Oblique Fields Research Articles

Phantosmia during proton radiation and differences in frequency of phantosmia rates based on proton craniospinal irradiation technique for pediatric brain tumor patients.

Unusual olfactory perception, often referred to as "phantosmia" or "cacosmia" has been reported during brain radiotherapy (RT), but is infrequent and does not typically interfere with the ability to deliver treatment. We seek to determine the rate of phantosmia for patients treated with proton craniospinal irradiation (CSI) and identify any potential clinical or treatment-related associations. We performed a retrospective review of 127 pediatric patients treated with CSI, followed by a boost to the brain for primary brain tumors in a single institution between 2016 and 2021. Proton CSI was delivered with passive scattering (PS) proton technique (n=53) or pencil beam scanning technique (PBS) (n=74). Within the PBS group, treatment delivery to the CSI utilized a single posterior (PA) field (n=24) or two posterior oblique fields (n=50). We collected data on phantom smell, nausea/vomiting, and the use of medical intervention. Our cohort included 80 males and 47 females. The median age of patients was 10years (range: 3-21). Seventy-one patients (56%) received concurrent chemotherapy. During RT, 104 patients (82%) developed worsening nausea, while 63 patients (50%) reported episodes of emesis. Of those patients who were awake during CSI (n=59), 17 (29%) reported phantosmia. In the non-sedated group, we found a higher rate of phantosmia in patients treated with PBS (n=16, 42%) than PS (n=1, 4.7%) (p=.002). Seventy-eight patients (61%) required medical intervention after developing nausea/vomiting or phantosmia during RT. Two patients required sedation due to the malodorous smell during CSI. We did not find any significant difference in nausea/vomiting based on treatment technique. Proton technique significantly influenced olfactory perception with greater rates of phantosmia with PBS compared to PS. Prospective studies should be performed to determine the cause of these findings and determine techniques to minimize phantosmia during radiation therapy.

Proton pencil beam scanning craniospinal irradiation (CSI) with a single posterior brain beam: Dosimetry and efficiency

This study explores the feasibility and potential dosimetric and time efficiency benefit of proton Pencil Beam Scanning (PBS) craniospinal irradiation with a single posterior-anterior (SPA) brain field. The SPA approach was compared to our current clinical protocol using Bilateral Posterior Oblique brain fields (BPO). Ten consecutive patients were simulated in the head-first supine position on a long BOS frame and scanned using 3 mm CT slice thickness. A customized thermoplastic mask immobilized the patient's head, neck, and shoulders. A vac-lock was used to secure the legs. PBS proton plans were robustly optimized with 3mm setup errors and 3.5% range uncertainties in the Eclipse V15.6 treatment planning system (n = 12 scenarios). In order to achieve a smooth gradient dose match at the junction area, at least 5 cm overlap region was maintained between the segments and 5 mm uncertainty along the cranial-cauda direction was applied to each segment independently as additional robust optimization scenarios. The brain doses were planned by SPA or BPO fields. All spine segments were planned with a single PA field. Dosimetric differences between the BPO and SPA approaches were compared, and the treatment efficiency was analyzed according to timestamps of beam delivery. Results: The maximum brain dose increases to 111.1 ± 2.1% for SPA vs. 109.0 ± 1.7% for BPO (p < 0.01). The dose homogeneity index (D5/D95) in brain CTV was comparable between techniques (1.037 ± 0.010 for SPA and 1.033 ± 0.008 for BPO). Lens received lower maximum doses by 2.88 ± 1.58 Gy (RBE) (left) and 2.23 ± 1.37 Gy (RBE) (right) in the SPA plans (p < 0.01). No significant cochlea dose change was observed. SPA reduced the treatment time by more than 4 minutes on average and ranged from 2 to 10 minutes, depending on the beam waiting and allocation time. SPA is dosimetrically comparable to BPO, with reduced lens doses at the cost of slightly higher dose inhomogeneity and hot spots. Implementation of SPA is feasible and can help to improve the treatment efficiency of PBS CSI treatment.

