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Latency Characterization of Gated Radiotherapy Treatment Beams Using a PIN Diode Circuit

Lempart, M. LU ; Kügele, M. LU ; Ambolt, L.; Blad, B. LU and Nordström, Fredrik LU (2016) In IRBM 37(3). p.144-151
Abstract
Background: Radiotherapy is based on the premise of accurate dose delivery to target volumes within a patient, while minimizing dose to surrounding tissues. Recent developments in the treatment of breast cancer have focused on “gating” the delivery of the treatment beams to minimize the effect of patient motion during treatment, and increasing separation between the target volume and organs at risk (OAR), such as lung, heart and left anterior descending coronary artery. The basic principle involves rapidly switching the treatment beam on or off depending on the patient breathing cycle. It is therefore important to know the characteristics of gated treatments such as latency. Methods: In this work an electrical PIN diode circuit (EPDC) was... (More)
Background: Radiotherapy is based on the premise of accurate dose delivery to target volumes within a patient, while minimizing dose to surrounding tissues. Recent developments in the treatment of breast cancer have focused on “gating” the delivery of the treatment beams to minimize the effect of patient motion during treatment, and increasing separation between the target volume and organs at risk (OAR), such as lung, heart and left anterior descending coronary artery. The basic principle involves rapidly switching the treatment beam on or off depending on the patient breathing cycle. It is therefore important to know the characteristics of gated treatments such as latency. Methods: In this work an electrical PIN diode circuit (EPDC) was designed for quality assurance (QA) purposes to examine beam latency timing properties. Evaluation of the EPDC was performed on a TrueBeam™ (Varian, Palo Alto) linear accelerator and its internal gating system. The EPDC was coupled to a moving stage to simulate a binary pattern with fast beam triggering within predefined limits, the so called “gating window”. Pulses of radiation were measured with the PIN diode and the results were compared to measurements of current produced across the linac target. Processing of the beam pulses and calculation of the latency timings was performed by an Atmega328P microcontroller. Results: For beam-on latencies, 2.11 ms (6 MV) and 2.12 ms (10 MV) were measured using the PIN diode, compared to 2.13 ms (6 MV) and 2.15 ms (10 MV) using the target current signal. For beam-off latencies, 57.69 ms (6 MV) and 57.73 ms (10 MV) were measured using the PIN diode, compared to 57.33 ms (6 MV) and 56.01 ms (10 MV) using the target current. Conclusions: PIN diodes can be used for accurate determination of the beam-on and beam-off latency characteristics, which could potentially lead to improvements in gated radiotherapy treatments, for example optimizing the gating windows and in estimating dosimetric errors associated with treatment beam latencies. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Clinical engineering, Linear accelerator, Radiation detectors, Radiotherapy, Respiratory gating, article, biomedical engineering, camera, integrated circuit, latent period, linear accelerator, pin diode circuit, radiation dose, respiratory gated radiotherapy
in
IRBM
volume
37
issue
3
pages
8 pages
publisher
Elsevier Masson SAS
external identifiers
  • Scopus:84964325829
  • Scopus:84964325829
ISSN
1959-0318
DOI
10.1016/j.irbm.2016.02.002
language
English
LU publication?
yes
id
69369bf1-3a85-4868-a52e-4cc598c53c83
date added to LUP
2016-07-25 14:06:36
date last changed
2016-10-20 10:59:23
@misc{69369bf1-3a85-4868-a52e-4cc598c53c83,
  abstract     = {Background: Radiotherapy is based on the premise of accurate dose delivery to target volumes within a patient, while minimizing dose to surrounding tissues. Recent developments in the treatment of breast cancer have focused on “gating” the delivery of the treatment beams to minimize the effect of patient motion during treatment, and increasing separation between the target volume and organs at risk (OAR), such as lung, heart and left anterior descending coronary artery. The basic principle involves rapidly switching the treatment beam on or off depending on the patient breathing cycle. It is therefore important to know the characteristics of gated treatments such as latency. Methods: In this work an electrical PIN diode circuit (EPDC) was designed for quality assurance (QA) purposes to examine beam latency timing properties. Evaluation of the EPDC was performed on a TrueBeam™ (Varian, Palo Alto) linear accelerator and its internal gating system. The EPDC was coupled to a moving stage to simulate a binary pattern with fast beam triggering within predefined limits, the so called “gating window”. Pulses of radiation were measured with the PIN diode and the results were compared to measurements of current produced across the linac target. Processing of the beam pulses and calculation of the latency timings was performed by an Atmega328P microcontroller. Results: For beam-on latencies, 2.11 ms (6 MV) and 2.12 ms (10 MV) were measured using the PIN diode, compared to 2.13 ms (6 MV) and 2.15 ms (10 MV) using the target current signal. For beam-off latencies, 57.69 ms (6 MV) and 57.73 ms (10 MV) were measured using the PIN diode, compared to 57.33 ms (6 MV) and 56.01 ms (10 MV) using the target current. Conclusions: PIN diodes can be used for accurate determination of the beam-on and beam-off latency characteristics, which could potentially lead to improvements in gated radiotherapy treatments, for example optimizing the gating windows and in estimating dosimetric errors associated with treatment beam latencies.},
  author       = {Lempart, M. and Kügele, M. and Ambolt, L. and Blad, B. and Nordström, Fredrik},
  issn         = {1959-0318},
  keyword      = {Clinical engineering,Linear accelerator,Radiation detectors,Radiotherapy,Respiratory gating,article,biomedical engineering,camera,integrated circuit,latent period,linear accelerator,pin diode circuit,radiation dose,respiratory gated radiotherapy},
  language     = {eng},
  month        = {06},
  number       = {3},
  pages        = {144--151},
  publisher    = {ARRAY(0x97da0c0)},
  series       = {IRBM},
  title        = {Latency Characterization of Gated Radiotherapy Treatment Beams Using a PIN Diode Circuit},
  url          = {http://dx.doi.org/10.1016/j.irbm.2016.02.002},
  volume       = {37},
  year         = {2016},
}