Identical Contours Research Articles

Continuing professional development - Radiation Therapy.

Journal of Medical Radiation SciencesEarly View Continuing Professional DevelopmentOpen Access Continuing professional development - Radiation Therapy First published: 08 February 2023 https://doi.org/10.1002/jmrs.655AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Maximise your CPD by reading the following selected article and answer the five questions. Please remember to self-claim your CPD and retain your supporting evidence. Answers will be available via the QR code and online at www.asmirt.org/news-and-publications/jmrs, as well as published in JMRS – Volume 70, Issue 4 December 2023. Radiation Therapy – Original Article Clinical evaluation of deep learning and atlas-based auto-segmentation for critical organs at risk in radiation therapy Gibbons E, Hoffmann M, Westhuyzen J, Hodgson A, Chick B, Last A. (2023) J Med Radiat Sci. https://doi.org/10.1002/jmrs.618 How are deep learning (DL) auto-segmentation contours produced on an incoming data set? DL models use deformable image registration to transform contours from a pre-defined library of similar data sets DL models predict contour location using optimised convolution ‘neural’ networks (CNNs) that have been trained to identify complex non-linear spatial relationships within data sets DL models generate contours by estimating spatial position on a data set using the Dice similarity coefficient (DSC) formula DL models require users to roughly contour the incoming data set by hand before the algorithm can fully optimise each organ at risk (OAR) Which of the following is correct in terms of the number of training data sets used for atlas and DL segmentation? Atlas-based auto-segmentation typically uses a larger number of training data sets than DL models If an atlas and DL auto-segmentation model are trained using the same number of data sets, they are likely to output identical contours The larger number of training data sets used in DL segmentation naturally incorporates a more diverse range of patient anatomy than atlas-based methods DL auto-segmentation models typically reach a performance plateau when trained on 10–30 data sets Which DL-based OARs experienced statistically significant time improvements over atlas-based OARs? Spinal Cord, Rectum, Bladder, Left Femoral Head Spinal Cord, Oral Cavity, Left Lung, Oesophagus, Heart Left Parotid, Spinal Cord, Left Lung, Rectum, Bladder, Left Femoral Head Left Parotid, Rectum, Bladder, Left Femoral Head For auto-segmented OAR contours, it is recommended that: All DL generated OARs should be reviewed by an expert clinician prior to clinical use All DL generated OARs are accurate enough to be used clinically without human review Only a specific list of DL generated OARs requires expert review prior to clinical use Only a specific list of atlas generated OARs require expert review prior to clinical use Why can vendor trained ‘generic’ DL models be beneficial to a radiation therapy workflow? They will always output contours that are quantitatively more accurate than a DL model trained by an individual department They are pre-optimised to output contours that will meet the specific contouring protocols for all departments worldwide The output contours will always require less editing time than a DL model trained by an individual department They can output quality contours without the time, data or resource requirements needed for departments to individually train their own DL models Recommended further reading: 1Brouwer CL, Boukerroui D, Oliveira J, et al. Assessment of manual adjustment performed in clinical practice following deep learning contouring for head and neck organs at risk in radiotherapy. Phys Imaging Radiat Oncol. 2020; 16: 54– 60. 2Sherer MV, Lin D, Elguindi S, et al. Metrics to evaluate the performance of auto-segmentation for radiation treatment planning: A critical review. Radiother Oncol. 2021; 160: 185– 91. 3van Dijk LV, Van den Bosch L, Aljabar P, et al. Improving automatic delineation for head and neck organs at risk by Deep Learning Contouring. Radiother Oncol. 2020; 142: 115– 23. Answers Scan this QR code to find the answers, or visit www.asmirt.org/news-and-publications/jmrs Early ViewOnline Version of Record before inclusion in an issue ReferencesRelatedInformation

Combining Step-and-Shoot Intensity Modulated Radiation Therapy Concomitant Boost to Tumor Bed and 3D Breast Field-in-Field Plans for Hypofractionated Breast Radiotherapy