Decoupling topological antiskyrmion and non-topological magnetic phases in D2d symmetric Mn–Ni–Ga single crystalline device

Here, we present the finding of two types of distinct Hall signals in the single crystalline Hall devices of a D2d symmetric antiskyrmion host Mn–Ni–Ga sample. The out-of-plane device, where the magnetic field is applied along the [001] direction, exhibits a dip-like anomaly in the Hall resistivity data, signifying the presence of topological Hall signal originating from the antiskyrmion phase. Most importantly, we demonstrate the robustness of the antiskyrmion phase against an oblique field where the topological Hall signal survives up to a tilting angle of 75° with respect to the c-axis. In contrast, the Hall resistivity data for the in-plane device exhibit an aberrant hump-like feature that can be tuned with applying a rotating magnetic field. We show that this hump-like anomaly emerges from the existence of a two-component anomalous Hall effect arising due to the presence of twinning microstructure. The present study provides an important insight into the stability and evolution of the antiskyrmion phase under the oblique magnetic fields and helps in decoupling of anomalous Hall signals in the non-topological magnetic phases.

Proton Radiation Therapy for Stage IIA/IIB Testicular Seminoma.

Testicular seminoma affects young men and is associated with very favorable prognosis. The evolution in treatment paradigm has focused on minimizing acute and especially late toxicities. Following orchiectomy, while surveillance is favored in Stage I patients, radiotherapy (RT) is a standard treatment option for de novo or relapsed stage IIA or select non-bulky stage IIB disease. Despite low doses, standard RT fields to paraaortic and pelvic lymphatics using x-rays exposes a large volume of uninvolved normal tissue/viscera to excess dose. This young patient population is especially vulnerable to risks of late RT toxicities including secondary malignancy. Proton beam therapy (PBT) has dosimetric advantage over x-ray-based RT due to lack of exit dose, and comparative dosimetric/modeling studies show significant sparing of uninvolved abdominal/pelvic organs. However, there is scant reported clinical data at this time for PBT. We review our early institutional outcomes with PBT for testicular seminoma. Single institution retrospective review from a tertiary care center of patients treated with PBT from 2013-2022 for testicular seminoma. Recurrence free (RFS) and overall survival (OS) were calculated from the completion of PBT. Toxicities were graded (Gr) using CTCAE v5.0. Four patients underwent PBT, median age 39 (range 36-47). All were Stage I at diagnosis (pT1b n = 3; pT2 n = 1) and were treated for recurrent stage II disease (IIA n = 3; IIB n = 1) at a median of 34 months from orchiectomy (range 3 - 74 months). Nodal extent included 2 with multiple paraaortic nodes, 1 with solitary paraaortic node and 1 with solitary pelvic node. PBT was delivered with pencil-beam scanning, treating paraaortic + ipsilateral pelvic fields (20 Gy in 10 fractions), then sequential boost to involved nodes (10 -16 Gy in 5-8 fractions). Typically, PA or posterior oblique fields were used to minimize dose to out-of-field abdominal/pelvic viscera. Treatment was well tolerated with minimal acute toxicities: fatigue Gr 1 (n = 3), nausea Gr 1 (n = 3). No Gr 2 or higher acute toxicities or significant late toxicities were observed. At median follow up of 30 months (range 3 - 54), no recurrences were observed, and RFS and OS were 100%. Two patients are without evidence of disease > 4 years post-treatment. In this case series, PBT for retroperitoneal and pelvic metastases in Stage IIA/IIB testicular seminoma was associated with oncologic efficacy with minimal toxicity. PBT reduces unnecessary dose to abdominal/pelvic organs compared to x-ray techniques, which is advantageous in young patients who have anticipated long-term survival. This is one of the few series reporting clinical outcomes of PBT in the management of seminoma. Randomized comparisons with x-ray approaches are impractical given the relatively low volume of patients receiving RT in modern seminoma management, so it is essential to report and track longitudinal outcomes across institutions to validate this approach.

Posterior Neck Coverage in Patients Receiving Regional Nodal Irradiation for Breast Cancer

