSION: SCC is effective as a negative oral contrast agent for small bowel marking at CT.     

CT对比剂血管外渗发生机制的讨论及防治措施

对比剂外渗是进行CT增强扫描的重要不良反应之一.由于CT增强扫描越来越广泛的应用于临床,外渗的发生率也有上升趋势.对比剂外渗常常导致组织坏死而影响肢体的形态及功能,大量的对比剂外渗甚至会引发骨筋膜室综合症,造成肢体的不可逆损伤.本文将通过分析对比剂外渗的发生机制及发生影响因素来探讨其防治措施,进一步引起临床对于对比剂外渗的重视及降低其发生率.     

Flattened inferior vena cava: A normal finding on unenhanced abdominal computed tomographic scan

Flattening of the infrahepatic inferior vena cava (IVC) on postcontrast computed tomographic (CT) scans has been reported as a sign of severe hypovolemia. The significance of this finding on unenhanced CT scans, however, has not been reported. We retro-spectively studied 60 consecutive outpatient abdominal CT scans in which both unenhanced and postcontrast sequences were performed. Flattening of the infrahepatic IVC on unenhanced CT images was noted in six patients (10%) without evidence of hypovolemia or extrinsic IVC compression. The degree of IVC fullness increased in 43 study patients overall (72%) after contrast administration. We propose several mechanisms for postcontrast IVC distention and conclude that a flattened infrahepatic IVC on unenhanced CT scans does not indicate hypovolemia in the absence of other suggestive clinical or CT findings.     

Comparison of liver perfusion parameters studied with conventional extravascular and experimental intravascular CT contrast agents

RATIONALE AND OBJECTIVES: To compare liver perfusion parameters obtained by using an extravascular contrast agent and a blood-pool agent. MATERIALS AND METHODS: Fifteen rabbits were imaged with a continuous 40-second single-slice computed tomography acquisition after a bolus injection of contrast agent (physiologic bolus duration 4-5 seconds, extravascular iohexol, n = 7; experimental nanoparticulated blood-pool agent WIN8883, n = 8). Time-density curves were generated for the aorta, portal vein, and liver. From the curves, arterial, portal, and total blood flows and hepatic perfusion index (HPI, arterial-to-total perfusion ratio) were determined by using two commonly applied fundamentally different analyzing methods: the single-compartment model and the peak gradient (PG) method. Also, the gamma variate fitting method was used. RESULTS: By using the single-compartment model, the obtained HPI and total blood flow were 0.14 +/- 0.04 and 2.29 +/- 0.40 (mL/min/mL(tissue)) for WIN8883, and 0.15 +/- 0.06 (P = .54) and 4.60 +/- 1.14 (mL/min/mL(tissue)) (P = .0002) for iohexol, respectively. With the PG, HPI and total blood flow were 0.15 +/- 0.08 and 1.27 +/- 0.24 (mL/min/mL(tissue)) for WIN8883, and 0.20 +/- 0.06 (P = .12) and 2.11 +/- 0.25 (mL/min/mL(tissue)) (P = .00002) for iohexol, respectively. With the blood pool agent, similar contrast enhancement to the conventional agent was achieved with about 36% reduced dosage of iodine per body weight (mg I/kg). CONCLUSIONS: HPI was found to be quite insensitive to different contrast agent types and analyzing methods. However, the arterial, portal and total liver blood flow values strongly depend on contrast agent type and modeling method.     

口服脂肪密度造影剂在胰腺及胃肠道CT检查中的应用价值

本文对76例口服12.5％花生油乳剂与103例口服2％碘水剂的腹部CT扫描进行比较,结果12.5％花生油乳剂在胰腺及胃肠道CT检查中优于2％碘水剂。作者认为,12.5％花生油乳剂可作为腹部CT扫描的常规口服造影剂。     

Long-residence-time nano-scale liposomal iohexol for X-ray-based blood pool imaging

