| Li Qingshan,Song Wei,Fu Tianxiao.A simulation study on the position variations of skin markers at different parts relative to the pelvic cavity[J].Chinese Journal of Radiological Medicine and Protection,2023,43(12):969-973 |
| A simulation study on the position variations of skin markers at different parts relative to the pelvic cavity |
| Received:August 08, 2023 |
| DOI：10.3760/cma.j.cn112271-20230808-00036 |
| KeyWords:Radiotherapy Pelvic cavity Localization Skin marker Position variation |
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| Abstract:: |
| Objective To analyze the activity of skin markers at different parts of the body surface and the correlations between their displacement deviations and pelvic filling volumes during conventional abdominal and pelvic radiotherapy.Methods A retrospective analysis was conducted on 15 patients receiving abdominal and pelvic radiotherapy with four times of computed tomography (CT) in the First Affiliated Hospital of Soochow University from January 2020 to January 2022. All CT images were divided into nine parts from the upper edge of L3 to the upper edge of the pubic symphysis: upper, middle, and lower parts in the right portion; upper, middle, and lower parts in the central portion; and upper, middle, and lower parts in the left part portions, No. 1-9 in sequence. The same blood-vessel or fascia intersection points near the same skin parts receiving the same dose fraction were used as the markers for skin positioning during simulated radiotherapy. The relative coordinates of the markers were measured, with the same point at the lower edge behind the L5 vertebral body set as the coordinate origin. Through pairwise comparison of each patient's four CT images, the three-dimensional displacement deviations and activity were calculated for all markers. In the left-right (L-R), superior-inferior (S-I), and anterior-posterior (A-P) directions, the differences in the displacement activity of the markers in the nine parts were compared using both the non-parametric Kruskal-Wallis test and the Descriptives. The correlations between the three-dimensional displacement deviations of all markers and the A-P displacement deviations of the No. 5 marker were analyzed using the Pearson correlation analysis.Results Differences existed in the displacement activity of the nine-part markers in the L-R, S-I, and A-P directions (H=36.66, 66.20, 92.15, P<0.05). No. 3 and 9 markers exhibited lower overall three-dimensional displacement activity (median: 2.40-3.75 mm) than other markers. The No. 5 marker manifested the highest A-P displacement activity, with a median of 9.20 mm. The A-P displacement deviation of No. 5 marker was correlated using the L-R displacement deviations of the No. 1, 2, 3, 7, 8 and 9 markers (r=-0.36 to 0.49, P<0.05), the S-I displacement deviations of the No. 4, 5, 6, and 9 markers (r=-0.34 to -0.24, P<0.05), and the A-P displacement deviations of the No. 1, 2, 3, 4, 6, 7, 8 and 9 markers (r=0.33-0.91, P<0.05).Conclusions Skin markers drawn in bilateral acetabular regions serve as the best choices for reposition in pelvic radiotherapy. Conventional skin markers made at the central parts are prone to suffer deviations in the S-I direction due to the influence of the abdominal and pelvic filling volumes. |
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