The epidemiology of pulmonary Mycobacterium abscessus species in Japanese population.

BACKGROUND: Mycobacterium abscessus species (MABS) is now a most virulent rapidly growing mycobacteria (RGM), and the rapid increase of MABS was recently observed worldwide, including in Japan. Thus, we gathered evidences of the presence of pulmonary MABS in Japanese population from Japanese articles. METHODS: we searched studies that addressed the isolation of pulmonary non-tuberculous Mycobacteria (NTM) or MABS from clinical respiratory specimens in Japan. RESULTS: the ratio of MABS to NTM was 3.04% (95% confidence interval [CI]: 2.51-3.68), found using the meta-analysis of single proportions. The estimated mean age of patients infected with MABS was 67.72 years (95% CI: 65.41-70.02), found using the meta-analysis of single means. The estimated proportion of females, never smoker, and the co-infection with Mycobacterium avium complex (MAC) was 66.75% (95% CI: 59.23-73.50), 67.57% (95% CI: 62.43-72.32), and 36.74% (95% CI: 25.30-49.90), respectively. The characteristics of MABS in Japan were considerably different from that in Europe and United States from the perspective of age, gender, and complications, wherein the patients in these countries tended to be younger, had lower number of females, and had more occurrences of hereditary diseases, including cystic fibrosis (CF). CONCLUSION: we hypothesized that the characteristics of MABS in the Japanese were involved in those of non-CF MABS, and the distribution of gender and age of MABS were similar to that of MAC in the Japanese.

[Analysis of Preventive Cases Using Resilience Engineering in Radiotherapy Department].

PURPOSE: Resilience engineering is the ability of a system to adjust its own functions and maintain the required behavior in the face of changes and disturbances, and resilience potential is a necessary requirement. We aimed to clarify the relationship between resilience potential and error prevention cases. METHOD: Based on the error cases reported in our department, we aggregated the relationship with resilience potential for each radiation treatment process. RESULT: As a result of tabulating the relationship, we were able to recognize and prevent errors by taking preventive measures from past cases. On the other hand, in cases that slipped through the check mechanism, errors were discovered because of a sense of discomfort in unusual situations, and some error cases could be prevented by increasing the resilience potential. CONCLUSION: This study found that preparation, observation, coping, and utilization of past experiences are related to resilience potential in preventive cases.

CT number calibration audit in photon radiation therapy.

BACKGROUND: Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs. PURPOSE: The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρe ). METHODS: A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρe over the multiple points on the curve (Δρm and Δρe,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρe for the specific TEMs (ΔρTEM and Δρe,TEM , respectively) were calculated by subtracting the ρ or ρe of the TEMs from the theoretical CT-ρ or CT-ρe calibration curve. RESULTS: The mean ± standard deviation (SD) of Δρm and Δρe,m for the Gammex phantom were -1.1 ± 1.2 g/cm3 and -0.2 ± 1.1, -0.3 ± 0.9 g/cm3 and 0.8 ± 1.3, and -0.9 ± 1.3 g/cm3 and 1.0 ± 1.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm and Δρe,m for the CIRS phantom were 0.3 ± 0.8 g/cm3 and 0.9 ± 0.9, 0.6 ± 0.6 g/cm3 and 1.4 ± 0.8, and 0.2 ± 0.5 g/cm3 and 1.6 ± 0.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρm for Tomotherapy TPSs was 2.1 ± 1.4 g/cm3 for soft tissues, which is larger than those for other TPSs. The mean ± SD of Δρe,TEM for the Gammex brain phantom (BRN-SR2) was -1.8 ± 0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs. CONCLUSIONS: Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes.

Association between hospital-acquired functional decline and 2-year readmission or mortality after cardiac surgery in older patients: a multicenter, prospective cohort study.

