Prevalence, severity, and predictors of symptom burden among adolescents and young adults with cancer.

BACKGROUND: Symptom burden in adolescents and young adults (AYA) with cancer is poorly characterized but impacts quality of life. METHODS: All Ontario, Canada AYA aged 15-29 years at diagnosis between 2010 and 2018 were linked to population-based healthcare databases, including to Edmonton Symptom Assessment System-revised (ESAS) scores, an 11-point scale routinely obtained at the time of cancer-related outpatient visits and collected provincially. Multistate models estimated mean duration of symptom severity states [none (0) vs. mild (1 vs. 2 vs. 3) vs. moderate (4-6) vs. severe (7-10)], trajectories, and subsequent mortality risk. Variables associated with severe symptoms were also determined. RESULTS: In total, 4296 AYA with ≥1 ESAS score within a year of diagnosis were included (median age 25 years). Prevalent moderate/severe symptoms included fatigue (59% of AYA) and anxiety (44%). Across symptom type, AYA reporting moderate symptoms were likelier to subsequently experience improvement versus worsening. Risk of death within 6 months increased with increasing symptom burden and was highest in AYA with severe dyspnea (9.0%), pain (8.0%), or drowsiness (7.5%). AYA in the poorest urban neighborhoods were more likely to experience severe symptoms than in the wealthiest areas, with twice the odds of reporting severe depression [adjusted odds ratio (OR) 1.95, 95th confidence interval (95% CI) 1.37-2.78], pain (OR: 1.94, 95% CI: 1.39-2.70), and dyspnea (OR: 1.96, 95% CI: 1.27-3.02). CONCLUSIONS: AYA with cancer experience substantial symptom burden. Risk of death increased with symptom severity. Interventions targeting cancer fatigue and anxiety, and targeting AYA in lower-income neighborhoods, are likely to improve quality of life in this population.

Health Literacy and Radiation Therapy: a Current State Assessment of Patient Education Materials.

In order to mitigate low levels of health literacy among patients, there is need to evaluate patient education (PE) materials and to ensure that the information is readily accessible to patients. The quality and comprehensiveness of radiation therapy materials were evaluated at fourteen cancer centres. To assess quality, PE leaders independently conducted readability, actionability and understandability assessments of materials. To evaluate comprehensiveness, an assessment was conducted of the scope of symptoms covered in extant materials, and the modality they were produced in (e.g. pamphlet, video). A total of 555 PE materials were reviewed for comprehensiveness and modality and seventy underwent evaluation against health literacy best practice standards. Most materials (n = 64, 91%) had a reading grade level above the recommended grade 6 ([Formula: see text] = 9, range = 4-12). Under half (n = 34, 49%) scored at or above the 80% threshold for understandability ([Formula: see text] = 74%, 33-100%) and just over half (n = 36, 51%) scored at or above the 80% target for actionability ([Formula: see text] = 71%, 33-100%). Only two cancer centres (n = 2/14, 14%) had PE materials covering the breadth of symptoms related to radiation therapy and the vast majority of materials were pamphlets (89%). Findings indicate that most radiation therapy PE materials used in cancer centres do not meet health literacy best practices, and there is a disparity between cancer centres in the topics that are available to patients and family. This evaluation highlights the need to better incorporate health literacy best practices into the development of radiation therapy PE materials and strategies to improve accessibility of such health information.

Primary care utilization for patients with newly diagnosed cancer during the COVID-19 pandemic: a population-based study.

