Search

Background Magnetic Resonance linear accelerator (MR-linac) systems represent a new type of technology that allows for online MR-guidance for high precision radiotherapy (RT). Currently, the first MR-linac installations are being introduced clinically. Since the imaging performance of these integrated MR-linac systems is critical for their application, a thorough commissioning of the MRI performance is essential. However, guidelines on the commissioning of MR-guided RT systems are not yet defined and data on the performance of MR-linacs are not yet available. Materials & methods Here we describe a comprehensive commissioning protocol, which contains standard MRI performance measurements as well as dedicated hybrid tests that specifically assess the interactions between the Linac and the MRI system. The commissioning results of four MR-linac systems are presented in a multi-center study. Results Although the four systems showed similar performance in all the standard MRI performance tests, some differences were observed relating to the hybrid character of the systems. Field homogeneity measurements identified differences in the gantry shim configuration, which was later confirmed by the vendor. Conclusion Our results highlight the importance of dedicated hybrid commissioning tests and the ability to compare the machines between institutes at this very early stage of clinical introduction. Until formal guidelines and tolerances are defined the tests described in this study may be used as a practical guideline. Moreover, the multi-center results provide initial bench mark data for future MR-linac installations.

Introduccion: el insulinoma pancreatico esporadico es un tumor con frecuencia benigno, generalmente solitario y menor de 20 mm. Cuando es funcionante, los pacientes experimentan sintomas relacionados con la produccion excesiva de insulina. El diagnostico es clinico, con confirmacion bioquimica y radiologica. El tratamiento suele ser quirurgico, pero en la actualidad se esta desarrollando la ablacion guiada por ultrasonido endoscopico. Material y metodos: realizamos una serie de casos prospectiva de pacientes con insulinoma pancreatico con sintomas de hipoglicemia severa, a quienes se les ofrecio el tratamiento ablativo con etanol al 96 % guiado por ultrasonido endoscopico como tratamiento alternativo a la cirugia. Resultados: el exito tecnico y clinico se consiguio en el 100 % de los casos. No se presentaron complicaciones asociados al procedimiento. Conclusion: el tratamiento del insulinoma sintomatico mediante ablacion por etanolizacion guiada por ultrasonido endoscopico podria ser una alternativa segura y eficaz a la cirugia en pacientes no candidatos o que rechacen la intervencion quirurgica.

Abstract: Introduction: Image-guided intensity-modulated radiation therapy is essential for oncology treatment of head-and-neck cancer patients. Aim: MV-kV and CBCT modalities were compared in case of IGRT treatment for head-and-neck cancer patients. Setup error, setup margin (SM), imaging and evaluation times and imaging doses were analyzed. Method: Eight patients’ elective treatment was evaluated, 66 orthogonal MV-kV images and 66 CBCT series were acquired. Setup error measurement was based on bony manual image registration in three translational directions. Normality test and F-test were performed followed by the comparison with independent-samples T-test (p

The objective of this study was to assess the recommended DVH parameter (e.g., D2 cc) addition method used for combining EBRT and HDR plans, against a reference dataset generated from an EQD2‐based DVH addition method. A revised DVH parameter addition method using EBRT DVH parameters derived from each patient's plan was proposed and also compared with the reference dataset. Thirty‐one biopsy‐proven cervical cancer patients who received EBRT and HDR brachytherapy were retrospectively analyzed. A parametrial and/or paraaortic EBRT boost were clinically performed on 13 patients. Ten IMRT and 21 3DCRT plans were determined. Two different HDR techniques for each HDR plan were analyzed. Overall D2 cc and D0.1 cc OAR doses in EQD2 were statistically analyzed for three different DVH parameter addition methods: a currently recommended method, a proposed revised method, and a reference DVH addition method. The overall D2 ccEQD 2 values for all rectum, bladder, and sigmoid for a conformal, volume optimization HDR plan generated using the current DVH parameter addition method were significantly underestimated on average −5 to −8% when compared to the values obtained from the reference DVH addition technique (P 0.099). When PM boosts were considered, there was an even greater average underestimation of −8~−10% for overall OAR doses of conformal HDR plans when using the current DVH parameter addition technique as compared to the revised DVH parameter addition. No statistically significant differences were found between the 3DCRT and IMRT techniques (P > 0.3148). It is recommended that the overall D2 cc EBRT doses are obtained from each patient's EBRT plan.

Large variations in the shape and size of the bladder volume are commonly observed in bladder cancer radiotherapy (RT). The clinical target volume (CTV) is therefore frequently inadequately treated and large isotropic margins are inappropriate in terms of dose to organs at risk (OAR); thereby making adaptive radiotherapy (ART) attractive for this tumour site. There are various methods of ART delivery, however, for bladder cancer, plan libraries are frequently used.A review of published studies on plan libraries for bladder cancer using four databases (Pubmed, Science Direct, Embase and Cochrane Library) was conducted. The endpoints selected were accuracy and feasibility of initiation of a plan library strategy into a RT department.Twenty-four articles were included in this review. The majority of studies reported improvement in accuracy with 10 studies showing an improvement in planning target volume (PTV) and CTV coverage with plan libraries, some by up to 24%. Seventeen studies showed a dose reduction to OARs, particularly the small bowel V45Gy, V40Gy, V30Gy and V10Gy, and the rectal V30Gy. However, the occurrence of no suitable plan was reported in six studies, with three studies showing no significant difference between adaptive and non-adaptive strategies in terms of target coverage. In addition, inter-observer variability in plan selection appears to remain problematic. The additional resources, education and technology required for the initiation of plan library selection for bladder cancer may hinder its routine clinical implementation, with eight studies illustrating increased treatment time required.While there is a growing body of evidence in support of plan libraries for bladder RT, many studies differed in their delivery approach. The advent of the clinical use of the MRI-linear accelerator will provide RT departments with the opportunity to consider daily online adaption for bladder cancer as an alternate to plan library approaches.

The use of MRI in radiotherapy planning and simulation is increasing rapidly and is beginning to be integrated into the external beam radiation therapy (EBRT) treatment process. Some have suggested that integrated MRI-linac systems, not the standalone MRI-Sim, represents the future of MRI in radiotherapy, and this is the claim debated in this month's Point/Counterpoint. This article is protected by copyright. All rights reserved.