BACKGROUND: Hospital-acquired functional decline (HAFD) is a new predictor of poor prognosis in hospitalized older patients. AIMS: We aimed to assess the impact of HAFD on the prognosis of older cardiac surgical patients 2 years after discharge. METHODS: This multicenter prospective cohort study assessed 293 patients with cardiac disease aged ≥ 65 years who underwent cardiac surgery at 7 Japanese hospitals between June 2017 and June 2018. The primary endpoint was the composite outcome of cardiovascular-related readmission and all-cause mortality 2 years after discharge. HAFD was assessed using the total Short Physical Performance Battery at hospital discharge. RESULTS: The primary outcome was observed in 17.3% of the 254 included patients, and HAFD was significantly associated with the primary outcome. Female sex (hazard ratio [HR], 2.451; 95% confidence interval [CI] 1.232-4.878; P = 0.011), hemoglobin level (HR, 0.839; 95% CI 0.705-0.997; P = 0.046), preoperative frailty (HR, 2.391; 95% CI 1.029-5.556; P = 0.043), and HAFD (HR, 2.589; 95% CI 1.122-5.976; P = 0.026) were independently associated with the primary outcome. The incidence rate of HAFD was 22%, with female sex (odds ratio [OR], 1.912; 95% CI 1.049-3.485; P = 0.034), chronic obstructive pulmonary disease (OR, 3.958; 95% CI 1.413-11.086; P = 0.009), and the time interval (days) between surgery and the start of ambulation (OR, 1.260, 95% CI 1.057-1.502; P = 0.010) identified as significant factors. DISCUSSION: HAFD was found to be an independent prognostic determinant of the primary outcome 2 years after discharge. CONCLUSION: HAFD prevention should be prioritized in the hospital care of older cardiac surgery patients.

Stoichiometric CT number calibration using three-parameter fit model for ion therapy.

PURPOSE: Treatment planning for ion therapy involves the conversion of computed tomography number (CTN) into a stopping-power ratio (SPR) relative to water. The purpose of this study was to create a CTN-to-SPR calibration table using a stoichiometric CTN calibration model with a three-parameter fit model for ion therapy, and to demonstrate its effectiveness by comparing it with a conventional stoichiometric CTN calibration model. METHODS: We inserted eight tissue-equivalent materials into a CTN calibration phantom and used six CT scanners at five radiotherapy institutes to scan the phantom. We compared the theoretical CTN-to-SPR calibration tables created using the three-parameter fit and conventional models to the measured CTN-to-SPR calibration table in three tissue types: lung, adipose/muscle, and cartilage/spongy bone. We validated the estimated SPR differences in all cases and in a worst-case scenario, which revealed the largest estimated SPR difference in lung tissue. RESULTS: For all cases, the means ± standard deviations of the estimated SPR difference for the three-parameter fit method model were -0.1 ± 1.0%, 0.3 ± 0.7%, and 2.4 ± 0.6% for the lung, adipose/muscle, and cartilage/spongy bone, respectively. For the worst-case scenario, the estimated SPR differences of the conventional and the three-parameter fit models were 2.9% and -1.4% for the lung tissue, respectively. CONCLUSIONS: The CTN-to-SPR calibration table of the three-parameter fit model was consistent with that of the measurement and decreased the calibration error for low-density tissues, even for the worst-case scenario.

Hospital-Acquired Functional Decline and Clinical Outcomes in Older Cardiac Surgical Patients: A Multicenter Prospective Cohort Study.

This study aimed to determine the effect of hospital-acquired functional decline (HAFD) on prognosis, 1-year post-hospital discharge, of older patients who had undergone cardiac surgery in seven Japanese hospitals between June 2017 and June 2018. This multicenter prospective cohort study involved 247 patients with cardiac disease aged ≥65 years. HAFD was defined as a decrease in the short physical performance battery at hospital discharge compared with before surgery. Primary outcomes included a composite outcome of frailty severity, total mortality, and cardiovascular readmission 1-year post-hospital discharge. Secondary outcomes were changes in the total score and sub-item scores in the Ki-hon Checklist (KCL), assessed pre- and 1-year postoperatively. Poor prognostic outcomes were observed in 33% of patients, and multivariate analysis identified HAFD (odds ratio [OR] 3.43, 95% confidence interval [CI] 1.75-6.72, p < 0.001) and low preoperative gait speed (OR 2.47, 95% CI 1.18-5.17, p = 0.016) as independent predictors of poor prognosis. Patients with HAFD had significantly worse total KCL scores and subscale scores for instrumental activities of daily living, mobility, oral function, and depression at 1-year post-hospital discharge. HAFD is a powerful predictor of prognosis in older patients who have undergone cardiac surgery.

