Recommendations for using analytical anisotropic algorithm and AcurosXB for epidermal dose calculations in breast radiotherapy from an in vivo Gafchromic film study.

BACKGROUND AND PURPOSE: This study recommends clinical epidermal dose calculation methods based on in-vivo film measurements and registered skin dose distributions with the Eclipse (Varian Medical Systems) treatment planning system's Analytical Anisotropic Algorithm (AAA) and Acuros XB (AXB) dose calculation algorithms. MATERIALS AND METHODS: Eighteen AAA V13.6 breast plans were recalculated using AXB (dose to medium) V13.5 with the same beam parameters and monitor units as in the original plans. These are compared against in-vivo Gafchromic film measurements from the lateral and inferior breast regions. Three skin structures in the treatment planning system are evaluated: a surface layer of voxels of the body contour, a 0.2 cm internal skin rind, and a 0.5 cm internal skin rind. RESULTS: Systematic shifts are demonstrated between the film measurements of skin dose and the Eclipse dose calculations. On average, the dose to the surface layer of pixels is underestimated by AAA by 8% and overestimated by AXB by 3%. A 5 mm skin rind extended into the body can increase epidermal dose calculations on average by 8% for AAA and 4% for AXB. CONCLUSION: This is the first study to register in-vivo skin dose distributions in the breast to the treatment planning system for comparison. Based on the results from this study it is recommended that epidermal dose is calculated with a 0.5 cm skin rind for the AAA algorithm and with rind thickness up to 0.2 cm for the AXB algorithm.

Four-dimensional treatment planning strategies for dynamic tumor tracking.

INTRODUCTION: Dynamic tumor tracking (DTT) is a motion management technique where the radiation beam follows a moving tumor in real time. Not modelling DTT beam motion in the treatment planning system leaves an organ at risk (OAR) vulnerable to exceeding its dose limit. This work investigates two planning strategies for DTT plans, the "Boolean OAR Method" and the "Aperture Sorting Method," to determine if they can successfully spare an OAR while maintaining sufficient target coverage. MATERIALS AND METHODS: A step-and-shoot intensity modulated radiation therapy (sIMRT) treatment plan was re-optimized for 10 previously treated liver stereotactic ablative radiotherapy patients who each had one OAR very close to the target. Two planning strategies were investigated to determine which is more effective at sparing an OAR while maintaining target coverage: (1) the "Boolean OAR Method" created a union of an OAR's contours from two breathing phases (exhale and inhale) on the exhale phase (the planning CT) and protected this combined OAR during plan optimization, (2) the "Aperture Sorting Method" assigned apertures to the breathing phase where they contributed the least to an OAR's maximum dose. RESULTS: All 10 OARs exceeded their dose constraints on the original plan four-dimensional (4D) dose distributions and average target coverage was V100%  = 91.3% ± 2.9% (ranging from 85.1% to 94.8%). The "Boolean OAR Method" spared 7/10 OARs, and mean target coverage decreased to V100%  = 87.1% ± 3.8% (ranging from 80.7% to 93.7%). The "Aperture Sorting Method" spared 9/10 OARs and the mean target coverage remained high at V100%  = 91.7% ± 2.8% (ranging from 84.9% to 94.5%). CONCLUSIONS: 4D planning strategies are simple to implement and can improve OAR sparing during DTT treatments. The "Boolean OAR Method" improved sparing of OARs but target coverage was reduced. The "Aperture Sorting Method" further improved sparing of OARs and maintained target coverage.

Toward a Skin Dose-Area Metric Predictive of Moist Desquamation Using In Vivo Skin Dosimetry and Skin Assessments.

