Feasibility Of Radiation Dose Planning Guided Surgical Resection In Spinal Tumours

Abstract

The objective of high dose stereotactic radiotherapy regardless of application is to treat the malignancy while minimizing the radiation dose to the surrounding healthy tissue. In the context of spinal tumours this paradigm is difficult since the rigid dose tolerance of the spinal cord precludes optimal dose coverage of the epidural disease. To achieve adequate coverage spine separation surgery is performed, increasing the distance from the spinal cord to the malignancy and facilitating adequate radiation treatment planning. This approach has been validated with delivery of maximum tolerable dose and local control rates over 90%. The objective of this dissertation is to establish the feasibility of intraoperative, dose guided, spine separation surgery. In the current clinical context, spine separation surgery is performed prior to radiation treatment planning and contours are placed based on postoperative resected tumour volumes. The extent of surgical resection is not dictated by the dosimetric constraints of the spinal cord and relies solely on the clinical expertise of the operating neurosurgeon. Further, though a skilled surgeon can perform precise tumour debulking with or without the aid of millimetre resolution neuronavigation devices, determination of surgical debulking progress with accuracy comparable to treatment delivery cannot be recognized without intraoperative imaging. To achieve this goal, we introduced pre-surgical dosimetric planning with tracked high frequency micro-ultrasound imaging into the operating theatre to inform the surgeon of the surgical progress while considering the dosimetric objectives. In this dissertation, we assessed the dosimetric advantage of spine separation surgery on a millimetre by millimetre basis in a retrospective simulation study. Feasibility of intraoperative navigation with submillimetre resolution was established by quantifying the application accuracy of surgical navigation in the context of cranial and spinal surgery. Accuracy quantification was performed, assessing our revolutionary optical topographical imaging system and benchmarked versus existing commercially available neuronavigation systems. Finally, to establish feasibility of radiation dose planning guided surgical resection we integrated a high frequency micro-ultrasound system into the operating theater during spine separation surgery. Thus, by implementing sub-millimetre high frequency micro-ultrasound imaging and neuronavigation, incremental gains towards establishing the feasibility of in traoperative dose planning by iteratively updating the extent of tumour resection were recognized.