The utilization of a 3-dimensional noncoplanar treatment plan to avoid pacemaker complications

doi:10.1016/j.meddos.2004.03.013

Medical Dosimetry

Volume 29, Issue 2, Summer 2004, Pages 92-96

https://doi.org/10.1016/j.meddos.2004.03.013 Get rights and content

Abstract

Treatment planning of thoracic patients having upper lobe lesions and a pacemaker presents quite a challenge. It is necessary to avoid the pacemaker as well as other critical structures in order to deliver the prescribed dose for local control. This case demonstrates the utilization of noncoplanar beams and asymmetric fields to limit the radiation dose to the pacemaker. The dose to the pacemaker was quantified by the information represented in the dose-volume histogram (DVH) of the computerized tomography (CT)-based treatment plan. The delivered dose was verified utilizing thermoluminescent dosimeters (TLDs) placed on the patient. Measurements of the daily dose from all of the treatment fields to include the open jaws during portal imaging were taken to sum the total possible dose the pacemaker may receive. The allowable dose to the pacemaker is dependent upon individual manufacturers. It was found that with proper treatment planning and appropriate precautions, a patient is able to receive full-prescribed dose with no risks of interfering with the pacemaker function.

Introduction

This case presents a 77-year-old man with a 120-pack-year tobacco history having a T2, N2 (Stage IIIA) non-small cell lung cancer to the right upper lobe who has undergone 2 cycles of induction chemotherapy and was evaluated for definitive irradiation. The patient had developed shortness of breath and dyspnea in April 2002. At that time, the patient was found to have an arrhythmia, and a pacemaker was placed. During the patient's clinical workup, it was noted on a V/Q nuclear medicine study that a probable thrombus on the right anterior segment of the upper lobe may be present. A computerized tomography (CT) scan revealed a right upper lobe lesion. On bronchoscopy, he was found to have an endobronchial tumor in the anterior segment of the right upper lobe, and a biopsy confirmed poorly-differentiated adenocarcinoma. His pulmonary function tests showed lower than normal lung function. Because of his pulmonary function results, he was not a surgical candidate, due to poor pulmonary status. CT scans taken in July 2002 compared with those taken in September 2002 showed an interval decrease in size of the right upper lobe lung mass since the induction chemotherapy. However, it was also noted that the lung lesion was located immediately inferior and partially overlapped the pacemaker.

The location of the patient's tumor relative to his pacemaker provided a unique challenge due to the documented sensitivity of this device to radiation. One alternative, to relocate the pacemaker away from the area to be irradiated, was discussed; however, due to his financial status as a self-pay, the personal costs were prohibitive. A simulation and preliminary plan were designed to relieve the patient of having to have the pacemaker moved at his expense.

Our hearts have a biochemical triggering system that keeps the heart beating regularly; when the system does not work properly, a pacemaker may be the solution.

A pacemaker has 2 parts—wires that connect to the heart, and a silver-dollar-size generator, powered by a battery. This battery-powered generator has an effective life of up to 12 years. The pacemaker wires or leads are connected to the heart through veins just below the collarbone. The device itself is implanted just beneath the skin below the collarbone.¹

Pacemakers were first developed in the early 1950s. These were external devices with serious drawbacks. In the 1960s, the first pacemaker was implanted and had a battery life of approximately 12 to 18 months. As time and technology progressed, a new “demand” pacemaker became available. This device provides pacing only when necessary, not at a “fixed” rate as before. The more advanced pacemakers are now programmable. They can sense and pace upper and lower chambers of the heart by using 2 leads. Dual-chamber pacemakers allow for synchronization and ensure efficient blood flow. These pacemakers will react to a person's activity level and mimic the heart's natural rhythm.

Pacemakers are extremely sensitive to radiation, and doses vary depending on manufacturer make and model. A pacemaker may either not pace, pace erratically, or pace inappropriately if the computer becomes deprogrammed due to radiation damage. If the pacemaker is exposed to sufficient radiation doses, irreversible damage may occur and the pacemaker must be considered permanently damaged.²

Section snippets

Simulation

The patient was simulated using a Philips PQ Series large-bore AcQSim CT-based simulator (Philips Medical Systems, Highland Heights, OH). He was placed in the supine position using a MED-TEC wingboard (MED-TEC, Inc., Orange City, IA) to extend the arms up over the head, and a MED-TEC Vac-Lok system for immobilization of the thorax. Images were obtained from the level of the mandible to below the lower edge of the liver, using 3-mm slices. During the simulation process, the isocenter was placed