Background Patients treated with radiotherapy for head and neck (H&N) cancer often experience anatomical changes. The potential compromises to Planning Target Volume (PTV) coverage or Organ at Risk (OAR) sparing has prompted the use of adaptive radiotherapy (ART) for these patients. However, implementation of ART is time and resource intensive. This study seeks to define a clinical trigger for H&N re-plans based on spinal cord safety using kV Cone-Beam Computed Tomography (CBCT) verification imaging, in order to best balance clinical benefit with additional workload. Methods Thirty-one H&N patients treated with Volumetric Modulated Arc Therapy (VMAT) who had a rescan CT (rCT) during treatment were included in this study. Contour volume changes between the planning CT (pCT) and rCT were determined. The original treatment plan was calculated on the pCT, CBCT prior to the rCT, pCT deformed to the anatomy of the CBCT (dCT), and rCT (considered the gold standard). The dose to 0.1 cc (D0.1cc) spinal cord was evaluated from the Dose Volume Histograms (DVHs). Results The median dose increase to D0.1cc between the pCT and rCT was 0.7 Gy (inter-quartile range 0.2–1.9 Gy, p Conclusions An adaptive re-plan can be triggered using spinal cord doses calculated on the CBCT/dCT. Implementing this trigger can reduce patient appointments and radiation dose by eliminating up to 90% of additional un-necessary CT scans, reducing the workload for radiographers, physicists, dosimetrists, and clinicians.

Purpose: To develop an infrared optical method of reducing surface-based registration error caused by respiration to improve radiotherapy setup accuracy for patients with abdominal or pelvic tumors. Materials and Methods: Fifteen patients with abdominal or pelvic tumors who received radiation therapy were prospectively included in our study. All patients were immobilized with vacuum cushion and underwent cone-beam computed tomography to validate positioning error before treatment. For each patient, after his or her setup based on markers fixed on immobilization device, initial positioning errors in patient left-right, anterior-posterior, and superior-inferior directions were validated by cone-beam computed tomography. Then, our method calculated mismatch between patient and immobilization device based on surface registration by interpolating between expiratory- and inspiratory-phase surface to find the specific phase to best match the surface in planning computed tomography scans. After adjusting the position of treatment couch by the shift proposed by our method, a second cone-beam computed tomography was performed to determine the final positioning error. A comparison between initial and final setup error will be made to validate the effectiveness of our method. Results: Final positioning error confirmed by cone-beam computed tomography is 1.59 (1.82), 1.61 (1.84), and 1.31 (1.38) mm, reducing initial setup error by 24.52%, 51.04%, and 53.63% in patient left-right, anterior-posterior, and superior-inferior directions, respectively. Wilcoxon test showed that our method significantly reduced the 3-dimensional distance of positioning error ( P < .001). Conclusion: Our method can significantly improve the setup precision for patients with abdominal or pelvic tumors in a noninvasive way by reducing the surface-based registration error caused by respiration.

Objective: Radiation treatment planning for locally advanced lung cancer can be technically challenging, as delivery of ≥60 Gy to large volumes with concurrent chemotherapy is often associated with significant risk of normal tissue toxicity. We clinically implemented a novel hybrid RapidArc technique in patients with lung cancer and compared these plans with 3-dimensional conformal radiotherapy and RapidArc-only plans. Materials/Methods: Hybrid RapidArc was used to treat 11 patients with locally advanced lung cancer having bulky mediastinal adenopathy. All 11 patients received concurrent chemotherapy. All underwent a 4-dimensional computed tomography planning scan. Hybrid RapidArc plans concurrently combined static (60%) and RapidArc (40%) beams. All cases were replanned using 3- to 5-field 3-dimensional conformal radiotherapy and RapidArc technique as controls. Results: Significant reductions in dose were observed in hybrid RapidArc plans compared to 3-dimensional conformal radiotherapy plans for total lung V20 and mean (−2% and −0.6 Gy); contralateral lung mean (−2.92 Gy); and esophagus V60 and mean (−16.0% and −2.2 Gy; all P < .05). Contralateral lung doses were significantly lower for hybrid RapidArc plans compared to RapidArc-only plans (all P < .05). Compared to 3-dimensional conformal radiotherapy, heart V60 and mean dose were significantly improved with hybrid RapidArc (3% vs 5%, P = .04 and 16.32 Gy vs 16.65 Gy, P = .03). However, heart V40 and V45 and maximum spinal cord dose were significantly lower with RapidArc plans compared to hybrid RapidArc plans. Conformity and homogeneity were significantly better with hybrid RapidArc plans compared to 3-dimensional conformal radiotherapy plans ( P < .05). Treatment was well tolerated, with no grade 3+ toxicities. Conclusion: To our knowledge, this is the first report on the clinical application of hybrid RapidArc in patients with locally advanced lung cancer. Hybrid RapidArc permitted safe delivery of 60 to 66 Gy to large lung tumors with concurrent chemotherapy and demonstrated advantages for reduction in low-dose lung volumes, esophageal dose, and mean heart dose.

