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 , K. Inoue , F. Thiele , E. Kozawa , J. Tanaka , M.
1
1 1
1
1
2
1
2
Niitsu ; Moroyama, Saitama/JP, Hidaka, Saitama/JP
Keywords:
Contrast agents, CT, Contrast agent-intravenous, Image
verification
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Page 1 of 17
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
severe liver cirrhosis, hemosiderosis, severe fatty liver, multiple liver tumors, status post
liver segmentectomy or lobectomy, or marked portosystemic shunt. Patients with renal
2
dysfunction (serum creatinine level > 1.5 mg/dL or eGFR < 45 mL/min/1.73 m ) 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 16.0 ´ 1.2 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
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
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).
2
2
LBW for females = 1.07×W-148×(W /H )
2
2
LBW for males = 1.10×W-128×(W /H )
Where W is the total body weight in kilograms, and H is the height in centimeters.
Images for this section:
Page 5 of 17
Table 1: Contrast media administered according to the patient's total body weight.
Page 6 of 17
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 316.9
(186-468, SD 44.1) in males and 354.4 (217-479, 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
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 < 0.0001). 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
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 810.8 mg I/
kg, and that in males was 732.2 mg I/kg. The difference was significant (p<0.0001, twotailed t-test), as shown in Fig. 2.
Page 9 of 17
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 < 0.0001). 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
Table 2: Patient Data
Page 11 of 17
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
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 < 0.0001). The four short horizontal lines indicate the standard deviations.
Page 13 of 17
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 < 0.0001). the four short horizontal lines indicate the
standard deviations.
Page 14 of 17
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
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Page 16 of 17
Personal Information
Takashi Ushimi PhD. Departoment of Radiology, Saitama medical University, Saitama,
Japan.
[email protected]
Kaiji Inoue PhD, Departoment of Radiology, Saitama-medical University, Saitama,
Japan.
[email protected]
Felix thiele. Department of Radiology, Saitama medical University, Saitama, Japan.
[email protected]
Eito Kozawa PhD, Department of Radiology, Saitama Medical University International
Medical Center, Saitama, Japan.
[email protected]
Junji Tanaka PhD, Department of Radiology, Saitama medical University, Saitama,
Japan.
[email protected]
Mamoru Niitsu PhD, Department of Radiology, Saitama medical University, Saitama,
Japan.
[email protected]
Page 17 of 17