Assessment of the Accuracy and Precision of a Patient Immobilization Device for Radiation Therapy in Canine Head and Neck Tumors

Abstract

The positioning accuracy and precision of a head and neck immobilization device for radiation therapy of tumors in the canine skull was evaluated. Nineteen dogs with a spontaneous tumor of the head were enrolled including 12 with an intracranial mass and seven with an intranasal or maxillary tumor. Three hundred thirty-three pairs of orthogonal digital portal radiographs were analyzed to assess patient displacement in the cranial-caudal, lateral, and dorso-ventral directions. The mean systematic displacement was 0.8, 1, and 0.9 mm. The mean random displacement was 1.9, 1.6, and 1.5 mm. These values resulted in an overall displacement of 2.1 mm in the cranial-caudal direction, 1.8mm in the lateral direction, and 1.7 mm in the dorsal-ventral direction. The mean displacement value of the three dimensional (3D) vector was 2.4 mm with a standard deviation of 2.1. Ninety-five percent of all vectors were < 6.4 mm. This study quantifies the precision and accuracy of this particular positioning device. Knowing the limitations and setup variability of the system being used to set patients up for daily radiotherapy is paramount to planning and delivering appropriate radiation doses, especially as more complex treatment methods are used.

Treatment of MRI‐Diagnosed Trigeminal Peripheral Nerve Sheath Tumors by Stereotactic Radiotherapy in Dogs

“…Thermoplastic masks, vacuum‐locked moldable bags, dental molds for bite blocks, and nonmigrating fiducials imbedded in tumors aid in replicating the dog and PTV positioning for subsequent treatments . External mobilization devices help position the body for treatment, and several immobilization systems have previously been evaluated for radiotherapy of the head and neck in dogs …”

“…26 External mobilization devices help position the body for treatment, and several immobilization systems have previously been evaluated for radiotherapy of the head and neck in dogs. 10,[27][28][29][30][31][32] There are several different treatment units and techniques available for delivering stereotactic radiation. Standalone stereotactic systems, such as Gamma Knife, where a stereotactic frame with multiple radioactive cobalt sources is affixed around the head, have been employed in human medicine.…”

Late presentation of canine nasal tumours in aUKreferral hospital and treatment outcomes

“…Plans utilized three to seven beams, created using a Mark 2 series 80 leaf multi-leaf collimator. Patients were immobilized in a head immobilization device made up of a thermoplastic mask and a customized head support, which were then secured to a plastic base frame with four-point fixation (Kent et al 2009). Portal imaging was carried out at the time of the first and at the time of the seventh fraction.…”

Invited Review—image Registration in Veterinary Radiation Oncology: Indications, Implications, and Future Advances

“…One of the most common practices immediately prior to treatment delivery is to generate a pair of orthogonal digitally reconstructed radiographs (DRRs) from the planning CT and to register simulated radiographs with megavoltage (MV) radiographs acquired by a flat‐panel imager (electronic portal imaging devices or EPIDs) attached to the linear accelerator (Fig. ) . More advanced on‐board imaging equipment involves cone‐beam CT systems or helical CT systems built into the treatment unit .…”