BACKGROUND: The COVID-19 pandemic greatly impacted primary care and cancer care. We studied how primary care utilization in Ontario, Canada changed for patients who were newly diagnosed with cancer just prior to the COVID-19 pandemic compared to those diagnosed in non-pandemic years. METHODS: This population-based, retrospective cohort study used linked healthcare databases to compare outcomes for patients with a new malignancy diagnosed within the year prior to the COVID-19 pandemic, between July 1 and September 30, 2019 (COVID-19 cohort) to those diagnosed in the same months in 2018 and 2017 (pre-pandemic cohort). We used Poisson regression models to compare rates of in-person and virtual visits to patients' usual primary care physician (PCP), emergency department (ED) visits, and hospitalizations, all reported per person-year of follow-up. RESULTS: In-person visits to usual PCPs decreased from 4.07/person-year in the pre-pandemic cohort to 2.58 in the COVID-19 cohort (p < 0.0001). Virtual visits to usual PCPs increased from 0.00 to 1.53 (p < 0.0001). Combined in-person and virtual visits to patients' usual PCPs was unchanged from 4.07 to 4.12 (p = 0.89). The rate of ED visits decreased from 0.99/person-year to 0.88 (p < 0.0001). Non-elective hospitalizations remained unchanged, from 0.49/person-year to 0.47 (p = 0.1675). CONCLUSION: There was a sizeable shift in primary care visits for cancer patients from in-person to virtual during the pandemic, although there was no resultant increase in hospitalizations. This suggests that early in the pandemic, virtual care allowed for continuity in utilization of primary care, though further studies are required to confirm this persisted later in the pandemic.

Anxiety and depression in patients with intracranial meningioma: a mixed methods analysis.

BACKGROUND: While diagnosis with a high-grade intracranial tumor is known to be associated with increased psychosocial burden, the burdens associated with meningioma are less well described. This study aimed to investigate the mental health burden in patients with meningiomas who have undergone surgical resection or serial observation, so as to identify and enhance awareness of gaps in care. METHODS: The Hospital Anxiety and Depression Scale (HADS) was administered to participants. Fisher's Exact tests were performed to evaluate frequency distributions and t-tests were applied to compare postoperative and non-surgical patients' HADS scores. Semi-structured interviews were completed on a subset of participants. Thematic analysis of interviews identified emerging themes. RESULTS: Thirty patients with intracranial meningiomas met inclusion criteria. The cohort's mean age was 56.01 years and 66.67% were women (n = 20). Fourteen underwent surgery; sixteen were treated conservatively with observation. The average time since diagnosis of the sample was 37.6 months. Prevalence of mild to severe symptoms of anxiety was 28.6% amongst surgical management patients and 50% for active surveillance patients (p = 0.325). The prevalence of mild to severe symptoms of depression was 7.14% amongst surgical management patients and 6.25% for active surveillance patients (p = 0.533). Emerging themes from eight interviews reveal the influence of resilience, uncertainty and time, social support, interactions with medical experts, and difficulties during recovery on mental health. CONCLUSION: The findings from the present study reveal that patients with meningiomas experience a significant mental health burden, illustrating the need for enhanced patient-centred care focusing on mental health.

Relationships, body image, and intimacy: A pilot to increase sexual health conversations between radiation therapists and cancer patients in Ontario.

BACKGROUND: In 2016, a sexual health guideline recommended that the first step to addressing sexual health and dysfunction resulting from cancer and its treatment is for healthcare providers to initiate sexual health conversations with patients. To action this, a sexual health knowledge translation (KT) pilot was developed. METHODS: The Relationships, Body image, and Intimacy (RBI) pilot was implemented at four regional cancer centres (RCCs) from January 2018 to February 2020 which focused on medical radiation therapists (MRT(T)s) initiating conversations with radiation therapy patients. MRT(T)s were recruited to be RBI champion role models and were trained on RBI topics, trained fellow MRT(T)s, and modelled best practice for sexual health conversations with cancer patients. Pilot interventions were developed to address barriers to RBI conversations. Both qualitative and quantitative data collection activities were implemented to evaluate pilot interventions. RESULTS: Before the RBI pilot, over 80% of MRT(T)s reported they did not initiate RBI conversations with patients. By the end of the pilot, over 52% of MRT(T)s reported initiating RBI conversations with all or almost all patients. Feedback from patients was positive. Barriers to comfort level with RBI topic were successfully addressed with continued education and training throughout the pilot. DISCUSSION: Results show increased RBI conversations during the pilot, and MRT(T)s reported increased comfort speaking with patients about RBI with continued practice. The RBI champions played a pivotal role in the pilot's success and increased MRT(T) comfort with RBI. Initial barriers to RBI conversations were less reported as the pilot progressed and RBI conversations were normalized for patients. CONCLUSIONS: The RBI pilot was a novel KT initiative focused on supporting MRT(T)s to ensure patients were aware of sexual health resources available to them during their radiation therapy. Knowledge gained from this pilot can easily be adapted to assist other health care providers and additional RCCs to confidently initiate RBI conversations with their patients.

