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ilustraciones Hemos desarrollado un software que utiliza conceptos de redes complejas y el método de la matriz de riesgo para realizar análisis de riesgo en servicios de radioterapia. Además de medir la importancia de las barreras y proyectar la implementación de barreras faltantes según su robustez, el software permite el estudio de la dinámica en servicios o modelos sometidos a fallas y ataques en las barreras. Para definir la red de sucesos y barreras, utilizamos una red bipartita y pesada que consta de un grupo de nodos que representan los sucesos iniciadores y otro que representa las barreras, cuyas conexiones son ponderadas por la robustez de las barreras. Se crearon estas redes para los modelos de errores y fallos potenciales (FMEA) en radioterapia convencional (MARR) y con técnicas avanzadas (MARRTA), y se utilizó un algoritmo para determinar los riesgos a partir de estas redes. La definición de la red permitió estudiar la dinámica de los modelos y servicios reales cuando se someten a fallas o ataques en sus barreras, definiendo cuatro fases según la fracción de barreras que fallan o se atacan, donde cada fase corresponde al dominio global de un nivel de riesgo específico. Durante la implementación del software, se obtuvieron análisis de riesgo de los modelos MARR y MARRTA, y se comprobó que los resultados obtenidos coinciden con los reportados. También realizamos el análisis de un caso hipotético donde el nivel base de frecuencia de los iniciadores del modelo MARRTA se aumentó en un nivel, encontrando que existe una fase de dominio del nivel de riesgo muy alto cuando se generan fallas en el 99% de las barreras. Además, estudiamos tres servicios reales identificando que la implementación de barreras con una robustez normal resultó en una mayor disminución de riesgos en comparación con la implementación de las barreras con mayor robustez. (Texto tomado de la fuente) We have developed a software that uses complex network concepts and the risk matrix method to perform risk analysis in radiotherapy services. In addition to measuring the importance of barriers and projecting the implementation of missing barriers according to their robustness, the software allows the study of dynamics in services or models subjected to failures and attacks on barriers. To define the event and barrier network, we use a weighted bipartite network consisting of a group of nodes representing initiating events and another representing barriers, whose connections are weighted by the robustness of the barriers. We create these networks for potential error and failure modes (FMEA) in conventional radiotherapy (MARR) and with advanced techniques (MARRTA), and then use an algorithm to determine risks from these networks. The network definition allowed us to study the dynamics of real services and models when subjected to failures or attacks on their barriers, defining four phases according to the fraction of barriers that fail or are attacked, where each phase corresponds to the global domain of a specific risk level. During the software implementation, we obtained risk analyses of the MARR and MARRTA models, verifying that we obtain the same results as reported. We also conducted the analysis of a hypothetical case where the base frequency level of the MARRTA model initiators was increased by one level, finding that there is a phase of very high-risk level dominance when failures occur in 99% of the barriers. Additionally, we studied three real services identifying that the implementation of barriers with normal robustness resulted in a greater decrease in risks compared to the implementation of barriers with higher robustness. Maestría Magíster en Física Médica Análisis de riesgo en Radioterapia

Background With advances in treatment, outcomes for early-stage breast cancer are improving. We investigated the combination of prone position and deep inspiration breath hold to decrease cardiac doses for left-sided breast radiotherapy. Material and Methods Fifteen patients with left-sided breast cancer were enrolled on a single-institution prospective study. Each patient underwent 2 prone positioned computed tomography simulation scans utilizing free breathing and breath-hold. Separate treatment plans for each computed tomography simulation scan were created using tangential fields, and heart and left lung doses were compared between free breathing and breath-hold plans. The technique with the lower mean dose for the heart was used for treatment. All patients were treated with a hypofractionated regimen of 40 to 42 Gy in 15 to 16 fractions, followed by a lumpectomy cavity boost of 10 Gy in 5 fractions when indicated. Wilcoxon paired signed rank tests and paired t tests were performed for statistical analysis of dosimetric endpoints. Results The median age of our patients was 58 years (range, 40-72 years). One patient was not able to tolerate prone positioning at simulation, leaving 14 patients with evaluable paired scans. The average mean heart dose with free breathing and with breath-hold was 0.93 Gy and 0.72 Gy, respectively (P = .0063). The average max heart dose with free breathing and with breath-hold was 15.70 Gy and 7.19 Gy, respectively (P = .001). The average mean left lung dose with free breathing and with breath-hold was 0.65 Gy and 0.88 Gy, respectively (P = .011). Conclusions Our results indicate that breath-hold using the real-time position management system may provide additional cardiac dose reduction in patients receiving prone left-breast radiotherapy treated with tangential fields.

PURPOSE: Although 24 Gy single-dose radiation therapy (SDRT) renders >90% 5-year local relapse-free survival in human solid tumor lesions, SDRT delivery is not feasible in ~50% of oligometastatic lesions owing to interference by dose/volume constraints of a serial organ at risk (OAR). Conformal OAR avoidance is based on a hypothetical model positing that the recently described SDRT biology specifically permits volumetric subdivision of the SDRT dose, such that high-intensity vascular drivers of SDRT lethality, generated within a major tumor subvolume exposed to a high 24 Gy dose (high-dose planning target volume [PTV(HD])), would equilibrate SDRT signaling intensity throughout the tumor interstitial space, rendering bystander radiosensitization of a minor subvolume (perfusion-modulated dose sculpting PTV [PTV(PMDS)]), dose-sculpted to meet a serial OAR dose/volume constraint. An engineered PTV(PMDS) may thus yield tumor ablation despite PMDS dose reduction and conformally avoiding OAR exposure to a toxic dose. METHODS AND MATERIALS: Dose fall-off within the PTV(PMDS) penumbra of oligometastatic lesions was planned and delivered by intensity modulated inverse dose painting. SDRT- and SDRT-PMDS–treated lesions were followed with periodic positron emission tomography/computed tomography imaging to assess local tumor control. RESULTS: Cumulative baseline 5-year local relapse rates of oligometastases treated with 24 Gy SDRT alone (8% relapses, n = 292) were similar in moderate PTV(PMDS) dose-sculpted (23-18 Gy, n = 76, 11% relapses, P = .36) and extreme dose-sculpted (

ClearRT helical kVCT imaging for the Radixact helical tomotherapy system recently received FDA approval and is available for clinical use. The system is intended to enhance image fidelity in radiation therapy treatment planning and delivery compared to the prior MV-based onboard imaging approach. The purpose of this work was to characterize the imaging performance of this system and compare this performance with that of clinical systems used in image-guided and/or adaptive radiotherapy (ART) or computed tomography (CT) simulation, including Radixact MVCT, TomoTherapy MVCT, Varian TrueBeam kV OBI CBCT, and the Siemens SOMATOM Definition Edge kVCT. A CT image quality phantom was scanned across clinically relevant acquisition modes for each system to evaluate image quality metrics, including noise, uniformity, contrast, spatial resolution, and CT number linearity. Similar noise levels were observed for ClearRT and Siemens Edge, whereas noise for the other systems was ∼1.5-5 times higher. Uniformity was best for Siemens Edge, whereas most scans for ClearRT exhibited a slight "cupping" or "capping" artifact. The ClearRT and Siemens Edge performed best for contrast metrics, which included low-contrast visibility and contrast-to-noise ratio evaluations. Spatial resolution was best for TrueBeam and Siemens Edge, whereas the three kVCT systems exhibited similar CT number linearity. Overall, these results provide an initial indication that ClearRT image quality is adequate for image guidance in radiotherapy and sufficient for delineating anatomic structures, thus enabling its use for ART. ClearRT also showed significant improvement over MVCT, which was previously the only onboard imaging modality available on Radixact. Although the acquisition of these scans does come at the cost of additional patient dose, reported CTDI values indicate a similar or generally reduced machine output for ClearRT compared to the other systems while maintaining comparable or improved image quality overall.

