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BACKGROUND: Auto-segmentation of organs-at-risk (OARs) in the head and neck (HN) on computed tomography (CT) images is a time-consuming component of the radiation therapy pipeline that suffers from inter-observer variability. Deep learning (DL) has shown state-of-the-art results in CT auto-segmentation, with larger and more diverse datasets showing better segmentation performance. Institutional CT auto-segmentation datasets have been small historically (n < 50) due to the time required for manual curation of images and anatomical labels. Recently, large public CT auto-segmentation datasets (n > 1000 aggregated) have become available through online repositories such as The Cancer Imaging Archive. Transfer learning is a technique applied when training samples are scarce, but a large dataset from a closely related domain is available. PURPOSE: The purpose of this study was to investigate whether a large public dataset could be used in place of an institutional dataset (n > 500), or to augment performance via transfer learning, when building HN OAR auto-segmentation models for institutional use. METHODS: Auto-segmentation models were trained on a large public dataset (public models) and a smaller institutional dataset (institutional models). The public models were fine-tuned on the institutional dataset using transfer learning (transfer models). We assessed both public model generalizability and transfer model performance by comparison with institutional models. Additionally, the effect of institutional dataset size on both transfer and institutional models was investigated. All DL models used a high-resolution, two-stage architecture based on the popular 3D U-Net. Model performance was evaluated using five geometric measures: the dice similarity coefficient (DSC), surface DSC, 95th percentile Hausdorff distance, mean surface distance (MSD), and added path length. RESULTS: For a small subset of OARs (left/right optic nerve, spinal cord, left submandibular), the public m

PURPOSE: This study aimed to analyse correlations between planning factors including plan geometry and plan complexity with robustness to patient setup errors. METHODS: Multiple-target brain stereotactic radiosurgery (SRS) plans were obtained through the Trans-Tasman Radiation Oncology Group (TROG) international treatment planning challenge (2018). The challenge dataset consisted of five intra-cranial targets with a 20 Gy prescription. Setup error was simulated using an in-house tool. Dose to targets was assessed via dose covering 99 % (D99 %) of gross tumour volume (GTV) and 98 % of planning target volume (PTV). Dose to organs at risk was assessed using volume of normal brain receiving 12 Gy and maximum dose covering 0.03 cc of brainstem. Plan complexity was assessed via edge metric, modulation complexity score, mean multi-leaf collimator (MLC) gap, mean MLC speed and plan modulation. RESULTS: Even for small (0.5 mm/°) errors, GTV D99 % was reduced by up to 20 %. The strongest correlation was found between lower complexity plans (larger mean MLC gap and lower edge metric) and higher robustness to setup error. Lower complexity plans had 1 %-20 % fewer targets/scenarios with GTV D99 % falling below the specified tolerance threshold. These complexity metrics correlated with 100 % isodose volume sphericity and dose conformity, though similar conformity was achievable with a range of complexities. CONCLUSIONS: A higher level of importance should be directed towards plan complexity when considering plan robustness. It is recommended when planning multi-target SRS, larger MLC gaps and lower MLC aperture irregularity be considered during plan optimisation due to higher robustness should patient positioning errors occur.

The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, the mechanisms by which it has been extended, and some of the challenges being addressed as it evolves. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS.

