ศึกษาระยะสแกนและปริมาณรังสีที่ผู้ป่วยได้รับในการเอกซเรย์คอมพิวเตอร์ ระบบทางเดินปัสสาวะที่โรงพยาบาลทุ่งสง

Sukhumarn  Singhapun

Authors

Sukhumarn Singhapun Specialist Physician in Radiology, Radiology Department, Thung Song Hospital

Keywords:

CT KUB, over scan, over scan length, radiation dose

Abstract

Background: Non-contrast computed tomography of the kidneys, ureters, and bladder (CT KUB) is the gold standard for diagnosing urinary tract stones. However, patients are exposed to high radiation doses. Limiting the scan range to the necessary anatomical area can effectively reduce radiation exposure without compromising diagnostic accuracy.

Objectives: To evaluate the vertebral level corresponding to the upper margin of the scan, and identify the upper pole of the kidneys in order to establish the most appropriate vertebral landmark for initiating CT KUB scans. In addition, the study determine the scan length, the extent of overscanning and radiation dose.

Materials and Methods: A retrospective descriptive study was conducted in 268 adult patients who underwent non-contrast CT KUB examinations at Thung Song Hospital Form 1 August 2024 to 31 July 2025.

Results: The upper pole of the kidneys was most frequently located at T12 (156 patients, 52.8%), while in 3 patients (1.1%) it was located at T10. The mean radiation dose was 653.15 ± 202.80 mGy·cm. Only 6 patients (2.2%) had scans that complied with both margin criteria, whereas 192 patients (71.6%) did not comply with either margin, and 70 patients (26.1%) failed to comply with one margin. The mean overscan length was 4.38 cm superiorly and 5.58 cm inferiorly.

Conclusion: Overscanning beyond the necessary anatomical boundaries was observed in 97.8% of cases, resulting in unnecessary radiation exposure. Using the T10 vertebral body as the superior landmark and the pubic symphysis as the inferior landmark is recommended to ensure complete coverage of the urinary tract while minimizing overscanning and reducing radiation dose.

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