Purpose: With the trend in radiotherapy moving toward dose escalation and hypofractionation, the need for highly accurate targeting increases. While MLC tracking is already being successfully used for motion compensation of moving targets in the prostate, current real-time target localization methods rely on repeated x-ray imaging and implanted fiducial markers or electromagnetic transponders rather than direct target visualization. In contrast, ultrasound imaging can yield volumetric data in real-time (3D + time = 4D) without ionizing radiation. The authors report the first results of combining these promising techniques—online 4D ultrasound guidance and MLC tracking—in a phantom. Methods: A software framework for real-time target localization was installed directly on a 4D ultrasound station and used to detect a 2 mm spherical lead marker inside a water tank. The lead marker was rigidly attached to a motion stage programmed to reproduce nine characteristic tumor trajectories chosen from large databases (five prostate, four lung). The 3D marker position detected by ultrasound was transferred to a computer program for MLC tracking at a rate of 21.3 Hz and used for real-time MLC aperture adaption on a conventional linear accelerator. The tracking system latency was measured using sinusoidal trajectories and compensated for by applying a kernel density prediction algorithm for the lung traces. To measure geometric accuracy, static anterior and lateral conformal fields as well as a 358° arc with a 10 cm circular aperture were delivered for each trajectory. The two-dimensional (2D) geometric tracking error was measured as the difference between marker position and MLC aperture center in continuously acquired portal images. For dosimetric evaluation, VMAT treatment plans with high and low modulation were delivered to a biplanar diode array dosimeter using the same trajectories. Dose measurements with and without MLC tracking were compared to a static reference dose using 3%/3 mm and 2%/2 mm γ-tests. Results: The overall tracking system latency was 172 ms. The mean 2D root-mean-square tracking error was 1.03 mm (0.80 mm prostate, 1.31 mm lung). MLC tracking improved the dose delivery in all cases with an overall reduction in the γ-failure rate of 91.2% (3%/3 mm) and 89.9% (2%/2 mm) compared to no motion compensation. Low modulation VMAT plans had no (3%/3 mm) or minimal (2%/2 mm) residual γ-failures while tracking reduced the γ-failure rate from 17.4% to 2.8% (3%/3 mm) and from 33.9% to 6.5% (2%/2 mm) for plans with high modulation. Conclusions: Real-time 4D ultrasound tracking was successfully integrated with online MLC tracking for the first time. The developed framework showed an accuracy and latency comparable with other MLC tracking methods while holding the potential to measure and adapt to target motion, including rotation and deformation, noninvasively.

Indication, doses, and technique of radiotherapy, for intrathoracic metastases are presented. The recommendations for delineation of the target volumes and organs at risk are detailed.

Dose prescription, delineation and dose calculation are clearly complicated when a patient have been operated on with insertion of prosthesis. Knowledge of the physical and material characteristics is needed to decrease incertitude of calculations. Recommendations for each step of treatments are proposed in this article allowing to optimization of the treatment safety.

Radiotherapy for Hodgkin's lymphoma has evolved over time but retains a dominant position in the treatment of early stage tumours. Its indications are more limited for non-Hodgkin's lymphomas, but the techniques follow the same principles whatever the histological type. This review presents the French recommendations in terms of preparation and choice of irradiation techniques.

Purpose: To quantify the performance of the Clarity ultrasound (US) imaging system (Elekta AB, Stockholm, Sweden) for real-time dynamic multileaf collimator (MLC) tracking. Methods: The Clarity calibration and quality assurance phantom was mounted on a motion platform moving with a periodic sine wave trajectory. The detected position of a 30 mm hypoechogenic sphere within the phantom was continuously reported via Clarity’s real-time streaming interface to an in-house tracking and delivery software and subsequently used to adapt the MLC aperture. A portal imager measured MV treatment field/MLC apertures and motion platform positions throughout each experiment to independently quantify system latency and geometric error. Based on the measured range of latency values, a prostate stereotactic body radiation therapy (SBRT) delivery was performed with three realistic motion trajectories. The dosimetric impact of system latency on MLC tracking was directly measured using a 3D dosimeter mounted on the motion platform. Results: For 2D US imaging, the overall system latency, including all delay times from the imaging and delivery chain, ranged from 392 to 424 ms depending on the lateral sector size. For 3D US imaging, the latency ranged from 566 to 1031 ms depending on the elevational sweep. The latency-corrected geometric root-mean squared error was below 0.75 mm (2D US) and below 1.75 mm (3D US). For the prostate SBRT delivery, the impact of a range of system latencies (400–1000 ms) on the MLC tracking performance was minimal in terms of gamma failure rate. Conclusions: Real-time MLC tracking based on a noninvasive US input is technologically feasible. Current system latencies are higher than those for x-ray imaging systems, but US can provide full volumetric image data and the impact of system latency was measured to be small for a prostate SBRT case when using a US-like motion input.

Introduction: Stereotactic body radiation therapy allows for the precise delivery of high-dose radiation to disease sites and is becoming increasingly used to treat nonspine bone metastases. Previous studies have shown that remineralization of lytic bone metastases follows after conventional radiotherapy. The objective of this study was to investigate changes in bone density in nonspine bone metastases following stereotactic body radiation therapy. Methods: A retrospective review was conducted for all patients treated with stereotactic body radiation therapy to nonspine bone metastases between May 2011 and April 2014. A minimum of 1 pretreatment and 1 posttreatment computed tomography scan was required. An independent musculoskeletal radiologist contoured the lesions on the most representative computed tomography slices. Density was measured in Hounsfield units and analyzed using pretreatment and posttreatment ratios. Results: Forty sites were treated (55% lytic, 30% sclerotic, and 15% mixed). The median follow-up duration was 7 months. Lytic osseous metastases from renal cell carcinoma progressed during initial follow-up imaging and then returned to baseline. Of 9 lytic lesions not from renal cell carcinoma, 6 showed an immediate increase in density and 2 remained stable. Six of 7 sclerotic lesions from prostate cancer showed decreased density throughout all follow-ups. Conclusion: Stereotactic body radiation therapy is efficacious in the remineralization of lytic and demineralization of sclerotic nonspine bone metastases.

Purpose: To present our clinical workflow of incorporating AlignRT for left breast deep inspiration breath-hold treatments and the dosimetric considerations with the deep inspiration breath-hold protocol. Material and Methods: Patients with stage I to III left-sided breast cancer who underwent lumpectomy or mastectomy were considered candidates for deep inspiration breath-hold technique for their external beam radiation therapy. Treatment plans were created on both free-breathing and deep inspiration breath-hold computed tomography for each patient to determine whether deep inspiration breath-hold was beneficial based on dosimetric comparison. The AlignRT system was used for patient setup and monitoring. Dosimetric measurements and their correlation with chest wall excursion and increase in left lung volume were studied for free-breathing and deep inspiration breath-hold plans. Results: Deep inspiration breath-hold plans had significantly increased chest wall excursion when compared with free breathing. This change in geometry resulted in reduced mean and maximum heart dose but did not impact lung V20 or mean dose. The correlation between chest wall excursion and absolute reduction in heart or lung dose was found to be nonsignificant, but correlation between left lung volume and heart dose showed a linear association. It was also identified that higher levels of chest wall excursion may paradoxically increase heart or lung dose. Conclusion: Reduction in heart dose can be achieved for many left-sided breast and chest wall patients using deep inspiration breath-hold. Chest wall excursion as well as left lung volume did not correlate with reduction in heart dose, and it remains to be determined what metric will provide the most optimal and reliable dosimetric advantage.

