scholarly journals Quantitative Assessment of 3D Dose Rate for Proton Pencil Beam Scanning FLASH Radiotherapy and Its Application for Lung Hypofractionation Treatment Planning

Cancers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 3549
Author(s):  
Minglei Kang ◽  
Shouyi Wei ◽  
J. Isabelle Choi ◽  
Charles B. Simone ◽  
Haibo Lin
Keyword(s):  
Dose Rate ◽  
Treatment Planning ◽  
Organs At Risk ◽  
Patient Treatment ◽  
Average Dose ◽  
Clinical Implementation ◽  
Flash Intensity ◽  
Dose Threshold ◽  
Rate Calculation ◽  
The Impact

To quantitatively assess target and organs-at-risk (OAR) dose rate based on three proposed proton PBS dose rate metrics and study FLASH intensity-modulated proton therapy (IMPT) treatment planning using transmission beams. An in-house FLASH planning platform was developed to optimize transmission (shoot-through) plans for nine consecutive lung cancer patients previously planned with proton SBRT. Dose and dose rate calculation codes were developed to quantify three types of dose rate calculation methods (dose-averaged dose rate (DADR), average dose rate (ADR), and dose-threshold dose rate (DTDR)) based on both phantom and patient treatment plans. Two different minimum MU/spot settings were used to optimize two different dose regimes, 34-Gy in one fraction and 45-Gy in three fractions. The OAR sparing and target coverage can be optimized with good uniformity (hotspot < 110% of prescription dose). ADR, accounting for the spot dwelling and scanning time, gives the lowest dose rate; DTDR, not considering this time but a dose-threshold, gives an intermediate dose rate, whereas DADR gives the highest dose rate without considering any time or dose-threshold. All three dose rates attenuate along the beam direction, and the highest dose rate regions often occur on the field edge for ADR and DTDR, whereas DADR has a better dose rate uniformity. The differences in dose rate metrics have led a large variation for OARs dose rate assessment, posing challenges to FLASH clinical implementation. This is the first attempt to study the impact of the dose rate models, and more investigations and evidence for the details of proton PBS FLASH parameters are needed to explore the correlation between FLASH efficacy and the dose rate metrics.

scholarly journals Hand Surgery and Fluoroscopic Eye Radiation Dosage

Hand ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 21-25 ◽  
Author(s):  
Mark L. Wang ◽  
C. Edward Hoffler ◽  
Asif M. Ilyas ◽  
William H. Kirkpatrick ◽  
Pedro K. Beredjiklian ◽  
...  
Keyword(s):  
Radiation Exposure ◽  
Dose Rate ◽  
Exposure Time ◽  
Radiation Dosage ◽  
Hand Surgery ◽  
Average Dose ◽  
Total Exposure ◽  
Significant Difference ◽  
Total Exposure Time ◽  
The Impact

Background: The purpose of this study is to (1) perform a prospective pilot comparison of the impact of large versus mini C-arm fluoroscopy on resultant eye radiation exposure and (2) test the hypothesis that the use of either modality during routine hand surgery does not exceed the current recommended limits to critical eye radiation dosage. Methods: Over a 12-month period, eye radiation exposure was prospectively measured by a board-certified hand surgeon using both large and mini C-arm fluoroscopy. For each modality, accumulated eye radiation dosage was measured monthly, while fluoroscopic radiation output was recorded, including total exposure time and dose rate. Results: A total of 58 cases were recorded using large C-arm and 25 cases using mini C-arm. Between the 2 groups, there was not a significant difference with total exposure time ( P = .88) and average dose rate per case ( P = .10). With the use of either modality, average monthly eye radiation exposure fell within the undetectable range (<30 mrem), significantly less than the current recommended limit of critical eye radiation (167 mrem/month). Conclusions: The impact of various fluoroscopic sources on eye radiation exposure remains relatively unexplored. In this study, the minimal detectable eye radiation dosages observed in both groups were reliably consistent. Our findings suggest that accumulated eye radiation dosage, from the use of either fluoroscopic modality, does not approach previously reported levels of critical radiation loads.

scholarly journals Initial Feasibility and Clinical Implementation of Daily MR-guided Adaptive Head and Neck Cancer Radiotherapy on a 1.5T MR-Linac System: Prospective R-IDEAL 2a/2b Systematic Clinical Evaluation of Technical Innovation