Purpose: Moist desquamation (MD) is a concerning acute side effect of radiation therapy for breast cancer, often seen in skin folds for patients having large or pendulous breasts. In vivo skin dosimetry, clinical assessments, and patient-reported skin reactions were used to determine a relationship between dose-area metrics and the development of MD, to lend insight into skin tolerances and possibly guide future treatment planning dose constraints. Methods and Materials: Skin dose was measured using GafChromic film on the inner surface of an early prototype carbon-fiber accessory for breast support to remove the inframammary fold in 20 patients at high risk of developing MD undergoing adjuvant whole breast radiation therapy. Prescribed doses were 42.5 Gray (Gy) in 16 fractions or 50 Gy in 25 fractions using 6 to 15 MV x-rays. To account for fraction size differences, analysis was performed using the equivalent dose in 2 Gy fractions using α/ß = 11 (EQD211). MD was assessed out to 2 weeks post radiation therapy by trained therapists and by a patient-reported outcome questionnaire. Results: Statistically significant differences in areas receiving 30 to 48 Gy (EQD211) were observed between patients who did and did not develop MD in the inframammary area. Patients receiving EQD211 maximum dose ≤ 46 Gy and ≥ 38 Gy to ≤ 50 cm2 of their breast skin did not develop MD. Conclusions: The findings of this study offer insight into the relationship between skin toxicity and areas of skin irradiated to doses up to 50 Gy. Potential skin dose constraints to test in future studies to prevent MD are suggested.

Monte Carlo Modeling of Dynamic Tumor Tracking on a Gimbaled Linear Accelerator.

Purpose and Aim: The Vero4DRT (Brainlab AG) linear accelerator is capable of dynamic tumor tracking (DTT) by panning/tilting the radiation beam to follow respiratory-induced tumor motion in real time. In this study, the panning/tilting motion is modeled in Monte Carlo (MC) for quality assurance (QA) of four-dimensional (4D) dose distributions created within the treatment planning system (TPS). Materials and Methods: Step-and-shoot intensity-modulated radiation therapy plans were optimized for 10 previously treated liver patients. These plans were recalculated on multiple phases of a 4D computed tomography (4DCT) scan using MC while modeling panning/tilting. The dose distributions on each phase were accumulated to create a respiratory-weighted 4D dose distribution. Differences between the TPS and MC modeled doses were examined. Results: On average, 4D dose calculations in MC showed the maximum dose of an organ at risk (OAR) to be 10% greater than the TPS' three-dimensional dose calculation (collapsed cone [CC] convolution algorithm) predicted. MC's 4D dose calculations showed that 6 out of 24 OARs could exceed their specified dose limits, and calculated their maximum dose to be 4% higher on average (up to 13%) than the TPS' 4D dose calculations. Dose differences between MC and the TPS were greatest in the beam penumbra region. Conclusion: Modeling panning/tilting for DTT has been successfully modeled with MC and is a useful tool to QA respiratory-correlated 4D dose distributions. The dose differences between the TPS and MC calculations highlight the importance of using 4D MC to confirm the safety of OAR doses before DTT treatments.

Reduction in Doses to Organs at Risk and Normal Tissue During Breast Radiation Therapy With a Carbon-Fiber Adjustable Reusable Accessory.

PURPOSE: This pilot study (ClinicalTrials.gov NCT04543851) investigates a novel breast positioning device using a low density, high tensile carbon-fiber cradle to support the breast, remove the inframammary fold, and reduce dose to organs at risk for whole breast radiation therapy in the supine position. METHODS AND MATERIALS: Thirty patients with inframammary folds ≥1 cm or lateral ptosis in supine treatment position were planned with standard positioning and with a carbon-fiber Adjustable Reusable Accessory (CARA) breast support. Twenty patients received whole breast with or without regional nodal irradiation with 42.5 Gy in 16 fractions or 50 Gy in 25 fractions using CARA. Median body mass index was 32 in this study. RESULTS: CARA removed all inframammary folds and reduced V20Gyipsilateral lung, V105%breast, and V50% body, without compromising target coverage. Median (range) V20Gyipsilateral lung for whole breast radiation therapy was 12.3% (1.4%-28.7%) with standard of care versus 10.9% (1.2%-17.3%) with CARA (Wilcoxon P = .005). Median V105% breast was 8.0% (0.0%-29%) with standard of care versus 4.0% (0.0%-23%) with CARA (P = .006) and median V50% body was 3056 mL (1476-5285 mL) versus 2780 mL (1415-5123 mL) with CARA (P = .001). CARA was compatible with deep inspiration breath hold and achieved median V25Gyheart = 0.1% (range 0%-1.9%) for all patients with left breast cancer. Skin reactions with CARA were consistent with historical data and daily variation in treatment setup was consistent with standard supine positioning. CONCLUSIONS: CARA can reduce V105%breast, lung and normal tissue dose, and remove the inframammary fold for breast patients with large or pendulous breasts and high body mass index treated in the supine position, without compromising target coverage. CARA will undergo further study in a randomized controlled trial.

