[In vitro evaluation of MR thermometry in the implementation of laser-induced thermotherapy]

MR-Guided Laser Ablation

MR-guided LITT is a safe and effective treatment modality that improves survival in well-selected patients who have liver metastases. A major advantage of MR-guided LITT is that it can be easily performed under local anesthesia in an outpatient setting with a low complication rate.

MR-guided ablation of head and neck tumors

Interstitial laser-induced thermotherapy (LITT) is a minimally invasive technique for lo-caltumor destruction within solid organs using optical fibers to deliver a high-energylaser to the target lesion. MR imaging is used both for placement of the laser in the tumorand for monitoring progress of thermocoagulation caused by the laser. The success ofLITT is dependent on the delivery of the optical fibers to the target area, real-time mon-itoringof the effects of the treatment, and subsequent evaluation of the extent of thermaldamage. The key to achieving these objectives is the imaging methods used. The thermo-sensitivityof certain MR sequences is the key to real-time monitoring, allowing accurateestimation of the extent of thermal damage.

Breast cancer metastases in liver: laser-induced interstitial thermotherapy--local tumor control rate and survival data

PURPOSE

To evaluate the local tumor control rate and survival data for magnetic resonance (MR) imaging-guided laser ablation of breast cancer liver metastases by using laser-induced interstitial thermotherapy (LITT).

MATERIALS AND METHODS

MR-guided LITT was performed in 232 female patients with 578 liver metastases from breast cancer. Survival rates were calculated with the Kaplan-Meier method. Indications for the procedure were defined for patients with no more than five metastases, none of which were larger than 5 cm in diameter, as follows: recurrent liver metastases after partial liver resection (8.2%), metastases in both liver lobes (45.2%), locally nonresectable tumors (19%), general contraindications for surgery (2.6%), or refusal to undergo surgical resection (25%).

RESULTS

Local recurrence rate at 6-month follow-up after LITT was 2.3% (five of 213) for metastases up to 2 cm in diameter, 4.3% (seven of 162) for metastases 2-3 cm in diameter, 3.2% (two of 63) for metastases 3-4 cm in diameter, and 1.9% (one of 52) for metastases larger than 4 cm in diameter. No additional local tumor progression was observed beyond 6 months. The mean survival rate for all treated patients, with calculation started on the date of diagnosis of the metastases treated with LITT, was 4.9 years (95% confidence interval: 4.3, 5.4). The median survival was 4.3 years; 1-year survival, 96%; 2-year survival, 80%; 3-year survival, 63%; and 5-year survival, 41%. The mean survival after the first LITT treatment was 4.2 years (95% confidence interval: 3.6, 4.8).

CONCLUSION

MR-guided LITT yields high local tumor control and survival rates in patients with liver metastases from breast cancer.

Colorectal carcinoma metastases in liver: laser-induced interstitial thermotherapy--local tumor control rate and survival data

PURPOSE

To evaluate the local tumor control and survival data for magnetic resonance (MR) imaging-guided laser-induced interstitial thermotherapy (LITT) of colorectal liver metastases.

MATERIALS AND METHODS

MR imaging-guided LITT was performed in 603 patients (mean age, 61.2 years) with 1,801 liver metastases of colorectal cancer. Survival rates were calculated by means of the Kaplan-Meier method. Local tumor control and tumor volume were evaluated with nonenhanced and contrast material-enhanced MR imaging. Indications for the procedure were defined for patients with five or fewer metastases, none of which were larger than 5 cm in diameter. The indications included recurrent liver metastases after partial liver resection in 37.6% of study patients, metastases in both liver lobes in 32.5%, locally nonresectable lesions in 11.3%, general contraindications for surgery in 4.6%, and refusal to undergo surgical resection in 13.9%.

RESULTS

Local recurrence rate at 6-month follow-up was 1.9% (nine of 474) for metastases up to 2 cm in diameter, 2.4% (13 of 539) for metastases 2.1-3.0 cm in diameter, 1.2% (four of 327) for metastases 3.1-4.0 cm in diameter, and 4.4% (13 of 294) for metastases larger than 4 cm in diameter. The mean survival rate for all treated patients, with calculation started on the date of diagnosis of the metastases (which were treated with LITT) was 4.4 years (95% CI: 4.0, 4.8) (1-year survival, 94%; 2-year survival, 77%; 3-year survival, 56%; 5-year survival, 37%). Median survival was 3.5 years (95% CI: 3.0, 3.9). Mean survival after the first LITT treatment was 3.8 years (95% CI: 3.4, 4.2). Median survival was 2.9 years (95% CI: 2.4, 3.3).

CONCLUSION

MR imaging-guided LITT yields high local tumor control and survival rates in well-selected patients with limited liver metastases of colorectal carcinoma.

MR-guided ablation of head and neck tumors

Interstitial laser-induced thermotherapy (LITT) is a minimally invasive technique for local tumor destruction within solid organs using optical fibers to deliver a high-energy laser to the target lesion. MR imaging is used both for placement of the laser in the tumor and for monitoring progress of thermocoagulation caused by the laser The success of LITT is dependent on the delivery of the optical fibers to the target area, real-time monitoring of the effects of the treatment, and subsequent evaluation of the extent of thermal damage. The key to achieving these objectives is the imaging methods used. The thermosensitivity of certain MR sequences is the key to real-time monitoring, allowing accurate estimation of the extent of thermal damage.

Thermal lesion conspicuity following interstitial radiofrequency thermal tumor ablation in humans: a comparison of STIR, turbo spin-echo T2-weighted, and contrast-enhanced T1-weighted MR images at 0.2 T

The purpose of this study was to compare the contrast between radiofrequency (RF) thermal liver lesions and surrounding tissue in T2-weighted turbo spin-echo sequences (TSE T2), short TI inversion recovery techniques (STIR), and contrast-enhanced (CE) T1-weighted spin-echo images. Nineteen RF thermal ablations were performed on eight patients with metastatic liver tumors. After ablation, contrast-to-noise ratios (CNRs) were calculated between mean signal amplitudes from three regions of interest (ROI) (lesion, surrounding edema, and normal tissue) using TSE T2-weighted, STIR, and contrast-enhanced T1-weighted (CE T1) sequences for each lesion. CNRs between the thermal lesion and normal liver tissue for both TSE T2-weighted (mean 0.9) and STIR (2.0) images were significantly lower than for CE T1-weighted (8.4) images (t-test, alpha = 0.05). However, CNRs between edema rim and the core of the thermal lesion for both TSE T2-weighted (8.1) and STIR images (7.2) were not significantly different (t-test, alpha = 0.05) from CNRs between lesion and normal tissue for CE T1-weighted images (8.4), nor was the CNR between edema rim and normal tissue for both TSE T2-weighted (10.3) and STIR (9.8) images. Although the edema was not visible on CE T1-weighted images, 18 of 19 lesions (94.7%) were surrounded by a hyperintense rim on TSE T2-weighted or STIR images. Both TSE T2-weighted and STIR sequences represent valid techniques for repeatable assessment of RF thermal lesions.