2020 ◽  
Author(s):  
Brigid A. McDonald ◽  
Sastry Vedam ◽  
Jinzhong Yang ◽  
Jihong Wang ◽  
Pamela Castillo ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Organs At Risk ◽  
Pass Rate ◽  
Random Errors ◽  
Clinical Implementation ◽  
Adaptive Treatment ◽  
Treatment Plans ◽  
On Line ◽  
The Impact

AbstractIntroductionThis prospective study is the first report of daily adaptive radiotherapy (ART) for head & neck cancers (HNC) using a 1.5T MR-linac, with particular focus on safety & feasibility and dosimetric results of an on-line rigid registration-based adapt-to-position (ATP) workflow.MethodsTen HNC patients received daily ART on a 1.5T/7MV MR-linac, six using ATP only and four using ATP with one off-line adapt-to-shape re-plan. Setup variability with custom immobilization masks was assessed by calculating the average systematic error (M), standard deviation of the systematic error (∑), and standard deviation of the random error (σ) of the isocenter shifts. Quality assurance was performed with a cylindrical diode array using 3%/3mm γ criteria. Adaptive treatment plans were summed for each patient to compare delivered dose with planned dose from the reference plan. The impact of dosimetric variability between adaptive fractions on the summation plan doses was assessed by tracking the number of optimization constraint violations at each individual fraction.ResultsThe random errors (mm) for the x, y, and z isocenter shifts, respectively, were M = − 0.3, 0.7, 0.1; ∑ = 3.3, 2.6, 1.4; and σ = 1.7, 2.9, 1.0. The median γ pass rate was 99.9% (range: 90.9%-100%). The differences between the reference and summation plan doses were within [-0.61%, 1.78%] for the CTV and [-11.74%, 8.11%] for organs at risk (OARs), though percent increases in OAR dose above 2% only occurred in three cases, each for a single OAR. All cases had at least two fractions with one or more constraint violations. However, in nearly all instances, constraints were still met in the summation plan despite multiple single-fraction violations.ConclusionDaily ART on a 1.5T MR-linac using an on-line ATP workflow is safe and clinically feasible for HNC and results in delivered doses consistent with planned doses.

scholarly journals A forward planned treatment planning technique for non-small-cell lung cancer stereotactic ablative body radiotherapy based on a systematic review of literature

2015 ◽  
Vol 14 (4) ◽  
pp. 425-437
Author(s):  
Anne C. Marchant ◽  
Sheela M. Macwan
Keyword(s):  
Treatment Planning ◽  
Organs At Risk ◽  
Target Volume ◽  
Clinical Implementation ◽  
Internal Target Volume ◽  
Stereotactic Ablative Body Radiotherapy ◽  
Starting Point ◽  
Dose Homogeneity ◽  
Set Up ◽  
The Uk

AbstractPurpose and MethodA systematic literature review of six computerised databases was undertaken in order to review and summarise a forward planned lung stereotactic ablative body radiotherapy (SABR) treatment planning (TP) technique as a starting point for clinical implementation in the author’s department based on current empirical research. The data were abstracted and content analysed to synthesise the findings based upon a SIGN quality checklist tool.FindingsA four-dimensional computed tomography scan should be performed upon which the internal target volume and organs at risk (OAR) are drawn. A set-up margin of 5 mm is applied to account for inter-fraction motion. The field arrangement consists of a combination of 7–13 coplanar and non-coplanar beams all evenly spaced. Beam modifiers are used to assist in the homogeneity of the beam, although a 20% planning target volume dose homogeneity is acceptable. The recommended fractionations by the UK SABR Consortium are 54 Gy in 3 fractions (standard), 55–60 Gy in 5 fractions (conservative) and 50–60 Gy in 8–10 fractions (very conservative). Conformity indices for both the target volume and OAR will be used to assess the planned distribution.ConclusionAn overview of a clinically acceptable forward planned lung SABR TP technique based on current literature as a starting point, with a view to inverse planning with support from the UK SABR Consortium mentoring scheme.

scholarly journals Clinical validation of a commercially available deep learning software for synthetic CT generation for brain

