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  1. Entrance dose measurement: a simple and reliable technique
    Banjade DP, Raj TA, Ng BS, Xavier S, Tajuddin AA, Shukri A
    Med Dosim, 2003;28(2):73-8.
    PMID: 12804703
    Verification of tumor dose for patients undergoing external beam radiotherapy is an important part of quality assurance programs in radiation oncology. Among the various methods available, entrance dose in vivo is one reliable method used to verify the tumor dose delivered to a patient. In this work, entrance dose measurements using LiF:Mg;Ti and LiF:Mg;Cu;P thermoluminescent dosimeters (TLDs) without buildup cap was carried out. The TLDs were calibrated at the surface of a water equivalent phantom against the maximum dose, using 6- and 10-MV photon and 9-MeV electron beams. The calibration geometry was such that the TLDs were placed on the surface of the "solid-water" phantom and a calibrated ionization chamber was positioned inside the phantom at calibration depth. The calibrated TLDs were then utilized to measure the entrance dose during the treatment of actual patients. Measurements were also carried out in the same phantom simultaneously to check the stability of the system. The dose measured in the phantom using the TLDs calibrated for entrance dose to 6-and 10-MV photon beams was found to be close to the dose determined by the treatment planning system (TPS) with discrepancies of not more than 4.1% (mean 1.3%). Consequently, the measured entrance dose during dose delivery to the actual patients with a prescribed geometry was found to be compatible with a maximum discrepancy of 5.7% (mean 2.2%) when comparison was made with the dose determined by the TPS. Likewise, the measured entrance dose for electron beams in the phantom and in actual patients using the calibrated TLDs were also found to be close, with maximum discrepancies of 3.2% (mean 2.0%) and 4.8% (mean 2.3%), respectively. Careful implementation of this technique provides vital information with an ability to confidently accept treatment algorithms derived by the TPS or to re-evaluate the parameters when necessary.
    Matched MeSH terms: Thoracic Neoplasms/radiotherapy*
  2. Fulltext Feasibility, safety and outcomes of stereotactic radiotherapy for ultra-central thoracic oligometastatic disease guided by linear endobronchial ultrasound-inserted fiducials
    Sidhu C, Tang C, Scott A, Yamini Ramamurty H, Yagnik L, Morey S, et al.
    Radiother Oncol, 2024 Dec;201:110547.
    PMID: 39332638 DOI: 10.1016/j.radonc.2024.110547
    BACKGROUND & PURPOSE: Local treatment of oligometastases has been found to improve survival and prognosis. Stereotactic body radiotherapy (SBRT) has emerged as a treatment option for oligometastases but its use in ultra-central (UC) areas can cause significant toxicity and mortality. Fiducial markers (FM) can be used to improve SBRT accuracy, and can be inserted in the central thorax using linear endobronchial ultrasound (EBUS) bronchoscopy. Outcomes of FM-guided SBRT for UC thoracic oligometastases is unknown.

    METHODS: A single-centre retrospective study investigating the feasibility, safety and outcomes of both linear EBUS-inserted FMs and subsequent FM-guided SBRT for UC-oligometastatic disease. Motion analyses of FMs were also performed.

    RESULTS: Thirty outpatients underwent 32 EBUS-FM insertion procedures with 100 % success, and no major procedural mortality or morbidity. Minor complications were 4.8 % incidence of delayed FM-displacement. UC FM-guided SBRT was completed in 20 patients with 99.9 % fractions delivered. Median SBRT dose delivered was 40 Gy over a median of 8 fractions. Majority of adverse events were Grade 1 and there was no SBRT-related mortality. Local control with SBRT was 95 %, with overall survival at 1-year and 3-years of 90 % and 56.3 % respectively. Median overall survival after SBRT was 43.6 months. FM movements in UC areas were recorded being greatest in the superior-inferior axis.

    CONCLUSION: Combined linear EBUS sampling and FM-insertion in UC thoracic oligometastatic disease is feasible and safe. UC-SBRT to oligometastases using FM guidance was found to have minimal complications and associated with moderate survival up to 3 years post-treatment.

    Matched MeSH terms: Thoracic Neoplasms/radiotherapy
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