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. 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