RATIONALE AND OBJECTIVES: Although soluble nonionic iodine compounds with low systemic toxic effects have been developed for use in computed tomography (CT), they have short residence times of a few minutes or mere seconds-insufficient time for blood pool imaging, even with high-speed multi-detector row spiral CT. Moreover, potential renal toxic effects preclude repeated administration of these contrast agents during imaging, as well as their use in patients with compromised renal function. The objective of this study was to develop and evaluate a CT contrast agent for blood pool imaging that remains in the blood for more than 3 hours and that is relatively nontoxic to the kidneys. MATERIALS AND METHODS: The authors assessed a liposomal iohexol formulation for its encapsulation efficiency in terms of milligrams of iodine per milliliter of lipid formulation and for its stability in phosphate buffer solution and in human plasma in vitro. Using a rabbit model, they also assessed the formulation's in vivo stability, residence time, and enhancement of contrast on images of various organ systems. RESULTS: The formulation, which contained 34.8 mg of iodine per milliliter of liposomal iohexol solution, remained stable in blood plasma both in vitro and in vivo, after injection into rabbit vasculature. An intravenous dose of 475 mg of iodine per kilogram of body weight produced contrast enhancement in the rabbit model of approximately 130 HU in the aorta and liver cortex and approximately 100 HU in the kidney cortex. Contrast enhancement was maintained for 3 hours after injection, and minimal clearance of the contrast agent via the kidneys was observed. CONCLUSION: The liposomal iohexol formulation tested in this study had a sufficient residence time for blood pool imaging in a rabbit model. Future experiments with long-residence-time iohexol formulations may lead eventually to applications in cardiac imaging and in early tumor detection.     

16层螺旋CT检查输尿管结石的应用价值

 目的 探讨16层螺旋CT在输尿管结石病例中的诊断价值.方法 应用东芝Aquilion 16层螺旋CT对142例临床拟诊输尿管病变病例进行检查分析,采用标准和低剂量扫描两组对比分析,对确诊输尿管结石病例减少造影剂用量行增强扫描.结果 两组扫描方法对输尿管结石诊断准确性无差异,低剂量组辐射剂量仅为标准组的37.12%.增强扫描适当减少造影剂用量,也能满足临床制定治疗方案前评估肾功能的要求.结论 16层螺旋CT对诊断输尿管结石有很高的准确性,适当降低扫描条件不影响结石检出率,适当减少造影剂用量不影响临床评价肾功能,但却减少了辐射剂量和患者费用,在临床中应该得到大力推广.     

多发伤螺旋CT增强检查中对比剂应用及安全管理

目的探讨多发伤螺旋CT增强检查中碘对比剂应用及安全性管理。方法回顾性分析2009年1月～2010年3月行螺旋CT增强检查的134例多发伤患者,男性106例,女性28例;年龄2～82岁,平均42.5岁。道路交通伤55例,刀刺伤15例,坠落伤39例,砸伤25例。对比剂主要采用欧乃派克(350mgI/ml)、优维显(370mgI/ml)、三代显(350mgI/ml),用量1.5～2ml/kg,注入速度3.0～4.0ml/s。制定多发伤CT增强检查流程,观察检查过程中生命体征及其他不良反应。结果螺旋CT增强扫描新发现血管等损伤59例次;5例注射对比剂时心率、呼吸加快,但血压稳定,129例无明显生命体征改变;未见恶心、呕吐、皮疹等不良反应症状。2例因躁动配合困难,镇静后行螺旋CT增强检查,导致检查时间延长之外,132例在8～10分钟之内顺利完成检查。结论多发伤螺旋CT增强检查有助于发现血管及实质性脏器损伤,以上3种对比剂安全、有效。     

Helical CT imaging of clinically suspected appendicitis: correlation of CT and histological findings