The Cost of Patient Education Materials Development: Opportunities to Identify Value and Priorities.

The study aim was to evaluate the costs associated with developing and reviewing patient education materials (pamphlets) across Ontario cancer centers. While patient education often produces a positive return on investment, limited efforts have been dedicated to optimizing the personnel, time, and capital dedicated to this feat across healthcare systems. Patient education leaders at 14 cancer centers completed a survey measure, estimating the number of hours spent developing and reviewing pamphlets and identifying the personnel involved in each procedural step. The time expended per center in each step was then combined with average salary data for the identified personnel to derive total cost estimates. Cancer centers spend on average $5672 (SD = $3180) developing (M = $4560, SD = $2620) and reviewing (M = $1112, SD = $654) one pamphlet. This cumulates to an average per annum spending of $65,401 (SD = $75,494) for pamphlet development and $19,819 (SD = $28,524) for annual pamphlet review at each cancer center. The cost and number of hours spent developing and reviewing pamphlets varied substantially between cancer centers. While the security of budgets for patient education varies across cancer centers, opportunities to optimize human capital and monetary resources should be considered. Results of the study can be used to advocate for sustainable investment into cancer education programs, improve the coordination of educational materials production and review, and ensure that resource quality and access are consistent across the province.

Prevalence and Workplace Drivers of Burnout in Cancer Care Physicians in Ontario, Canada.

PURPOSE: Provider well-being has become the fourth pillar of the quadruple aim for providing quality care. Exacerbated by the global COVID-19 pandemic, provider well-being has become a critical issue for health care systems worldwide. We describe the prevalence and key system-level drivers of burnout in oncologists in Ontario, Canada. METHODS: This is a cross-sectional survey study conducted in November-December 2019 of practicing cancer care physicians (surgical, medical, radiation, gynecologic oncology, and hematology) in Ontario, Canada. Ontario is Canada's largest province (with a population of 14.5 million), and has a single-payer publicly funded cancer system. The primary outcome was burnout experience assessed through the Maslach Burnout Inventory. RESULTS: A total of 418 physicians completed the questionnaire (response rate was 44% among confirmed oncologists). Seventy-three percent (n = 264 of 362) of oncologists had symptoms of burnout (high emotional exhaustion and/or depersonalization scores). Significant drivers of burnout identified in multivariable regression modeling included working in a hectic or chaotic atmosphere (odds ratio [OR] = 15.5; 95% CI, 3.4 to 71.5; P < .001), feeling unappreciated on the job (OR = 7.9; 95% CI, 2.9 to 21.3; P < .001), reporting poor or marginal control over workload (OR = 7.9; 95% CI, 2.9 to 21.3; P < .001), and not being comfortable talking to peers about workplace stress (OR = 3.0; 95% CI, 1.1 to 7.9; P < .001). Older age (≥ 56 years) was associated with lower odds of burnout (OR = 0.16; 95% CI, 0.1 to 0.4; P < .001). CONCLUSION: Nearly three quarters of participants met predefined standardized criteria for burnout. This number is striking, given the known impact of burnout on provider mental health, patient safety, and quality of care, and suggests Oncologists in Ontario may be a vulnerable group that warrants attention. Health care changes being driven by the COVID-19 pandemic provide an opportunity to rebuild new systems that address drivers of burnout. Creating richer peer-to-peer and leadership engagement opportunities among early- to mid-career individuals may be a worthwhile organizational strategy.

Delivery of Virtual Care in Oncology: Province-Wide Interprofessional Consensus Statements Using a Modified Delphi Process.

Virtual cancer care (i.e., teleoncology) was rapidly adopted during the COVID-19 pandemic to meet the needs of patients with cancer. However, there is a paucity of guidance for clinicians regarding virtual cancer care. We sought to develop consensus-based statements to guide the optimal provision of virtual care for clinicians caring for patients with cancer, using a modified Delphi consensus process with a 29-member panel consisting of an interprofessional group of clinicians caring for patients with cancer and patient representatives. The consensus process consisted of two rounds and one synchronous final consensus meeting. At the end of the modified Delphi process, 62 of 62 statements achieved consensus. Fifty-seven statements reached consensus in the first round of the process. Concerns regarding the ability to convey difficult news virtually and maintaining similar standards as in-person care without disproportionate strain on clinicians and patients were addressed in the consensus process. We achieved interprofessional consensus on virtual cancer care practices. Further research examining the impact of virtual cancer care on person-centred and clinical outcomes are needed to inform practices during the COVID-19 pandemic and beyond.