Protocol for a multicentre, prospective observational cohort study in Japan: association among hospital-acquired disability, regular exercise and long-term care dependency in older patients after cardiac surgery.

INTRODUCTION: Cardiac surgery for older patients, postoperative functional decline and the need for long-term care have received increasing attention as essential outcomes in recent years. Therefore, prevention of functional decline and long-term care dependency after cardiac surgery are important; however, our current understanding of postoperative functional trajectory and effects of postoperative regular exercise on long-term functional decline and long-term care dependency is limited. Therefore, we will conduct a multicentre, prospective cohort study to (1) examine the effect of hospital-acquired disability on long-term functional decline and long-term care dependency and (2) investigate the favourable effect of postoperative regular exercise on long-term functional decline and long-term care dependency in older patients after cardiac surgery. METHODS AND ANALYSIS: We designed a prospective, multicentre cohort study to enrol older patients aged≥65 years undergoing elective coronary artery bypass graft or valve surgery. We will conduct medical record reviews to collect data on patient demographics, comorbidities, operative details, progression of in-hospital postoperative cardiac rehabilitation and functional trajectory from a few days before cardiac surgery to the day before hospital discharge. They will be followed up for 2 years to obtain information on their health status including functional status, regular exercise and clinical events by mail. Primary endpoints of this study are long-term functional decline and long-term care dependency after cardiac surgery. Secondary endpoints are readmission due to cardiac events or all-cause mortality. ETHICS AND DISSEMINATION: The study protocol was approved by the Ethics Committee of the Department of Physical Therapy, Faculty of Health Science, Juntendo University, and of each collaborating hospital. We obtained written informed consent from all study participants after the description of the study procedures. Publication of the study results is anticipated in 2025.

Perioperative changes in physical performance affect short-term outcome in elderly cardiac surgery patients.

AIM: The effect of changes in physical performance during the perioperative period on the prognosis of older patients undergoing cardiac surgery has not been studied in detail. This study aimed to investigate the effect of perioperative changes in physical performance on the prognosis of older patients undergoing cardiac surgery. METHODS: A total of 223 patients were graded as either frail or non-frail according to a cutoff score of 9 based on preoperative Short Physical Performance Battery scores. The non-frail patients were further grouped into high, recovery, or decreased score groups, depending on their score at the time of discharge compared with preoperative scores. Basic characteristics, preoperative and postoperative clinical data, 6-month post-discharge mortality, readmission rates, and vital function (Kihon Checklist scores) were compared. RESULTS: In total, 16.1% of patients were in the frail group, while 18.4%, 35.4%, and 30.1% were in the decreased, recovery, and high score groups, respectively. The Short Physical Performance Battery scores in the decreased group were significantly lower at discharge, and the rate of readmission was significantly higher (17.7%, P < 0.05). In addition, the Kihon Checklist scores were significantly lower than the preoperative scores (5.7 ± 4.0 vs 8.6 ± 5.5, P < 0.05). CONCLUSIONS: Both preoperative and postoperative physical performance must be considered when predicting the prognosis of older patients undergoing cardiac surgery. Geriatr Gerontol Int 2021; 21: 676-682.

High lymphocyte population-related predictive factors for a long-term response in non-small cell lung cancer patients treated with pemetrexed: a retrospective observational study.