PURPOSE: The diagnosis of appendicitis is traditionally made on the basis of clinical findings supported by laboratory results. The aim of our study was to determine the accuracy and feasibility of using a relatively new technique of computed tomography (CT) using only colonic contrast medium. MATERIALS AND METHODS: A total of 50 patients clinically diagnosed as having appendicitis were prospectively examined before surgery with thin-collimation helical CT from the L3 level to the acetabular roof with only rectally administered colon contrast medium. The hard copy CT images were reviewed jointly by two radiologists and a consensus was reached for each patient. The results were then compared with the surgical and histological findings at appendicectomy. RESULTS: There were 35 true-positives, one false-positive, 12 true-negatives and two false-negatives for CT. This yielded an accuracy of 94%, sensitivity of 95%, specificity of 92%, positive predictive value of 97% and negative predictive value of 86%. The appendix was identified in 45 patients (90%) and obscured by an inflammatory mass in the remaining five. An alternative diagnosis was found in 10 of 12 normal CT examinations (83%). CONCLUSION: Helical CT with rectal contrast medium is a quick, well tolerated and accurate test to diagnose appendicitis. It can offer alternative, possibly non-surgical diagnosis in patients who would otherwise have undergone laparotomy.     

成人正常小肠CT表现

目的 :评价成人正常的小肠CT表现。材料和方法 :以口服水为对比剂 ,螺旋CT增强扫描检查健康人群 2 8例 ,分别测定非增强期、增强期 (动脉及门脉期 )的十二指肠、空肠、回肠的CT值和肠壁厚度。结果 :小肠CT值在非增强期分别为十二指肠 49± 2Hu、空肠 47± 3Hu、回肠 5 0± 2Hu ;而增强期中 ,动脉期三者CT值分别为 12 5± 5Hu、12 7± 4Hu、12 5±5Hu ,门脉期为 114± 3Hu、114± 3Hu、112± 4Hu。非增强期与增强期的CT值有统计学差别 ,而动脉期与门脉期则没有差别。各小肠壁平均厚度大多数在 3mm内。结论 :本组资料显示了成人正常小肠的CT表现 ,在对小肠病变的判断中 ,具有重要的参考价值     

Colonic diverticulitis: impact of imaging on surgical management – a prospective study of 542 patients

The aim of this study was to compare the performance of the CT and the water-soluble contrast enema (CE) in the diagnosis and the severity of acute left-colonic diverticulitis, and to recognize the impact of CT during the acute phase and after a first acute episode successfully treated medically. From 1986 to 1997, all patients admitted in our emergency center with clinically suspected left-colonic diverticulitis had a CE and a CT within 72 h of their admission, unless clinical findings required immediate laparotomy. They were prospectively included in the study if one or both radiological exams showed signs of acute diverticulitis and/or diverticulitis was surgically removed and histologically proven. Diverticulitis was considered moderate when CT showed localized thickening of the colonic wall (5 mm or more) and inflammation of pericolic fat and CE showed segmental lumen narrowing and tethered mucosa; it was considered severe when abscess and/or extraluminal air and/or contrast were observed on CT and when one or both of the latter signs were seen on CE. Five hundred forty-two patients entered the study; 465 patients (86%) had a CT exam, 439 (81%) had a CE, and 420 (77%) had both exams. The performance of CT is significantly superior to CE in terms of sensitivity (98 vs 92%, p<0.01), and in the evaluation of the severity of the inflammation (26 vs 9%, p<0.02). Moreover, of 69 patients who had an associated abscess seen on CT, only 20 (29%) had indirect signs of this complication on CE. During the acute phase the chances of medical treatment failure are statistically greater when diverticulitis is considered severe on CT than when it is considered moderate (26% for the severe diverticulitis vs 4% for the moderate ones, p<0.0001). After successful medical treatment of the acute episode, patients with severe diverticulitis on the CT had statistically greater incidence of secondary bad outcome than patients with moderate diverticulitis (36 vs 17%, p<0.0001). Computed tomography should be preferred to CE as the initial radiological exam of diverticulitis because of its statistically significant superiority in sensitivity and for its statistically much higher performance in the detection of severe infection, especially when an abscess is associated with the disease. The severity of diverticulitis on CT is statistically predictive of the risk of medical treatment failure during the acute phase and of the chances of bad secondary outcome after a successful medical treatment of the first episode.     