Patterns-of-failure studies suggest the posterior neck (PN) may harbor microscopic disease in patients with locally advanced breast cancer. We compared target coverage, lung dose, and toxic effects in patients treated with either an anterior oblique field (AO) or opposed oblique fields (OO) to address the superior axillary and supraclavicular nodal (SCV) regions. We identified 119 consecutively treated patients who received regional nodal irradiation, including a "third field," to address the superior axillary and supraclavicular nodal regions with a monoisocentric technique in our institution. Coverage of the axillary clinical target volume (CTV), SCV CTV and PN CTV was determined based on the delivered treatment plan. Wilcoxon rank-sum test and Fisher's exact test were used to compare coverage of the axillary, SCV, and PN CTVs, lung dosimetry, and toxic effects (graded by the Common Terminology Criteria for Adverse Events v4.0) between patients receiving an AO or OO. There were 29 patients in the AO group and 80 in the OO group. All patients in the AO group received conventionally fractionated radiation versus 61% in the OO group. Modestly hypofractionated plans were delivered to 39% of the OO group. The body mass index and anterior-posterior separation at the matchline (measured at the center of the carotid artery) were similar in both groups. The median volume (%) of the SCV CTV receiving at least 90% of the prescription dose (V90%) was 91% (85, 99) in the AO group and 93% (91, 95) in the OO group (P = 0.2). The median V90% of the PN CTV was 30% (12, 49) in the AO group and 100% (100, 100) in the OO group (P<0.001). The median V90% in the axillary levels I, II and III CTVs were 98%, 95% and 90%, respectively, in the AO group and all 100% in the OO group (P<0.001). Maximum dose and heterogeneity in the SCV CTV were similar in both groups. Including only patients who received conventionally fractionated plans, the mean lung dose (cGy) was 1216 in the AO group and 1328 in the OO group (P = 0045). The lung V5 Gy, V10 Gy and V20 Gy were similar in both groups. Ipsilateral upper extremity lymphedema (all grade 1) was 3.4% in the AO group and 2.5% in the OO group (p>0.9). Moist desquamation in the neck was 0% in the AO group and 1.2% in the OO group (p>0.9). Pneumonitis (all grade 1) was 0% in the AO group and 1.2% in the OO group (p>0.9). Compared to a single anterior field, opposed oblique fields provide superior axillary and posterior neck coverage without increasing toxicity.

Dosimetric comparison of robust angles in carbon-ion radiation therapy for prostate cancer.

The objective of this study is to compare the plan robustness at various beam angles. Hence, the influence of the beam angles on robustness and linear energy transfer (LET) was evaluated in gantry-based carbon-ion radiation therapy (CIRT) for prostate cancer. 10 patients with prostate cancer were considered, and a total dose of 51.6 Gy (Relative biological effectiveness (RBE) was prescribed for the target volume in 12 fractions. Five beam field plans comprising two opposed fields with different angle pairs were characterized. Further, dose parameters were extracted, and the RBE-weighted dose and LET values for all angle pairs were compared. All plans considering the setup uncertainty satisfied the dose regimen. When a parallel beam pair was used for perturbed scenarios to take into account set-up uncertainty in the anterior direction, the LET clinical treatment volume (CTV) D 95% standard deviation was 1.5 times higher, and the standard deviation of RBE-weighted CTV D 95% was 7.9 times higher compared to an oblique pair. The oblique beam fields were superior in terms of dose sparing for the rectum compared to the dose distribution using two conventional lateral opposed fields for prostate cancer.

Model of Angular Object Positioning Process by a System of Oblique Friction Force Fields on Parallel Planes

Abstract The primary contribution of the paper is a proposal of a method to minimize the angular positioning error in the process of transferring cuboidal objects between oblique friction force fields generated by two conveyors located on parallel planes. The research included infeed conveyors with two variants of inputs: angular and straight. It was assumed that the object, while moving between oblique conveyors at different heights, performs a 3D movement. The object is treated as a rigid body with a soft base, edges, and corners that can be subjected to significant local deformations. A modified nonlinear Kelvin model was used to describe the normal reaction forces at the contact points of the object with the bearing surfaces of the conveyors, and the modified static Bengisu–Akay friction model represents the tangential forces. Research shows that the use of a slight offset between the bearing surfaces of the conveyors and the highest possible proportion between the motion velocities of the infeed and outfeed conveyors have positive effect on improving the angular precision of the positioned objects. This conclusion applies to both variants of the infeed conveyor inputs. The results of the research have practical application in the design of high-performance conveyor transport systems, used in the processes of picking cuboidal objects, requiring a strictly defined angular orientation.

