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.

Abstract P345: Plasma Insulin Like Growth Factor Binding Protein-7 and Tissue Inhibitor of Metalloproteinase-2 are Associated with Reduced Renal Blood Flow and Change in Kidney Function After Revascularization in Human Atherosclerotic Renovascular Disease RVD

Background: Insulin-like growth factor binding protein7 (IGFBP-7) and tissue inhibitor of metalloproteinase-2 (TIMP-2) reflect G1-cell cycle arrest and are used as biomarkers for AKI. Recent studies show that these biomarkers rise in ischemic conditions and suggest that they actually may limit the severity of AKI. We tested the hypothesis that renal vein [IGFBP-7]*[TIMP-2] correlate with reductions in renal blood flow (RBF) and post-stent single kidney (SK)-GFR changes in patients with RVD undergoing contrast-based imaging and stent revascularization

Methods: Inpatient studies were performed during 150 mEq Na+ intake and ACE/ARB Rx in patients with hemodynamically severe RVD (n=29, Doppler velocity = 318 ± 100cm/sec, and eGFR= 34.7 ± 11.7 mL/ min) scheduled for renal artery stenting, and compared to essential hypertensive (EH) healthy controls (n=32). Cortical and medullary RBFs (by multidetector CT) and renal vein levels of IGFBP-7 and TIMP-2 were measured before renal artery stenting and 3 months later

Results: Pre-stenting IGFBP-7 and TIMP-2 levels were elevated in RVD compared to EH (18.5±2. vs 15.7±1.5 and 97.4±23.1vs 62.7±9.2 ng/mL respectively, P <0.0001). Baseline renal vein levels of IGFBP-7 * TIMP-2 correlated inversely with pre-stent RBF (r= - 0.53, P=0.01) and directly with the change (%) in SK-GFR observed 3 months after stenting

Conclusion: IGFBP-7 and TIMP-2 levels are elevated in patients with chronic RVD as a function of the baseline reduction in RBF, and associate with subsequent improvement in SK-GFR 3 months after revascularization. These data are consistent with renovascular occlusion inducing cell-cycle arrest that serves to protect kidney function.

Differences in GFR and Tissue Oxygenation, and Interactions between Stenotic and Contralateral Kidneys in Unilateral Atherosclerotic Renovascular Disease

BACKGROUND AND OBJECTIVES

Atherosclerotic renal artery stenosis (ARAS) can reduce renal blood flow, tissue oxygenation, and GFR. In this study, we sought to examine associations between renal hemodynamics and tissue oxygenation with single-kidney function, pressor hormones, and inflammatory biomarkers in patients with unilateral ARAS undergoing medical therapy alone or stent revascularization.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Nonrandomized inpatient studies were performed in patients with unilateral ARAS (>60% occlusion) before and 3 months after revascularization (n=10) or medical therapy (n=20) or patients with essential hypertension (n=32) under identical conditions. The primary study outcome was change in single-kidney GFR. Individual kidney hemodynamics and volume were measured using multidetector computed tomography. Tissue oxygenation (using R(2)* as a measure of deoxyhemoglobin) was determined by blood oxygen level-dependent magnetic resonance imaging at 3 T. Renal vein neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemoattractant protein-1 (MCP-1), and plasma renin activity were measured.

RESULTS

Total GFR did not change over 3 months in either group, but the stenotic kidney (STK) GFR rose over time in the stent compared with the medical group (+2.2[-1.8 to 10.5] versus -5.3[-7.3 to -0.3] ml/min; P=0.03). Contralateral kidney (CLK) GFR declined in the stent group (43.6±19.7 to 36.6±19.5 ml/min; P=0.03). Fractional tissue hypoxia fell in the STK (fraction R(2)* >30/s: 22.1%±20% versus 14.9%±18.3%; P<0.01) after stenting. Renal vein biomarkers correlated with the degree of hypoxia in the STK: NGAL(r=0.3; P=0.01) and MCP-1(r=0.3; P=0.02; more so after stenting). Renal vein NGAL was inversely related to renal blood flow in the STK (r=-0.65; P<0.001). Biomarkers were highly correlated between STK and CLK, NGAL (r=0.94; P<0.001), and MCP-1 (r=0.96; P<0.001).

CONCLUSIONS

These results showed changes over time in single-kidney GFR that were not evident in parameters of total GFR. Furthermore, they delineate the relationship of measurable tissue hypoxia within the STK and markers of inflammation in human ARAS. Renal vein NGAL and MCP-1 indicated persistent interactions between the ischemic kidney and both CLK and systemic levels of inflammatory cytokines.

Quantitative assessment of hepatic fibrosis in an animal model with magnetic resonance elastography

Chronic liver disease is a world-wide problem that causes progressive hepatic fibrosis as a hallmark of progressive injury. At present, the gold standard for diagnosing hepatic fibrosis is liver biopsy, which is an invasive method with many limitations, including questionable accuracy and risks of complications. MR elastography (MRE), a phase-contrast MRI technique for quantitatively assessing the mechanical properties of soft tissues, is a potential noninvasive diagnostic method to assess hepatic fibrosis. In this work, MRE was evaluated as a quantitative method to assess the in vivo mechanical properties of the liver tissues in a knockout animal model of liver fibrosis. This work demonstrates that the shear stiffness of liver tissue increases systematically with the extent of hepatic fibrosis, as measured by histology. A linear correlation between liver stiffness and fibrosis extent was well-defined in this animal model. An additional finding of the study was that fat infiltration, commonly present in chronic liver disease, does not significantly correlate with liver stiffness at each fibrosis stage and thus does not appear to interfere with the ability of MRE to assess fibrosis extent. In conclusion, MRE has the potential not only for assessing liver stiffness, but also for monitoring potential therapies for hepatic fibrosis.

Cdx protein interaction with Hoxa5 regulatory sequences contributes to Hoxa5 regional expression along the axial skeleton

Hox gene functions are intimately linked to correct developmental expression of the genes. The identification of cis-acting regulatory sequences and their associated trans-acting factors constitutes a key step in deciphering the mechanisms underlying the correct positioning of the functional domain of Hox genes along the anterior-posterior axis. We have identified DNA elements driving Hoxa5 regionalized expression in mice, using the 2.1-kb mesodermal enhancer (MES) localized in Hoxa5 3' flanking sequences as a starting point. The MES sequence comprises regulatory elements targeting Hoxa5 expression in the limbs, the urogenital and gastrointestinal tracts, and the cervical-upper thoracic region of the prevertebral column. A 164-bp DNA fragment within the MES caudally restricts Hoxa5 expression at the level of prevertebra 10, corresponding to the posterior limit of its functional domain. Cdx proteins directly bind to this element in vitro via two conserved sites. Preventing Cdx binding by mutating the sites causes caudal expansion of the transgene expression domain. Of all three murine Cdx proteins that bind this element in vitro, Cdx4 has emerged as a potential regional posterior repressor of Hoxa5 expression. The restrictive control provided by Cdx interactions with Hoxa5 regulatory sequences may be one of the critical events in cervicothoracic axial specification.

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.