CO2-enhanced CT imaging for the detection of pulmonary emboli: feasibility study in a porcine model

RATIONALE AND OBJECTIVES: The authors investigated the feasibility of using computed tomography (CT) with CO2 gas as a negative contrast agent for detecting pulmonary emboli in a porcine model. MATERIALS AND METHODS: Seven pigs with or without pulmonary emboli underwent thoracic imaging with multi-detector row spiral CT. To identify optimal injection and scanning protocols, the first four pigs were scanned repeatedly in the supine and prone positions with different scan delays (10, 15, and 20 seconds) and different volumes of CO2 (60, 120, 180, and 240 mL), which were hand infused (each infusion took 10-15 seconds). The last five pigs with emboli were scanned with iodinated contrast medium and then rescanned with 120 or 180 mL of CO2. The CO2 volumes and scan delays were qualitatively assessed. The supine and prone CT scans and the number and location of thrombi depicted in the CO2- and contrast material-enhanced CT scans were compared. RESULTS: Because the pulmonary artery in pigs is in the posterior anatomy, the prone position was more effective than the supine position with CO2 enhancement. An infusion of 120 mL of CO2 was sufficient to enhance the entire pulmonary artery, and scanning timed to coincide with the completion of infusion was the most effective. Both the CO2- and contrast-enhanced CT scans demonstrated all thrombi. Thrombi were more apparent on the CO2-enhanced CT scans than on the contrast-enhanced scans because of the high contrast interface between soft tissue and gas. However, two of the seven pigs with thrombi experienced abrupt cardiac arrest after CO2-enhanced scanning and could not be resuscitated. The cause of these events was not determined in the current study. CONCLUSION: The CT depiction of pulmonary emboli is feasible with CO2 gas as a negative contrast agent and may even be superior to that with iodinated contrast media. Further studies are required to evaluate the safety of this method and to develop an improved delivery of CO2 gas for this application.     

Tools of the trade for CTA: MDCT scanners and contrast medium injection protocols

The introduction of multi-detector row computed tomography (MDCT) scanners in 1998 ushered in new advances in CT angiography (CTA). The subsequent expansion of MDCT scanner capabilities, coupled with advances in understanding of contrast medium (CM) dynamics, has further improved the clinical availability and consistency of CTA. We will review recent advances in CT scanner technology and discuss early CM dynamics. Specifically, we describe an approach tailored to the available scanner technology and to patient size aimed at providing consistently robust CTA studies across all vascular territories. A rational method to design combined CTA scan/injection protocols to facilitate this goal will be described. Our current experience with a simplified protocol for CTA with 64-MDCT will also be explained.     

Curricula for Teaching MRI Safety,and MRI and CT Contrast Safety to Residents: How Effective Are Live Lectures and Online Modules?

PurposeThe advent of the diagnostic radiology core examination and the new ACGME “milestone” evaluation system for radiology residents places new emphasis on topics in MRI and CT safety, and MRI and CT contrast agents. We evaluated whether either lecture-based teaching or online modules would improve baseline resident knowledge in these areas, and assessed which intervention was more effective.MethodsBefore didactic intervention, 2 cohorts were created from 57 radiology residents, with equal numbers and a matched level of training. The residents were tested on their baseline knowledge of MRI, MRI contrast safety, and CT contrast safety, using a multiple-choice examination. One group attended a live, 1-hour lecture on the preceding topics. The other engaged in 3 short online educational modules. After 6 weeks, the residents were again tested with the same questions to assess for improvement in their understanding.ResultsBoth the module and lecture cohorts demonstrated a statistically significant increase in questions answered correctly on CT contrast safety (13.1%, P < .001, and 19.1%, P < .001, respectively), and on MRI and MRI contrast safety (12.9%, P < .001, and 14.4%, P < .001). The preintervention and postintervention scores, and degree of improvement postintervention, were similar for the module versus lecture groups, without a statistically significant difference (P = .70). Resident confidence improved in both groups, for both modalities.ConclusionsFocused didactic intervention improves resident knowledge of MRI and CT safety, and MRI and CT contrast agents. Live lectures and online modules can be equally effective, allowing residency programs flexibility.