Four-dimensional dose calculations for dynamic tumour tracking with a gimbal-mounted linear accelerator.

PURPOSE: In this study we present a novel method for re-calculating a treatment plan on different respiratory phases by accurately modeling the panning and tilting beam motion during DTT (the "rotation method"). This method is used to re-calculate the dose distribution of a plan on multiple breathing phases to accurately assess the dosimetry. METHODS: sIMRT plans were optimized on a breath hold computed tomography (CT) image taken at exhale (BHexhale ) for 10 previous liver stereotactic ablative radiotherapy patients. Our method was used to re-calculate the plan on the inhale (0%) and exhale (50%) phases of the four-dimensional CT (4DCT) image set. The dose distributions were deformed to the BHexhale CT and summed together with proper weighting calculated from the patient's breathing trace. Subsequently, the plan was re-calculated on all ten phases using our method and the dose distributions were deformed to the BHexhale CT and accumulated together. The maximum dose for certain organs at risk (OARs) was compared between calculating on two phases and all ten phases. RESULTS: In total, 26 OARs were examined from 10 patients. When the dose was calculated on the inhale and exhale phases six OARs exceeded their dose limit, and when all 10 phases were used five OARs exceeded their limit. CONCLUSION: Dynamic tumor tracking plans optimized for a single respiratory phase leave an OAR vulnerable to exceeding its dose constraint during other respiratory phases. The rotation method accurately models the beam's geometry. Using deformable image registration to accumulate dose from all 10 breathing phases provides the most accurate results, however it is a time consuming procedure. Accumulating the dose from two extreme breathing phases (exhale and inhale) and weighting them properly provides accurate results while requiring less time. This approach should be used to confirm the safety of a DTT treatment plan prior to delivery.

Plant defensin AhPDF1.1 is not secreted in leaves but it accumulates in intracellular compartments.

• Apart from their antifungal role, plant defensins have recently been shown to be involved in abiotic stress tolerance or in inhibition of root growth when added in plant culture medium. We studied the subcellular localization of these proteins, which may account for these different roles. • Stable and transient expression of AhPDF1.1::GFP (green fluorescent protein) fusion proteins were analysed in yeast and plants. Functional tests established that the GFP tag did not alter the action of the defensin. Subcellular localization of AhPDF1.1 was characterized: by imaging AhPDF1.1::GFP together with organelle markers; and by immunolabelling AhPDF1.1 in Arabidopsis halleri and Arabidopsis thaliana leaves using a polyclonal serum. • All our independent approaches demonstrated that AhPDF1.1 is retained in intracellular compartments on the way to the lytic vacuole, instead of being addressed to the apoplasm. • These findings challenge the commonly accepted idea of secretion of defensins. The subcellular localization highlighted in this study could partly explain the dual role of plant defensins on plant cells and is of major importance to unravel the mechanisms of action of these proteins at the cellular level.

Clinical and echocardiographic correlates of plasma B-type natriuretic peptide levels in patients with aortic valve stenosis and normal left ventricular ejection fraction.

BACKGROUND: Several studies suggest that BNP testing may help define the timing of aortic valve surgery in patients with aortic valve stenosis (AVS) prior onset of overt LV systolic dysfunction. The aim of this study was to identify clinical and echocardiographic correlates of plasma BNP levels in a large cohort of patients with AVS and preserved LV ejection fraction. METHOD AND RESULTS: One hundred thirty-five consecutive patients were prospectively included in the present study (Mean age 73 ± 13 years old, 66 (49%) male). Eighty-nine patients (66%) had severe AVS (aortic valve area <0.6 cm(2) /m(2) BSA). Plasma BNP levels, clinical and comprehensive Doppler echocardiography evaluation was performed in all patients. Independent clinical correlates of plasma BNP levels (R(2) = 0.19) were older age (P < 0.0001) and presence of AVS symptoms (P = 0.004). Independent echocardiographic correlates of plasma BNP levels (R(2) = 0.38) were E/Ea ratio (P = 0.01), LV mass index (P = 0.018), left atrial surface (P < 0.0001) and systolic pulmonary artery pressure (sPAP; P = 0.004). Overall, independent correlates of plasma BNP levels (R(2) = 0.47) were older age (P = 0.001), known coronary artery disease (P = 0.047), increased LV mass index (P = 0.001), left atrial enlargement (P = 0.002), and increased sPAP (P = 0.003). CONCLUSIONS: In patients with AVS and normal LV ejection fraction, plasma BNP predominantly reflects the clinical and echocardiographic consequences of afterload burden imposed on the left ventricle rather than the severity of valve stenosis, per se.

