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Comparison and Evaluation of the Results of Quantitative Analyses of Lung Perfusion Scan using Q-Metrix

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Tae Hwan Ha, Jung Jin Lim, Yong Ho Do, Sung Wook Cho and Gyeong Woon Noh

Department of Nuclear Medicine, Seoul National University Hospital, Seoul, Korea

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[Purpose] The lung segment ratio (LSR) which is obtained through quantitative analyses of lung perfusion scan images is calculated to evaluate the lung function pre and post surgery. Generally, the volume of the lung is not reflected because the LSR is calculated by ROI on the planar images. In this study, LSR was calculated through a quantitative analysis program, Q-Metrix (GE Healthcare, USA), using ROI and VOI after SPECT/CT was conducted, and results were compared and evaluated.

[Materials and Methods] Lung perfusion scan and lung perfusion SPECT/CT were conducted using Discovery 670 (GE Healthcare, USA) on 25 lung cancer patients who visited the authors’ hospital between August 1, 2015 and April 13, 2016. For the quantitative analysis, the LSR was obtained using a ROI tool as a way of typical calculation, also another LSR was calculated using the Q-Metrix program which requires ROI and VOI based on SPECT/CT data. Then the two results were compared.

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[Results] From lung perfusion scan image, the mean ratio of the upper, middle and lower segments in the right lung was 17.55%, 12.12%, and 26.46% respectively. The mean ratio of the upper and lower segments in the left lung was 20.50% and 23.14% respectively. The standard deviation of the two methods was 4.27(upper), 4.82(middle) and 5.69(lower) in the right lung and 4.7(upper) and 4.95(lower) in the left lung.

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[Conclusion] It is impossible to set an exact ROI because lung perfusion scan image is planar. Instead, acceptable results were obtained when exact lung segment ROI and VOI were set based on the Q-Metrix program and CT images. Therefore, use of the Q-Metrix program which is for calculating not only ROI but also VOI may be calculated more accurate results than use of lung perfusion scan images.

[Keywords] Q-Metrix, Lung segment ratio, lung volume