Magnetic resonance imaging-guided laser thermal ablation of renal tumours.

OBJECTIVE: To test the hypothesis that magnetic resonance imaging (MRI)-guided laser thermal ablation (LTA) of inoperable renal tumours is a safe, tolerable and potentially effective treatment. PATIENTS AND METHODS: Nine patients (aged 56-81 years) with malignant renal tumours underwent percutaneous LTA under MRI guidance in a 0.5 T open magnet. Real-time colour thermal mapping was used to monitor tumour ablation, and the follow-up was with gadolinium-enhanced MRI at 6 weeks and (where appropriate) 3-4 months after the procedure. Tumour volume and percentage tumour enhancement before and after ablation were compared. The percentage of tumour ablated on real-time T1-weighted thermal maps was compared with that on gadolinium-enhanced follow-up MRI. RESULTS: The mean (range) follow-up was 16.9 (3-32) months after the first ablation. The mean tumour size did not change significantly, but the mean percentage of viable tumour decreased significantly from 73.7% before to 29.5% after ablation (P = 0.012, Wilcoxon signed-ranks test). Thermal maps correlated moderately well with follow-up MRI in predicting the extent of tumour ablation (Pearson correlation coefficient 0.55). There were two minor and one major complication. CONCLUSION: In this pilot study of patients unsuitable for surgery, MRI-guided LTA of renal tumours was safe, feasible (being well tolerated by the patient) and significantly reduced enhancing tumour volume by a mean of 45%.

Upright dynamic MR defaecating proctography in an open configuration MR system.

We describe our experience evaluating an MR proctography technique using an open 0.5 T MR system. Evacuation of a gadolinium-containing rectal contrast agent was dynamically imaged in the upright position using a fast gradient echo sequence. Anatomical and functional abnormalities were documented. Results from 40 patients who underwent this technique are reported. The method is proposed as an alternative to conventional fluoroscopic proctography.

MR-guided laser thermoablation of inoperable renal tumors in an open-configuration interventional MR scanner: preliminary clinical experience in three cases.

A minimally invasive technique for performing magnetic resonance (MR)-guided laser interstitial thermoablation (LITT) for inoperable renal tumors is described. Three patients were treated using a percutaneous technique with real-time MR guidance in an open access interventional MR scanner. Laser therapy was delivered using a neodymium-YAG source via a water-cooled applicator system. Thermal lesions were monitored in real time using a color thermometry sequence. All patients were discharged the following day with no complications. Follow-up with gadolinium-enhanced MRI in a conventional high-field system confirmed necrosis in targeted tissue, and further treatment is planned for one patient. We concluded that LITT can be useful in treating inoperable renal malignancy and merits further evaluation. J. Magn. Reson. Imaging 1999;10:545-549.

MRI guidance of infra-red laser liver tumour ablations, utilising an open MRI configuration system: technique and early progress.

BACKGROUND/AIMS: Primary and secondary liver tumours are a common clinical problem, with a poor prognosis in most cases. Surgical resection offers the best outcome, but is only appropriate for the minority. Thermal ablation techniques have been described, but the lack of an optimal means of monitoring has limited their use. We undertook a pilot study to assess the feasibility and safety of an integrated MR-guided laser thermoablation technique under local anaesthesia using a real-time colourisation thermal monitoring technique in a newly developed open MR scanner. METHODS: Liver tumours were punctured after the administration of intravenous Mangafodipir trisodium (MnDPDP) using real-time MR image guidance under local or general anaesthesia, and treated using a water-cooled interstitial fibre and a Nd-YAG laser source. Twenty-seven procedures were performed in 12 patients. Therapy was monitored using a real-time MR colourisation sequence. Thermoablation was followed by a colour change in a region of interest. RESULTS: Thermal lesions of mean size 3 cm in diameter were produced with a maximum size of 5 cm. Eight out of 12 patients were discharged the next day with few significant complications. Repeat procedures have been performed in seven of 12 patients. Two patients with lesions of 3 cm diameter have had complete tumour ablation with only one procedure. CONCLUSION: Percutaneous laser thermoablation for liver tumours performed as an integrated one-step technique in an open configuration MR scanner is described. It can be safely performed under local anaesthesia in the majority of patients, with few side effects. MR control shows the site and size of the evolving thermal lesions, allowing appropriate action to be taken in terms of further burns, time of application and power applied.