Establishing best practices in cancer online support groups: protocol for a realist review.

INTRODUCTION: Considerable observational evidence suggests that cancer online support groups reduce feelings of isolation, depression and anxiety, enhance coping and self-management, and lead to better informed patients. Other studies indicate that cancer online support groups can increase distress. Yet no studies theorise the complex, context-dependent mechanisms by which cancer online support groups generate their-sometimes contrasting-outcomes. METHODS AND ANALYSIS: Guided by an integrated knowledge translation approach and the strategy for patient-oriented research, we will conduct a realist review of cancer online support groups in partnership with stakeholders. We will follow Pawson's five steps and existing quality standards to develop a program theory that explains how cancer online support groups work, for whom and in what circumstances. The specific research questions will be: what positive and negative outcomes have been reported on cancer online support groups? What are the mechanisms that are associated with these outcomes, in which contexts and for whom? Through a rigorous review of relevant scientific and grey literature, as well as ongoing dialogue with stakeholders, a program theory will be developed to explain who benefits from cancer online support groups and who does not, what benefits they derive (or do not), and the factors that affect these outcomes. ETHICS AND DISSEMINATION: The use of secondary data for this review precludes the need for ethical approval. Dissemination will be informed by the knowledge-to-action framework and will consist of tailored knowledge products that are conceived of collaboratively with stakeholders. These will include peer-reviewed publications on how cancer online support groups can be optimised and best practice recommendations to maximise the benefits experienced by people with cancer. These traditional scientific outputs, along with their respective evidence summaries, will be amplified through strategic social media events hosted and promoted by knowledge users. PROSPERO REGISTRATION NUMBER: CRD42021250046.

Reinventing the wheel: The incidence and cost implication of duplication of effort in patient education materials development.

OBJECTIVE: The development of patient education (PE) materials is costly and resource-intensive, and no mechanisms exist for sharing materials across cancer centers/hospitals to limit duplicated effort. The aim of this study was to explore the incidence and cost implication of duplicated PE efforts. METHODS: PE leaders from all (14) cancer centers in Ontario, Canada, submitted their collections of systemic therapy PE materials. Materials were categorized by topic and were coded as duplicate (more than one other material exists on the same topic and there was significant content and/or textual overlap), adapted (material was adapted from an existing material) or unique (no other material addresses the topic). RESULTS: 304 materials were included and <50 % of materials had duplicate content (n = 166, 55 %), a small proportion were adapted (n = 27, 9%), and less than half were unique (n = 111, 37 %). The majority of materials were considered amenable to adaptation meaning that the content was not dependent on a specific institutional context (n = 283, 93 %). The opportunity for cost savings if duplication of effort could be avoided is approximately $800 K for systemic therapy materials produced in cancer centers. CONCLUSION: There is need to refine the process for developing PE materials. Creating mechanisms of sharing can help facilitate equal access to materials and can result in significant cost savings. PRACTICE IMPLICATIONS: Efforts are needed to better coordinate the development of PE materials among patient educators. Better coordination would allow patient education programs to focus on other important challenges.

American Association of Physicists in Medicine Task Group 263: Standardizing Nomenclatures in Radiation Oncology.

