Failure modes and downtime of radiotherapy LINACs and multileaf collimators in Indonesia

S., Peiris, Gregory; Pawiro, Supriyanto Ardjo; Kasim, Muhammad; Sheehy, Suzanne

doi:10.1002/acm2.13756

Cited by 6 publications

(9 citation statements)

References 34 publications

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“…This allows to prevent new unplanned downtime and to save on travel time of the maintenance service staff. All these measures can be very useful especially in areas where the lack of access to maintenance services entails prolonged downtime 25 …”

Section: Discussionmentioning

confidence: 99%

MLC performance prognosis using a degradation model based on trajectory log data from a daily test

et al. 2022

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Purpose This paper investigates the feasibility of implementing a predictive maintenance program for a multileaf collimator (MLC) based on data collected in trajectory logs (TLs) obtained by conducting a simple daily test, with the aim of minimizing unscheduled downtime. Methods A dynamic field test was designed, and the TLs generated in the course of daily administration in a linear accelerator were collected to evaluate trajectory deviations of the MLC leaves as well as interlocks (COL 420219/20, COL 420207/08) reported by the machine. During this evaluation, we observed that the trajectory deviations of some leaves increased up to a threshold value beyond which certain interlocks began to appear in treatment fields in those leaves. An exponential degradation model was therefore developed to predict this drift and determine each leaf's remaining useful life (RUL). Once the applicability of the model was confirmed, we added a second accelerator equipped with an MLC with the same configuration to validate the model. Results The model was able to predict certain COL 420219/20 interlocks resulting from primary readout/expected position discrepancies and to estimate each leaf's RUL. In total, 11 cases (8 interlocks + 3 potential interlocks avoided due to service interventions [27.3% of the total]) were detected over 7 days in advance, with no false positive results. Scheduling of service interventions several days prior to MLC failure would therefore be possible. When these types of interlocks were not predicted by the model, they were always generated by leaf motor failure. Consequently, intervention time could also be optimized by directly replacing the motor. During the study period, for these types of interlocks, our approach would have reduced downtime from 35.25 to 4.00 h (88.7%) and from 34.75 to 22.83 h (34.3%) for each accelerator, respectively. For COL 420207/08 interlocks, which are generated by primary/secondary readout discrepancies, no correlation with leaf trajectory deviation increases recorded in the TLs was found. Throughout the study period, these types of interlocks requiring service intervention, also mainly for motor replacement, represented a downtime of 9.50 h for the first accelerator (21.2% of total downtime) and by 4.33 h (11.1% of total downtime) for the second accelerator. Conclusion This study demonstrates that by applying a predictive MLC maintenance program based on information collected in TLs, it is possible to predict certain interlocks and therefore schedule preemptive interventions to avoid their occurrence. This could optimize health‐care delivery performance and minimize the loss of treatment sessions.

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Section: Discussionmentioning

confidence: 99%

MLC performance prognosis using a degradation model based on trajectory log data from a daily test

et al. 2022

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“…The sheer number of moving parts and complexity of an MLC means that it is one of the most common failure points on a modern linac 8 . Recent analyses of linac failure modes in developing nations show that the MLC is the component responsible for the most faults causing more than one hour machine down time 9,10 . SPHINX utilizes no moving parts at all; as such, it is expected to show dramatically improved robustness compared to MLC‐based approaches.…”

Section: Introductionmentioning

confidence: 99%

“…SPHINX utilizes no moving parts at all; as such, it is expected to show dramatically improved robustness compared to MLC‐based approaches. Increased robustness is of particular importance in developing nations, where a single MLC leaf failure may take several days to rectify 10 …”

Section: Introductionmentioning

confidence: 99%

“…8 Recent analyses of linac failure modes in developing nations show that the MLC is the component responsible for the most faults causing more than one hour machine down time. 9,10 SPHINX utilizes no moving parts at all; as such, it is expected to show dramatically improved robustness compared to MLC-based approaches. Increased robustness is of particular importance in developing nations, where a single MLC leaf failure may take several days to rectify.…”

Section: Introductionmentioning

confidence: 99%

“…Increased robustness is of particular importance in developing nations, where a single MLC leaf failure may take several days to rectify. 10 To assess the viability of a SPHINX-based approach to radiotherapy delivery requires the existence of highquality SPHINX designs; however, the geometric complexity of the structure means this is not a trivial task. The goal of this work is to develop and test a method for optimizing SPHINX designs.…”

