Subjects
Object were consecutive 135 patients underwent 18F-FDG-PET/CT examination for routine clinical purpose,
who agreed to research,
in August 2013 to March 2014.
The 18F-FDG-PET/CT study has been performed for malignant discrimination; 11pts.,
for staging malignant disease; 47pts.,
for decision of treatment result; 5pts.,
for follow-up; 65pts.,
health screening; 3pts.
Four patients whose blood glucose is over 150 mg/dl and/or who had multiple liver tumors were excluded.
In the all patients,
after over 6 hr fasting,
each patient was injected with approximately 185MBq of fluorine-18 fluorodeogxlyucose(18F-FDG)(nihon mediphysics,
Tokyo,
Japan).
Body weight,
height,
and body fat percentage were measured by body fat analyzer (FitScan 100,
Tanita,
Japan) just before the PET/CT studies.
They were divided into three groups; low body mass index group (BMI <18.5),
normal BMI group (BMI 18.5-25),
and high BMI group(BMI >25)(Table 1).
They spent complete bedrest until PET/CT scan starting after the dosage of 18F-FDG.
F-18-FDG-PET/CT Imaging
All fluorodexoyglucose (FDG) PET/CT scans were performed from the top of the skull through the proximal femurs 60 min after F-18-FDG injection (185 MBq/body intravenously) on a Lu2SiO5 (4.0mm*4.0mm*20㎜).
Emission data were collected at 2.5-3.0 min of emission per bed position on a 168 × 168 pixel matrix,
using a Ge-68 source for attenuation correction and a gaussian filter of 5 mm in full width at half maximum.
PET/CT studies were obtained on Siemens Biograph TruePoint 16 (Siemens Healthcare,
Erlangen,
Germany).
SULPE and SULS were calculated using following equations:
SULPE=C(T)/(D/LBM1) , SULS=C(T)/(D/LBM2)
C(T): the total radioactivity concerntration.
D: injected dose (Bq).
The LBM13) and LBM2 were calculated using the following formula:
LBM1(Male) 3) =1.10 ×weight (kg) − 120 ×(weight ÷ height (cm))x(weight ÷ height)
LBM1(Female) 3) =1.07 ×weight (kg) − 148 ×(weight ÷ height(cm))x(weight ÷ height)
LBM2= weight (kg) − weight (kg) × body fat percentage
Measurements and Data Analysis
Volume of interests (VOIs) of constant size (radius: 5mm) were drawn sections of aortic arch and liver on axial CT slices (Figure 2).
VOIs were drawn in the peripheral right hepatic lobe avoiding large veins or the biliary ducts.
FDG uptake was measured and SUVmax,
SULS,
and SULPE were calculated.
The differences among SUVmax, SULS,
and SULPE were compared in all and for 3 groups: low BMI,
normal BMI,
and high BMI group.
SUVmax, SULS,
and SULPE were compared in all groups.
Moreover SULPE average among 3 groups was compared with SUVmax average among 3 groups.
Statistical methods
The Wilcoxon t-test wes used to compare SULS to SULPE in each groups.
The non-repeated measures ANOVA test was used analyze for SUVmax, SUVS,
and SUVPE each BMI groups.
The level of statistical significance was p < 0.05.