Purpose: To present our experiences in understanding and minimizing bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in a clinical cone beam computed tomography system. Methods: Bowtie-filter position and profile variations during gantry rotation were studied. Two previously proposed strategies (A and B) were applied to the clinical cone beam computed tomography system to correct bowtie-filter crescent artifacts. Physical calibration and analytical approaches were used to minimize the norm phantom misalignment and to correct for bowtie-filter normalization artifacts. A combined procedure to reduce bowtie-filter crescent artifacts and bowtie-filter normalization artifacts was proposed and tested on a norm phantom, CatPhan, and a patient and evaluated using standard deviation of Hounsfield unit along a sampling line. Results: The bowtie-filter exhibited not only a translational shift but also an amplitude variation in its projection profile during gantry rotation. Strategy B was better than strategy A slightly in minimizing bowtie-filter crescent artifacts, possibly because it corrected the amplitude variation, suggesting that the amplitude variation plays a role in bowtie-filter crescent artifacts. The physical calibration largely reduced the misalignment-induced bowtie-filter normalization artifacts, and the analytical approach further reduced bowtie-filter normalization artifacts. The combined procedure minimized both bowtie-filter crescent artifacts and bowtie-filter normalization artifacts, with Hounsfield unit standard deviation being 63.2, 45.0, 35.0, and 18.8 Hounsfield unit for the best correction approaches of none, bowtie-filter crescent artifacts, bowtie-filter normalization artifacts, and bowtie-filter normalization artifacts + bowtie-filter crescent artifacts, respectively. The combined procedure also demonstrated reduction of bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in a CatPhan and a patient. Conclusion: We have developed a step-by-step procedure that can be directly used in clinical cone beam computed tomography systems to minimize both bowtie-filter crescent artifacts and bowtie-filter normalization artifacts.

Imaging has become an essential tool in modern radiotherapy (RT), being used to plan dose delivery prior to treatment and verify target position before and during treatment. Ultrasound (US) imaging is cost-effective in providing excellent contrast at high resolution for depicting soft tissue targets apart from those shielded by the lungs or cranium. As a result, it is increasingly used in RT setup verification for the measurement of inter-fraction motion, the subject of Part I of this review (Fontanarosa et al 2015 Phys. Med. Biol. 60 R77-114). The combination of rapid imaging and zero ionising radiation dose makes US highly suitable for estimating intra-fraction motion. The current paper (Part II of the review) covers this topic. The basic technology for US motion estimation, and its current clinical application to the prostate, is described here, along with recent developments in robust motion-estimation algorithms, and three dimensional (3D) imaging. Together, these are likely to drive an increase in the number of future clinical studies and the range of cancer sites in which US motion management is applied. Also reviewed are selections of existing and proposed novel applications of US imaging to RT. These are driven by exciting developments in structural, functional and molecular US imaging and analytical techniques such as backscatter tissue analysis, elastography, photoacoustography, contrast-specific imaging, dynamic contrast analysis, microvascular and super-resolution imaging, and targeted microbubbles. Such techniques show promise for predicting and measuring the outcome of RT, quantifying normal tissue toxicity, improving tumour definition and defining a biological target volume that describes radiation sensitive regions of the tumour. US offers easy, low cost and efficient integration of these techniques into the RT workflow. US contrast technology also has potential to be used actively to assist RT by manipulating the tumour cell environment and by improving the delivery of radiosensitising agents. Finally, US imaging offers various ways to measure dose in 3D. If technical problems can be overcome, these hold potential for wide-dissemination of cost-effective pre-treatment dose verification and in vivo dose monitoring methods. It is concluded that US imaging could eventually contribute to all aspects of the RT workflow.

Purpose: A new cone-beam CT scanner for image-guided radiotherapy (IGRT) can independently rotate the source and the detector along circular trajectories. Existing reconstruction algorithms are not suitable for this scanning geometry. The authors propose and evaluate a three-dimensional (3D) filtered-backprojection reconstruction for this situation. Methods: The source and the detector trajectories are tuned to image a field-of-view (FOV) that is offset with respect to the center-of-rotation. The new reconstruction formula is derived from the Feldkamp algorithm and results in a similar three-step algorithm: projection weighting, ramp filtering, and weighted backprojection. Simulations of a Shepp Logan digital phantom were used to evaluate the new algorithm with a 10 cm-offset FOV. A real cone-beam CT image with an 8.5 cm-offset FOV was also obtained from projections of an anthropomorphic head phantom. Results: The quality of the cone-beam CT images reconstructed using the new algorithm was similar to those using the Feldkamp algorithm which is used in conventional cone-beam CT. The real image of the head phantom exhibited comparable image quality to that of existing systems. Conclusions: The authors have proposed a 3D filtered-backprojection reconstruction for scanners with independent source and detector rotations that is practical and effective. This algorithm forms the basis for exploiting the scanner's unique capabilities in IGRT protocols.

Image-guided radiotherapy (IGRT) has been integrated into daily clinical routine and can today be considered the standard especially with high-dose radiotherapy. Currently imaging is based on MV- or kV-CT, which has clear limitations especially in soft-tissue contrast. Thus, combination of magnetic resonance (MR) imaging and high-end radiotherapy opens a new horizon. The intricate technical properties of MR imagers pose a challenge to technology when combined with radiation technology. Several solutions that are almost ready for routine clinical application have been developed. The clinical questions include dose-escalation strategies, monitoring of changes during treatment as well as imaging without additional radiation exposure during treatment.