The cytosolic tail dipeptide Ile-Met of the pea receptor BP80 is required for recycling from the prevacuole and for endocytosis.

Pea (Pisum sativum) BP80 is a vacuolar sorting receptor for soluble proteins and has a cytosolic domain essential for its intracellular trafficking between the trans-Golgi network and the prevacuole. Based on mammalian knowledge, we introduced point mutations in the cytosolic region of the receptor and produced chimeras of green fluorescent protein fused to the transmembrane domain of pea BP80 along with the modified cytosolic tails. By analyzing the subcellular location of these chimera, we found that mutating Glu-604, Asp-616, or Glu-620 had mild effects, whereas mutating the Tyr motif partially redistributed the chimera to the plasma membrane. Replacing both Ile-608 and Met-609 by Ala (IMAA) led to a massive redistribution of fluorescence to the vacuole, indicating that recycling is impaired. When the chimera uses the alternative route, the IMAA mutation led to a massive accumulation at the plasma membrane. Using Arabidopsis thaliana plants expressing a fluorescent reporter with the full-length sequence of At VSR4, we demonstrated that the receptor undergoes brefeldin A-sensitive endocytosis. We conclude that the receptors use two pathways, one leading directly to the lytic vacuole and the other going via the plasma membrane, and that the Ileu-608 Met-609 motif has a role in the retrieval step in both pathways.

Impact of valvuloarterial impedance on left ventricular longitudinal deformation in patients with aortic valve stenosis and preserved ejection fraction.

BACKGROUND: Left ventricular (LV) longitudinal deformation is a good marker of intrinsic myocardial dysfunction in pressure overload cardiomyopathies. AIM: To assess the effect of valvuloarterial haemodynamic load on LV longitudinal deformation in patients with aortic valve stenosis (AVS) and preserved LV ejection fraction (LVEF). METHODS: Global LV longitudinal strain (GLS) was measured using speckle tracking imaging in a series of 82 consecutive patients with AVS (mean age 75+/-10 years; 50% men). The global (valvular+arterial) haemodynamic load imposed on the LV was estimated by the valvuloarterial impedance (Z(va)), and was calculated using either arm-cuff systolic peripheral blood pressure or systolic central aortic blood pressure estimated by SphygmoCor. RESULTS: Among this series of 82 patients with preserved LVEF, 79% had reduced LV GLS (<-18%). LV GLS correlated weakly with AVS severity, systemic vascular resistance and systemic arterial compliance. However, there was a good inverse correlation between increase in Z(va) and impairment of LV GLS (r=0.41 p<0.0001). On multivariable analysis, impaired GLS was associated with increased Z(va) (p<0.0001), increased E/Ea ratio (p=0.001) and increased LV end-diastolic volume index (p=0.021), while indices of valvular load were not. Utilization of estimated central aortic blood pressure in place of brachial pressure did not improve the performance of Z(va) to predict GLS. CONCLUSION: The magnitude of the global haemodynamic load as reflected by Z(va) is a powerful determinant of altered LV longitudinal deformation in AVS patients with preserved LVEF. The calculation of Z(va) may be useful to identify the patients who are potentially at higher risk for the development of myocardial dysfunction. Use of estimated central aortic pressure in the calculation of Z(va) does not appear to provide any incremental predictive value over that calculated with the simple measurement of brachial pressure.

Clinical significance of unsuspected rise in cardiac troponin in the setting of falls in older people.