The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, and the mechanisms by which it has been extended. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.In a randomized phase II clinical trial, the Trans Tasman Radiation Oncology Group compared single- versus multifraction stereotactic ablative body radiotherapy (SABR) in 90 patients with 133 oligometastases to the lung. The study found no differences in safety, efficacy, systemic immunogenicity, or survival between arms, with single-fraction SABR picked as the winner on the basis of cost-effectiveness. In this article, we report the final updated survival outcome analysis. The protocol mandated no concurrent or post-therapy systemic therapy until progression. Modified disease-free survival (mDFS) was defined as any progression not addressable by local therapy, or death. At a median follow-up of 5.4 years, the 3- and 5-year estimates for overall survival (OS) were 70% (95% CI, 59 to 78) and 51% (95% CI, 39 to 61). There were no significant differences between the multi- and single-fraction arms for OS (hazard ratio [HR], 1.1 [95% CI, 0.6 to 2.0]; P = .81). The 3- and 5-year estimates for disease-free survival were 24% (95% CI, 16 to 33) and 20% (95% CI, 13 to 29), with no differences between arms (HR, 1.0 [95% CI, 0.6 to 1.6]; P = .92). The 3- and 5-year estimates for mDFS were 39% (95% CI, 29 to 49) and 34% (95% CI, 24 to 44), with no differences between arms (HR, 1.0 [95% CI, 0.6 to 1.8]; P = .90). In this patient population, where patients receive SABR in lieu of systemic therapy, one-in-three patients are alive without disease in the long term. There were no differences in outcomes by fractionation schedule.

Pulmonary functional imaging has demonstrated potential to improve thoracic radiotherapy. The purpose of this study was twofold: 1) to quantify ventilation/perfusion relationships in lung cancer patients using a new functional imaging approach, gallium-68 (68Ga)-positron emission tomography/computed tomography (PET/CT); and 2) to compare ventilation/perfusion matching with diffusing capacity of the lung for carbon monoxide (DLCO). Voxel-wise correlations between ventilation and perfusion varied widely among 19 patients (range: 0.26-0.88). 68Ga-PET/CT-measured percent gas exchanging lung volume was moderately correlated with DLCO (≤0.59). Our findings suggested that 68Ga-PET/CT ventilation/perfusion imaging provided complementary information and a reasonable surrogate for gas exchange in lung cancer patients.

BACKGROUND: Biology-guided radiotherapy (BgRT) delivers dose to tumours triggered from positron emission tomography (PET) detection. Prostate specific membrane antigen (PSMA) PET uptake is abundant in the dominant intraprostatic lesion (DIL). This study investigates the feasibility of BgRT to PSMA-avid subvolume in the prostate region. METHODS: Patients enrolled in the prospective randomized trial ProPSMA at our institution were included (ID: ANZCTR12617000005358). Gross tumour volumes (GTVs) were delineated on the PET component of a PET/CT scan from a standardized uptake value (SUV) threshold technique. Suitability for BgRT requires a strong signal-to-background ratio with a surrounding tissue free of significant PSMA uptake. The signal-to-background ratio was quantified from the calculation of the normalized SUV (nSUV), defined as the ratio between SUVmax within the GTV and SUVmean inside a 3D margin expansion of the GTV. The PSMA distribution surrounding the tumour was quantified as a function of the distance from the GTV. RESULTS: In this cohort of 84 patients, 83 primary tumours were included. Prostate volume ranged from 19 cm3 to 148 cm3 (median = 52 cm3; IQR = 39 cm3 - 63 cm3). SUVmax inside the prostate was between 2 and 125 (median = 19; IQR = 11 - 30). More than 50% of GTVs generated with threshold between 25%SUVmax (median volume = 10.0 cm3; IQR = 4.5 cm3 - 20.0 cm3) and 50%SUVmax (median volume = 1.9 cm3; IQR = 1.1 cm3 - 3.8 cm3) were suitable for BgRT by using nSUV ≥ 3 and a margin expansion of 5 mm. CONCLUSIONS: It is feasible to identify GTVs suitable for BgRT in the prostate. These GTVs are characterized by a strong signal-to-background ratio and a surrounding tissue free of PSMA uptake.