Purpose: Accurate positioning of the target volume during treatment is paramount for stereotactic body radiation therapy (SBRT). In this work, the authors present the development of an in-house software tool to verify target position with an Elekta-Synergy linear accelerator using kV planar images acquired during treatment delivery. Methods: In-house software, SeedTracker, was developed in matlab to perform the following three functions: 1. predict intended seed positions in a planar view perpendicular to any gantry angle, simulating a portal imaging device, from the 3D seed co-ordinates derived from the treatment planning system; 2. autosegment seed positions in kV planar images; and 3. report the position shift based on the seed positions in the projection images. The performance of SeedTracker was verified using a CIRS humanoid phantom (CIRS, VA, USA) implanted with three Civco gold seed markers (Civco, IA, USA) in the prostate. The true positive rate of autosegmentation (TPRseg) and the accuracy of the software in alerting the user when the isocenter position was outside the tolerance (TPRtrig) were studied. Two-dimensional and 3D static position offsets introduced to the humanoid phantom and 3D dynamic offsets introduced to a gel phantom containing gold seeds were used for evaluation of the system. Results: SeedTracker showed a TPRseg of 100% in the humanoid phantom for projection images acquired at all angles except in the ranges of 80°–100° and 260°–280° where seeds are obscured by anatomy. This resulted in a TPRtrig of 88% over the entire treatment range for considered 3D static offsets introduced to the phantom. For 2D static offsets where the position offsets were only introduced in the anterior–posterior and lateral directions, the TPRtrig of SeedTracker was limited by both seed detectability and positional offset. SeedTracker showed a false positive trigger in the projection angle range between 130°–170° and 310°–350° (a maximum of 24% of treatment time) due to limited information that can be derived from monoscopic images. The system accurately determined the dynamic trajectory of the isocenter position in the superior and inferior direction for the studied dynamic offset scenarios based on the seed position in monoscopic images. Conclusions: The developed software has been shown to accurately autosegment the seed positions in kV planar images except for two 20° arcs where seeds are obscured by anatomical structures. The isocenter trajectories determined by the system, based on the monoscopic images, provide useful information for monitoring the prostate position. The developed system has potential application for monitoring prostate position during treatment delivery in linear accelerator based SBRT.

Purpose To choose the optimal brachytherapeutic modality for uterine cervical cancer, we performed simulation analysis. Methods and Materials For each high-risk clinical target volume (HR CTV), we compared four modalities [classical conventional intracavitary brachytherapy ( Conv ICBT), Image-guided ICBT (IGICBT), intracavitary/interstitial brachytherapy (ICISBT), and interstitial brachytherapy (ISBT) with perineal approach] using dose-volume histograms using eight sizes of HR CTV (2 × 2 × 2 cm to 7 × 4 × 4 cm) and organs at risk model. Results In Conv ICBT, the doses covered 90% of the HR CTV [ D 90 (HR CTV)] decreased from 197% prescribed dose (PD) for the HR CTV size (2 × 2 × 2 cm) to 73% PD for 5 × 4 × 4 cm, whereas the other three modalities could achieve 100% PD for all HR CTV sizes. The minimum doses received by the maximally irradiated 2-cm 3 volumes for organs at risks of IGICBT demonstrated lower values than those of Conv ICBT for the HR CTV size of 4 × 3 × 3 cm or smaller. ICISBT demonstrated lower values than those of IGICBT for 4 × 3 × 3 cm or larger. ISBT demonstrated lowest values for 5 × 4 × 4 cm or larger. Conclusions HR CTV size of 4 × 3 × 3 cm seems to be a threshold volume in this simulation analysis, and IGICBT is a better choice for smaller HR CTV than the threshold volume. On larger HR CTV, ICISBT or ISBT is the better choice.

Complete surgical resection is the potentially curative treatment for pancreatic cancer, but only fewer than 20% of those individuals will be found to be eligible for surgery. Here we report a 49-year-old man with locally advanced pancreatic cancer successfully treated with high-dose radiotherapy using helical tomotherapy (66 Gy/33 fractions, 2 Gy per day over 6.5 weeks). To our knowledge, this is the first reported case of locally advanced pancreatic cancer curatively treated with helical tomotherapy alone.

Adaptive radiotherapy (ART) strategies systematically monitor variations in target and neighbouring structures to inform treatment-plan modification during radiotherapy. This is necessary because a single plan designed before treatment is insufficient to capture the actual dose delivered to the target and adjacent critical structures during the course of radiotherapy. Magnetic resonance imaging (MRI) provides superior soft-tissue image contrast over current standard X-ray-based technologies without additional radiation exposure. With integrated MRI and radiotherapy platforms permitting motion monitoring during treatment delivery, it is possible that adaption can be informed by real-time anatomical imaging. This allows greater treatment accuracy in terms of dose delivered to target with smaller, individualised treatment margins. The use of functional MRI sequences would permit ART to be informed by imaging biomarkers, so allowing both personalised geometric and biological adaption. In this review, we discuss ART solutions enabled by MRI guidance and its potential gains for our patients across tumour types.

Purpose Several image-based retrospective sorting methods of 4D magnetic resonance imaging (4D MRI) have been proposed for respiratory motion reconstruction in external beam radiotherapy. However, the optimal strategy for providing accurate and artifact-free 4D MRI, ideally corresponding to an average breathing cycle, is not yet defined. This study presents a proactive comparison of three published image-based sorting methods, to define a groundwork for benchmarking in 4D MRI. Methods Three published 4D MRI methods were selected for image retrospective sorting: body area, mutual information, and navigator slice. The three image-based methods were compared against a conventional retrospective sorting method based on an external surrogate. Comparisons were performed by means of an MRI digital phantom, derived from the XCAT CT phantom generated with different patient-derived signals, for a total of 12 cases. Specific multislice MRI acquisitions were simulated for slice sorting and sagittal, coronal, and axial orientations were tested. An average 4D cycle was generated as ground truth. Results Individual and grouped patient analyses showed better performance of the navigator slice and mutual information in amplitude binning with respect to the body area strategy. Binning artifacts were reduced on the diaphragm with the slice navigator method due to the acquired internal information. Tumor motion description accurately matched the ground truth in the mutual information strategy with amplitude binning. The body area method followed the performance of the external surrogate and presented larger errors, since was not correlated with the internal anatomy. Sagittal and coronal orientations reported lower errors than axial slicing. Individual analysis showed the need of a patient-specific evaluation for the selection of the best method. Conclusions A comparison between three different image-based retrospective sorting methods for 4D MRI is proposed, providing guidelines for benchmark definition in MRI-guided radiotherapy.

