Radiation dose from kilovoltage cone beam computed tomography in an image-guided radiotherapy procedure.
OBJECTIVE
Image-guided radiation therapy has emerged as the new paradigm in radiotherapy. This work is to provide detailed information concerning the additional imaging doses to patients' radiosensitive organs from a kilovoltage cone beam computed tomography (kV CBCT) scan procedure.


METHODS
The Vanderbilt-Monte-Carlo-Beam-Calibration (VMCBC; Vanderbilt University, Nashville, TN) algorithm was used to calculate radiation dose to organs resulting from a kV CBCT imaging guidance procedure. Eight patients, including 3 pediatric and 5 adult patients, were investigated. The CBCT scans in both full- and half-fan modes were studied.


RESULTS
For a head-and-neck scan in half-fan mode, dose-volume histogram analyses show mean doses of 7 and 8 cGy to the eyes, 5 and 6 cGy to the spinal cord, 5 and 6 cGy to the brain, and 18 and 23 cGy to the cervical vertebrae for an adult and a 29-month-old child, respectively. The dose from a scan in full-fan mode is 10-20% lower than that in half-fan mode. For an abdominal scan, mean doses are 3 and 7 cGy to prostate and 7 and 17 cGy to femoral heads for a large adult patient and a 31-month-old pediatric patient, respectively.


CONCLUSIONS
Doses to radiosensitive organs can total 300 cGy accrued over an entire treatment course if kV CBCT scans are acquired daily. These findings provide needed data for clinicians to make informed decisions concerning additional imaging doses. The dose to bone is two to four times greater than dose to soft tissue for kV x-rays, which should be considered, especially for pediatric patients.
Ding
George X
GX
Vanderbilt-Ingram Cancer Center, Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, TN, USA.
Coffey
Charles W
CW
D000328:Adult; D000465:Algorithms; D001921:Brain / Q000000981:diagnostic imaging; D002138:Calibration; D002574:Cervical Vertebrae; D002675:Child, Preschool; D054893:Cone-Beam Computed Tomography / Q000009:adverse effects* / Q000379:methods; D005123:Eye / Q000000981:diagnostic imaging; D005270:Femur Head / Q000000981:diagnostic imaging; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D009010:Monte Carlo Method; D011829:Radiation Dosage; D011836:Radiation Tolerance; D011881:Radiotherapy, Computer-Assisted / Q000009:adverse effects*; D013116:Spinal Cord / Q000000981:diagnostic imaging