Objective of the present study was to investigate the tolerant radiation dose of nasal mucosa by observing and analyzing patients who received intensity-modulated radiation therapy (IMRT). Patients with nasopharyngeal carcinoma (N = 66) were selected for this study. The modified saccharin assay, endoscopy test, magnetic resonance imaging, and sino-nasal outcome test-20 (SNOT-20) survey were performed for the patients before and at 0 (T0), 3 (T1), 6 (T2), and 12 (T3) months after radiotherapy. The threshold doses of IMRT before radiotherapy and at T0, T1, T2, and T3 were determined as, respectively, 37 Gy, 37 Gy, 39 Gy, and 37 Gy for the saccharin test; 38 Gy, 37 Gy, 40 Gy, and 38 Gy for the endoscopy test; and 39 Gy, 37 Gy, 39 Gy, and 39 Gy for the nasal-related symptom scoring test. The modified saccharin assay, endoscopy test, and SNOT-20 survey revealed that a low dose (

Purpose To present a planning strategy for proton pencil-beam scanning when titanium implants need to be crossed by the beam. Methods We addressed three issues: the implementation of a CT calibration curve to assign to titanium the correct stopping power; the effect of artefacts on CT images and their reduction by a dedicated algorithm; the differences in dose computation depending on the dose engine, pencil-beam vs Monte-Carlo algorithms. We performed measurement tests on a simple cylinder phantom and on a real implant. These phantoms were irradiated with three geometries (single spots, uniform mono-energetic layer and uniform box), measuring the exit dose either by radio-chromic film or multi-layer ionization chamber. The procedure was then applied on two patients treated for chordoma. Results We had to set in the calibration curve a mass density equal to 4.37 g/cm3 to saturated Hounsfield Units, in order to have the correct stopping power assigned to titanium in TPS. CT artefact reduction algorithm allowed a better reconstruction of the shape and size of the implant. Monte-Carlo resulted accurate in computing the dose distribution whereas the pencil-beam algorithm failed due to sharp density interfaces between titanium and the surrounding material. Finally, the treatment plans obtained on two patients showed the impact of the dose engine algorithm, with 10–20% differences between pencil-beam and Monte-Carlo in small regions distally to the titanium screws. Conclusion The described combination of CT calibration, artefacts reduction and Monte-Carlo computation provides a reliable methodology to compute dose in patients with titanium implants.

Purpose Continuous monitoring of patient movement is crucial to administering safe radiation therapy (RT). Conventional optical approaches often cannot be used when the patient's surface is blocked by immobilization devices. Millimeter waves (mmWaves) are capable of penetrating nonconductive objects. In this study, we investigated using mmWave technology to monitor patient surface displacements, as well as breathing and cardiac phases, through clothing and body fixtures. Methods A mmWave device was mounted inside the bore of a ring-based radiotherapy linear accelerator and pointed at a reflective surface on top of the couch. Measurements were obtained at displacements of 10, 7.5, 5.0, 2.5, and 1.0 mm at heights 100, 150, and 200 mm below isocenter. Submillimeter displacements were performed at a height of 200 mm. Additionally, millimeter and submillimeter displacements were measured with and without a gown and body mold placed between the surface and the sensor. The device was programmed to transmit chirp signals at 77-81 GHz. The subject's surface was detected by fast Fourier transform (FFT) of the reflected chirp signal within a rough range bin. Fine displacements within that range bin were calculated through phase extraction and phase demodulation. The displacement data were sent through two separate bandpass filters with passbands of 0.1-0.6 and 0.8-2.0 Hz to obtain the subject's breathing and cardiac waveforms, respectively. The breathing and cardiac measurements were compared to those of a Vernier Respiration Monitor Belt and an electrocardiogram (EKG), respectively, to assess validity. Results The device was able to detect millimeter and submillimeter displacements as small as 0.1 mm, as well as monitor displacement with an accuracy within 1 mm in the presence of an obstructive object. The device's breathing and cardiac waveforms exhibited a strong phase correlation between the respiration monitor belt (ρ = 0.9156) and EKG (ρ = 0.7895), respectively. Conclusions The mmWave device can monitor surface displacements with an accuracy better than 0.1 mm without obstructions and better than 1 mm with obstructions. It can also provide real-time monitoring of breathing and cardiac waveforms simultaneously with high correlation with traditional respiratory and cardiac monitoring devices. Overall, mmWave technology demonstrates potential for motion monitoring in the field of radiation oncology.

Purpose Applicator digitization is one of the most critical steps in 3D high-dose-rate brachytherapy (HDRBT) treatment planning. Motivated by recent advances in deep-learning, we propose a deep-learning–assisted applicator digitization method for 3D CT image-based HDRBT. This study demonstrates its feasibility and potential in gynecological cancer HDRBT. Methods and Materials Our method consisted of two steps. The first step used a U-net to segment applicator regions. We trained the U-net using two-dimensional CT images with a tandem-and-ovoid (T&O) applicator and corresponding applicator mask images. The second step applied a spectral clustering method and a polynomial curve fitting method to extract applicator central paths. We evaluated the accuracy, efficiency, and robustness of our method in different scenarios including other T&O cases that were not used in training, a T&O case scanned with cone-beam CT, and Y-tandem and cylinder-applicator cases. Results In test cases with a T&O applicator, average 3D Dice similarity coefficient between automatic and manual segmented applicator regions was 0.93. Average distance between tip positions and average Hausdorff distance between applicator channels determined by our method and manually were 0.64 mm and 0.68 mm, respectively. Although trained only using CT images of T&O cases, our tool can also digitize Y-tandem, cylinder applicator, and T&O applicator scanned in cone-beam CT with error of tip position and Hausdorff distance Conclusions We have developed a deep-learning–assisted applicator digitization tool for 3D CT image–based HDRBT of gynecological cancer. The achieved accuracy, efficiency, and robustness made our tool clinically attractive.

Purpose Interstitial high-dose-rate brachytherapy (BT) is an alternative treatment option to stereotactic body radiotherapy (SBRT) for the ablative treatment of liver malignancies. The aim of the present comparative planning study was to reveal the possibilities and limitations of both techniques with regard to dosimetric properties. Methods and Materials Eighty-five consecutive patients with liver malignancy diagnosis were treated with interstitial BT between 12/2008 and 09/2009. The prescription dose of BT varied between 15 and 20 Gy, depending on histology. For dosimetric comparison, virtual SBRT treatment plans were generated using the original BT planning CTs. Additional margins reflecting the respiratory tumor motion were added to the target volumes for SBRT planning. Results The mean PTVBT was 34.7 cm3 (0.5–410.0 cm3) vs. a mean PTVSBRT of 73.2 cm3 (6.1–593.4 cm3). Regarding the minimum peripheral dose (D99.9), BT achieved the targeted prescription dose of 15 Gy/20 Gy better without violating organ at risk constraints. The dose exposure of the liver was significantly influenced by treatment modality. The liver exposure to 5 Gy was statistically lower with 611 ± 43 cm3 for BT as compared with 694 ± 37 cm3 for SBRT plans (20-Gy group, p = 0.001), corresponding to 41.8% vs. 45.9% liver volume, respectively. Conclusions To the best of our knowledge, this is the first report on the comparison of clinically treated liver BT treatments with virtually planned SBRT treatments. The planning study showed a superior outcome of BT regarding dose coverage of the target volume and exposed liver volume. Nevertheless, further studies are needed to determine ideal applicability for each treatment approach.

PURPOSE To apply the recent code of practice from the IAEA/AAPM, TRS 483, to helical tomotherapy (HT) for reference and relative dosimetry obtaining correction factors for the Exradin A1SL ionization chamber. METHODS The beam quality correction factor for the A1SL chamber was obtained through three different approaches following TRS 483 concepts and compared with published values. The determination of the reference absolute dose for the machine-specific reference (msr) field was complemented with relative dosimetry through the determination of output factors of small fields using different detectors. The response of A1SL was compared with correction-free film results and corrected output factors of other detectors. RESULTS A weighted mean beam quality correction factor of 0.9945± 0.0073 was obtained for the A1SL chamber which is in agreement with values reported in the literature. Output factors obtained with different detectors were in agreement, given the uncertainty level. Considering the film output factors as free of corrections, the average value for A1SL output factors corrections was 1.000 ± 0.007. CONCLUSIONS The beam quality correction factors for the A1SL chamber obtained through the three different pathways recommended by TRS 483 agreed with each other and also with published values. The measurements from the A1SL chamber normalized to the msr field in HT can be taken as output factors for small clinical field sizes without further corrections.