Background To investigate the feasibility and geometric accuracy of carina-based registration for CBCT-guided setup verification in esophageal cancer IGRT, compared with current practice bony anatomy-based registration. Methods Included were 24 esophageal cancer patients with 65 implanted fiducial markers, visible on planning CTs and follow-up CBCTs. All available CBCT scans (n = 236) were rigidly registered to the planning CT with respect to the bony anatomy and the carina. Target coverage was visually inspected and marker position variation was quantified relative to both registration approaches; the variation of systematic (Σ) and random errors (σ) was estimated. Results Automatic carina-based registration was feasible in 94.9% of the CBCT scans, with an adequate target coverage in 91.1% compared to 100% after bony anatomy-based registration. Overall, Σ (σ) in the LR/CC/AP direction was 2.9(2.4)/4.1(2.4)/2.2(1.8) mm using the bony anatomy registration compared to 3.3(3.0)/3.6(2.6)/3.9(3.1) mm for the carina. Mid-thoracic placed markers showed a non-significant but smaller Σ in CC and AP direction when using the carina-based registration. Conclusions Compared with a bony anatomy-based registration, carina-based registration for esophageal cancer IGRT results in inadequate target coverage in 8.9% of cases. Furthermore, large Σ and σ, requiring larger anisotropic margins, were seen after carina-based registration. Only for tumors entirely confined to the mid-thoracic region the carina-based registration might be slightly favorable. Electronic supplementary material The online version of this article (10.1186/s13014-018-0986-1) contains supplementary material, which is available to authorized users.

PURPOSE: Structure-based deformable image registration (DIR) can be used to calculate accumulated dose volume histogram parameters for cervical cancer brachytherapy (BT). The purpose of this study is to investigate dose warping uncertainties for the accumulated dose to the 2 cm(3) receiving the highest dose (D-2 cm(3)) in the rectal wall, using a physically realistic model (PRM) describing rectal wall deformation.METHODS AND MATERIALS: For 10 patients, treated with MRI-guided pulsed dose rate BT (two times 24 x 0.75 Gy, given in two applications BT1 and BT2), the planning images were registered with structure-based DIR. The resulting transformation vectors were used to accumulate the total rectum dose from BT. To investigate the dose warping uncertainty, a PRM describing rectal deformation was used. For point pairs on rectum(BTl) and rectum(BT2) that were at the same location according to the PRM, the dose for BT1 and BT2 was added (D-PRM) and compared to the DIR-accumulated dose (D-DIR) in the BT2 point. The remaining distance after DIR between corresponding point pairs, defined as the residual distance, was calculated.RESULTS: For points within the D-2 cm(3) volume, more than 75% was part of the D-2 cm(3) volume according to both PRM and DIR. The absolute dose difference was

Purpose Various localization and positioning systems utilizing radiographic or nonradiographic methods have been developed to improve the accuracy of radiation treatment. Each quality assurance (QA) procedure requires its own phantom and is independent from each other, so the deviation between each system is unavailable. The purpose of this work is to develop and evaluate a single-integrated QA phantom for different localization and positioning systems. Methods The integrated phantom was designed in three-dimensional (3D) CAD software and 3D printed. The phantom was designed with laser alignment marks, a raised letter "S" on the anterior surface for optical surface monitoring system registration, a core for radiofrequency (RF) tracking system alignment, eight internal fiducials for image alignment, and an isocentric bearing for Winston-Lutz test. Tilt legs and rotational stage were designed for rotational verification of optical surface mapping system and RF tracking system, respectively. The phantom was scanned using a CT scanner and a QA plan was created. This prototype phantom was evaluated against established QA techniques. Results The QA result between the proposed procedure and established QA technique are 1.12 ± 0.31 and 1.14 ± 0.31 mm, respectively, for RF tracking system and 0.18 ± 0.06 and 0.18 ± 0.05 mm for Winston-Lutz test. There is no significant difference for the QA results between the established QA and proposed procedure (P > 0.05, t test). The accuracy of rotational verification for surface mapping system and RF tracking system are less than 0.5 and 1° compared the predefined value. The isocenter deviation of each location system is around l mm. Conclusion We have designed and evaluated a novel-integrated phantom for radiographic and nonradiographic localization and positioning systems for radiotherapy. With this phantom, we will reduce the variation in measurements and simplify the QA procedures.

Purpose: This paper presents initial experimental results from a prototype of high dose rate (HDR) BrachyView, a novel in-body source tracking system for HDR brachytherapy based on a multipinhole tungsten collimator and a high resolution pixellated silicon detector array. The probe and its associated position estimation algorithms are validated and a comprehensive evaluation of the accuracy of its position estimation capabilities is presented. Methods: The HDR brachytherapy source is moved through a sequence of positions in a prostate phantom, for various displacements in x, y, and z. For each position, multiple image acquisitions are performed, and source positions are reconstructed. Error estimates in each dimension are calculated at each source position and combined to calculate overall positioning errors. Gafchromic film is used to validate the accuracy of source placement within the phantom. Results: More than 90% of evaluated source positions were estimated with an error of less than one millimeter, with the worst-case error being 1.3 mm. Experimental results were in close agreement with previously published Monte Carlo simulation results. Conclusions: The prototype of HDR BrachyView demonstrates a satisfactory level of accuracy in its source position estimation, and additional improvements are achievable with further refinement of HDR BrachyView’s image processingmore » algorithms.« less