Section: Introductionmentioning

confidence: 99%

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Bayesian optimization to design a novel x‐ray shaping device

et al. 2022

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Purpose In radiation therapy, x‐ray dose must be precisely sculpted to the tumor, while simultaneously avoiding surrounding organs at risk. This requires modulation of x‐ray intensity in space and/or time. Typically, this is achieved using a multi leaf collimator (MLC)—a complex mechatronic device comprising over one hundred individually powered tungsten ‘leaves’ that move in or out of the radiation field as required. Here, an all‐electronic x‐ray collimation concept with no moving parts is presented, termed “SPHINX”: Scanning Pencil‐beam High‐speed Intensity‐modulated X‐ray source. SPHINX utilizes a spatially distributed bremsstrahlung target and collimator array in conjunction with magnetic scanning of a high energy electron beam to generate a plurality of small x‐ray “beamlets.” Methods A simulation framework was developed in Topas Monte Carlo incorporating a phase space electron source, transport through user defined magnetic fields, bremsstrahlung x‐ray production, transport through a SPHINX collimator, and dose in water. This framework was completely parametric, meaning a simulation could be built and run for any supplied geometric parameters. This functionality was coupled with Bayesian optimization to find the best parameter set based on an objective function which included terms to maximize dose rate for a user defined beamlet width while constraining inter‐channel cross talk and electron contamination. Designs for beamlet widths of 5, 7, and 10 mm2 were generated. Each optimization was run for 300 iterations and took approximately 40 h on a 24‐core computer. For the optimized 7‐mm model, a simulation of all beamlets in water was carried out including a linear scanning magnet calibration simulation. Finally, a back‐of‐envelope dose rate formalism was developed and used to estimate dose rate under various conditions. Results The optimized 5–, 7–, and 10‐mm models had beamlet widths of 5.1 , 7.2 , and 10.1 mm2 and dose rates of 3574, 6351, and 10 015 Gy/C, respectively. The reduction in dose rate for smaller beamlet widths is a result of both increased collimation and source occlusion. For the simulation of all beamlets in water, the scanning magnet calibration reduced the offset between the collimator channels and beam centroids from 2.9 ±1.9 mm to 0.01 ±0.03 mm. A slight reduction in dose rate of approximately 2% per degree of scanning angle was observed. Based on a back‐of‐envelope dose rate formalism, SPHINX in conjunction with next‐generation linear accelerators has the potential to achieve substantially higher dose rates than conventional MLC‐based delivery, with delivery of an intensity modulated 100 × 100 mm2 field achievable in 0.9 to 10.6 s depending on the beamlet widths used. Conclusions Bayesian optimization was coupled with Monte Carlo modeling to generate SPHINX geometries for various beamlet widths. A complete Monte Carlo simulation for one of these designs was developed, including electron beam transport of all beamlets through scanning magnets, x‐ray production and collimation, a...

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Failure modes and downtime of radiotherapy LINACs and multileaf collimators in Indonesia

Pawiro

Kasim

et al. 2022

J Applied Clin Med Phys

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Background and purpose The lack of equitable access to radiotherapy (RA) linear accelerators (LINACs) is a substantial barrier to cancer care in low‐ and middle‐income countries (LMICs). These nations are expected to bear up to 75% of cancer‐related deaths globally by 2030. State‐of‐the‐art LINACs in LMICs experience major issues in terms of robustness, with mechanical and electrical breakdowns resulting in downtimes ranging from days to months. While existing research has identified the higher failure frequency and downtimes between LMICs (Nigeria, Botswana) compared to high‐income countries (HICs, the UK), there has been a need for additional data and study particularly relating to multileaf collimators (MLCs). Materials and methods This study presents for the first time the analysis of data gathered through a dedicated survey and workshop including participants from 14 Indonesian hospitals, representing a total of 19 LINACs. We show the pathways to failure of radiotherapy LINACs and frequency of breakdowns with a focus on the MLC subsystem. Results This dataset shows that LINACs throughout Indonesia are out of operation for seven times longer than HICs, and the mean time between failures of a LINAC in Indonesia is 341.58 h or about 14 days. Furthermore, of the LINACs with an MLC fitted, % of all mechanical faults are due to the MLC, and % of cases requiring a replacement component are related to the MLC. Conclusion These results highlight the pressing need to improve robustness of RT technology for use in LMICs, highlighting the MLC as a particularly problematic component. This work motivates a reassessment of the current generation of RT LINACs and demonstrates the need for dedicated efforts toward a future where cancer treatment technology is robust for use in all environments where it is needed.

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Failure modes and downtime of radiotherapy LINACs and multileaf collimators in Indonesia

Cited by 6 publications

References 34 publications

MLC performance prognosis using a degradation model based on trajectory log data from a daily test

MLC performance prognosis using a degradation model based on trajectory log data from a daily test

Bayesian optimization to design a novel x‐ray shaping device

Failure modes and downtime of radiotherapy LINACs and multileaf collimators in Indonesia

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