In cancer radiation therapy, large tumor motion due to respiration can lead to uncertainties in tumor target delineation and treatment delivery, thus making active motion management an essential step in thoracic and abdominal tumor treatment. In current practice, patients with tumor motion may be required to receive two sets of CT scans – the initial free-breathing 4-dimensional CT (4DCT) scan for tumor motion estimation and a second CT scan under appropriate motion management such as breath-hold or abdominal compression. The aim of this study is to assess the feasibility of a predictive model for tumor motion estimation in three-dimensional space based on machine learning algorithms. The model was developed based on sixteen imaging features extracted from non-4D diagnostic CT images and eleven clinical features extracted from the Electronic Health Record (EHR) database of 150 patients to characterize the lung tumor motion. A super-learner model was trained to combine four base machine learning models including the Random Forest, Multi-Layer Perceptron, LightGBM and XGBoost, the hyper-parameters of which were also optimized to obtain the best performance. The outputs of the super-learner model consist of tumor motion predictions in the Superior-Inferior (SI), Anterior-Posterior (AP) and Left-Right (LR) directions, and were compared against tumor motions measured in the free-breathing 4DCT scans. The accuracy of predictions was evaluated using Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) through ten rounds of independent tests. The MAE and RMSE of predictions in the SI direction were 1.23 mm and 1.70 mm; the MAE and RMSE of predictions in the AP direction were 0.81 mm and 1.19 mm, and the MAE and RMSE of predictions in the LR direction were 0.70 mm and 0.95 mm. In addition, the relative feature importance analysis demonstrated that the imaging features are of great importance in the tumor motion prediction compared to the clinical features. Our findings indicate that a super-learner model can accurately predict tumor motion ranges as measured in the 4DCT, and could provide a machine learning framework to assist radiation oncologists in determining the active motion management strategy for patients with large tumor motion.

Introduction Intrafractional motion can cause substantial uncertainty in precision radiotherapy. Traditionally, the target volume is defined to be sufficiently large to cover the tumor in every position. With the robotic treatment couch, a real‐time motion compensation can improve tumor coverage and organ at risk sparing. However, this approach poses additional requirements, which are systematically developed and which allow the ideal robotic couch to be specified. Methods and materials Data of intrafractional tumor motion were collected and analyzed regarding motion range, frequency, speed, and acceleration. Using this data, ideal couch requirements were formulated. The four robotic couches Protura, Perfect Pitch, RoboCouch, and RPSbase were tested with respect to these requirements. Results The data collected resulted in maximum speed requirements of 60 mm/s in all directions and maximum accelerations of 80 mm/s2 in the longitudinal, 60 mm/s2 in the lateral, and 30 mm/s2 in the vertical direction. While the two robotic couches RoboCouch and RPSbase completely met the requirements, even these two showed a substantial residual motion (40% of input amplitude), arguably due to their time delays. Conclusion The requirements for the motion compensation by an ideal couch are formulated and found to be feasible for currently available robotic couches. However, the performance these couches can be improved further regarding the position control if the demanded speed and acceleration are taken into account as well.

Purpose Thoracic re-irradiation (re-RT) of lung cancer has been challenged by the tolerance doses of normal tissues. We retrospectively analyzed local control, overall survival (OS) and toxicity after thoracic re-RT using highly conformal radiotherapy, such as intensity modulated radiotherapy and stereotactic body radiotherapy. Materials and methods Thirty-one patients who received high-dose thoracic re-RT were analyzed. Doses were recalculated to determine biologically equivalent doses. The median interval to re-RT was 15.1 months (range, 4.4 to 56.3 months), the median initial dose was 79.2 Gy10 (range, 51.75 to 150 Gy10), and the median re-RT dose was 68.8 Gy10 (range, 43.2 to 132 Gy10). Results Eighteen (58.1%) and eleven (35.5%) patients showed loco-regional recurrence and distant metastasis, respectively, after 17.4 months of median follow-up. The 1-year and 2-year local control rates were 60.2% and 43.7%, respectively. The median loco-regional recurrence-free-survival (LRFS) was 15.4 months, and the median OS was 20.4 months. The cumulative and re-RT biologically equivalent dose for α/β=10 (BED10) doses were the most significant prognostic factors. Cumulative BED10 ≥145 Gy10 and re-RT BED10≥68.7 Gy10 were significantly associated with longer OS (p=0.029 and p=0.012, respectively) and LRFS (p=0.003 and p=0.000, respectively). The most frequent acute toxicity was grade 1-2 pulmonary toxicity (41.9%). No acute grade 3 or higher toxicities occurred. Conclusion Our results show that high-dose thoracic re-RT of lung cancer can be safely delivered using highly conformal radiotherapy with favorable survival and acceptable toxicity. An optimal strategy to select patients who would benefit from re-RT is crucial in extending the indications and improving the efficacy with a sufficiently high dose.

PURPOSE With the introduction of dynamic tumor tracking in radiotherapy, it is possible to irradiate moving targets with minimal safety margins. However, most dynamic tumor tracking techniques rely on changing the beam geometry by, for example, adapting the multileaf collimator (MLC) positions or rotating the LINAC head. These changes are relative to a reference position which is determined by a specific breathing phase. Since these changes in the beam path also influence the delivered dose, choosing a different reference position based on a different breathing phase impacts the applied dose to the patient. This work investigates the influence of choosing different reference breathing phases on the dose distribution. METHODS The Vero system tracks the moving target by performing a pan and tilt rotation of the LINAC head. For 13 patients, the target position was extracted from every phase of a four-dimensional computed tomography (4DCT) and the pan and tilt values were determined with respect to three different reference phases. These reference phases were inspiration, expiration, and the midventilation. For all reference phases, a 4D dose calculation was performed on the 4DCT regarding the respective pan and tilt values. Furthermore, the applied dose to the target and surrounding organs at risk was calculated. To accumulate the dose distribution, weights from the actual patient breathing motion were determined. The weights were calculated from the breathing motions from different days to investigate the impact of daily variations in the breathing motion onto the accumulated dose distribution. All obtained values were then compared to the static treatment plan. RESULTS The mean and maximum doses applied to the target or surrounding organs at risk show no general behavior depending on the different reference phases. Nevertheless, for some patients, large differences (approx. 30%) in the applied dose to certain organs at risk could be observed, whereas the applied dose to the target shows no dependency on the different reference phases. However, the mean target dose is in all cases approx. 1.5% below the reference value from the static treatment plan. CONCLUSION Although no general dependency of the applied dose on the selected reference phase could be found, the choice of the reference phase can have great impact on the organ at risk dose for some patients. Thus, the choice of the reference phase used for patient positioning should be considered during treatment planning since it can be seen as a new degree of freedom of a treatment based on tracking.

Perirectal hyaluronate gel injection (HGI) appears to be a promising technique for healthy tissue dose sparing in pelvic radiotherapy. In this analysis, we report our initial experience of HGI in gynecologic brachytherapy, focusing on its safety and effectiveness for dose reduction to the rectum. Between July 2013 and May 2014, 36 patients received HGI for primary/salvage gynecologic brachytherapy. Dosimetric effect analysis was based on pre- and post-HGI computed tomography dataset registration with corresponding dose–volume histogram evaluation. The maximum dose to the most exposed 0.1 cm3 (D0.1cm3) and 2.0 cm3 (D2.0cm3) were used as index values for rectum and bladder dose evaluation. The dose indexes for target volume (TV) coverage were TV D90/V100. In all cases, HGI was well tolerated, with no acute or late adverse events documented at a median follow-up of 220 days (range, 18–1046 days). Rectum D2.0cm3 and D0.1cm3 were significantly decreased by HGI (P < 0.001 and P = 0.003, respectively), with no significant impact on dosimetric parameters of bladder and TV coverage. Factors correlating negatively with the dosimetric effect of HGI were an increasing number of interstitial catheters (P = 0.003) as well as Lcranial100% (P = 0.014) and Lcranial80% (P = 0.001) [i.e. the length from the anal verge to the most cranial point at which the 100% and 80% isodose lines, respectively, crossed the rectum]. The concept of HGI for gynecologic brachytherapy is plausible, and our initial experience indicates it to be an effective technique for rectal dose reduction in radiotherapy of intrapelvic tumours.