BACKGROUND: Biology-guided radiotherapy (BgRT) uses real-time functional imaging to guide radiation therapy treatment. Positron emission tomography (PET) tracers targeting prostate-specific membrane antigen (PSMA) are superior for prostate cancer detection than conventional imaging. This study aims at describing nodal and distant metastasis distribution from prostate cancer and at determining the proportion of metastatic lesions suitable for BgRT. METHODS: A single-institution patient subset from the ProPSMA trial (ID ACTRN12617000005358) was analysed. Gross tumour volumes (GTV) were delineated on the CT component of a PSMA PET/CT scan. To determine the suitability of BgRT tracking zones, the normalized SUV (nSUV) was calculated as the ratio of SUVmax inside the GTV to the SUVmean of adjacent three-dimensional shells of thickness 5 mm/10 mm/20 mm as a measure of signal to background contrast. Targets were suitable for BgRT if (1) nSUV was larger than an nSUV threshold and (2) non-tumour tissue inside adjacent shell was free of PET-avid uptake. RESULTS: Of this cohort of 84 patients, 24 had at least one pelvic node or metastatic site disease, 1 to 13 lesions per patient, with a total of 98 lesions (60 pelvic nodes/38 extra-pelvic nodal diseases and haematogenous metastases). Target volumes ranged from 0.08 to 9.6 cm3 while SUVmax ranged from 2.1 to 55.0. nSUV ranged from 1.9 to 15.7/2.4 to 25.7/2.5 to 34.5 for the 5 mm/10 mm/20 mm shell expansion. Furthermore, 74%/68%/34% of the lesions had nSUV ≥ 3 and were free of PSMA PET uptake inside the GTV outer shell margin expansion of 5 mm/10 mm/20 mm. Adjacent avid organs were another lesion, bladder, bowel, ureter, prostate, and liver. CONCLUSIONS: The majority of PSMA PET/CT-defined radiotherapy targets would be suitable for BgRT by using a 10-mm tracking zone in prostate cancer. A subset of lesions had adjacent non-tumour uptake, mainly due to the proximity of ureter or bladder, and may require exclusion from emission t

The report of the American Association of Physicists in Medicine (AAPM) Task Group No. 132 published in 2017 reviewed rigid image registration and deformable image registration (DIR) approaches and solutions to provide recommendations for quality assurance and quality control of clinical image registration and fusion techniques in radiotherapy. However, that report did not include the use of DIR for advanced applications such as dose warping or warping of other matrices of interest. Considering that DIR warping tools are now readily available, discussions were hosted by the Medical Image Registration Special Interest Group (MIRSIG) of the Australasian College of Physical Scientists & Engineers in Medicine in 2018 to form a consensus on best practice guidelines. This position statement authored by MIRSIG endorses the recommendations of the report of AAPM task group 132 and expands on the best practice advice from the 'Deforming to Best Practice' MIRSIG publication to provide guidelines on the use of DIR for advanced applications.

Delivering radiotherapy to patients in an upright position can allow for increased patient comfort, reduction in normal tissue irradiation, or reduction of machine size and complexity. This paper gives an overview of the requirements for the delivery of contemporary arc and modulated radiation therapy to upright patients. We explore i) patient positioning and immobilization, ii) simulation imaging, iii) treatment planning and iv) online setup and image guidance. Treatment chairs have been designed to reproducibly position seated patients for treatment and can be augmented by several existing immobilisation systems or promising emerging technologies such as soft robotics. There are few solutions for acquiring CT images for upright patients, however, cone beam computed tomography (CBCT) scans of upright patients can be produced using the imaging capabilities of standard Linacs combined with an additional patient rotation device. While these images will require corrections to make them appropriate for treatment planning, several methods indicate the viability of this approach. Treatment planning is largely unchanged apart from translating gantry rotation to patient rotation, allowing for a fixed beam with a patient rotating relative to it. Rotation can be provided by a turntable during treatment delivery. Imaging the patient with the same machinery as used in treatment could be advantageous for online plan adaption. While the current focus is using clinical linacs in existing facilities, developments in this area could also extend to lower-cost and mobile linacs and heavy ion therapy.