<h3>Purpose/Objective(s)</h3> To investigate the efficacy and safety of step-and-shoot intensity modulated radiation therapy (IMRT) concomitant boost (CB) to tumor bed (TB) combined with 3D breast field-in-field (FIF) plans for hypofractionated breast radiotherapy. <h3>Materials/Methods</h3> We initiated prospective cohort study since January, 2020. The patients with early-stage breast cancer or breast ductal carcinoma in situ who received breast-conserving surgery underwent sixteen-fraction treatment. All received prescribed dose of 40 Gy 3D FIF plans to breast, CB with 8 Gy to TB by IMRT. We applied the identical contours and PTV coverage to compare the original plans with the re-plans using conventional fractions of breast FIF followed by en face electron beams to TB on the same patients. Plan quality including maximum dose, RTOG conformal index (CI) and homogeneity index (HI) of PTV_TB, mean dose and volumes irradiated to doses of 5 Gy (V₅) of heart and V₂₀ of ipsilateral lung, in addition to acute toxicity and any recurrence were evaluated. Lyman normal tissue complication probability (NTCP) model for moderate to severe breast fibrosis established by Cambridge and EORTC trials was also calculated. Paired sample t-test and Wilcoxon signed-rank test were used. <h3>Results</h3> Thirty patients with sixty treatment plans were reviewed. The majority (19/30) were pathological prognostic stage I breast cancer and half of the patients were left-sided diseases. No patient experienced more than grade 2 acute toxicity. No recurrence was observed during the follow-up. Mean HI (D₂-D₉₈/D_p × 100; where D₂ = minimum dose to the 2% of the target volume, D₉₈ = minimum dose to the 98% of the target volume, and D_p = prescribed dose) of PTV_TB is 9.4 vs. 18.5 (<i>P</i> < .05). Maximum dose divided by reference dose was also lower in the CB group by 2.9% (<i>P</i> < .05). Mean CI is 1.45 in the CB group compared to 1.63 in the conventional fraction plans (<i>P</i> = .07). In terms of EQD2, mean dose and V₅ of heart for left-sided breast cancer are similar (<i>P</i> = .12 and 0.10). Besides, mean dose and V₂₀ of ipsilateral lung are comparable (<i>P</i> = .26 and 0.43). NTCP for breast fibrosis were all lower in the CB group (Mean: 20.02% vs. 22.13%; <i>P</i> < .05). <h3>Conclusion</h3> Hypofractionated breast radiotherapy combing 3D FIF plans and IMRT CB to TB decreased breast moderate to severe fibrosis by Lyman NTCP model and improved homogenous dose distributions without excessive dose to normal tissue, when compared to conventional fractions using FIF and electron beams. It may reduce the toxicity, and is also labor-saving for patients, radiation oncologists and staff.

Dosimetric analysis of breast cancer tumor bed boost: An interstitial brachytherapy vs. external beam radiation therapy comparison for deeply seated tumors

PurposeTo dosimetrically compare interstitial brachytherapy (MIBT) vs. EBRT (3DCRT and high-energy electron beams) for deep-seated tumor bed boosts (depth ≥4 cm) in early-stage breast cancer. Methods and MaterialsPlanning CTs of fifteen left-side breast cancer patients previously treated with MIBT boost chosen for this study. MIBT, 3DCRT (three-field technique), and enface high-energy electron (15–18 MeV) plans retrospectively generated on these images. To minimize intrapatient target contour inconsistency, due to a technical limitation for transferring identical contours from brachytherapy to EBRT planning system, spherical volumes delineated as hypothetical CTVs (CTV-H) (depth ≥4 cm with considering the geometry of the brachytherapy implant) instead of original lumpectomy cavities (which had irregular contours). In EBRT, PTV-H=CTV-H+5 mm. To account for beam penumbra, additional PTV-H to beam-edge margins added (3DCRT = 5 mm; electron = 10 mm). Included organs at risk (OARs) were ipsilateral breast, skin, ribs, lung, and heart. Prescribed dose-fractionations were 12 Gy/3fractions (MIBT) and 16 Gy/8fractions (EBRT) (BED = 24 Gy, breast cancer Alpha/Beta = 4 Gy). Biologically equivalent DVH parameters for all techniques compared. ResultsMean CTV-H depth was 6 cm. Normal breast V25%–V100%; skin V10%–V90%; rib V25%–V75%; lung V5%–V25%; heart V10%; mean lung dose; ribs/lung Dmax were lower in MIBT vs. 3CDRT. MIBT reduced breast V25%–V125%; skin V25%–V125%; rib V25%–V75% and V100%; lung V25%–V90%; heart V10%–V50%; skin/ribs/lung Dmax compared to electrons. In contrast, breast V125%–V250% and V175%–V250% were increased in MIBT vs. 3DCRT and electron plans, respectively. Electron plans had the minimum mean heart dose. ConclusionsFrom a dosimetric point of view, in deeply-seated lumpectomy beds, MIBT boost better protects OARs from exposure to medium and high doses of radiation compared to 3DCRT and high energy electron beams (except more ipsilateral breast hot spots).