ilustraciones, tablas La transición de los tratamientos de radioterapia hacia el hipofraccionamiento ha llevado a considerar nuevos objetivos de planeación. Estos nuevos objetivos se encuentran en las recomendaciones de el reporte número 91 de la ICRU, publicado en 2017. En el presente trabajo se estudiaron esquemas de radioterapia estereotáxica de 5 sesiones para tumores de próstata de bajo riesgo, meningioma, metástasis cerebral y carcinoma de pulmón de célula no pequeña. Se utilizaron 4 metodologías con usos diferentes de objetivos de dosis, volumen y gEUD tanto en el PTV como en estructuras auxiliares, llamadas cascarones concéntricos para comparar la caída de dosis en cada una de estas, así como sus dosis uniformes equivalentes generalizadas, probabilidades de complicación tumoral y probabilidades de complicación del tejido sano. También se realizó el control de calidad de paciente específico con el dispositivo ArcCheck y aplicando los índices γ y DTA. Se encontró que el uso de objetivos de gEUD en cascarones concéntricos al PTV, aumenta la caída de dosis máxima alrededor de 12 % y la dosis media en alrededor de 5 % en los primeros 10 mm por fuera del PTV. Además, los objetivos de gEUD lograron una mejor conformación del PTV por la dosis de prescripción y mostraron una reducción del índice de conformación entre 3 % y 7 %. Los análisis QA de paciente específico mostraron un buen desempeño de los planes con los parámetros γ (3mm, 3 %) mayores al 95 % y γ (2mm, 2 %) mayores al 90 %. Adicionalmente, se evidenció que en las metodologías donde se aplicaron los objetivos a los cascarones concéntricos obtuvieron TCP, NTCP y gEUD similares a la metodología con la que se desarrollan los planes en la actualidad, con una diferencia menor al 0.2 % en las TCP y NTCP. También se encontró que se debe tener precaución con la aplicación del modelo de Niemierko en el quiasma y los nervios ópticos, esto debido a las diferencias en los parámetros radiobiológicos reportados en la literatura. Otro resultado que vale la pena mencionar es que reducir la prioridad de los objetivos upper del PTV puede generar un aumento significativo en la dosis alrededor de éste. The transition to hypofractonation of radiation therapy treatments has outlined to considering new panning objectives. These new objectives are found in ICRU report No. 91, published in 2017. Different schemes of 5-session stereotaxic radiation therapy were created for tummors of prostate (low risk), meningioma, brain metastasis and non-small cell lung carcinoma. 4 different planning methodologies, with differnet approaches in the optimization objectives of the PTV and auxiliary structures named concentical shells, were used to compare the dose fall-off in each case, as well as the equivalent uniform doses, tummor control probability and normal tissue complication probability. Measurement of pacient-specific QA were done with the ArcCHECK appareil , using γ and DTA analysis. It was found that the use of gEUD objectives in concentrical shells around the PTV improves the dose fall-off around a 12 % and the mean doses around a 5 % in the first 10 mm outside the PTV in the plans. Furthermore, the gEUD objectives showed a better conformity of the PTV around 3 % and 7 %. The specific patient QA analysis demonstrated the good performance of the plans in the machine, showing γ (3mm, 3 %) parameters greater than 95 % and γ (2 mm, 2 %) greater than 90 %. Aditionally, the plans where objectives where defines in the concentical shells exhibited similar TCP, NTCP and gEUD to the traditional plans, with a difference in the TCP’s and NTCP’s lower than 0.2 %. Another interessant finding was that reducing the priority of upper type objectives in the PTV should result in an increment in the dose in its surroundings. (Text taken from source) Maestría Mágister en Física Médica Radioterapia

Introduction Selective Internal Radiation Therapy (SIRT) is used for the treatment of hepatic tumors. The aim of this retrospective study was to compare two dosimetric approaches based on 99mTc-MAA SPECT/CT and 90Y PET/CT, using Simplicit90Y™ versus the supplier suggested method of activity calculation. Material and methods A total of 19 patients underwent 21 SIRT after baseline angiography and 99mTc-MAA SPECT/CT, followed by 90Y PET/CT. Overlap between 99mTc-MAA and 90Y-microspheres was quantified with different thresholds isocontours. The perfused volume and tumor absorbed dose were estimated using Simplicit90Y™ based on SPECT/CT and PET/CT, then compared with the supplier suggested method. These data were related to overall survival to evaluate their prognostic impact. Results The overlap between PET/CT and SPECT/CT was dependent on thresholds, decreasing with an increasing threshold. The overlap between the 99mTc-MAA and 90Y-microspheres biodistributions versus the tumor distribution on morphological imaging was suboptimal, in particular for small tumor volume. The tumor absorbed dose estimated after 90Y PET/CT was not different from tumor absorbed dose estimated after SPECT/CT. The Perfused lobe absorbed dose was significantly lower while the volume of the perfused lobe was significantly higher when estimated by Simplicit90Y™ compared to the supplier suggested conventional approach. A statistical parameter based on overlap between tumor and 90Y-microspheres distribution as well as tumoral dosimetry was significantly related to the overall survival. Conclusion Post-treatment imaging remains paramount to estimate the irradiation dosimetry, due to an imperfect overlap. The perfused volume could be estimated from functional imaging, given its impact on dosimetry. Finally, survival seems related to tumoral overlap and dosimetry.

International audience; Radiomics is a field that has been growing rapidly for the past ten years in medical imaging and more particularly in oncology where the primary objective is to contribute to personalised and predictive medicine. This short review aimed at providing some insights regarding the potential value of radiomics for cancer patients treated with radiotherapy. Radiomics may contribute to each stage of the patients’ management: diagnosis, planning, treatment monitoring and post-treatment follow-up (toxicity and response). However, its applicability in clinical routine is currently hindered by several factors, including lack of automation, standardisation and harmonisation. A major effort must be carried out to automate the workflow, standardise radiomics good practices and carry out large-scale studies before any transfer to daily clinical practice.; La radiomique est un champ de recherche qui s’est incroyablement développé durant cette dernière décennie, en particulier en oncologie, où le but est principalement de contribuer à une médecine personnalisée et prédictive. Cette courte revue a pour but de fournir un aperçu de la valeur potentielle de la radiomique pour la prise en charge des patients atteints de cancer traités par irradiation. Le bénéfice de la radiomique se dessine en effet à chacune des étapes de la prise en charge, depuis le diagnostic jusqu’au suivi, en passant par la planification et la prédiction de la toxicité et de la réponse thérapeutique. Néanmoins, le transfert en routine clinique de la radiomique est pour l’instant ralenti par plusieurs facteurs, dont le manque d’automatisation, de standardisation et d’harmonisation. Un effort majeur doit être mené afin d’automatiser le processus, standardiser les bonnes pratiques et réaliser des études à grande échelle, avant tout transfert en routine clinique.

Purpose/objectivesRecently a 1.5 Tesla MR Linac has been FDA approved and is commercially available. Clinical series describing treatment methods and outcomes for upper abdominal tumors using a 1.5 Tesla MR Linac are lacking. We present the first clinical series of upper abdominal tumors treated using a 1.5 Tesla MR Linac along with the acquisition of intra-treatment quantitative imaging.Materials/methods10 patients with abdominal tumors were treated at our institution. Each patient enrolled in an IRB approved advanced imaging protocol. Both daily real-time adaptive and non-adaptive methods were used, and selection criteria are described. Adaptive plans were based on pre-beam motion-averaged or mid-position images derived from respiratory-correlated 4D-MRI. Quantitative intravoxel incoherent motion diffusion-weighted imaging and T2 mapping were acquired during plan adaptation. Real-time motion monitoring using cine MRI was performed during beam-on.ResultsMedian patient age was 68.2, five patients were female. Tumor types included liver metastatic lesions from melanoma and sarcoma, primary liver hepatocellular carcinoma (HCC), and regional abdominal tumors included pancreatic metastatic lesions from renal cell carcinoma (RCC) along with two cases of recurrent pancreatic cancer. Doses included 30 Gy in 6 fractions, 33 Gy in 5 fractions, 50 Gy in 5 fractions, 45 Gy in 3 fractions, and 60 Gy in 3 fractions, depending on the location and clinical circumstances. Treatments were feasible and were successfully completed in all patients without significant acute toxicity, technical complications, or need for back up CT based treatment plans.ConclusionsWe present a first clinical series of patients treated for pancreatic tumors, primary liver tumors, and secondary liver tumors with a 1.5 Tesla MR Linear accelerator using adapt-to-position and adapt-to-shape strategies. Treatments were well tolerated by all patients. Acquisition of fully quantitative MR imaging was feasible during the course of the treatment delivery workflow without extending overall treatment times.