BACKGROUND: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is established as the preferred method of mediastinal lymph node (LN) staging in non-small cell lung cancer (NSCLC). Selective (targeted) LN sampling is most commonly performed however studies in early stage NSCLC and locally advanced NSCLC confirm systematic EBUS-TBNA evaluation improves accuracy of mediastinal staging. This study aims to establish the rate of detection of positron emission tomography (PET)-occult LN metastases following systematic LN staging by EBUS-TBNA, and to determine the utility of systematic mediastinal staging for accurate delineation of radiation treatment fields in patients with locally advanced NSCLC. METHODS: Consecutive patients undergoing EBUS-TBNA for diagnosis/staging of locally advanced NSCLC will be enrolled in this international multi-centre single arm study. Systematic mediastinal LN evaluation will be performed, with all LN exceeding 6 mm to be sampled by TBNA. Where feasible, endoscopic ultrasound staging (EUS-B) may also be performed. Results of minimally invasive staging will be compared to FDG-PET. The primary end-point is proportion of patients in whom systematic LN staging identified PET-occult NSCLC metastases. Secondary outcome measures include (i) rate of nodal upstaging, (ii) false positive rate of PET for mediastinal LN assessment, (iii) analysis of clinicoradiologic risk factors for presence of PET-occult LN metastases, (iv) impact of systematic LN staging in patients with discrepant findings on PET and EBUS-TBNA on target coverage and dose to organs at risk (OAR) in patients undergoing radiotherapy. DISCUSSION: With specificity of PET of 90%, guidelines recommend tissue confirmation of positive mediastinal LN to ensure potentially early stage patients are not erroneously denied potentially curative resection. However, while confirmation of pathologic LN is routinely sought, the exact extent of mediastinal LN involvement in NSCL

Knowledge-based planning (KBP) can increase plan quality, consistency and efficiency. In this study, we assess the success of a using a publicly available KBP model compared with developing an in-house model for prostate cancer radiotherapy using a single, commercially available treatment planning system based on the ability of the model to achieve the centre's planning goals. Two radiation oncology centres each created a prostate cancer KBP model using the Eclipse RapidPlan software. These two models and a third publicly-available, shared model were tested at three centres in a retrospective planning study. The publicly-available model achieved lower rectum doses than the other two models. However, the planning-target-volume (PTV) doses did not meet the local planning goals and the model could not be adjusted to correct this. As a result, the plans most likely to satisfy local planning goals and requirements were created using an in-house model. For centres without an existing in-house model, a model created by another centre with similar planning goals was found to be preferred. Variations in local planning practices including contouring, treatment technique and planning goals can influence the relative performance of KBP. The value of publicly available KBP models could be enhanced through standardisation of planning goals and contouring guidelines, providing information related to the planning goals used to create the model and increased flexibility to allow local adaptation of the KBP model.

PURPOSE: Stereotactic ablative radiation therapy (SABR) delivered in a single fraction (SF) can be considered to have higher uncertainty given that the error probability is concentrated in a single session. This study aims to report the variation in technology and technique used and its effect on intrafraction motion based on a 10 years of experience in SF SABR. METHODS AND MATERIALS: Records of patients receiving SF SABR delivered at our instruction between 2010 and 2019 were included. Treatment parameters were extracted from the patient management database by using an in-house script. Treatment time was defined as the time difference between the first image acquisition to the last beam off of a single session. The intrafraction variation was measured from the 3-dimensional couch displacement measured after the first cone beam computed tomography (CBCT) acquired during a treatment. RESULTS: The number of SF SABR increased continuously from 2010 to 2019 and were mainly lung treatments. Treatment time was minimized by using volumetric modulated arc therapy, flattening filter-free dose rate, and coplanar field (24 ± 9 min). Treatment time increased as the number of CBCTs per session increased. The most common scenario involved both 2 and 3 CBCTs per session. On the average, a CBCT acquisition added 6 minutes to the treatment time. All treatments considered, the average intrafraction variation was 1.7 ± 1.6 mm. CONCLUSIONS: SF SABR usage increased with time in our institution. The intrafraction motion was acceptable and therefore a single fraction is an efficacious treatment option when considering SABR.