Indirect tone-prominence interaction in Kunming tone sandhi

Abstract Kunming exhibits a special kind of interaction between tone and prominence whereby the prosodic headedness is shown to play an indirect role in tone sandhi. Due to higher-ranked tonal faithfulness constraints, lower tones, which are universally unfavored in the head position, do not change to higher tones, and higher tones, which are universally unfavored in the non-head position, do not change to lower tones. Nonetheless, though the unfavored tone-(non-)head correlation does not directly trigger tone sandhi, it indirectly decides whether tone sandhi will take place. Falling tones, inter-syllabic tone segment disagreement, and tonal combinations with identical contours are marked tonal structures in the language. But not all these structures result in tone sandhi. The penalization of these structures is tied to an unfavored tone-(non-)head correlation; only when an undesired tone-(non-)head correlation is involved are the marked tonal structures penalized. The indirect tone-(non-)head interaction observed in Kunming is special but not unique to the language as a similar correlation is found in the Chinese dialects of Dongshi Hakka and Beijing Mandarin.

An in silico comparative dosimetric study of postmastectomy locoregional irradiation using intensity-modulated vs 3-dimensional conventional radiotherapy

An in silico dosimetric evaluation of intensity-modulated radiation therapy (IMRT) vs 3-dimensional conventional radiation therapy (3D-CRT) treatment plans in postmastectomy radiation therapy (PMRT) to the chest wall and regional lymphatics was conducted. Twenty-five consecutive patients with breast cancer referred for locoregional PMRT, stages T2-4 with N1-3, were planned to receive 50 Gy in 25 fractions with IMRT. Additionally, a 3D-CRT plan was generated using identical contours for the clinical target volumes (CTV), planning target volumes (PTV), and organs at risk (OAR). Treatment plans were assessed using dose-volume histogram (DVH) parameters of D98, D95, D50, D2, and homogeneity index for individual CTVs and PTVs. OARs evaluated were ipsilateral and contralateral lungs, heart, spinal cord, and opposite breast. Most DVH parameters pertaining to CTVs and PTVs significantly favored IMRT. V20 for ipsilateral and contralateral lungs, D33 of heart and maximum dose to spinal cord favored IMRT (all p < 0.001). The mean dose to the opposite breast was significantly lesser with 3D-CRT (5.8 ± 1.8 Gy vs 2.0 ± 1.0 Gy, p < 0.001). Thus, except for the mean dose to the opposite breast, the compliance to DVH constraints applied to PTV and OARs were significantly better with IMRT. At a median follow-up of 76 months (7-91), none had locoregional failure or pulmonary or cardiac morbidity. For PMRT, requiring comprehensive irradiation to both chest wall and regional lymphatics, IMRT offers superior dosimetric advantages over 3D-CRT. This was also corroborated by long-term outcomes in these patients treated with IMRT.

Top-Down Modulation on the Perception and Categorization of Identical Pitch Contours in Speech and Music.

