Development and validation of a tissue-equivalent test environment for detection of malfunctions in active medical implants caused by ionizing radiation (original) (raw)
Related papers
2020
Purpose: This study focused on determining risks from stereotactic radiotherapy using flattening filter-free (FFF) beams for patients with cardiac implantable electronic device (CIEDs). Two strategies were employed: a) a retrospective analysis of patients with CIEDs who underwent stereotactic radiosurgery (SRS)/SBRT at the Peter MacCallum Cancer Centre between 2014 and 2018 and b) an experimental study on the impact of FFF beams on CIEDs. Methods: A retrospective review was performed. Subsequently, a phantom study was performed using 30 fully functional explanted CIEDs from two different manufacturers. Irradiation was carried out in a slab phantom with 6-MV and 10-MV FFF beams. First, a repetition-rate test (RRT) with a range of beam pulse frequencies was conducted. Then, multifraction SBRT (48 Gy/4 Fx) and single-fraction SBRT (28 Gy/1 Fx) treatment plans were used for lung tumors delivered to the phantom. Results: Between 2014 and 2018, 13 cases were treated with an FFF beam (6 MV, 1400 MU/min or 10 MV, 2400 MU/min), and 15 cases were treated with a flattening filter (FF) beam (6 MV, 600 MU/min). All the devices were positioned outside the treatment field at a distance of more than 5 cm, except for one case, and no failures were reported due to SBRT/SRS. In the phantom rep-rate tests, inappropriate sensing occurred, starting at a rep-rate of 1200 MU/min. Cardiac implantable electronic device anomalies during and after delivering VMAT-SBRT with a 10-MV FFF beam were observed. Conclusions: The study showed that caution should be paid to managing CIED patients when they undergo SBRT using FFF beams, as it is recommended by AAPM TG-203. Correspondingly, it was found that for FFF beams although there is small risk from dose-rate effects, delivering high dose of radiation with beam energy greater than 6 MV and high-dose rate to CIEDs positioned in close vicinity of the PTV may present issues.
CIEDs (cardiac implantable electronic devices) error due to neutrons from X-ray therapy equipment
2021
Interdisciplinary collaboration is necessary for the advancement of medicine. A lack of collaboration can lead to misconceptions and a lack of theoretical understanding, which can affect the care afforded to patients. With the right collaborations between scientists in fields outside of medicine, misconceptions can be corrected and understanding improved. Assistant Professor Hiroaki Matsubara, Tokyo Women's Medical University, Japan, is a nuclear physicist who is applying his skills and expertise to advance the field of medicine. Nuclear physics is used in several key techniques and tools in medicine such as X-rays and radiotherapy. Matsubara is interested in the issues that can arise in patients with implanted cardiac devices that require radiotherapy. The radiation from radiotherapy can affect the proper functioning of cardiac implantable electronic devices (CIEDs), leading to dangerous malfunctions, even when the tumour being targeted is far from the heart. From gathering dat...
Physics in Medicine and Biology, 2014
The Virtual Family computational whole-body anatomical human models were originally developed for electromagnetic (EM) exposure evaluations, in particular to study how absorption of radiofrequency radiation from external sources depends on anatomy. However, the models immediately garnered much broader interest and are now applied by over 300 research groups, many from medical applications research fields. In a first step, the Virtual Family was expanded to the Virtual Population to provide considerably broader population coverage with the inclusion of models of both sexes ranging in age from 5 to 84 years old. Although these models have proven to be invaluable for EM dosimetry, it became evident that significantly enhanced models are needed for reliable effectiveness and safety evaluations of diagnostic and therapeutic applications, including medical implants safety. This paper describes the research and development performed to obtain anatomical models that meet the requirements necessary for medical implant safety assessment applications. These include implementation of quality control procedures, re-segmentation at higher resolution, more-consistent tissue assignments, enhanced surface processing and numerous anatomical refinements. Several tools were developed
Radiotherapy-induced malfunctions of cardiac implantable electronic devices in cancer patients
Internal and Emergency Medicine, 2019
The number of patients with cardiac implantable electronic devices (CIEDs) requiring radiation therapy (RT) for cancer treatment is increasing. The purpose of this study is to estimate the prevalence, possible predictors, and clinical impact of RT-related CIEDs malfunctions. We retrospectively reviewed the medical records of all pacemaker (PM)/implantable cardioverter-defibrillator (ICD) patients who underwent RT in the last 14 years. One hundred and twenty-seven patients who underwent 150 separate RT courses were analysed (99 with a PM and 27 with an ICD). Of note, 21/127 (16.6%) patients were PM-dependent. Neutron-producing RT was used in 37/139 (26.6%) courses, whereas non-neutron-producing RT was used in 102/139 (73.4%) courses. The cumulative dose (Dmax) delivered to the CIED exceeded 5 Gy only in 2/132 (1.5%) cases. Device malfunctions were observed in 3/150 (2%) RT courses, but none was life-threatening or led to a major clinical event and all were resolved by CIED reprogramming. In all cases, the Dmax delivered to the CIED was < 2 Gy. Two malfunctions occurred in the 37 patients treated with neutron-producing RT (5.4%), and 1 malfunction occurred in the 102 patients treated with non-neutron-producing RT (1%) (p = 0.17). Device relocation from the RT field was performed in 2/127 (1.6%) patients. RT in patients with CIED is substantially safe if performed in an appropriately organized environment, with uncommon CIEDs malfunctions and no major clinical events. Neutron-producing energies, rather than Dmax, seem to increase the risk of malfunctions. Device interrogation on a regular basis is advised to promptly manage CIED malfunctions.