BACKGROUND: Delivered organs at risk (OARs) dose may vary from planned dose due to interfraction and intrafraction motion during kidney SABR treatment. Cases of bowel stricture requiring surgery post SABR treatment were reported in our institution. This study aims to provide strategies to reduce dose deposited to OARs during SABR treatment and mitigate risk of gastrointestinal toxicity. METHODS: Small bowel (SB), large bowel (LB) and stomach (STO) were delineated on the last cone beam CT (CBCT) acquired before any dose had been delivered (PRE CBCT) and on the first CBCT acquired after any dose had been delivered (MID CBCT). OAR interfraction and intrafraction motion were estimated from the shortest distance between OAR and the internal target volume (ITV). Adaptive radiation therapy (ART) was used if dose limits were exceeded by projecting the planned dose on the anatomy of the day. RESULTS: In 36 patients, OARs were segmented on 76 PRE CBCTs and 30 MID CBCTs. Interfraction motion was larger than intrafraction motion in STO (p-value = 0.04) but was similar in SB (p-value = 0.8) and LB (p-value = 0.2). LB was inside the planned 100% isodose in all PRE CBCTs and MID CBCTs in the three patients that suffered from bowel stricture. SB D0.03cc was exceeded in 8 fractions (4 patients). LB D1.5cc was exceeded in 4 fractions (2 patients). Doses to OARs were lowered and limits were all met with ART on the anatomy of the day. CONCLUSIONS: Interfraction motion was responsible for OARs overdosage. Dose limits were respected by using ART with the anatomy of the day.

Artificial intelligence and radiomics have the potential to revolutionise cancer prognostication and personalised treatment. Manual outlining of the tumour volume for extraction of radiomics features (RF) is a subjective process. This study investigates robustness of RF to inter-observer variation (IOV) in contouring in lung cancer. We utilised two public imaging datasets: 'NSCLC-Radiomics' and 'NSCLC-Radiomics-Interobserver1' ('Interobserver'). For 'NSCLC-Radiomics', we created an additional set of manual contours for 92 patients, and for 'Interobserver', there were five manual and five semi-automated contours available for 20 patients. Dice coefficients (DC) were calculated for contours. 1113 RF were extracted including shape, first order and texture features. Intraclass correlation coefficient (ICC) was computed to assess robustness of RF to IOV. Cox regression analysis for overall survival (OS) was performed with a previously published radiomics signature. The median DC ranged from 0.81 ('NSCLC-Radiomics') to 0.85 ('Interobserver'-semi-automated). The median ICC for the 'NSCLC-Radiomics', 'Interobserver' (manual) and 'Interobserver' (semi-automated) were 0.90, 0.88 and 0.93 respectively. The ICC varied by feature type and was lower for first order and gray level co-occurrence matrix (GLCM) features. Shape features had a lower median ICC in the 'NSCLC-Radiomics' dataset compared to the 'Interobserver' dataset. Survival analysis showed similar separation of curves for three of four RF apart from 'original_shape_Compactness2', a feature with low ICC (0.61). The majority of RF are robust to IOV, with first order, GLCM and shape features being the least robust. Semi-automated contouring improves feature stability. Decreased robustness of a feature is significant as it may impact upon the features' prognostic capability.

Double mitral and aortic mechanical valves present an access challenge when planning a ventricular tachycardia (VT) ablation. In this case report, we describe a patient who was considered for stereotactic ablative radiotherapy but was unable to proceed due to unfavorable anatomy making them at high risk of fistula formation. The patient went on to have an endocardial VT ablation via mini-thoracotomy and transapical access without complication. This case highlights the need for careful consideration when planning treatment for patients with double mechanical valves.