Purpose. Methods and Materials

Transcription

1 The dose of contrast medium should be determined on the basis of estimated lean body weight (LBW) instead of the body weight--excessive amounts are currently given to females. Poster No.: C-2641 Congress: ECR 2013 Type: Scientific Exhibit Authors: T. Ushimi 1, K. Inoue 1, F. Thiele 1, E. Kozawa 2, J. Tanaka 1, M. Keywords: Niitsu 1 ; 1 Moroyama, Saitama/JP, 2 Hidaka, Saitama/JP Contrast agents, CT, Contrast agent-intravenous, Image verification Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 17

2 Purpose MDCT is now used commonly worldwide, its scan time has been shortened, and it is possible to scan the entire abdomen at a single breath hold. In addition, the technique of administering the contrast agent has improved. It has been reported (1) that a patient's body weight and the dose of contrast material are closely related to the degree of contrast enhancement. That is, to raise contrast enhancement of the liver 50 HU, about 0.5 g iodine per kg body weight of the patient is needed. In Japan, a fixed total dose of iodine per body weight is injected in 30 sec (2). With this technique, the peak time of maximum attenuation is stabilized and achieves good contrast of tumor-to-liver parenchyma. On CT images, the degree of contrast enhancement is influenced by multiple factors, such as contrast material dose, concentration, injection rate, and injection duration, as well as patient-related factors such as body weight, lean body weight, and cardiac output (3-9). Ho et al. reported (3) that contrast material dose based on the lean body weight (LBW) leads to increased patientto-patient uniformity of hepatic parenchymal and vascular enhancement. In addition, Kondo et al. reported (10) that the dose of iodine based on LBW achieved a consistent and precise change in hepatic CT number and reduced patient-to-patient variability. Body composition, especially lean mass, differs between men and women. This difference in lean mass presumably results in a difference in total blood volume per body weight, since adipose tissue is poorly perfused compared to solid organs, including muscle. Thus, determining the iodine dose per total body weight without considering sex may result in an excess amount being administered to women (11). Thus, the difference in the degree of contrast enhancement between males and females when the total amount of contrast material is based on the patient's total body weight was evaluated, and the difference between men and women when the dose was calculated by lean body mass was compared. Methods and Materials Patients Our university institutional review board approved this prospective study. Since this study was performed as part of routine procedures, informed consent of the patients was not required. All patients underwent CT examination for suspected liver, pancreatic, and renal diseases. Patients with the following clinical situations in whom liver parenchymal blood flow and/or its density could be different from those in normal patients were excluded: Page 2 of 17

3 severe liver cirrhosis, hemosiderosis, severe fatty liver, multiple liver tumors, status post liver segmentectomy or lobectomy, or marked portosystemic shunt. Patients with renal dysfunction (serum creatinine level > 1.5 mg/dl or egfr < 45 ml/min/1.73 m 2 ) or implanted electronic devices (pacemakers, defibrillators) were also excluded, as were patients who showed a very large abnormal fluid collection, such as pleural effusion, ascites, or pericardial effusion, on the precontrast scan. Imaging There are three types of MDCT in our facility. In order to equalize the quality of the images, a fixed MDCT (Emotion 16, Siemens, Germany) was used. This CT is able to acquire 16 slices per gantry rotation. A detector configuration of mm and a pitch of 1 were used in all patients. Gantry rotation time was 0.5 sec. The tube voltage was fixed at 130 kvp, and a tube current between 20 and 345 ma was applied to all patients (automatically set depending on the thickness of the patient's body). The reconstruction section and interval thickness was 5 mm without a gap. All image data were sent online to a picture archiving and communication system (DrABLE-EX, Fujitsu, Japan) for interpretation. All patients underwent abdominal CT scan with contrast enhancement as a routine examination. Contrast material was injected using a power injector (Autoenhance A-50, Nemonto-Kyorindo, Tokyo, Japan) with a 20-gauge catheter inserted into an antecubital or radial vein. The contrast medium used in all patients was prefilled syringes of contrast material. Bolus-tracking software (Carebolus, Siemens, Germany) was used to determine the scan delay for all patients. Arterial phase imaging was started immediately after the density of the abdominal aorta reached 150 HU. For portal phase imaging, scanning was done 8-10 sec after the start of the initial scan. Most patients were scanned during both the hepatic arterial phase and the portal venous phase (biphasic scanning). For all patients, the total amount of iodine was determined on the basis of total body weight (TBW) [target 600 mg I per body weight; males 597±4.4 mg I/kg, females 598±5.4 mg I/kg (mean±sd)] over a total injection time of 30±0.3 sec]. Contrast media were used according to the patient's total body weight (TBW), as shown in Table 1. Page 3 of 17