BACKGROUND: Regimens combining pemetrexed (PEM) and immune checkpoint inhibitors (ICIs) targeting programmed cell death-1 (PD-1) or programmed death-ligand 1 (PD-L1) are widely used for the treatment of advanced non-squamous non-small-cell lung cancer (NSq-NSCLC). Recently, PEM was shown to induce immunogenic cell death (ICD) and to enhance immune-regulatory genes. Some patients demonstrate an extremely long-term response to PEM. It is possible that the continued response in these patients is dependent on not only the pharmacological induction of cytotoxic cell death but also antitumor immunity. However, factors that can predict outcomes associated with long-term PEM administration using blood test results have not yet been elucidated. We investigated the clinical characteristics and predictive factors in patients with advanced NSq-NSCLC who underwent long-term PEM maintenance therapy. METHODS: In total, 504 patients with advanced NSq-NSCLC who received PEM combination therapy/monotherapy (n = 414) or paclitaxel (PTX) combination therapy (n = 90) between January 2010 and November 2019 were recruited; 381 patients were retained for the final analysis. Patients treated with PEM (n = 301) were divided into subgroups according to the total cycles of PEM (≥ 17 [n = 25] for the long-term administration group and ≤ 16 [n = 276] for the intermediate/short-term group) and compared with another population (n = 80) treated with PTX combination regimen. We investigated clinical features and predictive biomarkers, focusing on immune-regulatory factors, absolute lymphocyte count (ALC), neutrophil-to-lymphocyte ratio (NLR), and PD-1 and PD-L1 expression, to predict long-term response to PEM. RESULTS: The long-term PEM administration group exhibited a higher ALC and a lower NLR than the shorter-term group did. Both these markers displayed greater association with progression-free survival and overall survival in the PEM combination therapy group than in the PTX combination therapy group. Increased PD-1 lymphocytes were associated with the long-term PEM response group, as PD-L1 expression in tumors was associated with a high incidence of immune-related adverse effects following ICI administration. CONCLUSIONS: ALC, NLR, and PD-1 expression are PEM-mediated predictive biomarkers that are indirectly related to tumor immunity and can provide useful predictive information on the long-term response to PEM in patients with NSq-NSCLC.

Clinical Significance of Continuable Treatment with Nintedanib Over 12 Months for Idiopathic Pulmonary Fibrosis in a Real-World Setting.

PURPOSE: The INPULSIS-ON study suggested the safety and tolerability of long-term nintedanib treatment for idiopathic pulmonary fibrosis (IPF). However, there are no real-world studies on long-term nintedanib treatment. The main aim of the study was to investigate the efficacy and the tolerability of long-term treatment with nintedanib for IPF in clinical practice. PATIENTS AND METHODS: This retrospective study enrolled 104 IPF patients who underwent treatment with nintedanib. Among these patients, 51 were able to receive nintedanib for more than 12 months (ie, treatment with nintedanib over 12 months was possible [P group]) and 53 were not able to receive nintedanib for more than 12 months (ie, treatment with nintedanib over 12 months was impossible [I group]). The tolerability and efficacy of nintedanib were compared between the two groups. RESULTS: In the I group, 29 patients were unable to continue nintedanib therapy because of adverse effects, including diarrhea and nausea/anorexia. In addition, 19 and four patients could not continue nintedanib treatment because of IPF progression and worsening of performance status (PS), respectively. One patient suddenly died during nintedanib treatment. The incidence of nausea/anorexia in the I group was significantly higher than in the P group (49.06 vs 25.49%). The survival time was significantly longer in the P group than in the I group (35 vs 12 months). The decline in forced vital capacity was significantly larger in the I group than in the P group (165 vs 10 mL/year). Poor PS at nintedanib initiation was the only significant risk factor for nintedanib treatment discontinuation over 12 months. Finally, the survival time was significantly longer in patients with good PS than in those with poor PS (27 vs 13 months). CONCLUSION: Poor PS can result in discontinuation of nintedanib after 12 months. Long-term nintedanib treatment may be effective for survival.

Formulation of objective indices to quantify machine failure risk analysis for interruptions in radiotherapy.

