Comparison of failure modes and effects analyses and time for brachytherapy ring and tandem applicator digitization between manual and solid applicator source placement methods

PURPOSE

Ring and tandem (R&T) applicator digitization is currently performed at our institution by manually defining the extent of the applicators. Digitization can also be achieved using solid applicators: predefined, 3D models with geometric constraints. This study compares R&T digitization using manual and solid applicator methods through Failure Modes and Effects Analyses (FMEAs) and comparative time studies. We aim to assess the suitability of solid applicator method implementation for R&T cases METHODS: Six qualified medical physicists (QMPs) and two medical physics residents scored potential modes of failure of manual digitization in an FMEA as recommended by TG-100. Occurrence, severity, and detectability (OSD) values were averaged across respondents and then multiplied to form combined Risk Priority Numbers (RPNs) for analysis. Participants were trained to perform treatment planning using a developed solid applicator protocol and asked to score a second FMEA on the distinct process steps from the manual method. For both methods, participant digitization was timed. FMEA and time data were analyzed across methods and participant samples RESULTS: QMPs rated the RPNs of the current, manual method of digitization statistically lower than residents did. When comparing the unique FMEA steps between the two digitization methods, QMP respondents found no significant difference in RPN means. Residents, however, rated the solid applicator method as higher risk. Further, after the solid applicator method was performed twice by participants, the time to digitize plans was not significantly different from manual digitization CONCLUSIONS: This study indicates the non-inferiority of the solid applicator method to manual digitization in terms of risk, according to QMPs, and time, across all participants. Differences were found in FMEA evaluation and solid applicator technique adoption based on years of brachytherapy experience. Further practice with the solid applicator protocol is recommended because familiarity is expected to lower FMEA occurrence ratings and further reduce digitization times.

Pulse parameter optimizer: an efficient tool for achieving prescribed dose and dose rate with electron FLASH platforms

Purpose. Commercial electron FLASH platforms deliver ultra-high dose rate doses at discrete combinations of pulse parameters including pulse width (PW), pulse repetition frequency (PRF) and number of pulses (N), which dictate unique combinations of dose and dose rates. Additionally, collimation, source to surface distance, and airgaps also vary the dose per pulse (DPP). Currently, obtaining pulse parameters for the desired dose and dose rate is a cumbersome manual process involving creating, updating, and looking up values in large spreadsheets for every treatment configuration. This work presents a pulse parameter optimizer application to match intended dose and dose rate precisely and efficiently.Methods. Dose and dose rate calculation methods have been described for a commercial electron FLASH platform. A constrained optimization for the dose and dose rate cost function was modelled as a mixed integer problem in MATLAB (The MathWorks Inc., Version9.13.0 R2022b, Natick, Massachusetts). The beam and machine data required for the application were acquired using GafChromic film and alternating current current transformers (ACCTs). Variables for optimization included DPP for every collimator, PW and PRF measured using ACCT and airgap factors.Results. Using PW, PRF,Nand airgap factors as parameters, a software was created to optimize dose and dose rate, reaching the closest match if exact dose and dose rates are not achievable. Optimization took 20 s or less to converge to results. This software was validated for accuracy of dose calculation and precision in matching prescribed dose and dose rate.Conclusion. A pulse parameter optimization application was built for a commercial electron FLASH platform to increase efficiency in dose, dose rate, and pulse parameter prescription process. Automating this process reduces safety concerns associated with manual look up and calculation of these parameters, especially when many subjects at different doses and dose rates are to be safely managed.

Comparison of Gonadal Toxicity of Single-Fraction Ultra-High Dose Rate and Conventional Radiation in Mice

Purpose

Increasing evidence suggests that ultra-high-dose-rate (UHDR) radiation could result in similar tumor control as conventional (CONV) radiation therapy (RT) while reducing toxicity to surrounding healthy tissues. Considering that radiation toxicity to gonadal tissues can cause hormone disturbances and infertility in young patients with cancer, the purpose of this study was to assess the possible role of UHDR-RT in reducing toxicity to healthy gonads in mice compared with CONV-RT.

