Dosimetry and verification of ⁶⁰Co total body irradiation with human phantom and semiconductor diodes

Abstract

Total Body Irradiation (TBI) is a form of radiotherapy used for patients prior to bone marrow or stem cell transplant to destroy any undetectable cancer cells. The dosimetry characteristics of a 60Co unit for TBI were studied and a simple method for the calculation of the prescribed dose for TBI is presented. Dose homogeneity was verified in a human phantom. Dose measurements were made in water phantom (30 × 30 × 30 cm3), using farmer ionization chamber (0.6 cc, TM30010, PTW) and a parallel plate ionization chamber (TM23343, PTW). Point dose measurements for AP/PA irradiation were measured in a human phantom using silicon diodes (T60010L, PTW). The lung dose was measured with an ionization chamber (0.3 cc, TM31013). The validity of the proposed algorithm was checked at TBI distance using the human phantom. The accuracy of the proposed algorithm was within 3.5%. The dose delivered to the mid-lobe of the lung was 14.14 Gy and it has been reduced to 8.16 Gy by applying the proper shield. Dose homogeneity was within ±7% for all measured points. The results indicate that a good agreement between the total prescribed and calculated midplane doses can be achieved using this method. Therefore, it could be possible to use calculated data for TBI treatments.

Evaluation of off-axis wedge correction factor using diode dosimeters for estimation of delivered dose in external radiotherapy

“…Therefore, to determine PDD d (and PDD ex ) at non-reference SSDs, the Mayneord factor is needed. [ 21 ] In other words, PDD d (at non-reference SSD) = (Mayneord factor) × PDD d (at reference SSD).…”

Evaluation of the surface dose for total body irradiation (TBI) technique with parallel-opposed anterior posterior geometry

“…For more than 40 years, total body irradiation (TBI) has been used as an important part of patients' conditioning regimen prior to bone marrow transplantation (BMT). [1][2][3][4] TBI in conjunction with chemotherapy is applied for immunosuppression and eradicates mutant cancer cells prior to BMT. 5 Inadequate dose received by whole body in TBI reduces the chance of successful transplantation.…”

Fabrication of anthropomorphic phantoms for use in total body irradiations studies

“…10,16 Furthermore, the RANDO phantoms are constructed with a natural human skeleton cast inside material that is radiologically equivalent to soft tissue and disintegrates over time. 17 Allahverdi et al 18 studied TBI with cobalt-60 on the RANDO phantom; however, the authors did not consider the dosimetry for the lower limbs in the phantom and this is an important consideration when delivering TBI and TSET, since it is common for symptoms of skin cancers to first present on the lower limbs.…”