OBJECTIVES: To evaluate the effect of interruption in radiotherapy due to machine failure in patients and medical institutions using machine failure risk analysis (MFRA). MATERIAL AND METHODS: The risk of machine failure during treatment is assigned to three scores (biological effect, B; occurrence, O; and cost of labor and repair parts, C) for each type of machine failure. The biological patient risk (BPR) and the economic institution risk (EIR) are calculated as the product of B and O ( B × O ) and C and O ( C × O ), respectively. The MFRA is performed in two linear accelerators (linacs). RESULT: The multileaf collimator (MLC) fault has the highest BPR and second highest EIR. In particular, TrueBeam has a higher BPR and EIR for MLC failures. The total EIR in TrueBeam was significantly higher than that in Clinac iX. The minor interlock had the second highest BPR, whereas a smaller EIR. Meanwhile, the EIR for the LaserGuard fault was the highest, and that for the monitor chamber fault was the second highest. These machine failures occurred in TrueBeam. The BPR and EIR should be evaluated for each linac. Further, the sensitivity of the BPR, it decreased with higher T 1 / 2 and α/ß values. No relative difference is observed in the BPR for each machine failure when T 1 / 2 and α/ß were varied. CONCLUSION: The risk faced by patients and institutions in machine failure may be reduced using MFRA. ADVANCES IN KNOWLEDGE: For clinical radiotherapy, interruption can occur from unscheduled downtime with machine failures. Interruption causes sublethal damage repair. The current study evaluated the effect of interruption in radiotherapy owing to machine failure on patients and medical institutions using a new method, that is, machine failure risk analysis.

Development of a CT number calibration audit phantom in photon radiation therapy: A pilot study.

PURPOSE: In photon radiation therapy, computed tomography (CT) numbers are converted into values for mass density (MD) or relative electron density to water (RED). CT-MD or CT-RED calibration tables are relevant for human body dose calculation in an inhomogeneous medium. CT-MD or CT-RED calibration tables are influenced by patient imaging (CT scanner manufacturer, scanning parameters, and patient size), the calibration process (tissue-equivalent phantom manufacturer, and selection of tissue-equivalent material), differences between tissue-equivalent materials and standard tissues, and the dose calculation algorithm applied; however, a CT number calibration audit has not been established. The purposes of this study were to develop a postal audit phantom, and to establish a CT number calibration audit process. METHODS: A conventional stoichiometric calibration conducts a least square fit of the relationships between the MD, material weight, and measured CT number, using two parameters. In this study, a new stoichiometric CT number calibration scheme has been empirically established, using three parameters to harmonize the calculated CT number with the measured CT number for air and lung tissue. In addition, the suitable material set and the minimal number of materials required for stoichiometric CT number calibration were determined. The MDs and elemental weights from the International Commission on Radiological Protection Publication 110 were used as standard tissue data, to generate the CT-MD and CT-RED calibration tables. A small-sized, CT number calibration phantom was developed for a postal audit, and stoichiometric CT number calibration with the phantom was compared to the CT number calibration tables registered in the radiotherapy treatment planning systems (RTPSs) associated with five radiotherapy institutions. RESULTS: When a least square fit was performed for the stoichiometric CT number calibration with the three parameters, the calculated CT number showed better agreement with the measured CT number. We established stoichiometric CT number calibration using only two materials because the accuracy of the process was determined not by the number of used materials but by the number of elements contained. The stoichiometric CT number calibration was comparable to the tissue-substitute calibration, with a dose difference less than 1%. An outline of the CT number calibration audit was demonstrated through a multi-institutional study. CONCLUSIONS: We established a new stoichiometric CT number calibration method for validating the CT number calibration tables registered in RTPSs. We also developed a CT number calibration phantom for a postal audit, which was verified by the performances of multiple CT scanners located at several institutions. The new stoichiometric CT number calibration has the advantages of being performed using only two materials, and decreasing the difference between the calculated and measured CT numbers for air and lung tissue. In the future, a postal CT number calibration audit might be achievable using a smaller phantom.

Prognostic differences among patients with idiopathic interstitial pneumonias with acute exacerbation of varying pathogenesis: a retrospective study.