Exposure of the heart and cardiac valves in women irradiated for breast cancer 1970–2009

PurposeTo describe cardiac exposure from breast cancer radiotherapy regimens used during 1970–2009 for the development of dose–response relationships and to consider the associated radiation-risks using existing dose–response relationships. Material and methodsRadiotherapy charts for 771 women in the Netherlands selected for case control studies of heart disease after breast cancer radiotherapy were used to reconstruct 44 regimens on a typical CT-dataset. Doses were estimated for the whole heart (WH), left ventricle (LV) and cardiac valves. ResultsFor breast/chest wall radiotherapy average WH doses decreased during 1970–2009. For internal mammary chain (IMC) radiotherapy WH doses were highest during the 1980s and 1990s when direct anterior fields were used and reduced in the 2000s when oblique fields were introduced. Average doses varied substantially for IMC regimens (WH 2–33 Gy, LV < 1–23 Gy). For cardiac valves, at least one valve received >30 Gy from most regimens. ConclusionsRadiation-risks of IHD from breast/chest wall regimens likely reduced during 1970–2009. Direct anterior IMC regimens likely increased the risks of IHD and VHD over this time period but the use of oblique IMC fields from 2003 may have lowered these risks. These data provide a unique opportunity to develop dose–response relationships.

Analysis of coil element distribution and dimension for matrix gradient coils.

The goal of this work is to analyze the influence of the distributions and dimensions of the coil elements and to present a method for improving the performance of the matrix gradient coil. Three typical models (five structures in total) are presented, and a double-layer biplanar matrix gradient coil is used to install coil elements. Two metrics, namely, the role of coil elements and mutual inductance between coil elements, are proposed to assess the performance of coil systems. An optimization approach to design matrix gradient coils is introduced based on analyzing the distributions and dimensions of coil elements. The flexibility of the magnetic field generation of the designed coil structure is demonstrated by generating full third-order spherical harmonic fields and different oblique gradient fields. Matrix gradient coils with suitable distributions are capable of generating target magnetic fields. The role of coil elements quantitatively illustrates that the coil elements have different impacts on generating magnetic fields. Increasing the coil element dimension within a certain range can reduce the mutual inductance between coil elements and improve the performance of the coil system. The designed novel double-layer biplanar matrix gradient coil achieves an acceptable performance in generating different magnetic fields. The proposed metrics can provide theoretical support for designing matrix gradient coils and evaluating their performance. The role of coil elements contributes to analyzing the distributions of coil elements to decrease the number of coil elements and power amplifiers. The mutual inductance between coil elements can be a reference for designing the dimensions of coil elements.

RONC-14. Olfactory Perception During Proton Radiation and Differences in Frequency of Olfactory Perceptions Based on Proton Craniospinal Irradiation Technique for Pediatric Brain Tumor Patients.

Abstract BACKGROUND: Unusual olfactory perception has been reported during brain radiation treatments but is infrequent and does not typically interfere with the ability to deliver treatment or cause notable distress. Methods: We performed a retrospective review of 127 pediatric patients treated with proton radiation therapy (PRT) for primary brain tumors in a single institution between 2016-2021. Patients received PRT to the brain as part of craniospinal irradiation (CSI) followed by a boost to the brain. Proton CSI was delivered with 3D-CRT protons (n=53) or pencil beam scanning technique (PBS) (n=74). Within the PBS group, treatment delivery to the CSI utilized a single PA field (n=24) or two posterior oblique fields (n=50). We collected data on abnormal olfactory sensations, nausea/vomiting, and the use of medical intervention for those symptoms. Results: Our cohort included 80 males and 47 females. The median age of patients was 10 years old (range, 3 – 21). Seventy-one patients received concurrent chemotherapy. Prior to PRT, 31 patients were nauseous. During the radiation course, 104 patients developed worsening nausea while 63 patients reported emesis. Four patients vomited while receiving radiation. Seventeen patients reported olfactory perceptions during CSI. We found a higher rate of olfactory perception in patients treated with PBS (n=16, 22%) than 3D-CRT (n=1, 2%) (p=0.001) and, within the PBS group, patients treated with a single PA field (n=11, 46%) than two oblique fields (n=5, 10%) (p=0.002). Seventy-eight patients required intervention including addition of anti-emetic or anti-anxiety medication. Two patients required sedation due to the malodorous smell during CSI. We did not find any significant difference in nausea/vomiting based on treatment technique. Conclusions: PBS and PBS technique influence olfactory perceptions but not the occurrence of the rate of nausea/vomiting. Further studies should be performed to validate these findings and determine techniques to minimize unpleasant olfactory perceptions.