Multimodal imaging has become a standard for planning radiation therapy via magnetic resonance imaging (MRI) or positron emission tomography (PET) in many cancers. However, its use is now old, and its impact has not been much discussed in light of technological improvements in imaging and advances in radiotherapy. However, in 20 years, the exclusive functional imaging has been replaced by hybrid imaging (functional and anatomical) with successive improvements (flight time, detector modifications, digitisation, etc.) have enabled us to go from centimetric resolution to the current 3 to 4mm resolution. This article will specifically review PET technology, its latest advances and the potential impact on radiotherapy, particularly head and neck cancers.

To evaluate the ability of the American Joint Committee on Cancer (AJCC) 8th edition to predict local tumor control and globe salvage for children with retinoblastoma (RB).International, multicenter, registry-based retrospective case series.A total of 2854 eyes of 2097 patients from 18 ophthalmic oncology centers from 13 countries over 6 continents.International, multicenter, registry-based data were pooled from patients enrolled between January 2001 and December 2013. All RB eyes with adequate records to allow tumor staging by the AJCC 8th edition criteria and follow-up to ascertain treatment outcomes were included.Globe-salvage rates were estimated by AJCC clinical (cTNMH) categories and tumor laterality. Local treatment failure was defined as use of enucleation or external beam radiation therapy (EBRT), with or without plaque brachytherapy or intra-arterial chemotherapy (IAC).Unilateral RB occurred in 1340 eyes (47%). Among the 2854 eyes, tumor categories were cT1 to cT4 in 696 eyes (24%), 1334 eyes (47%), 802 eyes (28%), and 22 eyes (1%), respectively. Of these, 1275 eyes (45%) were salvaged, and 1179 eyes (41%) and 400 eyes (14%) underwent primary and secondary enucleation, respectively. The 2- and 5-year Kaplan-Meier cumulative globe-salvage rates without the use of EBRT by cTNMH categories were 97% and 96% for category cT1a tumors, 94% and 88% for cT1b tumors, 68% and 60% for cT2a tumors, 66% and 57% for cT2b tumors, and 32% and 25% for cT3 tumors, respectively. Risk of local treatment failure increased with increasing cT category (P0.001). Cox proportional hazards regression analysis confirmed a higher risk of local treatment failure in categories cT1b (hazard ratio [HR], 3.5; P = 0.004), cT2a (HR, 15.1; P0.001), cT2b (HR, 16.4; P0.001), and cT3 (HR, 45.0; P0.001) compared with category cT1a. Use of plaque brachytherapy and IAC improved local tumor control in categories cT1a (P = 0.031) and cT1b (P0.001).Multicenter, international, internet-based data sharing validated the 8th edition AJCC RB staging to predict globe-salvage in a large, heterogeneous, real-world patient population with RB.

Purpose Radiation therapy delivery during deep inspiration breath-hold (DIBH) reduces the irradiation of the heart and lungs and is therefore recommended for adults with mediastinal lymphoma. However, no studies have addressed the use of DIBH in children. This pilot study investigates the feasibility of and compliance with DIBH in children. Methods and Materials Children from the age of 5 years were recruited to a training session to assess their ability to perform DIBH. No children received radiation therapy. The children were placed in a potential radiation therapy position. The DIBH was voluntary and monitored using an optical surface system providing visual feedback. Children who performed 3 stable DIBHs of 20 seconds each and remained motionless were deemed DIBH compliant. Compliance, equipment suitability, and coaching were further assessed in a semistructured interview. Results We included 33 children (18 healthy and 15 hospitalized children with cancer) with a mean age of 8.5 years (range, 5-15). A total of 28 (85%) children were DIBH compliant. Twenty children were deemed immediately DIBH compliant, and 8 were deemed conditionally DIBH compliant, as DIBH compliance was presumed with custom-made immobilization and/or additional DIBH training. Mean age of the DIBH-compliant and the non-DIBH-compliant children was 8.9 years (range, 5-15) and 6 years (range, 5-9), respectively. Only 1 of 15 hospitalized children was not DIBH compliant and only 1 of all 33 children was unable to grasp the DIBH concept. The available DIBH equipment was suitable for children, and 94% reported that they were happy with training and performing DIBH. Conclusions This pilot study demonstrated that children from the age of 5 years can potentially comply with the DIBH technique and perform stable and reproducible DIBHs suitable for radiation therapy. Custom-made immobilization and adequate training will potentially increase DIBH compliance. A prospective clinical trial ( NCT03315546 ), investigating the dosimetric benefit of radiation therapy delivery in DIBH compared with free breathing with pediatric patients, has been initiated.

Artificial intelligence (AI) has strong logical reasoning ability and independent learning ability, which can simulate the thinking process of the human brain. AI technologies such as machine learning can profoundly optimize the existing mode of anticancer drug research. But at present AI also has its relative limitation. In this paper, the development of artificial intelligence technology such as deep learning and machine learning in anticancer drug research is reviewed. At the same time, we look forward to the future of AI.

Despite significant dosimetric gains, clinical implementation of the 4π non-coplanar radiotherapy on the widely available C-arm gantry system is hindered by limited clearance, and the need to perform complex coordinated gantry and couch motion. A robotic radiotherapy platform would be conducive to such treatment but a new conflict between field size and MLC modulation resolution needs to be managed for versatile applications. This study investigates the dosimetry and delivery efficiency of purposefully creating many isocenters to achieve simultaneously high MLC modulation resolution and large tumor coverage. An integrated optimization framework was proposed for simultaneous beam orientation optimization (BOO), isocenter selection, and fluence map optimization (FMO). The framework includes a least-square dose fidelity objective, a total variation term for regularizing the fluence smoothness, and a group sparsity term for beam selection. A minimal number of isocenters were identified for efficient target coverage. Colliding beams excluded, high-resolution small-field 4π intensity-modulated radiotherapy (IMRT) treatment plans with 50 cm source-to-isocenter distance (SID-50) on 10 Head and Neck (H&N) cancer patients were compared with low-resolution large-field plans with 100 cm SID (SID-100). With the same or better target coverage, the average reduction of [Dmean, Dmax] of 20-beam SID-50 plans from 20-beam SID-100 plans were [2.09 Gy, 1.19 Gy] for organs at risk (OARs) overall, [3.05 Gy, 0.04 Gy] for parotid gland, [3.62 Gy, 5.19 Gy] for larynx, and [3.27 Gy, 1.10 Gy] for mandible. R50 and integral dose were reduced by 5.3% and 9.6%, respectively. Wilcoxon signed-rank test showed significant difference (p

Purpose A retrospective analysis of the dose delivery system (DDS) performances of the initial clinical operation at CNAO (Centro Nazionale di Adroterapia Oncologica) is reported, and compared with the dose delivery accuracy following the implementation of a position feedback control. Methods Log files and raw data of the DDS were analyzed for every field of patients treated with protons and carbon ions between January 2012 and April 2013 (~3800 fields). To investigate the DDS accuracy, the spot positions and the number of particles per spot measured by the DDS and prescribed by the treatment planning system were compared for each field. The impact of deviations on dose distributions was studied by comparing, through the gamma-index method, 2 three-dimensional (3D) physical dose maps (one for prescribed, one for measured data), generated by a validated dose computation software. The maximum gamma and the percentage of points with gamma ≤ 1 (passing volume) were studied as a function of the treatment day, and correlated with the deviations from the prescription in the measured number of particles and spot positions. Finally, delivered dose distributions of same treatment plans were compared before and after the implementation of a feedback algorithm for the correction of small position deviations, to study the effect on the delivery quality. A double comparison of prescribed and measured 3D maps, before and after feedback implementation, is reported and studied for a representative treatment delivered in 2012, redelivered on a polymethyl methacrylate (PMMA) block in 2018. Results Systematic deviations of spot positions, mainly due to beam lateral offsets, were always found within 1.5 mm, with the exception of the initial clinical period. The number of particles was very stable, as possible deviations are exclusively related to the quantization error in the conversion from monitor counts to particles. For the chosen representative patient treatment, the gamma-index evaluation of prescribed and measured dose maps, before and after feedback implementation, showed a higher variability of maximum gamma for the 2012 irradiation, with respect to the reirradiation of 2018. However, the 2012 passing volume is >99.8% for the sum of all fields, which is comparable to the value of 2018, with the exception of one day with 98.2% passing volume, probably related to an instability of the accelerating system. Conclusions A detailed retrospective analysis of the DDS performances in the initial period of CNAO clinical activity is reported. The spot position deviations are referable to beam lateral offset fluctuations, while almost no deviation was found in the number of particles. The impact of deviations on dose distributions showed that the position feedback implementation and the increased beam control capability acquired after the first years of clinical experience led to an evident improvement in the DDS stability, evaluated in terms of gamma-index as a measure of the impact on dose distributions. However, the clinical effect of the maximum gamma variability found in the 2012 representative irradiation is mitigated by averaging along the number of fractions, and the high percentage of passing volumes confirmed the accuracy of the delivery even before the feedback implementation.

