Thesis Defense: Feasibility of Radiation Dose Planning Guided Surgical Resection in Spinal Tumours

Event Date/Time: 
Thu, 06/22/2017 - 10:00am
KHE 332

Presenter: Raphael Jakubovic M.Sc., PhD Candidate
Department of Biomedical Physics
Ryerson University & Sunnybrook Health Sciences Centre

Supervisors: Dr. Victor Yang, Dr. Ana Pejović-Milić


The objective of high dose stereotactic radiotherapy regardless of application is to treat the malignancy while minimizing the 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 near the spinal cord. 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 intra-operative, 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 post-operative 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 neuro-navigation devices, determination of surgical debulking progress with accuracy comparable to treatment delivery cannot be recognized without intra-operative imaging. To achieve this goal, we introduced pre-surgical dosimetric planning with tracked high frequency 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 review. Feasibility of intra-operative 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 surface imaging system and benchmarked versus existing commercially available neuro-navigation systems. Finally, to establish feasibility we integrated a high frequency ultrasound system into the operating theater during spine separation surgery. Thus, by implementing sub-millimetre high-frequency ultrasound imaging and neuro-navigation, incremental gains towards establishing the feasibility of intra-operative dose planning by iteratively updating the extent of tumour resection were recognized.