Whether pitch in language and music is governed by domain-specific or domain-general cognitive mechanisms is contentiously debated. The aim of the present study was to investigate whether mechanisms governing pitch contour perception operate differently when pitch information is interpreted as either speech or music. By modulating listening mode, this study aspired to demonstrate that pitch contour perception relies on domain-specific cognitive mechanisms, which are regulated by top–down influences from language and music. Three groups of participants (Mandarin speakers, Dutch speaking non-musicians, and Dutch musicians) were exposed to identical pitch contours, and tested on their ability to identify these contours in a language and musical context. Stimuli consisted of disyllabic words spoken in Mandarin, and melodic tonal analogs, embedded in a linguistic and melodic carrier phrase, respectively. Participants classified identical pitch contours as significantly different depending on listening mode. Top–down influences from language appeared to alter the perception of pitch contour in speakers of Mandarin. This was not the case for non-musician speakers of Dutch. Moreover, this effect was lacking in Dutch speaking musicians. The classification patterns of pitch contours in language and music seem to suggest that domain-specific categorization is modulated by top–down influences from language and music.

SU‐E‐T‐730: The Dosimetry Variation Sourced From Different Kinds of TPSs Should Be Pay Attention in Adaptive Radiation Therapy of Non‐Small Cell Lung Carcinoma SBRT

Purpose:The purpose of this work was to study the differences in dosimetry computed with two treatment planning systems (TPSs) in adaptive radiation therapy of non‐small cell lung carcinoma stereotactic body radiotherapy (SBRT).Methods:3 patients with non‐small cell lung carcinoma SBRT were selected in this study. Some information, including dose‐volume histogram (DVH) data, image data and structure data, were exported from the TPS‐Eclipse 10.0 (Varian Medical Systems, Palo Alto, CA). All data were imported in Image Guided Radiotherapy Workstation Software (IGRTWS 1.0, Shanghai STFK medical device Co, Ltd, China), which is a kind of software in house for adaptive radiation therapy. Then, dosimetry was recalculated by IGRTWS.Results:There is a clinically variation in the small volume organs calculations between this two kinds of software for identical contours. The DVHs of small volume organs were also obviously different. The max dose, the min dose and the mean dose were also obviously different in small volume organs. However, the large volume of organs were less different in volume, DVHs, max dose, min dose and mean dose.Conclusion:We infer that the CT scan slice and pixel widths, the resolution of dose calculation grids and the TPS manufacturer, may be the main influence factors, which lead to the results.The results indicate that we should pay attention to the dosimetry variation sourced from different kinds of TPSs in adaptive radiation therapy of non‐small cell lung carcinoma SBRT, due to which volume of PTV is much smaller than other kinds of cancer PTV usually.

SU‐E‐T‐337: Dynamic Tomotherapy Delivery with Running‐Start‐Stop: Comparing to Conventional Tomotherapy and VMAT Deliveries

Purpose: Despite of superior target dose uniformity, previous studies of helical tomotherapy (HT) show inferior longitudinal conformity and longer deliver time compared to volumetric‐modulated arc therapy (VMAT) plans, due to fixed jaw size with conventional HT. Dynamic delivery techniques were introduced to overcome these problems. This study is to compare the dosimetric performance of dynamic tomotherapy delivery (5.0cm jaw running‐start‐stop (RSS)) with fixed jaw HT and VMAT deliveries. Methods: Sixteen patient cases, including brain, head&amp;neck (HN), lung and prostate, were selected and de‐identified prior to treatment planning. VMAT plans were generated using Varian RapidArc™ (RA) (one or two arcs) and HT plans using TomoTherapy® (fixed 2.5cm jaw). The tomotherapy RSS plans were generated using tomotherapy's research engine and optimized based on 5.0cm dynamic jaw, which allows larger jaw opening for lower dose gradient and smaller jaw opening at the target border when sharp penumbra is required. All 16 cases were planned based on identical contours, prescriptions, and planning objectives. Dose indices for targets and critical organs were compared based on dose‐volume histograms, delivery time, and monitor units. Results: The average delivery time was reduced from 4.8min (HT) to 2.92min (RSS). RSS showed comparable target dose homogeneity to HT. Three delivery techniques showed comparable normal tissue sparing for lung cases, with improved sparing of cord with RSS. For prostate cases, RSS showed improved bladder and rectum doses compared to HT due to better longitudinal sparing. Superior normal tissue sparing was observed in RSS plans for optical nerves in brain cases and larynx or parotids for HN cases. Conclusions: Tomotherapy RSS with 5.0cm dynamic jaw is overall comparable, if not better, to 2.5cm fixed jaw HT, with faster treatment delivery. It also showed improved longitudinal dose conformity to critical structures adjacent to the target, which is comparable to RA technique. Yu Chen is employee of Accuray‐Tomotherapy, Inc.