Purpose: Next-generation extremely rapid radiation therapy systems could mitigate the need for motion management, improve patient comfort during the treatment, and increase patient throughput for cost effectiveness. Such systems require an on-board imaging system that is competitively priced, fast, and of sufficiently high quality to allow good registration between the image taken on the day of treatment and the image taken the day of treatment planning. In this study, three different detectors for a custom on-board CT system were investigated to select the best design for integration with an extremely rapid radiation therapy system. Methods: Three different CT detectors are proposed: low-resolution (all 4 × 4 mm pixels), medium-resolution (a combination of 4 × 4 mm pixels and 2 × 2 mm pixels), and high-resolution (all 1 × 1 mm pixels). An in-house program was used to generate projection images of a numerical anthropomorphic phantom and to reconstruct the projections into CT datasets, henceforth called “realistic” images. Scatter was calculated using a separate Monte Carlo simulation, and the model included an antiscatter grid and bowtie filter. Diagnostic-quality images of the phantom were generated to represent the patient scan at the time of treatment planning. Commercial deformable registration software was used to register the diagnostic-quality scan to images produced by the various on-board detector configurations. The deformation fields were compared against a “gold standard” deformation field generated by registering initial and deformed images of the numerical phantoms that were used to make the diagnostic and treatment-day images. Registrations of on-board imaging system data were judged by the amount their deformation fields differed from the corresponding gold standard deformation fields—the smaller the difference, the better the system. To evaluate the registrations, the pointwise distance between gold standard and realistic registration deformation fields was computed. Results: By most global metrics (e.g., mean, median, and maximum pointwise distance), the high-resolution detector had the best performance but the medium-resolution detector was comparable. For all medium- and high-resolution detector registrations, mean error between the realistic and gold standard deformation fields was less than 4 mm. By pointwise metrics (e.g., tracking a small lesion), the high- and medium-resolution detectors performed similarly. For these detectors, the smallest error between the realistic and gold standard registrations was 0.6 mm and the largest error was 3.6 mm. Conclusions: The medium-resolution CT detector was selected as the best for an extremely rapid radiation therapy system. In essentially all test cases, data from this detector produced a significantly better registration than data from the low-resolution detector and a comparable registration to data from the high-resolution detector. The medium-resolution detector provides an appropriate compromise between registration accuracy and system cost.

Die Strahlentherapieplanung mit der funktionellen Magnetresonanztomographie (fMRT) zielt auf eine Hochprazisionsradiotherapie ab. Mit den modernen Technologien ist es moglich, die Strahlentherapie nahezu exakt an das Tumorvolumen anzupassen und dadurch das umliegende gesunde Gewebe zu schonen. Da die Strahlentherapie mit millimetergenauer Prazision appliziert werden kann, ist eine ebenso genaue Tumorabgrenzung essenziell. In der konventionellen Strahlentherapie ist die Durchfuhrung einer Planungs-CT Standard. Bei vielen Tumorentitaten ist eine MRT notwendig, um den Tumor besser abgrenzen zu konnen. Die konventionelle Strahlentherapie behandelt den gesamten Tumor mit einer homogenen Strahlendosis. In der Tumorgenese spielen Vorgange wie Zellproliferation, Hypoxie, Neoangiogenese, Perfusion und mikrovaskulare Hyperpermeabilitat eine wichtige Rolle. Die funktionelle MRT erlaubt es, eine Vielzahl dieser Prozesse durch unterschiedliche MR-Parameter darzustellen. Dadurch konnen die Volumina im Tumor identifiziert werden, die eine hohere Aggressivitat besitzen, haufig radioresistent sind und so ein Rezidiv verursachen. Daher sollen sie mit einer hoheren Strahlendosis behandelt werden. Diese Rationale, den Tumor inhomogen aufgrund seiner biologischen Charakteristika zu bestrahlen, bezeichnet man als „dose painting“. „Dose painting“ ist technisch durchfuhrbar und der klinische Vorteil ist durch Berucksichtigung der individuellen Tumorbiologie und der daraus folgend unterschiedlicher Therapieantwort abzuleiten. Durch eine an die Tumoreigenschaften angepasste Strahlentherapie werden bessere Therapieergebnisse erwartet. Die Implementation des „dose painting“ erfordert eine enge interdisziplinare Kooperation zwischen Radioonkologen, Radiologen, Medizinphysikern und Strahlenbiologen.

Purpose: To develop and establish a comprehensive gating commissioning and quality assurance procedure in compliance with TG-142. Methods: Eight Varian TrueBeam Linacs were used for this study. Gating commissioning included an end-to-end test and baseline establishment. The end-to-end test was performed using a CIRS dynamic thoracic phantom with a moving cylinder inside the lung, which was used for carrying both optically simulated luminescence detectors (OSLDs) and Gafchromic EBT2 films while the target is moving, for a point dose check and 2D profile check. In addition, baselines were established for beam-on temporal delay and calibration of the surrogate, for both megavoltage (MV) and kilovoltage (kV) beams. A motion simulation device (MotionSim) was used to provide periodic motion on a platform, in synchronizing with a surrogate motion. The overall accuracy and uncertainties were analyzed and compared. Results: The OSLD readings were within 5% compared to the planned dose (within measurement uncertainty) for both phase and amplitude gated deliveries. Film results showed less than 3% agreement to the predicted dose with a standard sinusoid motion. The gate-on temporal accuracy was averaged at 139 ± 10 ms for MV beams and 92 ± 11 ms for kV beams. The temporal delay of the surrogatemore » motion depends on the motion speed and was averaged at 54.6 ± 3.1 ms for slow, 24.9 ± 2.9 ms for intermediate, and 23.0 ± 20.1 ms for fast speed. Conclusions: A comprehensive gating commissioning procedure was introduced for verifying the output accuracy and establishing the temporal accuracy baselines with respiratory gating. The baselines are needed for routine quality assurance tests, as suggested by TG-142.« less

Purpose: This work presents a method of collision predictions for external beam radiotherapy using surface imaging. The present methodology focuses on collision prediction during treatment simulation to evaluate the clearance of a patient’s treatment position and allow for its modification if necessary. Methods: A Kinect camera (Microsoft, Redmond, WA) is used to scan the patient and immobilization devices in the treatment position at the simulator. The surface is reconstructed using the skanect software (Occipital, Inc., San Francisco, CA). The treatment isocenter is marked using simulated orthogonal lasers projected on the surface scan. The point cloud of this surface is then shifted to isocenter and converted from Cartesian to cylindrical coordinates. A slab models the treatment couch. A cylinder with a radius equal to the normal distance from isocenter to the collimator plate, and a height defined by the collimator diameter is used to estimate collisions. Points within the cylinder clear through a full gantry rotation with the treatment couch at 0° , while points outside of it collide. The angles of collision are reported. This methodology was experimentally verified using a mannequin positioned in an alpha cradle with both arms up. A planning CT scan of the mannequin was performed, two isocenters were marked in pinnacle, and this information was exported to AlignRT (VisionRT, London, UK)—a surface imaging system for patient positioning. This was used to ensure accurate positioning of the mannequin in the treatment room, when available. Collision calculations were performed for the two treatment isocenters and the results compared to the collisions detected the room. The accuracy of the Kinect-Skanect surface was evaluated by comparing it to the external surface of the planning CT scan. Results: Experimental verification results showed that the predicted angles of collision matched those recorded in the room within 0.5°, in most cases (largest deviation −1.2°). The accuracy study for the Kinect-Skanect surface showed an average discrepancy between the CT external contour and the surface scan of 2.2 mm. Conclusions: This methodology provides fast and reliable collision predictions using surface imaging. The use of the Kinect-Skanect system allows for a comprehensive modeling of the patient topography including all the relevant anatomy and immobilization devices that may lead to collisions. The use of this tool at the treatment simulation stage may allow therapists to evaluate the clearance of a patient’s treatment position and optimize it before the planning CT scan is performed. This can allow for safer treatments for the patients due to better collision predictions and improved clinical workflow by minimizing replanning and resimulations due to unforeseen clearance issues.

