Purpose: To compare IMRT plans delivered with a conventional linear accelerator (Varian 2100EX) and a Helical Hi‐Art Tomotherapy accelerator and the dose differences to critical organs and structures surrounding the tumor volume. Method and Materials: Five patient plans were generated using both the Varian Eclipse treatment planning system and the Tomotherapy treatment planning system. A sampling of different treatment sites were chosen for the study, which include an esophagus, a hilum/lung, a para‐aortic, a pelvis, and an orbital case. IMRT plans were created with the goal of reducing dose to surrounding critical organs and structures while achieving similar satisfactory target coverage. Radiation doses were taken at three volumes of 25%, 50% and 75% for comparison. Also a mean dose and a max dose for spinal cord are provided. The plans generated represent the best dosimetric effort within clinically permitted time frame. Results: The critical organs for each case are highlighted in yellow in the supporting documentation. Tomotherapy plans show an average improvement of mean doses to the critical organs by 31.83% over the conventional linear accelerator plans. For spinal cord doses, the average improvement of maximum doses shows an 18.75% advantage to the Tomotherapy plan over the conventional linac. Conclusions: Examination of the dose volume histograms determined that the Tomotherapy unit was superior for thoracic cases, significantly reducing total lung doses. In most cases, the data show that the Tomotherapy plans provide better overall dosimetric characteristics. Also note that only five cases were compared in this study but similar results can be expected in most other cases.

Purpose: Patients who have had prior radiation therapy often present with recurrent/residual disease in the previously irradiated area. However, additional radiation is often not feasible because the maximum tolerated dose for normal critical organs have already been reached. We present a case of a patient with metastatic endometrial cancer who was retreated to the ninth rib/vertebral body with Tomotherapy although the spine had already received 4500 cGy. Method and Materials: A patient with metastatic disease to the ninth right rib and vertebral body was treated with 4400 cGy in 2003. The patient was recently found to have recurrent/progressive disease in the area of prior treatment. A PET scan was taken prior to treatment and an PET/CT fusion was performed in order to aid in the contouring of the tumor volume. The tumor volume(rib) wrapped around the liver and ended at the ninth vertebral body right next to the spinal cord. A Tomotherapy plan was generated to maximally cover the tumor volume while minimizing the dose to the spinal cord and liver. The positioning of the patient was verified daily with an MVCT. Results: Treatment plans generated using the Tomotherapy treatment planning system and the ability of the Tomotherapy machine to verify patient set‐up daily show that the Tomotherapy unit was able to deliver 6000 cGy to the tumor volume while only delivering a maximum dose of 575 cGy to the spine with an average of only 179 cGy. Dose the liver was kept to a minimum with an average of 1804 cGy. Conclusions: Examination of the dose volume histograms determined that the Tomotherapy unit shows was able to keep at a minimum the doses to the spinal cord and liver and surrounding structures thus making Tomotherapy a useful tool in treating patients with prior radiation.

Purpose: To review the dosimetry results of whole breast irradiation using a helical Tomotherapy Hi‐Art device and discuss the feasibility of such treatment technique by comparing the data with linear accelerator based Eclipse field‐in‐field (FIF) technique. Method and Materials: Twenty breast plans were generated using a Tomotherapy Hi‐Art planning system. Among them, 11 were left breast cases and 9 were right breast cases. Treatment planning techniques such as contour delineation and optimization strategy/parameters were described. Key dosimetric results including target dose coverage and organs‐at‐risk (OAR) dose statistics were compiled and presented. Radio‐biological consequences to the OARs were studied using the normal tissue complication probability (NTCP) models. A retrospective study using the forward FIF planning technique was also performed for those 20 patients as comparison benchmark. Results: On the ipsilateral side, the Tomotherapy plans performed slightly better than the forward FIF plans in target coverage and dose uniformity (p=0.0018), and significantly better in OAR high dose statistics such as V20 in lung (p=0.0001) and V30 in heart (p=0.0003). Meanwhile, the Tomotherapy plans delivered slightly higher average dose to both ipsilateral and contralateral OAR, including the heart, the lung, the breast, the esophagus, and the spinal cord. However, the differences in NTCPs between the two techniques for the total lung (p=0.298) and the heart (p=0.268) were statistically insignificant, whereas the NTCPs for the esophagus were too low to compare. Conclusion: The Tomotherapy technique can provide better target coverage for breast cancer treatment. The differences in NTCPs associated with slightly higher mean doses to the OAR were insignificant comparing with the forward FIF technique.