The methodology of Micro-CT imaging of body surface malignant tumors

Abstract

Objective This study is to investigate the parameter settings and imaging effects of Micro-CT scanning externalmalignancies during operation and summarize the characteristics of Micro-CT images regarding external soft tissue and tumors. Methods According to the inclusion criteria, patients with externalmalignancies admitted to the Department of Plastic and Reconstructive Surgery of the First Medical Center of the PLA General Hospital from October 2018 to January 2020 were collected. Through the surgical resection of tumors, the isolated tumor specimens were divided into appropriate sizes (length × width × thickness not exceeding 5 cm×3 cm×3 cm), placed on the Micro-CT scanning bed, and scanned with different parameters. (1) Scanning with different times: with the fixedscanning voltage (50 kV for sarcoma, 70 kV for other tumors), the same specimen was scanned with 4min and 14min protocols respectively. (2) Scanning with different voltages: with the fixed scanning time (4 min), the same specimen was scanned with 30, 50, 70, and 90 kV voltages respectively. After comparing the imaging results with different scanning times and different scanning voltages, the optimal scanning parameters for different tumors were obtained. (3) The regions of interest for radiology were taken from the specimens, and pathological HE stained slides were prepared. Digital slices were obtained by precice automatic digital slice scanning system. The slices were compared with Micro-CT corresponding cross-sectional images and the radiological characteristics of different tissues were recorded. Results A total of 27 patients were included/incorporated into the study and there were 15 males and 12 females, aged from 33 to 82, with an average age of 63.9 years old, including 16 cases of skin squamous cell carcinoma, 2 cases of basal cell carcinoma, and 2 cases of extramammary Paget′s disease, 1 case of melanoma, 3 cases of cutaneous fibrosarcoma, 1 case of angiosarcoma, and 2 cases of liposarcoma. A total of 65 groups were compared between Micro-CT images and pathology slides. (1) Scanning time: both 4 min and 14 min scanning times can obtain clear images which can meet requirements for morphology observation and identification of margins of tumors. (2) Scanning voltage: as for squamous cell carcinoma, the quality of images obtained by the scanning voltage of 30 and 50 kV is poor, while by the voltage of 70 and 90 kV is high. As for sarcoma, the quality of images obtained by the scanning voltage of 30 kV is poor; by the voltage of 50 kV is high and the contrast between tumor and subcutaneous fat is low by the scanning voltage of 70 and 90 kV. (3) The radiological morphology of external tumors and surrounding tissues are similar with the pathology slides. The boundary between skin and subcutaneous tissue is clear and the hair follicles are clearly distinguishable. The radiological characteristics of tumors are related to the type of tumors and the density of tumors, including high-density shadows, thicker than normal skin, no hair follicles and some small calcification points. The boundary between squamous cell carcinoma or sarcoma and normal skin or subcutaneous can be distinguished. As for the tumors in the skin, such as basal cell carcinoma, extra-mammary Paget′s disease, etc. the imaging results are poor. Conclusions The Micro-CT scanning parameters need to be set according to the type of the tumor. The scanning time has little effect on the evaluation of the tumor. It is recommended to choose the protocol of 4 min during operation. The recommended scanning voltage of squamous cell carcinoma is 70 kV and the voltage of sarcoma is 50 kV. Micro-CT can clearly imaging the skin structure of soft tissue specimens on the body surface; configuration is identifiable for tumors that invade beyond skin and have a large heterogeneity of density compared with surrounding tissues; for tumors that do not exceed the dermis, the imaging effect is not good. Key words: Micro-CT; Neoplasms; Squamous cell carcinoma; Dermatofibrosarcoma protuberans; Pathology