Thermoluminescent dosimeter measurements

To ensure the pacemaker would be safe and to confirm the DVH data, thermoluminescent dosimeters (TLDs) were used to measure the radiation dose. Four TLDs were placed on the outer edge of the pacemaker and 1 in the center on top of the pacemaker. Because this plan utilized 6- and 18-MV photons, readings were taken on 2 separate occasions with the appropriate thickness of bolus placed over the TLDs for accurate buildup. The results are displayed in Table 1. The report of Task Group 34 formed by

Results

The DVH illustrates the end results of the 4-field noncoplanar beam arrangement (Fig. 6). The GTV received 100% of the total dose of 63 Gy, while the CTV, PTV, and mediastinum were covered by 95% of the total dose. The spinal cord received a maximum dose of 35 Gy. In addition, 28 Gy was delivered to approximately 12% of the heart. The right and left lungs were combined to represent a total lung volume of which only 35% of the total lung received 20 Gy, while limiting the esophagus volume to

Conclusions

As technology continues to advance, we will be faced with more challenges in treatment planning. This case has shown that with the complete patient history, preplanning, teamwork, and technology we are able to treat cases that historically may have been impossible. Using a noncoplanar treatment beam arrangement allowed for optimal tumor coverage while sparing the pacemaker as well as all other critical structures. The beam arrangement utilized gave the opportunity to give the most advantageous

References (3)

Medtronic, Inc. Minneapolis, MN. Version B3. http://www.medtronic.com. Accessed...

There are more references available in the full text version of this article.

Cited by (16)

Case study thoracic radiotherapy in an elderly patient with pacemaker: The issue of pacing leads
2012, Medical Dosimetry
Citation Excerpt :
It is necessary to avoid the pacemaker as well as other critical structures to deliver the prescribed dose for local control. As a matter of fact, it is well demonstrated that ionizing radiation can interfere with circuits in permanent pacemakers.4–7 The underlying mechanisms and types of radiotherapy-induced pacemaker dysfunction have been described in preclinical studies in which the pacemaker was directly exposed to radiotherapy.5
To assess clinical outcome of patients with pacemaker treated with thoracic radiation therapy for T8-T9 paravertebral chloroma. A 92-year-old male patient with chloroma presenting as paravertebral painful and compressive (T8-T9) mass was referred for radiotherapy in the Department of Radiation Oncology, Institut Curie. The patient presented with cardiac dysfunction and a permanent pacemaker that had been implanted prior. The decision of Multidisciplinary Meeting was to deliver 30 Gy in 10 fractions for reducing the symptoms and controlling the tumor growth. The patient received a total dose of 30 Gy in 10 fractions using 4-field conformal radiotherapy with 20-MV photons. The dose to pacemaker was 0.1 Gy but a part of the pacing leads was in the irradiation fields. The patient was treated the first time in the presence of his radiation oncologist and an intensive care unit doctor. Moreover, the function of his pacemaker was monitored during the entire radiotherapy course. No change in pacemaker function was observed during any of the radiotherapy fractions. The radiotherapy was very well tolerated without any side effects. The function of the pacemaker was checked before and after the radiotherapy treatment by the cardiologist and no pacemaker dysfunction was observed. Although updated guidelines are needed with acceptable dose criteria for implantable cardiac devices, it is possible to treat patients with these devices and parts encroaching on the radiation field. This case report shows we were able to safely treat our patient through a multidisciplinary approach, monitoring the patient during each step of the treatment.
The effect of stereotactic body radiotherapy (SBRT) using flattening filter-free beams on cardiac implantable electronic devices (CIEDs) in clinical situations
2020, Journal of Applied Clinical Medical Physics
Radiotherapy of patients with implantable electronical devices
2020, Klinicka Onkologie
Management of radiotherapy patients with implanted cardiac pacemakers and defibrillators: A Report of the AAPM TG-203<sup>†</sup>
2019, Medical Physics
A review and analysis of stereotactic body radiotherapy and radiosurgery of patients with cardiac implantable electronic devices
2019, Australasian Physical and Engineering Sciences in Medicine
Dosimetric study to assess the feasibility of intraoperative radiotherapy with electrons (ELIOT) as partial breast irradiation for patients with cardiac implantable electronic device (CIED)
2018, Breast Cancer Research and Treatment

View all citing articles on Scopus

View full text