In-Vivo Real-Time Magnetic Resonance Monitoring of Endoscopic Laser Applications in the Porcine Gastrointestinal Tract

Background and Study Aims: Endoscopic laser therapy involves a risk of perforation, mainly because the depth of tissue destruction is not visible. Magnetic resonance (MR) imaging is capable of showing temperature changes, and is therefore suitable for monitoring thermal therapies such as laser. This animal study assessed the feasibility of real-time MR monitoring of endoscopic laser applications in the gastrointestinal tract.

Materials and Methods: The procedures were carried out using an MR-compatible endoscope in three live pigs in a 0.5-Tesla interventional MR system. Nd:YAG laser applications were performed in the lower gastrointestinal tract (n = 7) and upper gastrointestinal tract (n = 5), and were monitored using real-time color-coded T1-weighted gradient echo sequences. The postmortem macroscopic tissue coagulation sizes were compared with the lesion diameters seen on real-time MR.

Results: The endoscope did not cause any artifacts during continuous MR imaging. Ten of the twelve laser lesions were visible with temperature-sensitive MR imaging, and their sizes correlated well with the diameters of the postmortem macroscopic coagulation zones (r = 0.76, P = 0.009). Two laser lesions were not visible on MR due to technical limitations inherent with the healthy animal model.

Conclusions: The formation of endoscopic laser lesions in the porcine gastrointestinal tract can be accurately visualized using real-time temperature-sensitive MR imaging. This new technique has the potential to spare healthy tissue while ensuring full treatment coverage of the targeted lesion with fewer therapy sessions.

References

• 1 Spinelli P, Fante M D al, Mancini A. Endoscopic palliation of malignancies of the upper gastrointestinal tract using Nd:YAG laser: results and survival in 308 treated patients.  Lasers Surg Med. 1991;  11 550-555
• 2 Mathus-Vliegen E M, Tytgat G N. Analysis of failures and complications of neodymium:YAG laser photocoagulation in gastrointestinal tract tumors: a retrospective survey of 18 years experience.  Endoscopy. 1990;  22 17-23
• 3 Schulze S, Fischerman K. Palliation of oesophagogastric neoplasms with Nd:YAG laser treatment.  Scand J Gastroenterol. 1990;  25 1024-1027
• 4 Vogl T J, Mack M G, Straub R, et al. Magnetic resonance imaging-guided abdominal interventional radiology: laser-induced thermotherapy of liver metastases.  Endoscopy. 1997;  29 577-583
• 5 Cline H E, Hynynen K, Watkins R D, et al. Focused US system for MR imaging-guided tumor ablation.  Radiology. 1995;  194 731-777
• 6 Klotz H P, Flury R, Schonenberger A, et al. Experimental cryosurgery of the liver under magnetic resonance guidance.  Comput Aided Surg. 1997;  2 340-345
• 7 Steiner P, Botnar R, Dubno B, et al. Radiofrequency-induced thermoablation: monitoring with T1-weighted and proton-frequency-shift MR imaging in an interventional 0.5-T environment.  Radiology. 1998;  206 803-810
• 8 Matsumoto R, Oshio K, Jolesz F A. Monitoring of laser and freezing-induced ablation in the liver with T1-weighted imaging.  J Magn Reson Imaging. 1993;  3 770-776
• 9 Lufkin R B. Interventional MRI.  St. Louis, MO; Mosby, 1999
• 10 Steiner P, Zweifel K, Botnar R, et al. MR guidance of laser disc decompression: preliminary in vivo experience.  Eur Radiol. 1998;  8 592-597
• 11 Klotz H P, Flury R, Erhart P, et al. Magnetic resonance-guided laparoscopic interstitial laser therapy of the liver.  Am J Surg. 1997;  174 448-451
• 12 Kulling D, Feldman D R, Kay C L, et al. Local staging of esophageal cancer using endoscopic magnetic resonance imaging: prospective comparison with endoscopic ultrasound.  Endoscopy. 1998;  3 745-749
• 13 Kulling D, Feldman D R, Kay C L, et al. Local staging of anal and distal colorectal tumors with the magnetic resonance endoscope.  Gastrointest Endosc. 1998;  47 172-178
• 14 Inui K, Nakazawa S, Yoshino J, Ukai H. Endoscopic MRI.  Pankreas. 1998;  16 413-417
• 15 Anzai Y, Lufkin R, DeSalles A, et al. Preliminary experience with MR-guided thermal ablation of brain tumors.  Am J Neuroradiol. 1995;  16 39-48
• 16 Steiner P, Botnar R, Goldberg N, et al. Monitoring of radiofrequency tissue ablation in an interventional magnetic resonance environment: preliminary ex vivo and in vivo results.  Invest Radiol. 1997;  32 671-678
• 17 Schoenenberger A W, Steiner P, Debatin J F, et al. Real-time monitoring of laser diskectomies with a superconducting, open-configuration MR system.  AJR Am J Roentgenol. 1997;  169 863-867