Dosimetric Evaluation of 4 Field Three-Dimensional Conformal Radiation Therapy and 7 Field Intensity Modulated Radiation Therapy in Esophageal Cancer Treated with Definitive Chemoradiation

Background: The present study aimed to evaluate dosimetrically and correlate the lung and heart dose volume histogram (DVH) of the 4 Field three-dimensional conformal radiotherapy (3DCRT) with 7 field intensity modulated radiotherapy (IMRT) in patients with oesophageal cancers. Method: This retrospective dosimetric study considered 20 oesophagus cancer patients treated with definitive chemoradiation with IMRT technique. In the 7 field IMRT technique, the first phase delivered a dose of 36Gy/18fr followed by 18Gy/9fr in two weeks in the second phase. In the 3DCRT technique, the first phase was planned with 4 field technique with two parallel opposed and two posterior oblique fields, followed by the 3 field technique in the second phase. The assessments of the techniques were performed using Differential DVH analysis of the right and left lungs, heart, and the spinal cord. The values of the mean dose, V20 (Volume receiving 20 Gy), and V30 (volume receiving 30 Gy) were assessed for any correlations. Results: The DVH of V20 in IMRT showed 5 % less lung volume irradiation compared to the 3DCRT plans and over 20% less V30 for irradiated heart volume. The study demonstrated a statistical advantage of using 7 field IMRT over 4 field 3DCRT in reducing the mean percentage dose to both lungs, heart, and spinal cord. Conclusion: 7 field IMRT is superior to 4 field 3DCRT plans in significantly reducing the average percentage of irradiated volume of both the lung and heart in esophageal cancer radiation therapy.

RADT-34. OLFACTORY PERCEPTION DURING PROTON RADIATION AND DIFFERENCES IN FREQUENCY OF OLFACTORY PERCEPTIONS BASED ON PROTON CRANIOSPINAL IRRADIATION TECHNIQUE FOR PEDIATRIC BRAIN TUMOR PATIENTS

Abstract BACKGROUND Unusual olfactory perception has been reported during brain radiation treatments but is infrequent and does not typically interfere with the ability to deliver treatment or cause notable distress. METHODS We performed a retrospective review of 127 pediatric patients treated with proton radiation therapy (PRT) for primary brain tumors in a single institution between 2016-2021. Patients received PRT to the brain as part of craniospinal irradiation (CSI) followed by a boost to the brain. Proton CSI was delivered with 3D-CRT protons (n=53) or pencil beam scanning technique (PBS) (n=74). Within the PBS group, treatment delivery to the CSI utilized a single PA field (n=24) or two posterior oblique fields (n=50). We collected data on abnormal olfactory sensations, nausea/vomiting, and the use of medical intervention for those symptoms. RESULTS Our cohort included 80 males and 47 females. The median age of patients was 10 years old (range, 3 – 21). Seventy-one patients received concurrent chemotherapy. Prior to PRT, 31 patients were nauseous. During the radiation course, 104 patients developed worsening nausea while 63 patients reported episodes of emesis. Four patients vomited while receiving radiation. Seventeen patients reported olfactory perceptions during CSI. We found a higher rate of olfactory perception in patients treated with PBS (n=16, 22%) than 3D-CRT (n=1, 2%) (p=0.001) and, within the PBS group, patients treated with a single PA field (n=11, 46%) than two oblique fields (n=5, 10%) (p=0.002). Seventy-eight patients required intervention including addition of anti-emetic or anti-anxiety medication. Two patients required sedation due to the malodorous smell during CSI. We did not find any significant difference in nausea/vomiting based on treatment technique. CONCLUSIONS PBS and PBS technique influence olfactory perceptions but not the occurrence of the rate of nausea/vomiting. Further studies should be performed to validate these findings and determine techniques to minimize unpleasant olfactory perceptions.

Flared front pile supported breakwater in oblique waves

ABSTRACT Flared Front Pile Supported Breakwater (FPSB) is a new re-curved type of breakwater well suited for areas with a higher tidal variation. FPSB is expected to provide the required tranquility on its leeside as a significant amount of energy in the incoming waves will be dissipated while traversing over the re-curve. The hydrodynamic performance of FPSB in two water depths is experimentally studied under oblique wave incidence. The paper briefly explains the variation of the reflection coefficient, transmission coefficient, loss coefficient, non-dimensional pressures, and non-dimensional run-up as a function of the relative water depth and scattering parameter of the re-curve pile supported breakwater and that with a vertical front face (VPSB). The results obtained for FPSB shows that its hydrodynamic performance characteristics are better than that of VPSB in oblique wave fields.