Methods and Materials

Radiation was delivered to the abdomen or pelvis of female (8 or 16 Gy) and male (5 Gy) C57BL/6J mice, respectively, at conventional (∼0.4 Gy/s) or ultrahigh (>100 Gy/s) dose rates using an IntraOp Mobetron linear accelerator. Organ weights along with histopathology and immunostaining of irradiated gonads were used to compare toxicity between radiation modalities.

Results

CONV-RT and UHDR-RT induced a similar decrease in uterine weights at both studied doses (∼50% of controls), which indicated similarly reduced ovarian follicular activity. Histologically, ovaries of CONV- and UHDR-irradiated mice exhibited a comparable lack of follicles. Weights of CONV- and UHDR-irradiated testes were reduced to ∼30% of controls, and the percentage of degenerate seminiferous tubules was also similar between radiation modalities (∼80% above controls). Pairwise comparisons of all quantitative data indicated statistical significance between irradiated (CONV or UHDR) and control groups (from P ≤ .01 to P ≤ .0001) but not between radiation modalities.

Conclusions

The data presented here suggest that the short-term effects of UHDR-RT on the mouse gonads are comparable to those of CONV-RT.

A framework for automated and streamlined kV cone beam computed tomography image quality assurance: a multi-institutional study

The purpose of this study was to develop and evaluate a framework to support automated standardized testing and analysis of Cone Beam Computed Tomography (CBCT) image quality QA across multiple institutions. A survey was conducted among the participating institutions to understand the variability of the CBCT QA practices. A commercial, automated software platform was validated by seven institutions participating in a consortium dedicated to automated quality assurance. The CBCT image analysis framework was used to compare periodic QA results among 23 linear accelerators (linacs) from seven institutions. The CBCT image quality metrics (geometric distortion, spatial resolution, contrast, HU constancy, uniformity and noise) data are plotted as a function of means with the upper and lower control limits compared to the linac acceptance criteria and AAPM recommendations. For example, mean geometric distortion and HU constancy metrics were found to be 0.13 mm (TG142 recommendation: ≤2 mm) and 13.4 respectively (manufacturer acceptance specification: ≤±50).Image upload and analysis process was fully automated using a MATLAB-based platform. This analysis enabled a quantitative, longitudinal assessment of the performance of quality metrics which were also compared across 23 linacs. For key CBCT parameters such as uniformity, contrast, and HU constancy, all seven institutions used stricter goals than what would be recommended based on the analysis of the upper and lower control limits. These institutional goals were also found to be stricter than that found in AAPM published guidance. This work provides a reference that could be used to machine-specific optimized tolerance of CBCT image maintenance via control charts to monitor performance we well as the sensitivity of different tests in support of a broader quality assurance program. To ensure the daily image quality needed for patient care, the optimized statistical QA metrics recommended to using along with risk-based QA.

Validating kQ =1.0 assumption in TG51 with PTW 30013 farmer chamber for Varian TrueBeam's 2.5 MV imaging beam

AAPM Report 142 recommends and the State of Ohio requires that the imaging dose be quantified in radiotherapy applications. Using the TG51 dose calibration protocol for MV Imaging dose measurement requires knowledge of the k_Q parameter for the beam quality and the ionization chamber type under investigation. The %dd(10)_x of the Varian TrueBeam 2.5 MV imaging beam falls outside the range of the available data for the calculation of the k_Q value. Due to the similarities of the 2.5 MV imaging beam and the ⁶⁰Co beam, we and others made the assumption that k_Q = 1.0 in TG51 calculations. In this study, we used the TG21 and TG51 calibration protocols in conjunction to validate that k_Q = 1.0 for the 2.5 MV imaging beam using a PTW 30013 farmer chamber. Standard measurements for TG51 absolute dosimetry QA were performed at 100 cm SSD, 10 cm depth, 10 × 10 field size, delivering 100 Monitor Units to a waterproof Farmer Chamber (PTW TN30013) for both 2.5 and 6 MV. Both the TG21 and TG51 formalisms were used to calculate the dose to water per MU at d_max (D_w/MU) for the 6 MV beam. The calculated outputs were 1.0005 and 1.0004 cGy/MU respectively. The TG21 formalism was then used to calculate (D_w/MU) for the 2.5 MV imaging beam. This value was then used in the TG51 formalism to find k_Q for the 2.5 MV imaging beam. A k_Q value of 1.00 ± 0.01 was calculated for 2.5 MV using this method.

