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A new fiber-optic system with an active unbalanced Michelson interferometer (AUMI) was designed for multi-zone perimeter intrusion detection by employing only two single-mode fibers for each sensing zone. A pump laser at the monitor site was used to remotely pump the erbiumdoped fibers located, respectively, at the two arms of the AUMI for each sensing zone. Configured into a fiber laser cavity, the AUMI served as an optical switch that would modulate the optical power when one arm of the AUMI was perturbed by intrusion to induce a phase offset variation. In the study, an armored cable with a length of 200 meters in total was divided into four sections each guarding a perimeter zone. The experimental results showed that the AUMI system correctly responded to perturbations induced by footstepping on a fiber cable buried underground, vibrating a netted fence, or knocking a window. A high alarm-upon-intrusion rate and zero false alarm rate could be reached by using the presented detection algorithm. Index Terms-Pump laser, Michelson interferometer, multi-zone perimeter intrusion detection, fiber laser cavity. I. INTRODUCTION F IBER-OPTIC perimeter intrusion detection (PID) systems offer some advantages over counterparts using wired or wireless hardwares [1]-[3]. They can find applications in detecting and locating unauthorized excavation of buried pipelines and trespassing intruders in order to protect premises for personal, commercial, and utility purposes. Many types of fiber-optic PID systems have been recently studied for not only detecting intrusion but providing locating ability for multiple events [4]-[6]. Some of these systems are Manuscript

Purposes: To verify the output factors (OFs) of Gamma Knife Model B2 by various conventional dosimeters and to determine an effective correction factor for compensating the dosimeter sizes. Method and Materials: The TLDs, radiochromic films, PTW 31002 ion chamber and the diamond detector were used to obtain the OFs, normalized to the 18 mm helmet, for four helmets. The factors were measured in the centre of an 80 mm polystyrene spherical phantom that was positioned at the mechanical center of the machine. The dosimeters were placed in the center of the sphere using different cassettes and oriented their effective center in the center of helmet coordinate system. Based on the volumetric averaging theory we used the specificity of dose profile of the 4 mm helmet to correct the measurement by the integrated Gaussian curve method. Results: The relative OFs measured with TLDs/ion chamber, before applying correction factors, were 0.977/0.967, 0.905/0.845 and 0.755/0.313 for the 14, 8 and 4 mm helmets, respectively. After applying correction factors, the results show a reasonable agreement with the data used in the current RTP system for Gamma Knife procedure. The results also showed great spatial accuracy. The symmetry of spatial distribution was 1.84%, 0.59%, 1.25%, and 1.16% for the 4, 8, 14 and 18 mm helmets, respectively. And the distance between mechanical center and dosimetric center was less than 0.25mm for all four helmets. Conclusion: The accuracy of the measurements was affected by a number of factors, especially the dosimeter size. This work provides the potential for using conventional dosimeters, with appropriate correction factor, to determine and to evaluate the clinical dosimetric parameters for Gamma Knife Unit for routine QA procedure. With the verification of spatial accuracy, Gamma Knife unit could be used to treat functional disorder case accurately.

Purpose: Patients who have had prior radiation therapy often present with recurrent/residual disease in the previously irradiated area. However, additional radiation is often not feasible because the maximum tolerated dose for normal critical organs have already been reached. We present a case of a patient with metastatic endometrial cancer who was retreated to the ninth rib/vertebral body with Tomotherapy although the spine had already received 4500 cGy. Method and Materials: A patient with metastatic disease to the ninth right rib and vertebral body was treated with 4400 cGy in 2003. The patient was recently found to have recurrent/progressive disease in the area of prior treatment. A PET scan was taken prior to treatment and an PET/CT fusion was performed in order to aid in the contouring of the tumor volume. The tumor volume(rib) wrapped around the liver and ended at the ninth vertebral body right next to the spinal cord. A Tomotherapy plan was generated to maximally cover the tumor volume while minimizing the dose to the spinal cord and liver. The positioning of the patient was verified daily with an MVCT. Results: Treatment plans generated using the Tomotherapy treatment planning system and the ability of the Tomotherapy machine to verify patient set‐up daily show that the Tomotherapy unit was able to deliver 6000 cGy to the tumor volume while only delivering a maximum dose of 575 cGy to the spine with an average of only 179 cGy. Dose the liver was kept to a minimum with an average of 1804 cGy. Conclusions: Examination of the dose volume histograms determined that the Tomotherapy unit shows was able to keep at a minimum the doses to the spinal cord and liver and surrounding structures thus making Tomotherapy a useful tool in treating patients with prior radiation.