Feasibility study of using two dimensional array ion-chamber to verifiy relative dose distribution calculated with Acuros BV / 中华放射医学与防护杂志

Objective To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm.Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices.Methods Based on self-built measurement phantoms,the dose distribution on the same slice of the phantom was measured with PTW729 and film,respectively,under the same measurement condition and plan.The dose distributions obtained by the two method were compared with the result calculated with Acuros BV,separately,by using γ analytical tool.And the stability of the PTW729 was tested.Results The γ comparison value was 95.9％ between the film and Acuros BV,98.9％ between the PTW729 and Acuros BV and 88.0％ between the film and PTW729,with 95.0％,i00.0％,and 100.0％,in their stability test respectively.Conclusions PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.

Feasibility study of using two dimensional array ion-chamber to verifiy relative dose distribution calculated with Acuros BV / 中华放射医学与防护杂志

Objective@#To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm. Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices.@*Methods@#Based on self-built measurement phantoms, the dose distribution on the same slice of the phantom was measured with PTW729 and film, respectively, under the same measurement condition and plan. The dose distributions obtained by the two method were compared with the result calculated with Acuros BV, separately, by using γ analytical tool. And the stability of the PTW729 was tested.@*Results@#The γ comparison value was 95.9% between the film and Acuros BV, 98.9% between the PTW729 and Acuros BV and 88.0% between the film and PTW729, with 95.0%, 100.0%, and 100.0%, in their stability test respectively.@*Conclusions@#PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.

Ultrasonic transducers for medical diagnostic imaging

Over the past decades, ultrasound imaging technology has made tremendous progress in obtaining important diagnostic information from patients in a rapid, noninvasive manner. Although the technology has benefited from sophisticated signal processing technology and imaging system integration, much of this progress has been derived from the development of ultrasonic transducers that are in direct contact with patients. An overview of medical ultrasonic imaging transducers is presented in this review that describes their structure, types, and application fields. The structural components of a typical transducer are presented in detail including an active layer, acoustic matching layers, a backing block, an acoustic lens, and kerfs. The types of transducers are classified according to the dimensions of ultrasound images: one-dimensional array, mechanical wobbling, and two-dimensional array transducers. Advantages of each transducer over the other and the technical issues for further performance enhancement are described. Application of the transducers to various clinical imaging fields is also reviewed.

A Pilot Research for Real-Time Specific Patient Quality Assurance Using the Hybrid Optimized Vmat Phantom (Hovp) in Volume Modulated Arc Therapy / 의학물리

The purpose of this was to investigate the measurement of fluence dose map for the specific patient quality assurance. The measurement of fluence map was performed using 2D matrixx detector. The absorbed dose was measured by a glass detector, Gafchromic film and ion chamber in Hybrid Optimized VMAT Phantom (HOVP). For 2D Matrixx, the results of comparison were average passing rate 85.22%+/-1.7 (RT_Target), 89.96%+/-2.15 (LT_Target) and 95.14%+/-1.18 (G4). The dose difference was 11.72%+/-0.531, -11.47%+/-0.991, 7.81%+/-0.857, -4.14%+/-0.761 at the G1, G2, G3, G4. In HOVP, the results of comparison for film were average passing rate (3%, 3 mm) 93.64%+/-3.87, 90.82%+/-0.99. We were measured an absolute dose in steep gradient area G1, G2, G3, G4 using the glass detector. The difference between the measurement and calculation are 8.3% (G1), -5.4% (G2), 6.1% (G3), 7.2% (G4). The using an Ion-chamber were an average relative dose error -1.02%+/-0.222 (Rt_target), 0.96%+/-0.294 (Lt_target). Though we need a more study using a transmission detector. However, a measurement of real-time fluence map will be predicting a dose for real-time specific patient quality assurance in volume modulated arc therapy.