Abstract
Interstitial laser phototherapy (ILP) is a technique whereby laser energy is directly applied into tumors at variable depths. This technique is attractive, since it is minimally invasive and carries a low morbidity. It may allow treatment of deep and difficult to reach tumors in the head and neck and other areas when improved noninvasive monitoring techniques of laser–tissue interactions are developed. Recent studies demonstrate, respectively, the efficiency of ultrasound (UTZ) and magnetic resonance imaging (MRI) for real time interstitial needle placement in tumors, identification of vessels, monitoring and quantifying laser-induced tissue damages. We present a case in which a patient with recurrent, metastatic base of skull carcinoma has been managed successfully with repeat ILP using MRI and UTZ guidance. Under heavy sedation, needles were placed in the tumor using MRI or UTZ guidance. Tumors were treated with a 600 μm flexible Nd:YAG laser fiberoptic passed through the needles. Laser-induced tissue photoablation was monitored using real time color flow Doppler UTZ or near real time fast spin-echo T2-weighted MRI. Posttreatment fine needle aspiration cytologic study demonstrated the presence of cellular debris and no viable cancer cells. Posttreatment follow-up MRI scans showed significant reduction of tumor size, and positron emission tomography (PET) revealed interval decrease in tumor metabolism. Treatments were accompanied by pain relief and improved functional abilities. ILP has now evolved into a minimally invasive outpatient surgical procedure. Appropriate development of MRI pulse sequences providing real time images and MR-compatible laser delivery systems will allow us to optimize the three-dimensional control and monitoring of laser–tissue interaction and render this technique clinically practical.
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