Quality assurance for a six degrees-of-freedom table using a 3D printed phantom

Purpose

To establish a streamlined end‐to‐end test of a 6 degrees‐of‐freedom (6DoF) robotic table using a 3D printed phantom for periodic quality assurance.

Methods

A 3D printed phantom was fabricated with translational and rotational offsets and an imbedded central ball‐bearing (BB). The phantom underwent each step of the radiation therapy process: CT simulation in a straight orientation, plan generation using the treatment planning software, setup to offset marks at the linac, registration and corrected 6DoF table adjustments via hidden target test, delivery of a Winston‐Lutz test to the BB, and verification of table positioning via field and laser lights. The registration values, maximum total displacement of the combined Winston‐Lutz fields, and a pass or fail criterion of the laser and field lights were recorded. The quality assurance process for each of the three linacs were performed for the first 30 days.

Results

Within a 95% confidence interval, the overall uncertainty values for both translation and rotation were below 1.0 mm and 0.5° for each linac respectively. When combining the registration values and other uncertainties for all three linacs, the average deviations were within 2.0 mm and 1.0° of the designed translation and rotation offsets of the 3D print respectively. For all three linacs, the maximum total deviation for the Winston‐Lutz test did not exceed 1.0 mm. Laser and light field verification was within tolerance every day for all three linacs given the latest guidance documentation for table repositioning.

Conclusion

The 3D printer is capable of accurately fabricating a quality assurance phantom for 6DoF positioning verification. The end‐to‐end workflow allows for a more efficient test of the 6DoF mechanics while including other important tests needed for routine quality assurance.

Effects of general practice-based nurse-counselling on ambulatory blood pressure and antihypertensive drug prescription in patients at increased risk of cardiovascular disease

Lifestyle programmes delivered by academic nurse-counsellors in a primary care setting lowered blood pressure (BP) among at-risk patients. We examined whether the programmes could be successfully implemented by nurses employed in Australian general practices. In a randomised controlled trial, 212 of 591 eligible 20-75-year olds with hypertension, Type II diabetes or coronary disease from seven practices volunteered. Patients were randomised to: a 'Low' group with one face-to-face individual counselling session, then monthly telephone contacts for 1 year (n=69); a 'High' group with individual face-to-face counselling up to 1 h monthly for 1 year (n=74) or a control group receiving usual care only (n=69), and were evaluated at baseline and 12 and 18 months later; 164 individuals completed the study. Patients' usual doctors continued to prescribe in all groups. Changes in 24 h ambulatory BP did not differ significantly between groups at 12 months (Low, -2+/-2/1+/-1 mmHg; High, +4+/-2/1+/- 1 mmHg; usual care, +1+/-2/1+/-1 mmHg) or 18 months (-2+/-2/2+/-1 mmHg; -4+/-2/3+/-2 mmHg; -1+/-2/2+/- 1 mmHg, respectively). Antihypertensive drugs prescribed decreased by 12 months in 33% of the High, 5% of the Low and 13% of the control groups (P=0.008) and by 36, 7 and 16% at 18 months (P=0.018). After 18 months, targets for BP control were not met in about 60% of patients and almost 50% had clinic BP above 140/90 mmHg. Year-long interaction with nurse-counsellors may influence longer-term antihypertensive drug prescription, possibly by improving compliance. Suboptimal BP control suggests that continuing physician education on BP targets is needed.