Purpose: Multiparametric positron emission tomography (PET)/magnetic resonance imaging (MRI) as a one-stop shop for radiation therapy (RT) planning has great potential but is technically challenging. We studied the feasibility of performing multiparametric PET/MRI of patients with head and neck cancer (HNC) in RT treatment position. As a step toward planning RT based solely on PET/MRI, a deep learning approach was employed to generate synthetic computed tomography (sCT) from MRI. This was subsequently evaluated for dose calculation and PET attenuation correction (AC). Methods and Materials: Eleven patients, including 3 pilot patients referred for RT of HNC, underwent PET/MRI in treatment position after a routine fluorodeoxyglucose-PET/CT planning scan. The PET/MRI scan protocol included multiparametric imaging. A convolutional neural network was trained in a leave-one-out process to predict sCT from the Dixon MRI. The clinical CT-based dose plans were recalculated on sCT, and the plans were compared in terms of relative differences in mean, maximum, near-maximum, and near-minimum absorbed doses for different volumes of interest. Comparisons between PET with sCT-based AC and PET with CT-based AC were assessed based on the relative differences in mean and maximum standardized uptake values (SUVmean and SUVmax) from the PET-positive volumes. Results: All 11 patients underwent PET/MRI in RT treatment position. Apart from the 3 pilots, full multiparametric imaging was completed in 45 minutes for 7 out of 8 patients. One patient terminated the examination after 30 minutes. With the exception of 1 patient with an inserted tracheostomy tube, all dosimetric parameters of the sCT-based dose plans were within ±1% of the CT-based dose plans. For PET, the mean difference was 0.4 ± 1.2% for SUVmean and –0.5 ± 1.0% for SUVmax. Conclusions: Performing multiparametric PET/MRI of patients with HNC in RT treatment position was clinically feasible. The sCT generation resulted in AC of PET and dose calculations sufficiently accurate for clinical use. These results are an important step toward using multiparametric PET/MRI as a one-stop shop for personalized RT planning.

Radiotherapy treatment planning requires accurate modeling of the delivered patient dose, including radiation scatter effects, multi-leaf collimator (MLC) leaf transmission, interleaf-leakage, etc. In fluence map optimization (FMO), a simple dose model is used to first generate an intermediate plan based on pencil-beams. In a second step (segmentation phase), this intermediate plan is then converted into a deliverable treatment plan with MLC segments. In this paper, we investigate novel approaches for the use of a clinical dose engine (CDE) for segmentation of FMO plans in robotic radiotherapy. Segments are sequentially added to the plan. Generation of each next segment is based on the total 3D dose distribution, resulting from already selected segments and the desired FMO dose, considering all treatment beams as candidates for delivery of the new segment. Three versions of the segmentation algorithm were investigated with differences in the integration of the CDE. The combined use of pencil-beams and segments in a segmentation method is non-trivial. Therefore, new methods were developed for the use of segment doses calculated with the CDE in combination with pencil-beams, used for the selection of new segments. For 20 patients with prostate cancer and 12 with liver cancer, segmented plans were compared with FMO plans. All three versions of the proposed segmentation algorithm could well mimic FMO dose distributions. Segmentation with a fully integrated CDE provided the best plan quality and lowest numbers of monitor units and segments at the cost of increased calculation time.

Magnetic resonance imaging (MRI) is often combined with computed tomography (CT) in prostate radiotherapy to optimise delineation of the target and organs-at-risk (OAR) while maintaining accurate dose calculation. Such a dual-modality workflow requires two separate imaging sessions, and it has some fundamental and logistical drawbacks. Due to the availability of new MRI hardware and software solutions, CT examinations can be omitted for prostate radiotherapy simulations. All information for treatment planning, including electron density maps and bony anatomy, can nowadays be obtained with MRI. Such an MRI-only simulation workflow reduces delineation ambiguities, eases planning logistics, and improves patient comfort; however, careful validation of the complete MRI-only workflow is warranted. The first institutes are now adopting this MRI-only workflow for prostate radiotherapy. In this article, we will review technology and workflow requirements for an MRI-only prostate simulation workflow.

In this article we aim to introduce the main considerations in integrating magnetic resonance imaging (MRI) into the radiotherapy workflow. We will cover the use of MRI for improved delineation, considerations regarding MRI-only workflows, and the potential of functional imaging techniques. The challenges of implementing each of these will be discussed to ensure safe usage in radiotherapy.

Aims Magnetic resonance image-guided radiotherapy (MRIgRT) has been clinically implemented since 2014. This technology offers improved soft-tissue visualisation, daily imaging, and intra-fraction real-time imaging without added radiation exposure, and the opportunity for adaptive radiotherapy (ART) to adjust for anatomical changes. Here we share the longest single-institution experience with MRIgRT, focusing on trends and changes in use over the past 4.5 years. Materials and methods We analysed clinical information, including patient demographics, treatment dates, disease sites, dose/fractionation, and clinical trial enrolment for all patients treated at our institution using MRIgRT on a commercially available, integrated 0.35 T MRI, tri-cobalt-60 device from 2014 to 2018. For each patient, factors including disease site, clinical rationale for MRIgRT use, use of ART, and proportion of fractions adapted were summated and compared between individual years of use (2014–2018) to identify shifts in institutional practice patterns. Results Six hundred and forty-two patients were treated with 666 unique treatment courses using MRIgRT at our institution between 2014 and 2018. Breast cancer was the most common disease, with use of cine MRI gating being a particularly important indication, followed by abdominal sites, where the need for cine gating and use of ART drove MRIgRT use. One hundred and ninety patients were treated using ART in 1550 fractions, 67.6% (1050) of which were adapted. ART was primarily used in cancers of the abdomen. Over time, breast and gastrointestinal cancers became increasingly dominant for MRIgRT use, hypofractionated treatment courses became more popular, and gastrointestinal cancers became the principal focus of ART. Discussion MRIgRT is widely applicable within the field of radiation oncology and new clinical uses continue to emerge. At our institution to date, applications such as ART for gastrointestinal cancers and accelerated partial breast irradiation (APBI) for breast cancer have become dominant indications, although this is likely to continue to evolve.

The desire to utilise soft-tissue image guidance at the time of radiation treatment has led to the development of several hybrid magnetic resonance imaging (MRI) linear accelerators (linacs). These systems have the potential to realise the benefits of MRI on the treatment table with the ability of real-time motion management and adaption on a patient-specific basis. There are several MRI-linacs currently being implemented covering both low and high magnetic field strength and two beam-field orientations. Clinical trials have only recently begun with this technology, but their future use as standard radiotherapy practice seems assured. This review article summarises the challenges faced in developing such hybrid technology, the differences and advantages of each of the currently exploited solutions, and their current status.

The reference standard treatment for cervical cancer is concurrent chemoradiotherapy followed by magnetic resonance imaging (MRI)-guided brachytherapy. Improvements in brachytherapy have increased local control rates, but late toxicity remains high with rates of 11% grade ≥3. The primary clinical target volume (CTV) for external-beam radiotherapy includes the cervix and uterus, which can show significant inter-fraction motion. This means that generous margins are required to cover the primary CTV, increasing the radiation dose to organs at risk and, therefore, toxicity. A number of image-guided radiotherapy techniques (IGRT) have been developed, but motion can be random and difficult to predict prior to treatment. In light of the development of integrated MRI linear accelerators, this review discusses the potential value of MRI in external-beam radiotherapy. Current solutions for managing pelvic organ motion are reviewed, including the potential for online adaptive radiotherapy. The impacts of the use of MRI in tumour delineation and in the delivery of stereotactic ablative body radiotherapy (SABR) are highlighted. The potential role and challenges of using multi parametric MRI to guide radiotherapy are also discussed.