OBJECTIVES: To assess the clinical significance of unsuspected rise in cardiac troponin I (cTnI) levels in elderly patients who have fallen. DESIGN: Monocentre prospective observational pilot study. PARTICIPANTS: Consecutive elderly patients (age >65 years) referred to the emergency department after being immobilised on the ground after a fall. MEASUREMENTS: Clinical, laboratory and Doppler echocardiography data were collected on admission to assess the cardiac correlates of increased cTnI. The survival endpoint was a composite of death or cardiovascular event. RESULTS: 60 patients were included in this study. Mean age was 81+/-8 years. Cardiac TnI was > or =0.05 ng/ml in at least one blood sample in 40 patients (67%). New diagnosis of cardiac disease was performed in 14 patients, 13 of them had cTnI > or =0.05 ng/ml. Transient apical ballooning was diagnosed in six patients. During a median follow-up of 92 (49-131) days death occurred in six patients, myocardial infarction in three, stroke in one and acute heart failure in five. Cardiac TnI > or =0.05 ng/ml was a predictor of these events (p=0.034). CONCLUSION: An unsuspected rise in cTnI correlates with new diagnosis of cardiac disease and is a potential marker of stress induced cardiomyopathy in elderly patients who fall. Cardiac TnI might be a strong predictor of outcome in these patients.

Characterization of a putative 3-deoxy-D-manno-2-octulosonic acid (Kdo) transferase gene from Arabidopsis thaliana.

The structures of the pectic polysaccharide rhamnogalacturonan II (RG-II) pectin constituent are remarkably evolutionary conserved in all plant species. At least 12 different glycosyl residues are present in RG-II. Among them is the seldom eight-carbon sugar 3-deoxy-d-manno-octulosonic acid (Kdo) whose biosynthetic pathway has been shown to be conserved between plants and Gram-negative bacteria. Kdo is formed in the cytosol by the condensation of phosphoenol pyruvate with d-arabinose-5-P and then activated by coupling to cytidine monophosphate (CMP) prior to its incorporation in the Golgi apparatus by a Kdo transferase (KDTA) into the nascent polysaccharide RG-II. To gain new insight into RG-II biosynthesis and function, we isolated and characterized null mutants for the unique putative KDTA (AtKDTA) encoded in the Arabidopsis genome. We provide evidence that, in contrast to mutants affecting the RG-II biosynthesis, the extinction of the AtKDTA gene expression does not result in any developmental phenotype in the AtkdtA plants. Furthermore, the structure of RG-II from the null mutants was not altered and contained wild-type amount of Rha-alpha(1-5)Kdo side chain. The cellular localization of AtKDTA was investigated by using laser scanning confocal imaging of the protein fused to green fluorescent protein. In agreement with its cellular prediction, the fusion protein was demonstrated to be targeted to the mitochondria. These data, together with data deduced from sequence analyses of higher plant genomes, suggest that AtKDTA encodes a putative KDTA involved in the synthesis of a mitochondrial not yet identified lipid A-like molecule rather than in the synthesis of the cell wall RG-II.

Identification and isolation of a pectin methylesterase isoform that could be involved in flax cell wall stiffening.

Pectin methylesterases (PMEs) are ubiquitous enzymes present in the plant cell wall. They catalyse the demethylesterification of homogalacturonic acid units of pectins, which, in turn, can be associated with different physiological phenomena. In this study, different flax (Linum usitatissimum L.) PME isoforms were observed: neutral (pI 7.0 and 7.5, MW: 110 kDa), basic (pI 8.3 and 8.5, MW: 110 kDa) and very basic (pI>9.5, MW: 38 kDa). In an attempt to identify most of the expressed cell wall LuPME isoforms, polyclonal antibodies were raised against a conserved region of PME. These antibodies allowed the purification of the very basic PME isoform (pI 9.5, MW: 36 kDa) from flax cells, designated LuPME5. This isoform corresponds to the Lupme5 cDNA isolated, at the same time, from flax hypocotyls, by using the RACE-PCR technique. Semi-quantitative PCR experiments showed that the Lupme5 transcript was highly expressed in the hypocotyl zones where elongation is being achieved. Thus, this enzyme may be involved in cell wall stiffening.