Global or local shape discrimination of radial frequency patterns?

Purpose. Color vision performs below luminance vision on global shape discrimination measured with radial frequency patterns (Mullen & Beaudot, Vision Research, 2002). This effect might reflect a genuine deficit of color on global shape processing, or it might originate from the fact that color vision is poorer at encoding local orientation. In a series of experiments we test and compare the role of local orientation cues in the shape discrimination of radial frequency (RF) patterns for chromatic and achromatic vision. Methods. Stimuli are contours described by the 4th derivative of a gaussian and form radial patterns (global task) or parts of the pattern (local task). We designed the following tasks in order to separate the role of local-orientation and global cues in the shape discrimination task: 1) we compare performance for the discrimination of local parts (corners or sides) of a RF pattern versus circular arcs of the same radius; 2) we compare the performance for the detection of line modulation versus radial frequency modulation for otherwise identical contours; 3) we compare the effect on shape discrimination of varying the spatial frequencies of the contour of the radial frequency pattern. Data were fitted with a model that uses changes in local curvature to discriminate shape. Results. We find very little performance difference between the local-orientation based tasks and the global shape discrimination task, regardless of whether stimuli were chromatic or achromatic. Conclusions. We conclude that performance on the shape discrimination of radial frequency patterns is limited by local orientation cues in our experiments. While RF patterns presumably exploit a global shape processing mechanism, this affords little or no performance advantages in the task.

A Procera® Custom Abutment Fabricated by Scanning the Provisional Abutment

Patient: The patient was a 56-year-old male presenting with a missing maxillary right central incisor. Subsequently, an endosseous implant was fiited. After a 6 month healing period, a provisional abutment was fabricated to an optimal shape on the provisional titanium component. After confirming custom-guided tissue healing and appropriate emergence profile, the provisional abutment was scanned using the Procera® scanner. The CAD/CAM custom titanium definitive abutment and the definitive porcelain fused to the metal crown were delivered as an esthetic implant restoration.Discussion: Compared to conventional procedures, the following advantages can be seen: 1. There is no access hole in the provisional restorations. 2. Appropriate soft-tissue contours can be induced by modification of provisional restoration. 3. A definitive abutment with the identical contours can be reliably obtained using CAM. 4. An extra temporary plastic component is not necessary. The disadvantages are: 1. The provisional abutment using the temporary cylinder has to be made. 2. The Procera® scanner has to be set up chair-side. 3. The patient has to wait during scanning.Conclusion: A custom Procera® abutment with an ideal emergence profile can be fabricated by scanning the provisional abutment with appropriate soft-tissue contours.

Po-topic IV-13: Dose optimization in hdr brachytherapy for cervical cancer using FDG-PET