Propagating vortices in ferrofluidic Couette flow under magnetic fields – Part II: Oblique orientated fields

This work provides a numerical investigations of propagating vortex flow states (pVs) for ferrofluidic Couette flow with small aspect ratio and fixed non-rotating end-walls. The system is subjected to oblique magnetic fields as superposition of axial and transverse orientated fields. Such field configuration breaks the basic system symmetries and renders all flow structures to be inherently three-dimensional with complexer flow dynamics. Under oblique field configuration pV states are not direct present at onset. Instead oscillating flow states (oVs) bifurcate out of the stationary state. Basically these oVs hold same symmetries as pVs, which eventually evolve in a smooth transformation out of the oVs. pVs under oblique fields appear periodic or quasi-periodic, which render them topological speaking to exist on either two- or one-dimensional invariant manifolds as 2-torus or limit cycle (1-torus) solutions, respectively. In detail, structural modifications and changes in spatial and temporal behavior for pV solutions are studied with changing the magnetic field strength of the applied magnetic field.

Using Cherenkov imaging to monitor the match line between photon and electron radiation therapy fields on biological tissue phantoms.

.Significance: Due to patients’ respiratory movement or involuntary body movements during breast cancer radiotherapy, the mismatched adjacent fields in surface exposure regions could result in insufficient dosage or overdose in these regions, which would lead to tissue injury, excessive skin burns, and potential death. Cherenkov luminescence imaging (CLI) could be used to effectively detect the matching information of adjacent radiation fields without extra radiation or invasive imaging.Aim: Our objective was to provide a biological experimental basis for monitoring matching of adjacent radiation fields between photon and electron fields due to introduced shifts during radiotherapy by CLI technique.Approach: A medical accelerator was used to generate photon and electron fields. An industrial camera system was adopted to image the excited CLI signal during irradiation of chicken tissue with yellow (group A and group C experiments) or black color (group B experiment). The following introduced shifts were tested: 10, 5, 2, and 0 mm toward superior or inferior direction. A model was introduced to deal with matching error analysis of adjacent radiation fields due to introduced shifts with adapted plans used to treat neoplasms of the right breast with supraclavicular nodes or internal mammary lymph node.Results: The matching values between photon and electron fields were consistent with the tested introduced shifts during yellow chicken irradiation. In group A, average discrepancies were and for photon fields and electron fields in anterior/posterior (AP) direction, with 87% and 75% of measurement within 1 mm, respectively. In group C, average discrepancies were and for oblique photon field with gantry angles of 330 deg and 150 deg, with 66% and 65% of measurement within 1 mm, respectively. The average discrepancies were for electron field in the AP direction, with 94% of measurement within 1 mm. The matching error introduced by the proposed method was less than 1.5 mm for AP fields and 2 mm for oblique incidence fields. However, the field matching could not be monitored with black chicken tissue irradiation due to a weak CLI signal that could hardly be extracted from background noise in group B.Conclusions: CLI is demonstrated for the quantitative monitoring of the field match line on light biological tissue phantoms and has potential for monitoring of field matching in surface tissue during breast cancer radiotherapy.

Implementation of carbon fibre treatment couches in the XiO® and Monaco® Treatment Planning Systems

Abstract Purpose: Carbon fibre treatment couches on linear accelerators provide a strong, rigid framework for patient support. Patient safety is a priority, therefore the dosimetric properties of treatment couches need to be accurately incorporated in treatment plans, to minimize differences between planned and delivered dose. This study aims to determine the attenuation effect of treatment couches for 3-D Conformal Radiotherapy (3-D CRT) and to validate the implementation thereof in the XiO and Monaco treatment planning systems (TPS). Material and methods: Attenuation measurements were performed on the ELEKTA Connexion couches of the ELEKTA Precise and Synergy-Agility linear accelerators. Measurements were made at 10° intervals in RMI-457 Solid water (30 cm x 30 cm x 30 cm) using a PTW Farmer-type ionization chamber (TW30013) positioned at the accelerator’s isocentre. The percentage attenuation was calculated as the ratio of the electrometer readings for parallel-opposed fields. The Computed Tomography (CT) data sets of the set-ups were obtained on a Philips Big Bore 16-slice CT scanner and exported to the TPS. The individual couch structures were delineated and electron density (ED) values were assigned using the commissioned CT-to-ED curve. Test treatment plans were generated with 100MU per field at 10° gantry intervals. Results: The percentage attenuation was determined to be within 2% and 3% for beams perpendicular to the couch surface for XiO and Monaco, respectively. The maximum attenuation was observed for oblique fields which was significantly higher than the manufacturer specified values. TPS validation showed an agreement to 1% for XiO and Monaco. At extreme oblique angles, both planning systems overestimated this effect up to a maximum of 4%. Conclusions: Couch attenuation differs significantly with gantry angle and beam energy. As a result, the treatment couch models should be included in all treatment planning calculations.