A substantial barrier to the single- and multi-institutional aggregation of data to supporting clinical trials, practice quality improvement efforts, and development of big data analytics resource systems is the lack of standardized nomenclatures for expressing dosimetric data. To address this issue, the American Association of Physicists in Medicine (AAPM) Task Group 263 was charged with providing nomenclature guidelines and values in radiation oncology for use in clinical trials, data-pooling initiatives, population-based studies, and routine clinical care by standardizing: (1) structure names across image processing and treatment planning system platforms; (2) nomenclature for dosimetric data (eg, dose-volume histogram [DVH]-based metrics); (3) templates for clinical trial groups and users of an initial subset of software platforms to facilitate adoption of the standards; (4) formalism for nomenclature schema, which can accommodate the addition of other structures defined in the future. A multisociety, multidisciplinary, multinational group of 57 members representing stake holders ranging from large academic centers to community clinics and vendors was assembled, including physicists, physicians, dosimetrists, and vendors. The stakeholder groups represented in the membership included the AAPM, American Society for Radiation Oncology (ASTRO), NRG Oncology, European Society for Radiation Oncology (ESTRO), Radiation Therapy Oncology Group (RTOG), Children's Oncology Group (COG), Integrating Healthcare Enterprise in Radiation Oncology (IHE-RO), and Digital Imaging and Communications in Medicine working group (DICOM WG); A nomenclature system for target and organ at risk volumes and DVH nomenclature was developed and piloted to demonstrate viability across a range of clinics and within the framework of clinical trials. The final report was approved by AAPM in October 2017. The approval process included review by 8 AAPM committees, with additional review by ASTRO, European Society for Radiation Oncology (ESTRO), and American Association of Medical Dosimetrists (AAMD). This Executive Summary of the report highlights the key recommendations for clinical practice, research, and trials.

Electrical Characterization of Glycerin: Water Mixtures: Implications for Use as a Coupling Medium in Microwave Tomography.

We examine the broadband behavior of complex electrical properties of glycerin and water mixtures over the frequency range of 0.1 - 25.0 GHz, especially as they relate to using these liquids as coupling media for microwave tomographic imaging. Their combination is unique in that they are mutually miscible over the full range of concentrations which allows them to be tailored to dielectric property matching for biological tissues. While the resultant mixture properties are partially driven by differences in the inherent low frequency permittivity of each constituent, relaxation frequency shifts play a disproportionately larger role in increasing the permittivity dispersion while also dramatically increasing the effective conductivity over the frequency range of 1 to 3 GHz. For the full range of mixture ratios, the relaxation frequency shifts from 17.5 GHz for 0% glycerin to less than 0.1 GHz for 100% glycerin. Of particular interest is the fact that the conductivity stays above 1.0 S/m over the 1-3 GHz range for glycerin mixture ratios (70-90% glycerin) we use for microwave breast tomography. The high level of attenuation is critical for suppressing unwanted multipath signals. This paper presents a full characterization of these liquids along with a discussion of their benefits and limitations in the context of microwave tomography.

Toxicology and teratology of the active ingredients of professional therapy MuscleCare products during pregnancy and lactation: a systematic review.

BACKGROUND: The rates of muscle aches, sprains, and inflammation are significantly increased during pregnancy. However, women are afraid to use systemic analgesics due to perceptions of fetal risks. Thus, topical products are important alternatives to consider for those women. Of interest, Professional Therapy MuscleCare (PTMC) has shown to be effective in alleviating the myofascial pain as reported in a randomized, placebo-controlled double-blinded comparative clinical study of five topical analgesics. However, to date, there is no complete review or long-term safety studies on the safety of these products during pregnancy and lactation. Thus, the aim of this article was to review toxicological, developmental, and reproductive effects associated with the use of PTMC products. METHODS: We performed a systematic review on safety of PTMC from all toxicological articles investigating the effects of PTMC's ingredients. This search was conducted through medical and toxicological databases including, Web of Science, EMBASE, Medline, and Micromedix. Both reported and theoretical adverse effects were extensively reviewed. RESULTS: Of the 1500 publications reviewed, 100 papers were retrieved and included in the review. Although some ingredients in PTMC products might cause adverse reproductive effects at high systemic doses, these doses are hundreds to thousands fold greater than those systemically available from topical use at the recommended maximum dose (i.e. 10 g/day). CONCLUSIONS: This study provides evidence that, when used as indicated, PTMC is apparently safe for pregnant women and their unborn babies as well as for breastfed infants.

Dosimetric review of cardiac implantable electronic device patients receiving radiotherapy.