4 Table 1: Contrast media administered according to the patient's total body weight. References: - Moroyama, Saitama/JP TBW within 2 weeks before the abdominal CT scan was obtained from the history. If these data were not available, the patients were weighed using a commercial digital weight scale (BC-500, Tanita, Tokyo, Japan) just before the CT examination. The syringe in our hospital that contains the largest amount of iodine was iomeprol (Iomeron 350, 135 ml), which can be used in a patient with a TBW of up to 79 kg. Patients with a TBW > 79 kg were excluded from this study because the amount of iodine administered could not reach the target level of 600 mg I/kg. Quantitative assessment All contrast-attenuation measurements were shared and performed once per patient by four board-certified radiologists with more than 10 years of experience in reading abdominal CT scans (J.T. 32 years, T.U. 24 years, K.I. 14 years, Y.S. 12 years). Attenuation measurements for each patient were obtained by manually placing round or oval-shaped regions of interest (ROIs) within the abdominal aorta at the level of the orifice of the superior mesenteric artery, the hepatic portal vein at approximately its main part, and in the liver parenchyma at approximately the level of the main part of the Page 4 of 17

5 portal vein. Aortic wall calcification or mural thrombus was carefully avoided during ROI placement. Intrahepatic vessels were also carefully avoided during ROI placement in the liver parenchyma by referring to the postcontrast image at the same level. Postcontrast CT value measurements were done during the hepatic portal phase in the same way. The ROI in the liver parenchyma in portal-phase images was placed as close as possible to that in the precontrast image. The degree of contrast enhancement was calculated by subtracting the CT numbers on precontrast images from those on postcontrast images. The three values (liver parenchyma, portal vein, abdominal aorta) were added together to yield a single summed measurement. The average of this difference was calculated separately in male and female patients, and the difference between the sexes was analyzed statistically. Estimated lean body weight (LBW) values in males and females were also calculated and compared with the total dose of iodine administered. The estimated LBW values were obtained by the following formulas (12, 13). LBW for females = 1.07 W-148 (W 2 /H 2 ) LBW for males = 1.10 W-128 (W 2 /H 2 ) Where W is the total body weight in kilograms, and H is the height in centimeters. Images for this section: Page 5 of 17

6 Table 1: Contrast media administered according to the patient's total body weight. Page 6 of 17

7 Results Between August 3, 2009 and December 28, 2012, 697 nonconsecutive patients (382 males, 315 females) were enrolled in this study. The patients' age, height, TBW, and calculated LBW are shown in Table 2. Table 2: Patient Data References: - Moroyama, Saitama/JP The amount of iodine administered was 597±3.9 mg I/kg over a total injection time of 30±0.3 sec. The average increase in the sum of the three densities was ( , SD 44.1) in males and ( , SD 46.3) in females. This difference was significant (p<0.0001, two-tailed t-test), as shown in Fig. 1. Page 7 of 17

8 Fig. 1: Difference in summed attenuation between precontrast and the portal phase. Statistical analysis using a two-tailed t-test revealed that the difference in summed attenuation between precontrast and the portal phase in women is greater than that in men (p < ). The four short horizontal lines indicate the standard deviations. References: - Moroyama, Saitama/JP Attenuation in the aorta, portal vein, and liver parenchyma in the precontrast and postcontrast (portal venous phase) images in males and females is shown in Table 3. Page 8 of 17

9 Table 3: Average attenuation in the aorta, portal vein, and liver parenchyma in the precontrast/portal venous phase in men and women. References: - Moroyama, Saitama/JP The total dose of iodine administered for the estimated LBW for females was mg I/ kg, and that in males was mg I/kg. The difference was significant (p<0.0001, twotailed t-test), as shown in Fig. 2. Page 9 of 17

10 Fig. 2: Administered Iodine dose per Lean body weight. Statistical analysis using a two-tailed t-test revealed that the difference in administered iodine dose per lean body weight is greater than that in men (p < ). the four short horizontal lines indicate the standard deviations. References: - Moroyama, Saitama/JP Therefore, the average dose of iodine administered to female patients, on a per kilogram of LBW basis, exceeded that in males by 10.7%. Images for this section: Page 10 of 17

11 Table 2: Patient Data Page 11 of 17

12 Table 3: Average attenuation in the aorta, portal vein, and liver parenchyma in the precontrast/portal venous phase in men and women. Page 12 of 17

13 Fig. 1: Difference in summed attenuation between precontrast and the portal phase. Statistical analysis using a two-tailed t-test revealed that the difference in summed attenuation between precontrast and the portal phase in women is greater than that in men (p < ). The four short horizontal lines indicate the standard deviations. Page 13 of 17

14 Fig. 2: Administered Iodine dose per Lean body weight. Statistical analysis using a twotailed t-test revealed that the difference in administered iodine dose per lean body weight is greater than that in men (p < ). the four short horizontal lines indicate the standard deviations. Page 14 of 17

