First French experiences of total body irradiations using helical TomoTherapy(®).

PURPOSE: Dynamic conformal radiotherapy with helical TomoTherapy(®) (HT) offers a more quantitative paradigm for total body irradiation. Treatment planning, delivery, dose verification of the first French experiences of total body irradiation using helical TomoTherapy(®) are presented.

MATERIALS AND METHODS: Patients planned for total body irradiation at our institution from February 2012 to May 2013 were reported. Total body irradiation consisted in a single fraction of 2Gy. Planning target volume was divided in two due to the limited translation length of the table. Delivery quality assurance was performed with cylindrical phantom, ionization chamber and films. Thermoluminescent dosimeters and radiochromic films were used for in vivo dosimetry and junction region heterogeneity assessment.

RESULTS: Six patients were included. One finally did not receive the treatment but dosimetric data were analyzed. Planned V95% was covered by D95% and V2% did not exceed D107% for five of the six patients. The mean relative difference between measured and calculated absolute dose of the Delivery quality assurance was always less than 2.5% (mean value±SD: 1%±0.67%). Gamma index (3%; 3mm) was less than 1 for at least 93% of the points (value±SD: 97.4±1.6% and 96.6±2.5% for upper and lower part of treatment respectively). Difference between in vivo measured and calculated dose was above 5% for only two out of 15 points (maximum: 10.2%, mean: 0.73±4.6%). Junction region heterogeneity was in average 5.8±1%. The total treatment session of total body irradiation lasted 120min, with a mean beam on time of 17.2±0.6 and 11.2±1.6min for upper and lower part of the body respectively.

CONCLUSION: Total body irradiation using helical TomoTherapy(®) guaranteed high dose homogeneity throughout the body and dose verification was achievable, showing small difference between planned and delivered doses.