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Purpose: After implementing a new total body irradiation (TBI) technique in clinic, in vivo dosimetry check is essential. We use a navel tool, radiophotoluminescent glass dosimeter (RPLGD), for in vivo dose measurement. It has superior physical and dosimetric characteristics than thermoluminenscent dosimeter (TLD). Method and Materials:Bilateral TBI is performed with the Siemens Prius Linac with a nominal energy of 6 MV photon beam. The patient is at the lying position and the source to midpoint of the patient is 415 cm. Water bags are used to compensate the change in body thickness and arms are positioned laterally at the mid AP‐thickness level to block the lungs. In vivo dose measurements were performed with RPLGDs placed bilaterally at five levels to obtain the entrance dose and exit dose : on brain, chest, abdomen, thigh and lower legs. The midline dose is the average of entrance dose and exit dose. The prescribed dose is 120 cGy per fraction to the umbilicus to a total of 1200 cGy. Results: The absolute dose measured on dose prescribed point is 123.6 cGy and the difference between the prescription and measurement is 3%. The dose at five different levels are normalized to that at the abdomen level. The relative doses of brain, chest, thigh and lower legs are 89%, 99%, 1.03% and 88% respectively. The absorbed doses at brain and lower leg levels may be overcompensated and these can be adjusted by modifying the thickness of water bags. Conclusions: In our preliminary result, RPLGD is an ideal dosimeter to perform the in vivo dose measurement, not only the better physical and dosimetric characteristics but the easy process without annealing and the ability to be readout repeatedly. Conclusion, the RPLGD is a useful tool to for in vivo dosimetry in clinic.

Purpose: To verify the necessity of 6D localization detection and correction in radiation therapy. Methods: An anthropomorphic head and neck phantom was used to test the BrainLab ExacTrac x‐ray imaging system. After initial positioning, both ExacTrac and the on‐board kV CBCT were used to detect the offset at the same position, using both manual and automatic registration algorithms. Then 6D offset including rotational errors up to 5 degree were introduced. Both ExacTrac and CBCT were used to correct the offsets and the residual errors were evaluated. Finally, 6D offset detected by ExacTrac for a C‐Spine patient was reported. Results: The differences in 3D offset detected by ExacTrac and CBCT were 1.5 ± 1.2(Lateral), 2.7 ± 2.7(Vertical), and 4.0 ± 6.3(longitudinal) mm with manual registration while the corresponding differences decreased to 0.6 ± 0.3, 1.0 ± 0.3, and 0.3 ± 0.3 when automatic registration were used. CBCT corrected the translational offset to within 0.5 mm but the rotational errors remained and detected by the ExacTrac system (Yaw=2.1, Roll=1.1, Pitch=1.4 degree). When similar offset was introduced and corrected using ExacTrac, the residual error detected by both CBCT and ExacTrac were within 0.5 mm / 0.5 degree. The average offset from the 112 ExacTrac x‐ray corrections for the C‐Spine patient was 0.6 ± 1.6 (lateral), 5.4 ± 8(vertical), 1.6±1.1(longitudinal) mm, and 0.7 ± 0.6 (pitch), 0.7 ± 0.4(roll), 1.2 ± 0.7 (yaw) degree. Larger rotational errors, with a maximum of 2.7 degree (corresponds to about 1.5 to 4.5 mm offset for a POI 10 to 30 cm away from the isocenter), were observed when couch rotational were involved. Conclusion: Rotational errors are common in patient localization, especially when couch rotation is involved. Both appropriate imaging system and 6D robotic couch are necessary to detect and correct the rotational localization errors.