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Minna Lerner ◽  
Joakim Medin ◽  
Christian Jamtheim Gustafsson ◽  
Sara Alkner ◽  
Carl Siversson ◽  
...  
Keyword(s):  
Treatment Planning ◽  
Organs At Risk ◽  
Ct Images ◽  
The Body ◽  
Pass Rate ◽  
Geometric Distortion ◽  
Patient Treatment ◽  
Patient Specific ◽  
Body Contour ◽  
Mean Values

Abstract Background Most studies on synthetic computed tomography (sCT) generation for brain rely on in-house developed methods. They often focus on performance rather than clinical feasibility. Therefore, the aim of this work was to validate sCT images generated using a commercially available software, based on a convolutional neural network (CNN) algorithm, to enable MRI-only treatment planning for the brain in a clinical setting. Methods This prospective study included 20 patients with brain malignancies of which 14 had areas of resected skull bone due to surgery. A Dixon magnetic resonance (MR) acquisition sequence for sCT generation was added to the clinical brain MR-protocol. The corresponding sCT images were provided by the software MRI Planner (Spectronic Medical AB, Sweden). sCT images were rigidly registered and resampled to CT for each patient. Treatment plans were optimized on CT and recalculated on sCT images for evaluation of dosimetric and geometric endpoints. Further analysis was also performed for the post-surgical cases. Clinical robustness in patient setup verification was assessed by rigidly registering cone beam CT (CBCT) to sCT and CT images, respectively. Results All sCT images were successfully generated. Areas of bone resection due to surgery were accurately depicted. Mean absolute error of the sCT images within the body contour for all patients was 62.2 ± 4.1 HU. Average absorbed dose differences were below 0.2% for parameters evaluated for both targets and organs at risk. Mean pass rate of global gamma (1%/1 mm) for all patients was 100.0 ± 0.0% within PTV and 99.1 ± 0.6% for the full dose distribution. No clinically relevant deviations were found in the CBCT-sCT vs CBCT-CT image registrations. In addition, mean values of voxel-wise patient specific geometric distortion in the Dixon images for sCT generation were below 0.1 mm for soft tissue, and below 0.2 mm for air and bone. Conclusions This work successfully validated a commercially available CNN-based software for sCT generation. Results were comparable for sCT and CT images in both dosimetric and geometric evaluation, for both patients with and without anatomical anomalies. Thus, MRI Planner is feasible to use for radiotherapy treatment planning of brain tumours.

scholarly journals Impact of 68Ga-DOTATOC PET/MRI on robotic radiosurgery treatment planning in meningioma patients: first experiences in a single institution

2019 ◽  
Vol 46 (6) ◽  
pp. E9 ◽  
Author(s):  
Güliz Acker ◽  
Anne Kluge ◽  
Mathias Lukas ◽  
Alfredo Conti ◽  
Diana Pasemann ◽  
...  
Keyword(s):  
Treatment Planning ◽  
Organs At Risk ◽  
Target Volume ◽  
Data Sets ◽  
Robotic Radiosurgery ◽  
Volume Delineation ◽  
Complex Shapes ◽  
Target Volumes ◽  
Skull Base Lesions ◽  
The Impact