Evidence for new alleles in the protein kinase adenosine monophosphate-activated gamma(3)-subunit gene associated with low glycogen content in pig skeletal muscle and improved meat quality

Several quantitative trait loci (QTL) affecting muscle glycogen content and related traits were mapped to pig chromosome 15 using a three-generation intercross between Berkshire x Yorkshire pigs. On the basis of the QTL location the PRKAG3 (protein kinase, AMP-activated, gamma(3)-subunit) gene was considered to be a good candidate for the observed effects. Differences in the PRKAG3 gene sequences of the founder animals of the intercross were analyzed. The RN(-) mutation previously reported was not present in the cross but three missense substitutions and a polymorphic short interspersed element (SINE) were identified. To confirm the hypothesis that at least one of these mutations was associated with differences in meat quality, >1800 animals from several unrelated commercial lines were genotyped for the candidate substitutions and an association study was performed. The results demonstrate the presence of new economically important alleles of the PRKAG3 gene affecting the glycogen content in the muscle and the resulting meat quality. Haplotype analysis was shown to resolve the effects of PRKAG3 more clearly than analysis of individual polymorphisms. Because of their prevalence in the more common commercial breeds, the potential implications for the pig industry and consumers are considerably greater than the original discovery of the RN(-) mutation. Furthermore, these results illustrate that additional alleles of genes involved in major mutations may play a significant role in quantitative trait variation.

A controlled trial of nurse counselling on lifestyle change for hypertensives treated in general practice: preliminary results

1. We assessed whether a lifestyle modification programme implemented by nurse counsellors in a general practice setting would improve blood pressure (BP) control in treated hypertensive patients. 2. Patients were randomized into a control group or one of two intervention groups who received either a high or low level of counselling. 3. Patients in the intervention groups had appointments every 4th week for 18 weeks. The low intervention group had one practice appointment and five telephone counselling appointments while the high intervention group had six appointments in their general practice. The patients were counselled using a stage of change behavioural model and motivational interviewing to: reduce alcohol consumption, dietary fat and salt intake and weight; cease smoking; and increase leisure time physical activity. 4. Compared with controls the low intervention group showed significant decreases in alcohol and salt intake while the high intervention resulted in significant decreases in both weight and BP. 5. We conclude that nurse counselling targeted to specific aspects of lifestyle can improve BP control and weight in treated hypertensive patients over 18 weeks. Its longer term effectiveness in the management of hypertension warrants further evaluation.

Primary immunisations in Liverpool. II: Is there a gap between consent and completion?

The association between completion of primary dipht eria, tetanus and pertussis, measles, mumps, and rubella and polio immunisation courses in Liverpool and five sociodemographic factors, namely the child's sex, position in the family, family type, migration into Liverpool since birth, and local deprivation was examined. Only 68% of children were fully immunised by their second birthday. The immunisation rate for pertussis was 74%, compared with 85-89% for the other antigens. Children who had older siblings, were recorded as living with one parent, had moved into Liverpool or who lived in areas of high deprivation were less likely to complete the full set of antigens and individual courses. Boys were significantly less likely than girls to be fully immunised against pertussis. Differences in the completion of pertussis immunisation associated with the child's sex and with local deprivation were a direct reflection of differences in rates of parental consent. Parental consent did not wholly account for significantly lower rates among children with older siblings, those living with a lone parent, and those who had moved into Liverpool, however. This may reflect the practical difficulties of attending immunisation clinics. To achieve immunisation targets, a more flexible and targeted approach is required of health professionals. This may include the careful targeting of efforts to increase consent and the improvement of access to immunisations by providing domiciliary services or by opportunistic immunisation of infants when they are in contact with primary and community health care services.

Primary immunisations in Liverpool. I: Who withholds consent?

The association between parents in Liverpool consenting to their children being invited for primary immunisations and five sociodemographic factors, namely sex, position of child in the family, family type, migration into Liverpool since birth, and local deprivation was examined. Rates of consent to invitation were over 97% for each antigen except pertussis, which had a consent rate of 83%. Consent to invitation for pertussis vaccine was least likely to have been given for boys, children with older siblings, those recorded as living with a single parent, and those in the most deprived areas. Local deprivation also had an effect on consent to the measles, mumps, and rubella vaccine. Migration into Liverpool had a significant effect on consent to invitation for all antigens except pertussis. The child's sex, family type, and local deprivation had no effect on consent to diphtheria, tetanus, and polio immunisations. Maximising pertussis vaccine uptake will require more attention to be paid to those parents who have been identified as being less likely to give consent. It is particularly important that consistent and clear advice about immunisations is made available to parents with two or more children, lone parents, and those living in materially deprived areas. Our findings challenge some of the assumptions underlying the principles of 'first parent visiting', at least so far as pertussis is concerned.