Abstract
The objective was to compare the dosimetry of Helical TomoTherapy (TOMO) and Gamma Knife (GK) treatment plans for tumor and normal brain in the treatment of single and multiple brain tumors. An anthropomorphic Rando Head phantom was used to compare the dosimetry of TOMO and GK. Eight brain tumors of various shapes, sizes and locations were used to generate 10 plans. The radiation dose was 20 Gy prescribed to the 100% isodose line for TOMO plans and to the 50% for the GK plans. Dose Volume Histograms for tumor and brain were compared. Equivalent Uniform Dose (gEUD), Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were performed and used for plan comparisons. Average minimum, mean, median and maximum tumor doses were 19.93, 27.83, 27.38, 39.60 Gy for GK and 20.17, 20.60, 20.59, 20.90 Gy for TOMO. Average gEUD values for tumor and normal brain were 25.0 and 7.2 Gy for GK and 20.7 and 8.1 Gy for TOMO. Conformity indices (CI) were similar for both modalities. Gradient indices (GI) were greater for TOMO. A combination plan was also generated using all eight tumors. TOMO was able to target all eight tumors simultaneously resulting in mean tumor and brain doses of 20.5 and 9.35 Gy, respectively. Due to the maximum limit of 50 beams per plan, GK was unable to provide a treatment plan for all eight tumors. GK provides an advantage for all tumor sizes with respect to tumor and normal brain dose. Clinical studies are needed to correlate these dosimetric findings with patient outcomes.PACS number: 87.55‐x
Highlights
Brain metastases occur in 20%–40% of adult patients with cancer, and the incidence of this disease has been increasing approaching 200,000 new cases per year
28 Kumar et al.: Dosimetric comparison of TomoTherapy and Gamma Knife for brain tumors 28 to surgery or whole brain radiation therapy.[2,3,4] In addition, stereotactic radiosurgery has been used for the treatment of recurrences after whole brain radiation therapy.[1,5] The radiobiological advantage of stereotactic radiosurgery relies on its ability to deliver single, very high-dose fractions in a small volume with submillimeter accuracy
Stereotactic radiosurgery can be delivered using various equipment and techniques including Gamma Knife, linacs, CyberKnife and more recently Helical TomoTherapy.[9,10] These techniques differ regarding a number of treatment planning and treatment delivery parameters including the source of radiation beams, the method of beam delivery, the quality assurance processes, and the resultant tumor and normal tissue dosimetry
Summary
Brain metastases occur in 20%–40% of adult patients with cancer, and the incidence of this disease has been increasing approaching 200,000 new cases per year. This increase can be attributed to the earlier diagnosis of the disease due to advances and higher utilization of imaging technology. Stereotactic radiosurgery can be delivered using various equipment and techniques including Gamma Knife, linacs, CyberKnife and more recently Helical TomoTherapy.[9,10] These techniques differ regarding a number of treatment planning and treatment delivery parameters including the source of radiation beams, the method of beam delivery (coplanar versus noncoplanar beams), the quality assurance processes, and the resultant tumor and normal tissue dosimetry. Most GK models (B and C series) are designed for brain only stereotactic radiosurgery, while occasionally providing limited access to peripheral brain lesions or those located close to the foramen magnum.[11]
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