15 Conclusion Due to the short scanning time using MDCT, the injection speed and timing of administration of contrast material must be more precisely planned and performed. There are several protocols for dynamic contrast material-enhanced CT imaging for the adult abdomen. Among them, the most widely used technique is that in which the total dose of iodine is fixed based on the patient's total body weight (600 mg I/kg) with a fixed injection duration of 30 sec. Ho et al. reported (3) that contrast material dose based on the LBW leads to increased patient-to-patient uniformity of hepatic parenchymal and vascular enhancement in routine body CT scans, because adipose tissue is poorly perfused. Furthermore, Kondo et al. reported (10) that a dose of iodine based on LBW achieve consistent and precise changes in hepatic CT number and reduced patient-to-patient variability. It is well known that males and females differ greatly in the proportion of adipose tissue to total body weight. In most populations, the percentage of fat to TBW is 10-15% in adult men and 20-30% in adult women. This difference increases rapidly during puberty, is maintained into the fifth decade of life, and then declines gradually after middle age (14, 15). In the present study, the degree of contrast enhancement was 11.8% greater in female than in male patients when the total amount of iodine administered was determined on the basis of total body weight regardless of the patient's sex. Similarly, the iodine dose per calculated LBW was 10.7% higher in women than in men. Both results suggest that the amount of iodine required for female patients may be reduced, which could help avoid the administration of excess contrast material to female patients. This may contribute to the health of female patients and could help reduce medical costs. One limitation of this study is that patients with a TBW > 79 kg were excluded because syringes that contained larger amounts of iodine were not available in our institution. Therefore, the results of this study may have limited implications in North America and Europe. In this study, the patients were not classified by age, and the body mass index of the patients was not considered. Additional studies that include more patients and larger amounts of iodine and that classify patients according to age and body mass index are needed. The iodine dose per LBW was 10.7% higher and the degree of contrast enhancement was 11.8% higher in females than in males. Both results suggest that the amount of contrast material for females could be reduced by 10%. References Page 15 of 17

16 1. Heiken JP, Brink JA, McClennan BL,et al. Dynamic incremental CT: effect of volume and concentration of contrast material and patient weight on hepatic enhancement. Radiology 1995; 195: Ichikawa T, Erturk SM, Arai T. Multiphasic contrast-enhanced multidetectorrow CT of liver: combination of fixed injection duration and patient's bodyweight-tailored dose of contrast material. Eur J Radiol 2006; 58: Ho LM, Nelson RC, DeLong DM. Determining contrast medium dose and rate on basis of lean body weight: dose this strategy improve patient-topatient uniformity of hepatic enhancement during multi-detector row CT? Radiology 2007; 243: Yamashita Y, Komohara Y, Takahashi M, et al. Abdominal Helical CT: evaluation of optimal doses of intravenous contrast material - a prospective randomized study. Radiology 2000; 216: Awai K, Takada K, Onishi H, et al. Aortic and hepatic enhancement and tumor-to-liver contrast: analysis of the effect of different concentrations of contrast material at multi-detector row helical CT. Radiology 2002; 224: Kanematsu M, Goshima S, Kondo H, et al. Optimizing scan delays of fixed duration contrast injection in contrast-enhanced biphasic multidetector -row CT for the liver and the detection of hypervascular hepatocellular carcinoma. J Comput Assist Tomogr 2005; 29: Foley WD, Hoffmann RG, Quiroz FA, et al. Hepatic helical CT: contrast material injection protocol. Radiology 1994; 192: Tublin ME, Tessler FN, Cheng SL, et al. Effect of injection rate of contrast medium on pancreatic and hepatic helical CT Radiology 1999; 210: Bae KT, Heiken JP, Brink JA, et al. Aortic and hepatic contrast medium enhancement at CT. II. Effect of reduced cardiac output in a porcine model. Radiology 1998; 207: Kondo H, Kanematsu M, Goshima S, et al. Body Size Indexes for Optimizing Iodine Dose for Aortic and Hepatic Enhancement at Multidetector CT: Comparidon of Total Body Weight, Lean Body Weight, and Blood Volume. Radiology 2010; 54: Tanaka J, Kozawa E, Inoue K, et al. Should the dose of contrast medium be determined solely on the basis of body weight regardless of the patient's sec? JJRadiol 2011; 29: Hume R. Prediction of lean body mass from height and weight. J Clin Pathol 1966; 19: Hallynck th, Soep HH, Thomis JA, et al. Should clearance be normalized to body surgace or to lean body mass? Br J Clin Pharmacol 1981; 11: Pichard C, Kyle UG, Bracco D, et al. Reference values of fat-free and fat masses by bioelectrical impedance analysis in 3393 healthy subjects. Nutrition 2000; 16: Wang Z, Heo M, Kotler DP, et al. Muscularity in adult humans: proportions of adipose tissue free body mass and skeletal muscle. Am J Hum Biol 2001; 13: Page 16 of 17

17 Personal Information Takashi Ushimi PhD. Departoment of Radiology, Saitama medical University, Saitama, Japan. Kaiji Inoue PhD, Departoment of Radiology, Saitama-medical University, Saitama, Japan. Felix thiele. Department of Radiology, Saitama medical University, Saitama, Japan. Eito Kozawa PhD, Department of Radiology, Saitama Medical University International Medical Center, Saitama, Japan. Junji Tanaka PhD, Department of Radiology, Saitama medical University, Saitama, Japan. Mamoru Niitsu PhD, Department of Radiology, Saitama medical University, Saitama, Japan. Page 17 of 17