Model of positioning objects by the system of oblique friction force fields on horizontal and vertically offset planes

The paper presents a model of the process of angular positioning of cuboidal objects using a system of two oblique friction force fields produced by the conveyor belts located on parallel planes a and b, offset vertically by value H. It has been assumed that, while moving from friction force field a to lower placed field b, the object performs a 3D motion and comes into contact with the friction force fields at the corners, edges or the base surface. The object is treated as a rigid body with a soft surface of the bottom, which can be subjected to significant local deformations when interacting with obstacles. Two continuous collision models were used to describe the normal reaction forces at the contact points of the object with the bearing surfaces of the conveyors: the nonlinear MSC Adams model and the modified nonlinear Kelvin model. In addition, three friction models were included, i.e. two static Bengisu-Akay and MSC Adams models and one dynamic LuGre model. Numerical and experimental research demonstrate that the use of friction force fields with vertical offset of a short distance (e.g. H = 0.005 m) enhances the rotation angle Φ minimization of the object positioned.

Clinical Outcomes, Cosmesis and Quality of Life in Hypofractionation Versus Conventional Fractionation Radiotherapy to Whole Breast and Regional Nodes: A Phase II Randomized Study

Whole Breast Radiotherapy (WBRT) is indicated as adjuvant treatment in the multimodality management of Breast Cancer after Breast Cancer Surgery (BCS). Regional Nodal Irradiation (RNI) improves outcomes in patients with positive nodes after axillary dissection. Hypofractionation in WBRT is equivalent to standard fractionation in terms of long-term outcomes, but the role of hypofractionation in the settings of RNI has not been explored. We prospectively conducted a phase II randomized study comparing Hypofractionation and Standard fractionation in WBRT with RNI to evaluate clinical outcomes, cosmesis and quality of life (QOL) between the two modalities. Women aged ≥ 18 years with breast cancer undergoing BCS and axillary dissection were recruited in the study after Institutional Ethics Committee approval. 52 patients were randomized into two groups, with 26 patients in arm 1 (standard fractionation) WBRT 50Gy/25fraction/5weeks followed by boost 16Gy/8fraction and other 26 patients in arm II (hypofractionation) WBRT 40Gy/15fraction/3 weeks followed by boost 10Gy/4fraction. Contouring was done as per the standard RTOG guidelines. WBRT was planned using forward planning IMRT. Direct or oblique photon fields were used for RNI of SCF/ Axillary region as clinically indicated. Contouring and planning was done on MONACO treatment planning system. Clinical acute toxicity, late toxicity was noted with RTOG acute toxicity criteria. Quality of life (QOL) was assessed with EORTC BR 23 questionnaire. Statistical analysis was done with SPSS v 21 and p-value < 0.05 was considered as significant. All patients received planned allocated treatment and were eligible for analysis. At treatment completion, the Grade II skin toxicity was higher in arm I compared to arm II, with 84% vs 11% (p <0.01), Grade III skin toxicity was not noted in arm II, but present in 3(11%) patients of arm I (p <0.01). The skin toxicity at 6 months was similar at 6 months with only Grade I skin toxicity. At completion of radiation, good cosmesis was noted in 8(32%) patients of arm I and 20(77%) patients of arm II, whereas fair cosmesis was observed in 17 (65%) patients of arm I and 6(23%) patients of arm II. The cosmesis at 6 months post radiation was excellent in 21(80%) patients of arm I and 23(88%) patients of arm II, and good cosmesis was seen in 5(20%) patients of arm I and 3(12%) patients of arm II. The cosmesis improved in both the arms at 6 months, and the results were comparable between the groups. There was no significant difference in subcutaneous toxicity, arm toxicity or lymphedema between the two arms at 3 and 6 months. There was no difference in QOL between two arms at 3 and 6 months. WBRT with RNI is feasible with hypofractionation and it is not associated with decreased clinical outcomes as compared to standard fractionation. Lymphedema was similar with hypofractionation. The clinical acute toxicity, cosmesis and QOL was similar with hypofractionation and standard fractionation.