BACKGROUND: Acute exacerbation of chronic fibrosing idiopathic interstitial pneumonias (AE-IIPs) is associated with a high mortality rate. In 2016, an international working group proposed a revised diagnostic criteria for AE-IIPs, suggesting that it be classified as idiopathic or triggered. Many factors are known to trigger AE-IIPs, including surgery, infection, and drugs. However, it is unknown which AE-IIPs triggers have a worse prognosis. We aimed to investigate the prognosis of patients with various clinical types of AE-IIPs, particularly infection-triggered, non-infection triggered, and idiopathic AE-IIPs. METHODS: We retrospectively collected data from 128 chronic fibrosing IIPs (CF-IIPs) patients who were hospitalized by respiratory failure between April 2009 and March 2019 at Juntendo University Hospital. Among these patients, we evaluated 79 patients who developed AE-IIPs and 21 who developed pneumonia superimposed on CF-IIPs. Patients with AE-IIPs were classified into three types: idiopathic, infection-triggered, and non-infection-triggered AE-IIPs. We analyzed differences in patient characteristics, examination findings; level of serum markers, results of pulmonary function, and radiological findings, prior treatment for baseline CF-IIPs, and prognosis. We then evaluated the risk factor for early death (death within 30 days from the onset of AE-IIPs) associated with AE-IIPs. RESULTS: Among the patients who developed AE-IIPs, 34 were characterized as having idiopathic, 25 were characterized as having infection-triggered, and 20 were categorized as having non-infection-triggered AE-IIPs. Survival time for pneumonia superimposed on IIPs was significantly longer than that for any AE-IIPs. Survival time for bacterial pneumonia superimposed on CF-IIPs was significantly longer than that for AE-IIPs (for each idiopathic and all triggered IIPs). Thereafter, survival time for infection-triggered was significantly longer than for idiopathic or non-infection-triggered AE-IIPs. The mortality rate was significantly lower in infection-triggered AE-IIPs than in other types of AE-IIPs. Furthermore, the incidence of infection-triggered AE-IIPs in winter was significantly higher than that in other seasons. Moreover, the clinical AE-IIPs types and radiological findings at AE-IIP onset were significant risk factors for AE-IIPs-induced early death. CONCLUSIONS: Our findings suggest that patients with infection-triggered AE-IIPs can expect a better prognosis than can patients with other clinical types of AE-IIPs.

Factors related to physical functioning decline after cardiac surgery in older patients: A multicenter retrospective study.

BACKGROUND: As few studies have examined physical functioning changes after cardiac surgery, the factors related to the decline in physical functioning remain unclear. This study aimed to investigate the factors related to physical functioning decline after cardiac surgery in older patients. METHODS: The final study sample consisted of 523 older (≥65 years) patients (age 74.2±6.1 years, 66% male) who underwent cardiac surgery at 8 Japanese institutions. We excluded patients who were unable to walk independently or had a slow gait speed (<0.8m/s) before surgery, and those who were unable to regain independent walking after surgery. We divided the patients into two groups, a decline-in-gait-speed group and a non-decline-in-gait-speed group, according to whether their gait speed was less than 0.8m/s at discharge. We analyzed patients' clinical characteristics to identify the factors that predicted the postoperative decline in gait speed. RESULTS: Eighty-nine patients (17.0%) showed a postoperative decline in gait speed. Multivariate logistic regression analysis showed that the following factors predicted a postoperative decline in gait speed: age [odds ratio (OR) 1.06, 95% confidence interval (CI) 1.02-1.11]; estimated glomerular filtration rate (OR 0.98, CI 0.96-0.99); preoperative gait speed (OR 0.01, CI 0.00-0.08); and the postoperative day on which the patient could walk independently (OR 1.08, CI 1.02-1.14). CONCLUSIONS: Physical functioning declined in 17% of patients after surgery. The decline could be predicted by several clinical factors, including some that are modifiable. These results suggest that further interventional research on rehabilitation before and after cardiac surgery for older patients might help overcome the decline in physical functioning.

Tolerance levels of mass density for CT number calibration in photon radiation therapy.