A formal communication process was established and evaluated for the management of patients with cardiac implantable electronic devices (CIEDs) receiving radiation therapy (RT). Methods to estimate dose to the CIED were evaluated for their appropriateness in the management of these patients. A retrospective, institutional review board (IRB) approved study of 69 patients with CIEDs treated with RT between 2005 and 2011 was performed. The treatment sites, techniques, and the estimated doses to the CIEDs were analyzed and compared to estimates from published peripheral dose (PD) data and three treatment planning systems(TPSs) - UMPlan, Eclipse's AAA and Acuros algorithms. When measurements were indicated, radiation doses to the CIEDs ranged from 0.01-5.06 Gy. Total peripheral dose estimates based on publications differed from TLD measurements by an average of 0.94 Gy (0.05-4.49 Gy) and 0.51 Gy (0-2.74 Gy) for CIEDs within 2.5 cm and between 2.5 and 10 cm of the treatment field edge, respectively. Total peripheral dose estimates based on three TPSs differed from measurements by an average of 0.69 Gy (0.02-3.72 Gy) for CIEDs within 2.5 cm of the field edge. Of the 69 patients evaluated in this study, only two with defibrillators experienced a partial reset of their device during treatment. Based on this study, few CIED-related events were observed during RT. The only noted correlation with treatment parameters for these two events was beam energy, as both patients were treated with high-energy photon beams (16 MV). Differences in estimated and measured CIED doses were observed when using published PD data and TPS calculations. As such, we continue to follow conservative guidelines and measure CIED doses when the device is within 10 cm of the field or the estimated dose is greater than 2 Gy for pacemakers or 1 Gy for defibrillators.

Video-rate optical dosimetry and dynamic visualization of IMRT and VMAT treatment plans in water using Cherenkov radiation.

PURPOSE: A novel technique for optical dosimetry of dynamic intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans was investigated for the first time by capturing images of the induced Cherenkov radiation in water. METHODS: A high-sensitivity, intensified CCD camera (ICCD) was configured to acquire a two-dimensional (2D) projection image of the Cherenkov radiation induced by IMRT and VMAT plans, based on the Task Group 119 (TG-119) C-Shape geometry. Plans were generated using the Varian Eclipse treatment planning system (TPS) and delivered using 6 MV x-rays from a Varian TrueBeam Linear Accelerator (Linac) incident on a water tank doped with the fluorophore quinine sulfate. The ICCD acquisition was gated to the Linac target trigger pulse to reduce background light artifacts, read out for a single radiation pulse, and binned to a resolution of 512 × 512 pixels. The resulting videos were analyzed temporally for various regions of interest (ROI) covering the planning target volume (PTV) and organ at risk (OAR), and summed to obtain an overall light intensity distribution, which was compared to the expected dose distribution from the TPS using a gamma-index analysis. RESULTS: The chosen camera settings resulted in 23.5 frames per second dosimetry videos. Temporal intensity plots of the PTV and OAR ROIs confirmed the preferential delivery of dose to the PTV versus the OAR, and the gamma analysis yielded 95.9% and 96.2% agreement between the experimentally captured Cherenkov light distribution and expected TPS dose distribution based upon a 3%/3 mm dose difference and distance-to-agreement criterion for the IMRT and VMAT plans, respectively. CONCLUSIONS: The results from this initial study demonstrate the first documented use of Cherenkov radiation for video-rate optical dosimetry of dynamic IMRT and VMAT treatment plans. The proposed modality has several potential advantages over alternative methods including the real-time nature of the acquisition, and upon future refinement may prove to be a robust and novel dosimetry method with both research and clinical applications.

Superficial dosimetry imaging based on Cerenkov emission for external beam radiotherapy with megavoltage x-ray beam.

PURPOSE: Cerenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for the Cerenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of optical Cerenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams. METHODS: In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams. Cerenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based on Cerenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50-200 × 200 mm(2)), incident angles (0°-70°) and imaging regions were all varied. RESULTS: The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that their Cerenkov emission is proportional to dose. Directly simulated local intensity of Cerenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of Cerenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the results show there is good potential for real-time superficial dose monitoring. Dose imaging under normal ambient room lighting was validated, using gated detection and a breast phantom. CONCLUSIONS: This study indicates that Cerenkov emission imaging might provide a valuable way to superficial dosimetry imaging in real time for external beam radiotherapy with megavoltage x-ray beams.