Normal Tissue Complication Probability for Hematologic and Gastrointestinal Toxicity in Postoperative Whole Pelvic Radiotherapy for Gynecologic Malignancies using Intensity Modulated Proton Therapy with Robust Optimization

Hematologic toxicity (HT) and gastrointestinal toxicity (GI) are often observed in the postoperative whole pelvic radiotherapy (WPRT) for gynecologic malignancies since the irradiation field contains large volume of the bone marrow (BM) and bowel bag (BB). Although proton beam therapy with single field uniform dose optimization has a potential of the risk reduction of HT compared with intensity modulated X-ray therapy (IMXT), the risk reduction of GI has not been previously described. Thus, the aim of this in silico study was to evaluate the risk of HT and GI using intensity modulated proton therapy with robust optimization (robust IMPT). This dosimetric planning study included 9 patients who had previously undergone hysterectomy and WPRT at our institution from 2008 to 2020. For robust IMPT planning, we used two posterior oblique fields and a 3.5% beam specific margin from the distal and proximal edges of clinical target volume (CTV) in water equivalent space to discern the range uncertainty. The prescribed dose was 45 GyE in 25 fractions for 99% of the CTV (CTV D99). We evaluated CTV coverage using following indicators, CTV D99, conformity index (CI), homogeneity index (HI); dose volume statistics of BM received 10 and 20 GyE (BM V10 and BM V20), and BB received 40 GyE (BB V40); the planning robustness for CTV by shifting each 5 mm for six axes; and the risk of HT and GI using the Lyman-Kutcher-Burman normal tissue complication probability (LKB-NTCP) model. The parameters of LKB-NTCP model were determined to calculate the risk of grade ≥ 3 acute HT and chronic GI such as obstruction or perforation. We performed the comparative evaluation of NTCP value for HT and GI between robust IMPT and IMXT prescribed 45 GyE in 25 fractions for 95% of the planning target volume with 7-fields step and shoot technique. The Wilcoxon signed rank test was used for all statistical comparisons. In the LKB-NTCP modeling analysis, the NTCP values for robust IMPT were significantly lower than IMXT (HT: 0.06±0.02 for robust IMPT and 0.19±0.03 for IMXT, p<0.05, and GI: 0.01±0.004 for robust IMPT and 0.03±0.01 for IMXT, p<0.05, respectively). Moreover, robust IMPT was excellent CTV coverage; the mean and standard deviation of CTV D99, CI, and HI was 45.63±0.21 GyE, 1.00±0.001, and 0.03±0.01, respectively. The dose volume statistics for BM V10, BM V20 and BB V40 were 61.41±4.47%, 53.12±4.75%, and 17.77±3.45%, respectively. Changes in the mean value of CTV D99 in the shifted plan were within 2%, except for the anterior shift plan (left: -1.05%, right: -0.91%, superior: -0.97%, inferior: -1.17%, anterior: -2.59%, and posterior: -0.10%). Robust IMPT for WPRT reduced the risk of HT and GI without compromising CTV coverage, compared with IMXT. These results indicate that robust IMPT has a clinical advantage in reducing the risk of HT and GI in the treatment of gynecologic malignances.

Effect of a Dc Oblique Magnetic Field on the Magnetic Susceptibility of the Super-Paramagnetics Nanoparticles in Very Low Damping

The Magnetic Susceptibility of an individual Super-Paramagnetic nanoparticle in a presence of DC Oblique magnetic fields of arbitrary amplitude is investigated using Brown’s continuous diffusion model. The susceptibility is calculated and compared when for extensive ranges of the anisotropy, the dc magnetic fields in the very low damping with Matrix continued Fraction. It is shown that the shape of the Spectrum of Super-Paramagnetic nanoparticles is substantially altered by applying a dc oblique field. There is also an inherent geometric dependence of the complex susceptibility on the damping parameter arising from coupling of longitudinal and transverse relaxation modes