Cardiovascular Implantable Electronic Devices Dose Estimates for Radiotherapy Patient Management
Management for radiation therapy patients with Cardiovascular Implantable Electronic Devices (CIEDs) is incomplete. Manufacturers of CIEDs provide varying dose thresholds and precautions, which leads to ambiguity in planning patients’ treatments. In cases where radiotherapy patients have a CIED, an American Association of Physicists in Medicine (AAPM) task group (TG 34⁵) developed a guideline for medical physicists to follow. However, specific calculations for the CIED dose need to be performed prior to application of the guide. Radiation oncology clinics would benefit from knowing typical CIED doses received from different treatments in order to expedite risk analyses. By utilizing previous patients’ treatment plans – varying in target location and radiation delivery mode – average dose received by a CIED was measured and compared to the average recommended threshold of 2 Gy. This was done for eleven different treatment plans. Most cases showed a cumulative dose well below the recommended 2 Gy, ranging from 3-53 cGy. However, two cases showed values that would raise concern – a 3D spine with a cumulative dose of 159 cGy and a volume modulated arc therapy (VMAT) head/neck of 329 cGy. With such large doses, this indicated a higher risk of CIED malfunction leading to potential patient complications.
Radiation dose verification using real tissue phantom in modern radiotherapy techniques
Journal of Medical Physics, 2014
In vitro dosimetric verification prior to patient treatment has a key role in accurate and precision radiotherapy treatment delivery. Most of commercially available dosimetric phantoms have almost homogeneous density throughout their volume, while real interior of patient body has variable and varying densities inside. In this study an attempt has been made to verify the physical dosimetry in actual human body scenario by using goat head as "head phantom" and goat meat as "tissue phantom". The mean percentage variation between planned and measured doses was found to be 2.48 (standard deviation (SD): 0.74), 2.36 (SD: 0.77), 3.62 (SD: 1.05), and 3.31 (SD: 0.78) for three-dimensional conformal radiotherapy (3DCRT) (head phantom), intensity modulated radiotherapy (IMRT; head phantom), 3DCRT (tissue phantom), and IMRT (tissue phantom), respectively. Although percentage variations in case of head phantom were within tolerance limit (< ± 3%), but still it is higher than the results obtained by using commercially available phantoms. And the percentage variations in most of cases of tissue phantom were out of tolerance limit. On the basis of these preliminary results it is logical and rational to develop radiation dosimetry methods based on real human body and also to develop an artificial phantom which should truly represent the interior of human body.
Radiation‐Induced Effects in Multiprogrammable Pacemakers and Implantable Defibrillators
Pacing and Clinical Electrophysiology, 1991
Twenty‐three multiprogrammable pacemakers and four implantable cardioverter defibrillators (ICDs) containing either complementary metal‐oxide semiconductor (CMOS) or CMOS/Bipolar integrated circuit (IC) technology were exposed to 6‐MV photon and 18‐MeV electron radiation at various dose levels. Of the 17 pacemakers exposed to photon radiation eight failed before 50 Gy, whereas four of the six pacemakers exposed to electron radiation failed before 70 Gy. Photon scatter doses were well tolerated. For the ICDs detection and charging time increased with accumulated radiation dose, the charging time increased catastrophically at < 50 total pulses delivered when compared with the charging time of six implanted ICDs. Sensitivity and output energy delivered by the ICD pulse were constant during the test. It was found that devices using the shorter channel length IC technology (i.e., 3 p‐m CMOS) were per se harder to ionizing radiation than the devices using larger channel length IC techn...
—Monte Carlo codes are among the most used tools for calculations and simulations relating to medical physics and particularly for studies of low dose medical applications. The results, presented in this paper, were focused on the optimization of a medical phantom for mapping the absorbed doses produced by ionizing radiation. The cobalt 60 irradiator of the CNSTN (the National Centre for Nuclear Science and Technology) served as the experimental validation platform for the present study. Monte-Carlo modeling of the irradiator was carried out with Geant4 tool. Part of dose deposition results, obtained with this model, has been validated using as reference previous experimental data, performed on the same irradiator. The same Geant4 model was then adapted to our study case, with the development of a more specific configuration, suitable for the diagnosis of the effects induced by gamma radiation beams at different energies. The distribution study of doses produced by these photons, inside a water filled phantom, was thus realized. The numerical results obtained, with the Geant4 model, show variable behaviours according to the studied energies. An analytical model is then proposed, for the prediction of these dose distributions.
Canadian Journal of Cardiology, 2015
in 124 (70%) patients, 32 (25%) of whom failed their first shock at 24AE5 J. The only factor independently associated with test failure was a lower LVEF [OR 0.95, 95% CI (0.92-0.99)]. At 43AE32 months of follow-up, 6 patients had appropriate ICD shocks, 2 of whom had failed DTs at implant. Only 1 shock failure was observed during follow-up, occurring in a patient who failed DT at implant (he subsequently survived). DT was not predictive of shock efficacy. Overall survival rates were similar in patients with or without DT (p¼0.57) and whether or not the first DT shock was successful (p¼0.77). CONCLUSION: The first attempt at DT fails in a high proportion (25%) of right-sided implants. Nevertheless, DT failure and lack of DT were not associated with future shock efficacy or overall survival. These results challenge the pertinence of routine DT in patients with right-sided ICDs and underscore the need for a randomized prospective controlled trial.