Superficial dosimetry imaging of Cerenkov emission in electron beam radiotherapy of phantoms.

Cerenkov emission is generated from ionizing radiation in tissue above 264 keV energy. This study presents the first examination of this optical emission as a surrogate for the absorbed superficial dose. Cerenkov emission was imaged from the surface of flat tissue phantoms irradiated with electrons, using a range of field sizes from 6 cm × 6 cm to 20 cm × 20 cm, incident angles from 0° to 50°, and energies from 6 to 18 MeV. The Cerenkov images were compared with the estimated superficial dose in phantoms from direct diode measurements, as well as calculations by Monte Carlo and the treatment planning system. Intensity images showed outstanding linear agreement (R(2) = 0.97) with reference data of the known dose for energies from 6 to 18 MeV. When orthogonal delivery was carried out, the in-plane and cross-plane dose distribution comparisons indicated very little difference (± 2-4% differences) between the different methods of estimation as compared to Cerenkov light imaging. For an incident angle 50°, the Cerenkov images and Monte Carlo simulation show excellent agreement with the diode data, but the treatment planning system had a larger error (OPT = ± 1~2%, diode = ± 2~3%, TPS = ± 6-8% differences) as would be expected. The sampling depth of superficial dosimetry based on Cerenkov radiation has been simulated in a layered skin model, showing the potential of sampling depth tuning by spectral filtering. Taken together, these measurements and simulations indicate that Cerenkov emission imaging might provide a valuable method of superficial dosimetry imaging from incident radiotherapy beams of electrons.

Effect of radiation therapy on permanent pacemaker and implantable cardioverter-defibrillator function.

BACKGROUND: Radiation therapy's (RT's) effects on cardiac implantable electronic devices (CIEDs) such as implantable cardioverter-defibrillators (ICDs) and pacemakers (PMs) are not well established, leading to device removal or relocation in preparation for RT. OBJECTIVE: To determine the effect of scattered RT on CIED performance. METHODS: We analyzed 69 patients--50 (72%) with PMs and 19 (28%) with ICDs--receiving RT at the University of Michigan. Collected data included device model, anatomic location, and treatment beam energies, treatment type, and estimated dose to the device. Patients were treated with either high-energy (16-MV) and/or low-energy (6 MV) photon beams with or without electron beams (6-16 MeV). The devices were interrogated with pre- and post-RT and/or weekly with either in-treatment or home interrogation, depending on the patient's dependence on the device and the estimated or measured delivered dose. Outcomes analyzed were inappropriate ICD therapies, device malfunctions, or device-related clinical events. RESULTS: The PMs were exposed to 84.4 ± 99.7 cGy of radiation, and the ICDs were exposed to 92.1 ± 72.6 cGy of radiation. Two patients with ICDs experienced a partial reset of the ICD with the loss of historic diagnostic data after receiving 123 and 4 cGy, respectively. No device malfunction or premature battery depletion was observed at 6-month follow-up from RT completion. CONCLUSIONS: CIED malfunction due to indirect RT exposure is uncommon. Regular in-treatment or home interrogation should be done to detect and treat these events and to ensure that diagnostic data are preserved.

Characterization of an Implicitly Resistively-Loaded Monopole Antenna in Lossy Liquid Media.

Microwave tomographic imaging of the breast for cancer detection is a topic of considerable interest because of the potential to exploit the apparent high-dielectric property contrast between normal and malignant tissue. An important component in the realization of an imaging system is the antenna array to be used for signal transmission/detection. The monopole antenna has proven to be useful in our implementation because it can be easily and accurately modeled and can be positioned in close proximity to the imaging target with high-element density when configured in an imaging array. Its frequency response is broadened considerably when radiating in the liquid medium that is used to couple the signals into the breast making it suitable for broadband spectral imaging. However, at higher frequencies, the beam patterns steer further away from the desired horizontal plane and can cause unwanted multipath contributions when located in close proximity to the liquid/air interface. In this paper, we have studied the behavior of these antennas and devised strategies for their effective use at higher frequencies, especially when positioned near the surface of the coupling fluid which is used. The results show that frequencies in excess of 2 GHz can be used when the antenna centers are located as close as 2 cm from the liquid surface.