The purpose of this study was to investigate the possibility of dose optimization in high-dose rate (HDR) intracavitary brachytherapy for the treatment of cervical cancer with tumor volumes delineated using positron emission tomography (PET). 18F-fluorodeoxyglucose (FDG)-PET scans were acquired for 10 patients with implanted tandem and ovoid (T&O) applicators containing tubes of FDG. The FDG-PET images were transferred to a commercial 3D treatment planning system where the tumor volume was defined using a binary threshold technique. Tumor tissue was identified on FDG-PET images as any voxel in the 3D data set with counts greater than a fixed threshold fraction (40%) of the peak intensity of the tumor. This threshold level was selected from information gained by correlation of FDG-PET volumes with volume of cervical tumor clearly defined on CT scan images in a series of patients with cervical cancer. The bladder and rectum were contoured by the physician who treated the patients. The tandem and ovoid applicators, which contained catheters filled with FDG, had a characteristic appearance on the FDG-PET images and were uniquely identified by their expected positions. FDG-PET based 3D treatment plans were first simulated for conventional HDR delivery. The source distribution, based on our clinical protocols, was designed to deliver 6.5 Gy to Point A under ideal conditions. Point A was identified according to the classical definition relative to the reconstructed applicators. There were nine active dwell positions in the tandem and three active positions in each of the ovoids. Maintaining identical contours on the FDG-PET images, investigational treatment plans were then created my manipulating dwell positions and dwell times. The new plans used an integrated reference air kerma that was equivalent to the conventional plans. The source arrangement that best maximized tumor coverage was found to be a tandem hypothetically extended by 2 cm superiorly, continuing along its original trajectory. The extended tandem included 15 active dwell positions. Dwell times were customized to optimize dose distributions to the individual GTV versus dose distributions for the two sets of plans were compared by percent tumor coverage and by minimum dose within tumor. The optimized plans demonstrate improvement in both tumor coverage (mean 33.0%, std 15.1%, median 31.4%) and peripheral dose (mean 32.3%, std 43.9%, median 36.0%). The optimized plans demonstrate bladder reference point doses that are increased (mean 14.1%, std 32.5%, median 13.6%) and rectal dose that are decreased (mean −31.3%, std 22.2%, median −35.2%). This study demonstrates the potential for improving HDR brachytherapy dose distributions for FDG-PET-defined cervical cancer. Superior tumor coverage and peripheral dose can be achieved by utilizing a single extended tandem applicator compared with conventional T&O dose distributions, and by optimizing source weighting to conform to the geometry of the tumor. Acceptable levels of toxicity based on bladder and rectal dose volume histograms were observed in the investigational plans of most patients.

Discrepancies in volume calculations between different radiotherapy treatment planning systems

It has been determined that, contrary to expectation, there is a clinically significant variation in the volume calculations of different RTPS (Radiotherapy Treatment Planning System) for identical contours. The situation was investigated prior to a multi-centre trial to determine whether tumour volume is an independent prognostic factor in NSCLC (non-small cell lung cancer) and included four of the commercially available RTPS. The four RTPS tested were, Theraplan Plus V3.0, Cadplan V6.2, Focus V2.6 and ADAC V3.0. Five randomly chosen clinical target related volumes (3 GTVs, one PTV and one CTV) from the trial database originally marked on the Cadplan system were transferred to the other four systems and the resulting volumes were calculated. It was found that Cadplan consistently underestimated the volume relative to the other three systems by 6-12%. This systematic underestimation was found to be caused by different assumptions made by the Cadplan system about the axial outer slice extension of the volume. Cadplan truncates the volume, while the other three systems extrapolate it by half the slice thickness at each end. A short program was written to apply the same method of volume extension to the Cadplan volume that is utilised by the other systems. This produced calculated volumes that were within +/- 1.0% of the average of the volumes calculated by the other three planning systems, and the maximum deviation from the average for any planning system was then reduced to 1.5%. This program was implemented at all participating trial centres utilising Cadplan, thus reducing the intersystem variability to a negligible factor in comparison to the estimates of inter-physician variation. This unexpected finding has significant implications for the validity of multi-centre trials using dose volume histograms, and indeed the adoption of any clinical protocol employing dose volume histogram constraints derived from experience at another centre employing a different RTPS.

Extension of the Contour-Distortion Method in Relativistic Three-Particle Scattering

The results of a previous paper, showing how to relate the physical three-baryon scattering amplitude to the solution of a generalized Bethe-Salpeter equation with a nonsingular kernel, are extended to include c.m. energies up to the threshold for production of a meson. The distorted contours that are involved for each term of the perturbation expansion are no longer topological products of identical contours in the space of each complex four-momentum, and the final integral equations are more complicated than before.