Correlation of SUV According to the Body Weight and Body Surface Area in PET/CT Imaging

PET/CT 검사 시 체중과 체표면적에 따른 SUV의 상관관계

Purpose: There are several methods of measuring SUV in PET/CT imaging including $SUV_{bw}$ which uses the body weight, $SUV_{bsa}$ which that uses body surface area and $SUV_{lbm}$ which uses lean body mass. Currently, Seoul National University Hospital uses $SUV_{bw}$ method which minimizes the variability. In this study, we compared and analyzed the correlation between $SUV_{bw}$ and $SUV_{bsa}$ according to patients' body mass index. Materials and Methods: Using Biograph mCT40 (Siemens, Germany), we conducted $^{18}F-FDG$ PET/CT imaging on 70 patients (41 males, 29 females; ages $58.04{\pm}12.44$). We classified the patients as underweight (BMI<20), normal weight (20$${\leq_-}$$BMI<25), overweight (25$${\leq_-}$$BMI<30), obese (30$${\leq_-}$$BMI<35) and severely obese (35$${\leq_-}$$BMI) according to the patient's sex, age and BIM. Then, bone, liver and lungs were set as ROI for calculation of maximum values of $SUV_{bw}$ and $SUV_{bsa}$, through Syngo.via VA11A analysis program. Results: Comparing the five groups divided according to the BMI by the standard differences between $SUV_{bw}$ to $SUV_{bsa}$, $SUV_{max}$ was measured to be $0.66{\pm}0.15$, $0.78{\pm}0.35$, $0.77{\pm}0.21$, $1.00{\pm}0.44$, $1.53{\pm}0.38$ for bones in underweight, normal weight, overweight, obese and severely obese groups, respectively. For liver, values of $SUV_{max}$ were $1.64{\pm}0.16$, $2.06{\pm}0.34$, $2.19{\pm}0.21$, $2.52{\pm}0.21$ and $2.74{\pm}0.40$ in the same order. And for lung, values of $SUV_{max}$ were $0.69{\pm}0.33$, $0.54{\pm}0.17$, $0.62{\pm}0.23$, $0.83{\pm0.29}$, $1.03{\pm}0.30$. Conclusion: By comparing and analyzing the differences between $SUV_{bw}$ and $SUV_{bsa}$ in this study, it was found that the differences between $SUV_{bw}$ and $SUV_{bsa}$ increased as patient's BMI increased. Thus, there is room for error in the values of SUV depending on the methods of calculations, and appropriate methods must be applied according to the circumstances in clinical settings.

PET/CT 검사에서 정량적 지표로 이용되는 SUV를 측정하는 방법 중 $SUV_{bw}$와 $SUV_{bsa}$를 환자의 BMI에 따라 비교하여 상관관계를 분석하였다. 실험을 위해 사용된 PET/CT scanner는 본원에서 사용하고 있는 Biograph mCT 40 (Siemens, Germany)이다. ROI는 bone, liver, lung에 각각 $4.5cm^2$ 면적으로 그렸으며 Syngo.via VA11A를 사용하여 $SUV_{max}$와 $SUV_{mean}$을 구하였다. 70명의 환자를 대상으로 시행한 PET/CT 영상으로 $SUV_{bw}$와 $SUV_{bsa}$를 비교 분석한 결과 환자의 BMI가 커질수록 $SUV_{bw}$와 $SUV_{bsa}$의 차이가 증가함을 보이며 $SUV_{mean}$보다 $SUV_{max}$에서의 차이가 더 많이 나타났다. Liver에서의 차이는 bone과 lung에 비해 상대적으로 높았고, bone과 lung에서는 유의한 차이는 없었다. 따라서 SUV를 산출하는 방법에 따라 오차가 발생할 가능성이 있으므로, 체중의존성을 줄이기 위해 임상에서는 실정에 맞게 적용하여 시행해야 할 것 으로 사료된다.