OBJECTIVEFor stereotactic radiosurgery (SRS) planning, precise contouring of tumor boundaries and organs at risk is of utmost importance. Correct interpretation of standard neuroimaging (i.e., CT and MRI) can be challenging after previous surgeries or in cases of skull base lesions with complex shapes. The aim of this study was to evaluate the impact of 68Ga-DOTATOC PET/MRI on treatment planning for image-guided SRS by CyberKnife.METHODSThe authors retrospectively identified 11 meningioma treatments in 10 patients who received a 68Ga-DOTATOC PET/MRI prior to SRS. The planning target volume (PTV) used for the patients’ treatment was defined as the reference standard. This was contoured by a treating radiosurgeon (RS0) using fused planning CT and PET/MRI data sets. The same tumors were then contoured by another experienced radiosurgeon (RS1) and by a less-experienced radiosurgeon (RS2), both blinded to PET data sets. A comparison of target volumes with focus on volume-based metrics and distance to critical structures was performed. RS1 and RS2 also filled in a questionnaire analyzing the confidence level and the subjective need for the implementation of PET data sets for contouring.RESULTSAnalysis showed a subjective personal preference for PET/MRI in all cases for both radiosurgeons, particularly in proximity to critical structures. The analysis of the planning volumes per physician showed significantly smaller RS2-PTV in comparison to RS1-PTV and to RS0-PTV, whereas the median volumes were comparable between RS1-PTV and RS2-PTV (median: RS0: 4.3 cm3 [IQR 3.4–6.5 cm3] and RS1: 4.5 cm3 [IQR 2.7–6 cm3] vs RS2: 2.6 cm3 [IQR 2–5 cm3]; p = 0.003). This was also reflected in the best spatial congruency between the 2 experienced physicians (RS0 and RS1). The percentage of the left-out volume contoured by RS1 and RS2 compared to RS0 with PET/MRI demonstrated a relevant left-out-volume portion in both cases with greater extent for the less-experienced radiosurgeon (RS2) (RS1: 19.1% [IQR 8.5%–22%] vs RS2: 40.2% [IQR 34.2%–53%]). No significant differences were detected regarding investigated critical structures.CONCLUSIONSThis study demonstrated a relevant impact of PET/MRI on target volume delineation of meningiomas. The extent was highly dependent on the experience of the treating physician. This preliminary study supports the relevance of 68Ga-DOTATOC PET/MRI as a tool for radiosurgical treatment planning of meningiomas.

scholarly journals FLASH Radiotherapy Using Single-Energy Proton PBS Transmission Beams for Hypofractionation Liver Cancer: Dose and Dose Rate Quantification

2022 ◽  
Vol 11 ◽  
Author(s):  
Shouyi Wei ◽  
Haibo Lin ◽  
J. Isabelle Choi ◽  
Robert H. Press ◽  
Stanislav Lazarev ◽  
...  
Keyword(s):  
Liver Cancer ◽  
Dose Rate ◽  
Treatment Planning ◽  
High Dose Rate ◽  
High Dose ◽  
Average Dose ◽  
Plan Quality ◽  
Intensity Modulated Proton Therapy ◽  
Dose Metrics ◽  
Dose Constraints

PurposeThis work aims to study the dose and ultra-high-dose rate characteristics of transmission proton pencil beam scanning (PBS) FLASH radiotherapy (RT) for hypofractionation liver cancer based on the parameters of a commercially available proton system operating under FLASH mode.Methods and MaterialsAn in-house treatment planning software (TPS) was developed to perform intensity-modulated proton therapy (IMPT) FLASH-RT planning. Single-energy transmission proton PBS plans of 4.5 Gy × 15 fractions were optimized for seven consecutive hepatocellular carcinoma patients, using 2 and 5 fields combined with 1) the minimum MU/spot chosen between 100 and 400, and minimum spot time (MST) of 2 ms, and 2) the minimum MU/spot of 100, and MST of 0.5 ms, based upon considerations in target uniformities, OAR dose constraints, and OAR FLASH dose rate coverage. Then, the 3D average dose rate distribution was calculated. The dose metrics for the mean dose of Liver-GTV and other major OARs were characterized to evaluate the dose quality for the different combinations of field numbers and minimum spot times compared to that of conventional IMPT plans. Dose rate quality was evaluated using 40 Gy/s volume coverage (V40Gy/s).ResultsAll plans achieved favorable and comparable target uniformities, and target uniformity improved as the number of fields increased. For OARs, no significant dose differences were observed between plans of different field numbers and the same MST. For plans using shorter MST and the same field numbers, better sparing was generally observed in most OARs and was statistically significant for the chest wall. However, the FLASH dose rate coverage V40Gy/s was increased by 20% for 2-field plans compared to 5-field plans in most OARs with 2-ms MST, which was less evident in the 0.5-ms cases. For 2-field plans, dose metrics and V40Gy/s of select OARs have large variations due to the beam angle selection and variable distances to the targets. The transmission plans generally yielded inferior dosimetric quality to the conventional IMPT plans.ConclusionThis is the first attempt to assess liver FLASH treatment planning and demonstrates that it is challenging for hypofractionation with smaller fractional doses (4.5 Gy/fraction). Using fewer fields can allow higher minimum MU/spot, resulting in higher OAR FLASH dose rate coverages while achieving similar plan quality compared to plans with more fields. Shorter MST can result in better plan quality and comparable or even better FLASH dose rate coverage.

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