Tumor Localization Techniques Richard Kao April 10, 2001 Computer Integrated Surgery II

Current Oncology Research Tumor Localization Pre-operative localization techniques that provide the greatest accuracy before irradiating the lesion area Prevent tumor extension after treatment

Definitions Clinical Target Volume (CTV) –Area to be irradiated, built from 3-D imaging modalities Delineation –Outlining the area of the tumor, including providing a perimeter to prevent tumor extension

Three Techniques CT and/or MRI Hookwire Localization Bioimpedance

Papers Jansen, E. et al. “Target volumes in radiotherapy for high-grade malignant glioma of the brain.” Radiotherapy and Oncology, vol. 56, pp , Sato, M. et al. “Laparoscopic hepatic surgery guided by hookwire localization.” Lee, B. et al. “Bioimpedance: Novel Use of a Minimally Invasive Techniques for Cancer Localization in the Intact Prostrate.” The Prostrate, vol. 39, pp , 1999.

CT Computerized Tomography (CT) Provides geometric superiority 2-cm margin of error after postmortem analysis Radiation

MRI Magnetic Resonance Imaging (MRI) Provides diagnostic superiority 2-3 cm margin of error after postmortem analysis Availability and costs

Jansen’s Findings Patients had high-grade malignant astrocytoma, most common primary brain tumor Found a lack of uniform guidelines Discrepancy between tumor extension and CT and/or MRI results Trade-off between probability of complications and the expected benefit for the patient Had to add a 2-cm ring around images

Jansen’s Findings (cont.) CT and MRI separately provide good information on both macro- and microscopic tumor extension Ideal situation is to use both For CTVs less than 250 cm 3, use single CTV For larger tumors, use a second TV with a smaller margin of irradiation

Sato’s Findings Patients with small Hepatocellular Carcinomas (HCCs) Helical and angiographic CT used to locate these lesions Use CT to guide a 21-gauge guide needle to the lesion, then insert a hookwire through needle and withdraw the needle, leaving hookwire in place

Hookwire Localization CT used to confirm hookwire in place Microwave Coagulation Therapy (MCT) on HCCs Complete tumor ablation Radiation

Bioimpedance Electrical property of biological tissue Electric current is limited in living tissue by highly insulating cell membranes Different tissue architecture may impede current differently, allowing detection of differences between normal and cancerous tissue

Lee’s Findings Prostrate cancer diagnosed by transrectal ultrasound- guided sextant needle biopsy Imprecise method Use two bioimpedance needles 1 mm apart, 3 mm into prostrate surface

Lee’s Findings (cont.) Cancerous areas had higher impedance ( ohms) Non-cancerous tissue had lower impedance ( ohms) Bioimpedance successful but still invasive and imprecise for different types

Conclusions CT with MRI is effective but brings up questions regarding radiation and availability Hookwire Localization requires CT scans both pre- and postoperation Bioimpedance successful, but invasive and not appropriate for all types of tumor localization

Conclusions (cont.) Using amorphous wires and magnetic fields to implement the Barkhausen effect, we provide a precise, reliable alternative that is readily available Avoid pitfalls of these other techniques Applicable to more areas than tumor localization, including catheter tip location, seed implants in brachytherapy, and probe tip location in surgical procedures