Computed tomography (CT) data are required to calculate the dose distribution in a patient's body. Generally, there are two CT number calibration methods for commercial radiotherapy treatment planning system (RTPS), namely CT number-relative electron density calibration (CT-RED calibration) and CT number-mass density calibration (CT-MD calibration). In a previous study, the tolerance levels of CT-RED calibration were established for each tissue type. The tolerance levels were established when the relative dose error to local dose reached 2%. However, the tolerance levels of CT-MD calibration are not established yet. We established the tolerance levels of CT-MD calibration based on the tolerance levels of CT-RED calibration. In order to convert mass density (MD) to relative electron density (RED), the conversion factors were determined with adult reference computational phantom data available in the International Commission on Radiological Protection publication 110 (ICRP-110). In order to validate the practicability of the conversion factor, the relative dose error and the dose linearity were validated with multiple RTPSes and dose calculation algorithms for two groups, namely, CT-RED calibration and CT-MD calibration. The tolerance levels of CT-MD calibration were determined from the tolerance levels of CT-RED calibration with conversion factors. The converted RED from MD was compared with actual RED calculated from ICRP-110. The conversion error was within ±0.01 for most standard organs. It was assumed that the conversion error was sufficiently small. The relative dose error difference for two groups was less than 0.3% for each tissue type. Therefore, the tolerance levels for CT-MD calibration were determined from the tolerance levels of CT-RED calibration with the conversion factors. The MD tolerance levels for lung, adipose/muscle, and cartilage/spongy-bone corresponded to ±0.044, ±0.022, and ±0.045 g/cm3 , respectively. The tolerance levels were useful in terms of approving the CT-MD calibration table for clinical use.

A novel risk analysis of clinical reference dosimetry based on failure modes and effects analysis.

PURPOSE: The output of a linear accelerator (linac) is one of the most important quality assurance (QA) factors in radiotherapy. However, there is no quantitative rationale for frequency and tolerance. The purpose of this study is to develop a novel risk analysis of clinical reference dosimetry based on failure modes and effects analysis (FMEA). METHODS: Clinical reference dosimetry data and the daily output data of two linacs (Clinac iX and Clinac 6EX) at Hiroshima University Hospital were analyzed. The analysis involved the number of patients per year for five types of fractionations. Risk priority number (RPN) is defined as the product of occurrence (O), severity (S), and detectability (D) in standard FMEA. In addition, we introduced "severity due to output drifting" (mean output change per day) (S') and the number of patients per year for five types of fractionations (W). We calculated the RPN = O × S × D × S' × W and quantitatively evaluated the risk for clinical reference dosimetry. RESULTS: Fewer fractions and less output calibration frequency resulted in higher RPN. Since clinical reference dosimetry data has a drift effect, which is missing in human processes, it was essential to use S' in addition to standard FMEA. Moreover, the parameter W was important in evaluating interinstitutional QA for clinical reference dosimetry. The relative risk of Clinac 6EX to Clinac iX was different approximately by twofold. CONCLUSIONS: We developed a novel index that can quantitatively evaluate risk for clinical reference dosimetry of each facility and machines in common on the basis of FMEA.

Interfractional diaphragm changes during breath-holding in stereotactic body radiotherapy for liver cancer.

AIM AND BACKGROUND: IGRT based on bone matching may produce a large target positioning error in terms of the reproducibility of expiration breath-holding on SBRT for liver cancer. We evaluated the intrafractional and interfractional errors using the diaphragm position at the end of expiration by utilising Abches and analysed the factor of the interfractional error. MATERIALS AND METHODS: Intrafractional and interfractional errors were measured using a couple of frontal kV images, planning computed tomography (pCT) and daily cone-beam computed tomography (CBCT). Moreover, max-min diaphragm position within daily CBCT image sets with respect to pCT and the maximum value of diaphragm position difference between CBCT and pCT were calculated. RESULTS: The mean ± SD (standard deviation) of the intra-fraction diaphragm position variation in the frontal kV images was 1.0 ± 0.7 mm in the C-C direction. The inter-fractional diaphragm changes were 0.4 ± 4.6 mm in the C-C direction, 1.4 ± 2.2 mm in the A-P direction, and -0.6 ± 1.8 mm in the L-R direction. There were no significant differences between the maximum value of the max-min diaphragm position within daily CBCT image sets with respect to pCT and the maximum value of diaphragm position difference between CBCT and pCT. CONCLUSIONS: Residual intrafractional variability of diaphragm position is minimal, but large interfractional diaphragm changes were observed. There was a small effect in the patient condition difference between pCT and CBCT. The impact of the difference in daily breath-holds on the interfractional diaphragm position was large or the difference in daily breath-holding heavily influenced the interfractional diaphragm change.

