tumor localization techniques richard kao april 10, 2001 computer integrated surgery ii
TRANSCRIPT
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
Papers
• Jansen, E. et al. “Target volumes in radiotherapy for high-grade malignant glioma of the brain.” Radiotherapy and Oncology, vol. 56, pp. 151-156, 2000.
• Sato, M. et al. “Laparoscopic hepatic surgery guided by hookwire localization.” 2000.
• Lee, B. et al. “Bioimpedance: Novel Use of a Minimally Invasive Techniques for Cancer Localization in the Intact Prostrate.” The Prostrate, vol. 39, pp. 213-218, 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 cm3, 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 (932 + 170 ohms)
• Non-cancerous tissue had lower impedance (751 + 151 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