Purpose: Radiation therapy workflow encounters challenges in daily patient repositioning. Foam immobilization molds were a developed solution in collaboration with .decimalTM (Sanford, FL) at our facility. This addressed a variety of treatment modalities including proton therapy, MRI guided therapy, SBRT as well as clinical indications for routinely difficult setups such as extremity treatment. It was also used to exact patient treatment positions to PET scan positions for better targeting of metastases. This presentation details the clinical indications for this device, its use, and its accuracy.
Methods: To date, foam immobilizers have been applied to 15 different cases. First, a patient body contour from volumetric imaging was transferred to .decimalTM for foam manufacture. For each device, 3D volumetric scans of the patient with and without the foam molds were compared for fit to patient anatomy as determined by rotational corrections from image fusion using Eclipse treatment planning system (Varian Palo Alto, CA). For fractionated treatment courses, the daily setup standard deviations were evaluated to check interfraction setup variations using the foam immobilization device.
Results: The .decimalTM foam immobilizers provided excellent fit, with low average pitch 1.19° ± 1.24°, yaw 1.01° ± 1.19°, and roll 0.95° ± 1.20°. There was consistent daily setup variability, with a mean rectangular shift of 3.90 mm ± 3.32 mm and a mean angular shift of 0.56° ± 0.70°. Rectangular shifts may have been larger due to unusual cases that were offset at initial setup for imaging purposes.
Conclusion: We have developed a method for creating patient specific foam immobilization that can be used to replicate the patient diagnostic scan position or can be used to immobilize patients in configurations that are not possible with conventional vacuum molds. This process was used on several cases and can be implemented to any treatment site or treatment modality.