Tolerance levels of CT number to electron density table for photon beam in radiotherapy treatment planning system.

The accuracy of computed tomography number to electron density (CT-ED) calibration is a key component for dose calculations in an inhomogeneous medium. In a previous work, it was shown that the tolerance levels of CT-ED calibration became stricter with an increase in tissue thickness and decrease in the effective energy of a photon beam. For the last decade, a low effective energy photon beam (e.g., flattening-filter-free (FFF)) has been used in clinical sites. However, its tolerance level has not been established yet. We established a relative electron density (ED) tolerance level for each tissue type with an FFF beam. The tolerance levels were calculated using the tissue maximum ratio (TMR) and each corresponding maximum tissue thickness. To determine the relative ED tolerance level, TMR data from a Varian accelerator and the adult reference computational phantom data in the International Commission on Radiological Protection publication 110 (ICRP-110 phantom) were used in this study. The 52 tissue components of the ICRP-110 phantom were classified by mass density as five tissues groups including lung, adipose/muscle, cartilage/spongy-bone, cortical bone, and tooth tissue. In addition, the relative ED tolerance level of each tissue group was calculated when the relative dose error to local dose reached 2%. The relative ED tolerances of a 6 MVFFF beam for lung, adipose/muscle, and cartilage/spongy-bone were ±0.044, ±0.022, and ±0.044, respectively. The thicknesses of the cortical bone and tooth groups were too small to define the tolerance levels. Because the tolerance levels of CT-ED calibration are stricter with a decrease in the effective energy of the photon beam, the tolerance levels are determined by the lowest effective energy in useable beams for radiotherapy treatment planning systems.

Split-VMAT technique to control the expiratory breath-hold time in liver stereotactic body radiation therapy.

PURPOSE: In this study, we demonstrate the feasibility of using split-arcs in volumetric modulated arc therapy (VMAT), tailored for expiratory breath-hold in stereotactic body radiation therapy (SBRT) for liver tumors. We compare it with three-dimensional conformal radiation therapy (3D-CRT) and continuous-VMAT, for ten randomly selected hepatocellular carcinoma cases. METHODS: Four coplanar and four non-coplanar beams were used for the 3D-CRT plans. A pair of partial arcs, chosen using a back-and-forth rotating motion, were used for the continuous-VMAT plans. Split-VMAT plans were created using the same arc range as the continuous-VMAT plans, but were split into smaller arcs (<90°), to simulate an expiratory breath hold of <15s. The dose distribution, treatment delivery efficiency, and patient specific quality assurance of the split-VMAT, were verified to ensure that the outcomes were equal, or better than, those for 3D-CRT and continuous-VMAT. The prescription was 48Gy/4 fractions, to 95% of the PTV, using 10MV FFF X-ray beams. RESULTS: The mean dose of the liver-GTV was lower in the split-VMAT compared with that of 3D-CRT. Split-VMAT was more conformal compared with 3D-CRT. The total treatment time for split-VMAT was shorter than that of 3D-CRT. Similar dosimetric indices were observed for split-VMAT and continuous-VMAT. All VMAT plans passed the gamma acceptance test. CONCLUSIONS: Split-VMAT designed to accommodate an expiratory breath-hold period of 15s is a feasible and efficient use of liver SBRT, because it does not compromise the quality of the plan, when compared with 3D-CRT or continuous-VMAT.