The purpose of this study is to create a new pseudo-computed tomography (CT) imaging approach under superposed ultrasound (US) deformation fields based on step-by-step local registration. Scanned CT and US 3D image datasets of three patients with postoperative cervical carcinoma were selected, including CT (CTsim) and US images (USsim) acquired during simulated positioning process and cone beam CT (CBCT) and US images for positioning verification (USpv) acquired after treatment for 10 times. Regions of interest such as urinary bladders were segmented out and accepted local registration to obtain different deformation fields. These deformation fields were successively performed according to their order and then applied to localized CT images to obtain pseudo-CT (CTps). After filtering, we obtained the final correct pseudo-CT (CTpsf). The pseudo-CT based on the mask of the whole imaging region of US images (WCTps) were acquired as control. Then, we compared CTpsf, CTps, WCTps, and CBCT in terms of their similarity in anatomical structure and differences in pseudo-CT and CTsim in terms of dosimetry. Structural similarity degree between CTpsf and CBCT was larger compared with that between CTps and WCTps. Target regions and dosages of endangered organs between CTpsf and CTsim were different under the same calculation conditions based on the Monte Carlo algorithm. Compared with the VMAT plan of CTsim, the pass rate of CTpsf in γ analysis under the standards of 2% dosage difference and 2-mm distance difference was 91.8%. The imaging quality of CTpsf was better compared with WCTps and CTps. It exhibited high similarity with CBCT in anatomical structure and had favorable application prospect in adaptive radiotherapy. Graphical abstract The local deformation registration is performed between the ultrasound images based on different regions of interest, and then stepwise applied to localized CT images to obtain pseudo-CT. After filtering, the corrected pseudo CT image is obtained.

Background and objective: Tracking mobile tumor regions during the treatment is a crucial part of image-guided radiation therapy because of two main reasons which negatively affect the treatment process: (1) a tiny error will lead to some healthy tissues being irradiated; and (2) some cancerous cells may survive if the beam is not accurately positioned as it may not cover the entire cancerous region. However, tracking or delineation of such a tumor region from magnetic resonance imaging (MRI) is challenging due to photometric similarities of the region of interest and surrounding area as well as the influence of motion in the organs. The purpose of this work is to develop an approach to track the center and boundary of tumor region by auto-contouring the region of interest in moving organs for radiotherapy. Methods: We utilize a nonrigid registration method as well as a publicly available RealTITracker algorithm for MRI to delineate and track tumor regions from a sequence of MRI images. The location and shape of the tumor region in the MRI image sequence varies over time due to breathing. We investigate two approaches: the first one uses manual segmentation of the first frame during the pretreatment stage; and the second one utilizes manual segmentation of all the frames during the pretreatment stage. Results: We evaluated the proposed approaches over a sequence of 600 images acquired from 6 patients. The method that utilizes all the frames in the pretreatment stage with moving mesh based registration yielded the best performance with an average Dice Score of 0.89 ± 0.04 and Hausdorff Distance of 3.38 ± 0.10 mm. Conclusions: This study demonstrates a promising boundary tracking tool for delineating the tumor region that can deal with respiratory movement and the constraints of adaptive radiation therapy.

PURPOSE Motion prediction can compensate for latency in image-guided radiotherapy and has been an active area of research. However, motion predictions are subject to error and variations. We have developed and evaluated a novel motion prediction confidence estimation framework to improve the efficacy and robustness of prediction-based radiotherapy gating decision-making. The specific scenario of adaptive gating in magnetic resonance imaging (MRI)-guided radiotherapy is studied as an example, but the method generalizes to other modalities and motion management setups. METHODS The proposed prediction confidence estimator is based on a generic training/testing paradigm and consists of a weighted combination of three components: the prediction model's goodness of fit, variation in the prediction using a leave-one-out process and the velocity of the tracked target. Roughly, these terms quantify respectively the consistency between prediction and the training data, the robustness of model inference, and the stability due to target speed. The weight parameters and the action level in triggering beam-off decision are optimized. The method is assessed and validated in 8 healthy volunteer and 13 patient studies using a 0.35T MRI-guided radiotherapy system predicting 0.25-0.33 s ahead. The effect of the action level on the predicted gating decision accuracy, beam-on positive predictive value (PPV) and median distance between the predicted and ground-truth target centroids were evaluated. Statistical significance was evaluated using a paired t-test. The tradeoff between these performance metrics and gating duty cycle was assessed. RESULTS Use of the confidence estimator threshold increased gating accuracy by up to 2.42%, increased PPV by up to 3.00%, and reduced the median centroid distance up to 0.28 mm. The confidence estimator threshold on average increased gating accuracy to 96.5% (P = 2.08 × 10-4 ), increased PPV to 96.7% (P = 1.46 × 10-5 ), reduced the median centroid distance to 0.54 mm (P = 1.71 × 10-5 ) at the cost of reducing the gating duty cycle by 14.3% to 48.5%. Hyperparameter tuning revealed that contrary to intuition, the velocity term offered only minimal performance improvement in some cases but also introduced potential stability issues. The combination of goodness of fit and leave-one-out prediction variation provided the most effective confidence estimator, yielding universally better performance in gating decisions. CONCLUSION Confidence estimation utilizing prediction model fitness criterion and validation principles can complement prediction methods to guide MRI-guided radiotherapy gating. Results from both volunteer and patient studies showed improved gating quality.

High-precision radiotherapy (HPR) of recurrent high grade glioma (HGG) requires accurate spatial allocation of these infiltrative tumors. We investigated the impact of 18F-FET PET on tumor delineation and progression of recurrent HGG after HPR with carbon ions. T1 contrast enhanced MRI and 18F-FET-PET scans of 26 HGG patients were fused with radiotherapy planning volumes. PET-positive (PET+) tumor volumes using different isocontours (I%) were systematically investigated and compared with MRI-derived gross tumor volumes (GTV). Standardized uptake ratios (SUR) were further correlated with GTV and tumor progression patterns. In grade IV glioma, SUR > 2.92 significantly correlated with poor median overall survival (6.5 vs 13.1 months, p = 0.00016). We found no reliable SUR cut-off criteria for definition of PET+ volumes. Overall conformity between PET and MRI-based contours was low, with maximum conformities between 0.42–0.51 at I40%. The maximum sensitivity and specificity for PET+ volumes outside of GTV predicting tumor progression were 0.16 (I40%) and 0.52 (I50%), respectively. In 75% of cases, FLAIR hyperintense area covered over 80% of PET+ volumes. 18F-FET-PET derived SUR has a prognostic impact in grade IV glioma. The value of substantial mismatches between MRI-based GTV and PET+ volumes to improve tumor delineation in radiotherapy awaits further validation in randomized prospective trials.

International audience; Ion beam therapy enables a highly accurate dose conformation delivery to the tumor due to the finite range of charged ions in matter (i.e. Bragg peak (BP)). Consequently, the dose profile is very sensitive to patients anatomical changes as well as minor mispositioning, and so it requires improved dose control techniques. Proton interaction vertex imaging (IVI) could offer an online range control in carbon ion therapy. In this paper, a statistical method was used to study the sensitivity of the IVI technique on experimental data obtained from the Heidelberg Ion-Beam Therapy Center.The vertices of secondary protons were reconstructed with pixelized silicon detectors. The statistical study used the x2 test of the reconstructed vertex distributions for a given displacement of the BP position as a function of the impinging carbon ions. Different phantom configurations were used with or without bone equivalent tissue and air inserts.The inflection points in the fall-off region of the longitudinal vertex distribution were computed using different methods, while the relation with the BP position was established. In the present setup, the resolution of the BP position was about 4–5 mm in the homogeneous phantom under clinical conditions (106 incident carbon ions). Our results show that the IVI method could therefore monitor the BP position with a promising resolution in clinical conditions.