Image-guided radiotherapy (IGRT) aims to take into account the anatomical variations occurring during the course of radiotherapy, by direct or indirect visualization of the target volume followed by a corrective action. The movements of the target, or at least the set-up errors are corrected by moving the treatment table, corresponding to the simplest and most validated IGRT modality in a standard practice. The deformations of the target volume and organs at risk are however much more common, and unfortunately much more complicated to consider, requiring multiple planning before or during the treatment, corresponding to the adaptive radiotherapy strategies. The planning target volume must be carefully chosen according to these anatomic variations. This article reviews the modalities of IGRT, standard or under evaluation, according to the different tumour sites.

In the present study, we investigated the clinical effects of image-guided iodine-125 ((125)I) seed on unresectable pancreatic cancer. Twenty-five patients with unresectable pancreatic cancer were enrolled in this study, including 13 patients with seed implantation and 12 patients as control. The survival status, clinical benefits, objective curative effects, and relevant tumor markers were analyzed to assess the feasibility and safety of interstitial (125)I seed implantation. We found that the clinical benefit rate of the seed implantation group is 92.3 % (12/13), compared with 41.7 % (5/12) in the control, and the difference was statistically significant (p 0.05). In conclusion, (125)I seed implantation provides a safe and effective method to inhibit the tumor development, relieve pain, and improve quality of life for unresectable pancreatic cancer. These findings need to be validated by conducting further studies with larger cohorts.

Poster: "2014 CSM / R-0205 / Inter- and intra-fraction motion in stereotactic body radiotherapy for spinal and paraspinal tumours using cone beam computed tomography and positional correction in six degrees of freedom " by: " R. Finnigan , B. Lamprecht, K. Jones, T. Barry, J. Boyd, B. Burmeister, M. Foote; WOOLLOONGABBA/AU"

Several imaging and image guidance reviews are present in the literature for both photon and proton (ion) [1–9] beam therapy. In the present commentary we discuss imaging technology presently avail...

A method is presented in which the couch position is predicted before the treatment instead of obtaining a reference position at the first treatment fraction. This prevents systematic differences in patient posture between preparation and treatment. In literature, only limited data are available on couch positioning. We position our patients at the planned couch position, allowing a small difference between skin marks and lasers, followed by online imaging. For a 3-month period, our standard deviations (mm) in couch position in the vertical, longitudinal, and lateral directions were head and neck-1.6, 2.8, and 2.5; thorax-2.9, 5.5, and 4.5; breast-3.0, 4.1, and 4.0; and pelvis-3.5, 4.0, and 4.7, respectively. We have improved the reproducibility of patient posture in our institute by using the predicted couch position. Our data may serve as a reference for other institutes because the couch position variation is less than that published in literature.

Medical image fusion plays an important role in diagnosis and treatment of diseases such as image-guided radiotherapy and surgery. Although numerous medical image fusion methods have been proposed, most of these approaches are sensitive to the noise and usually lead to fusion image distortion, and image information loss. Furthermore, they lack universality when dealing with different kinds of medical images. In this paper, we propose a new medical image fusion to overcome the aforementioned issues of the existing methods. It is achieved by combining with rolling guidance filter (RGF) and spiking cortical model (SCM). Firstly, saliency of medical images can be captured by RGF. Secondly, a self-adaptive threshold of SCM is gained by utilizing the mean and variance of the source images. Finally, fused image can be gotten by SCM motivated by RGF coefficients. Experimental results show that the proposed method is superior to other current popular ones in both subjectively visual performance and objective criteria.

In this review, we review the literature on the use of PET in radiation treatment planning, with an emphasis on describing our institutional methodology (where applicable). This discussion is intended to provide other radiation oncologists with methodological details on the use of PET imaging for treatment planning in radiation oncology, or other oncologists with an introduction to the use of PET in planning radiation therapy.

Indication, doses, and technique of radiotherapy for salivary glands carcinoma are presented, and the contribution of neutrons and carbon ions. The recommendations for delineation of the target volumes and organs at risk are detailed.

High dose rate (HDR) brachytherapy treatment planning is conventionally performed manually and/or with aids of preplanned templates. In general, the standard of care would be elevated by conducting an automated process to improve treatment planning efficiency, eliminate human error, and reduce plan quality variations. Thus, our group is developing AutoBrachy, an automated HDR brachytherapy planning suite of modules used to augment a clinical treatment planning system. This paper describes our proof-of-concept module for vaginal cylinder HDR planning that has been fully developed. After a patient CT scan is acquired, the cylinder applicator is automatically segmented using image-processing techniques. The target CTV is generated based on physician-specified treatment depth and length. Locations of the dose calculation point, apex point and vaginal surface point, as well as the central applicator channel coordinates, and the corresponding dwell positions are determined according to their geometric relationship with the applicator and written to a structure file. Dwell times are computed through iterative quadratic optimization techniques. The planning information is then transferred to the treatment planning system through a DICOM-RT interface. The entire process was tested for nine patients. The AutoBrachy cylindrical applicator module was able to generate treatment plans for these cases with clinical grade quality. Computation times varied between 1 and 3 min on an Intel Xeon CPU E3-1226 v3 processor. All geometric components in the automated treatment plans were generated accurately. The applicator channel tip positions agreed with the manually identified positions with submillimeter deviations and the channel orientations between the plans agreed within less than 1 degree. The automatically generated plans obtained clinically acceptable quality.