Purpose: To validate the dosimetric accuracy and clinical robustness of a commercially available software for magnetic resonance (MR) to synthetic computed tomography (sCT) conversion, in an MR imaging–only workflow for 170 prostate cancer patients. Methods and Materials: The 4 participating centers had MriPlanner (Spectronic Medical), an atlas-based sCT generation software, installed as a cloud-based service. A T2-weighted MR sequence, covering the body contour, was added to the clinical protocol. The MR images were sent from the MR scanner workstation to the MriPlanner platform. The sCT was automatically returned to the treatment planning system. Four MR scanners and 2 magnetic field strengths were included in the study. For each patient, a CT-treatment plan was created and approved according to clinical practice. The sCT was rigidly registered to the CT, and the clinical treatment plan was recalculated on the sCT. The dose distributions from the CT plan and the sCT plan were compared according to a set of dose-volume histogram parameters and gamma evaluation. Treatment techniques included volumetric modulated arc therapy, intensity modulated radiation therapy, and conventional treatment using 2 treatment planning systems and different dose calculation algorithms. Results: The overall (multicenter/multivendor) mean dose differences between sCT and CT dose distributions were below 0.3% for all evaluated organs and targets. Gamma evaluation showed a mean pass rate of 99.12% (0.63%, 1 SD) in the complete body volume and 99.97% (0.13%, 1 SD) in the planning target volume using a 2%/2-mm global gamma criteria. Conclusions: Results of the study show that the sCT conversion method can be used clinically, with minimal differences between sCT and CT dose distributions for target and relevant organs at risk. The small differences seen are consistent between centers, indicating that an MR imaging–only workflow using MriPlanner is robust for a variety of field strengths, vendors, and treatment techniques.

In interstitial high-dose rate brachytherapy, liver cancer is treated by internal radiation, requiring percutaneous placement of applicators within or close to the tumor. To maximize utility, the optimal applicator configuration is pre-planned on magnetic resonance images. The pre-planned configuration is then implemented via a magnetic resonance-guided intervention. Mapping the pre-planning information onto interventional data would reduce the radiologist’s cognitive load during the intervention and could possibly minimize discrepancies between optimally pre-planned and actually placed applicators. We propose a fast and robust two-step registration framework suitable for interventional settings: first, we utilize a multi-resolution rigid registration to correct for differences in patient positioning (rotation and translation). Second, we employ a novel iterative approach alternating between bias field correction and Markov random field deformable registration in a multi-resolution framework to compensate for non-rigid movements of the liver, the tumors and the organs at risk. In contrast to existing pre-correction methods, our multi-resolution scheme can recover bias field artifacts of different extents at marginal computational costs. We compared our approach to deformable registration via B-splines, demons and the SyN method on 22 registration tasks from eleven patients. Results showed that our approach is more accurate than the contenders for liver as well as for tumor tissues. We yield average liver volume overlaps of 94.0 ± 2.7% and average surface-to-surface distances of 2.02 ± 0.87 mm and 3.55 ± 2.19 mm for liver and tumor tissue, respectively. The reported distances are close to (or even below) the slice spacing (2.5 – 3.0 mm) of our data. Our approach is also the fastest, taking 35.8 ± 12.8 s per task. The presented approach is sufficiently accurate to map information available from brachytherapy pre-planning onto interventional data. It is also reasonably fast, providing a starting point for computer-aidance during intervention.

Real-time monitoring and amendment of patient position is important for the radiotherapy. However, using electronic portal imaging device (EPID) and cone beam computer tomography (CBCT) in the clinical practice generate different degrees of delay, so that they cannot achieve the purpose of real-time application. Meanwhile, a few products come with the function of the real-time monitoring and amendment, such as CyberKnife, which is too expensive for the common people. The objective of this study is to develop and test a novel independent system to monitor treatment center and amend the position of patient, which is applicable to most accelerators, based on binocular location. The system monitors the treatment center by tracking the markers attached to the patient. Once the treatment center shifts, the system uses the magic finger, which is developed to control the treatment bet automatically to adjust the treatment bed position. To improve the monitoring accuracy, we trained the data collected from the clinic based on SVM (Support Vector Machine). Thus, the training results assist users to adjust the feasible degree of the monitoring. The experiment results showed that using this new monitoring system, the monitoring resolution reached 0.5 mm, and the error ratio of the judgment was less than 1.5%.

Objectives:This study aimed to assess head and neck cancer patient satisfaction with the use of a touch-screen computer patient-completed questionnaire for assessing Adult Co-morbidity Evaluation 27 co-morbidity scores prior to treatment, along with its clinical reliability.Methods:A total of 96 head and neck cancer patients were included in the audit. An accurate Adult Co-morbidity Evaluation 27 co-morbidity score was achieved via patient-completed questionnaire assessment for 97 per cent of participants.Results:In all, 96 per cent of patients found the use of a touch-screen computer acceptable and would be willing to use one again, and 62 per cent would be willing to do so without help. Patients were more likely to be willing to use the computer again without help if they were aged 65 years or younger (χ2test;p= 0.0054) or had a performance status of 0 or 1 (χ2test;p= 0.00034).Conclusion:Use of a touch-screen computer is an acceptable approach for assessing Adult Co-morbidity Evaluation 27 scores at pre-treatment assessment in a multidisciplinary joint surgical–oncology clinic.

Purpose To compare the prognosis of elderly patients with early oesophageal carcinoma between radical elective nodal prophylactic irradiation and involved-field irradiation and to estimate the failure modes and adverse effects, then to provide the patients the safe and individual therapeutic regimens. Material and methods The charts of 96 patients aged 65 and over with early stage oesophageal carcinoma receiving radical radiotherapy in our department were retrospectively analysed. Of all the patients, 49 received elective nodal prophylactic irradiation and the other 47 received involved-field irradiation. After completion of the whole treatment, we analysed short-term effects, tumour local control, overall survival of the patients, failure modes and adverse effects. Results The 1-, 3-, and 5-year local control rate in elective nodal irradiation and involved-field irradiation groups were 80.6%, 57.4%, 54.0% and 65.4%, 46.5%, 30.5% respectively, and the difference was statistically significant (χ2 = 4.478, P = 0.03). The differences of overall survival and progression-free survival were not significant (P > 0.05). The difference of 1-, 3-, and 5-years local regional failure rate was statistically significant between elective nodal prophylactic irradiation and involved-field irradiation groups, except for the overall failure and distant metastasis rates. The overall incidence of radiation-induced oesophagitis after elective nodal irradiation or involved-field irradiation was 79.6% and 59.6%, and the difference was statistically significant (χ2 = 4.559, P = 0.03). The difference of radiation pneumonitis between elective nodal prophylactic irradiation and involved-field irradiation was not significant (12.2% vs 14.9%; χ2 = 0.144, P = 0.7). Conclusion For elderly patients with early stage oesophageal carcinoma receiving radical radiotherapy, although elective nodal prophylactic irradiation could increase the incidence of radiation-induced oesophagitis, patients could tolerate the treatment and benefit from local control.

Background: We evaluated the efficacy, toxicity, and dose responses of re-irradiation with stereotactic body radiotherapy (SBRT) in patients with recurrent non- small cell lung cancer (NSCLC) after previous irradiation. Patients and Methods: 28 patients were included. Previous median radiation doses were 54 and 66 Gy. The median interval time between previous radiotherapy and SBRT was 14 months. The median follow-up time after SBRT was 9 months (range 3-93 months). To evaluate the effectiveness of SBRT, local control, overall survival, and treatment-related toxicity were reported. Results: SBRT doses and fractionation ranged from 60 to 30 Gy and from 3 to 8, respectively, according to previous doses, location of the recurrence, and interval time. 65% of tumor recurrences overlapped with previous treatment, while 35% of tumors recurred outside of the previous treatment. 4 patients had local progression after SBRT at their first follow-up. The Kaplan-Meier estimates of the 1- and 2-year actuarial overall survival were 71 and 42%, respectively. The mean survival following SBRT was 32.8 months, and the median survival was 21 months. No grade 3 or higher toxicities were observed. Conclusion: Robotic SBRT is a tolerable treatment option with manageable toxicity which can be used with radical or palliative intent in carefully selected patients with locally recurrent tumors after previous irradiation.