•KB-model for irradiation of nodes + prostate + vesicles in post-prostatectomy patients.•The step-validation increased the confidence in using KB-optimization.•Automatic KB-model showed better/equal ...performances compared to clinical plans.•The interaction of a planner further improved planning performances.•A gEUD reduction (up to 9 Gy) was seen in both KB optimization modalities.
To develop and apply a stepping approach for the validation of Knowledge-based (KB) models for planning optimization: the method was applied to the case of concomitant irradiation of pelvic nodes and prostate + seminal−vesicles bed irradiation in post-prostatectomy patients.
The clinical VMAT plans of 52 patients optimized by two reference planners were selected to generate a KB-model (RapidPlan, v.13.5 Varian). A stepping-validation approach was followed by comparing KB-generated plans (with and without planner-interaction, RP and only-RP respectively) against delivered clinical plans (RA). The validation followed three steps, gradually extending its generalization: 20 patients used to develop the model (closed-loop); 20 new patients, same planners (open-loop); 20 new patients, different planners (wide-loop). All plans were compared, in terms of relevant dose-volume parameters and generalized equivalent uniform dose (gEUD).
KB-plans were generally better than or equivalent to clinical plans. For RPvsRA, PTVs coverage was comparable, for OARs RP was always better. Comparing only-RPvsRA, PTVs coverage was always better; bowel\bladder V50Gy and D1%, bowel\bladder\rectum Dmean, femoral heads V40Gy and penile bulb V50Gy were significantly improved. For RPvsRA gEUD reduction >1 Gy was seen in 80% of plans for rectum, bladder and bowel; for only-RPvsRA, this was found in 50% for rectum/bladder and in 70% for bowel.
An extensive stepping validation approach of KB-model for planning optimization showed better or equal performances of automatically generated KB-plan compared to clinical plans. The interaction of a planner further improved planning performances.
•Dual-energy and K-edge subtraction imaging.•Rotational radiotherapy of breast cancer.•Phase-contrast imaging with coherence areas of about 10 μm.
MariX is a research infrastructure conceived for ...multi-disciplinary studies, based on a cutting-edge system of combined electron accelerators at the forefront of the world-wide scenario of X-ray sources. The generation of X-rays over a large photon energy range will be enabled by two unique X-ray sources: a Free Electron Laser and an inverse Compton source, called BriXS (Bright compact X-ray Source). The X-ray beam provided by BriXS is expected to have an average energy tunable in the range 20–180 keV and intensities between 1011 and 1013 photon/s within a relative bandwidth ΔE/E=1–10%. These characteristics, together with a very small source size (~20 μm) and a good transverse coherence, will enable a wide range of applications in the bio-medical field. An additional unique feature of BriXS will be the possibility to make a quick switch of the X-ray energy between two values for dual-energy and K-edge subtraction imaging. In this paper, the expected characteristics of BriXS will be presented, with a particular focus on the features of interest to its possible medical applications.
The need of a fs-scale pulsed, high repetition rate, X-ray source for time-resolved fine analysis of matter (spectroscopy and photon scattering) in the linear response regime is addressed by the ...conceptual design of a facility called MariX (Multi-disciplinary Advanced Research Infrastructure for the generation and application of X-rays) outperforming current X-ray sources for the declared scope. MariX is based on the original design of a two-pass two-way superconducting linear electron accelerator, equipped with an arc compressor, to be operated in CW mode (1 MHz). MariX provides FEL emission in the range 0.2–8 keV with 108 photons per pulse ideally suited for photoelectric effect and inelastic X-ray scattering experiments. The accelerator complex includes an early stage that supports an advanced inverse Compton source of very high-flux hard X-rays of energies up to 180 keV that is well adapted for large area radiological imaging, realizing a broad science programme and serving a multidisciplinary user community, covering fundamental science of matter and application to life sciences, including health at preclinical and clinical level.
To investigate the potential role of an additional magnetic resonance imaging (MRI) examination performed during neoadjuvant chemoradiation therapy (CRT) in the prediction of pathological response in ...locally advanced rectal cancer (LARC).
Forty-eight consecutive patients with LARC underwent neoadjuvant CRT. MRI studies at 1.5 T, including high-resolution T2-weighted sequences that were acquired parallel and perpendicular to the main axis of the tumour were performed before (preMRI), during (midMRI), and 6–8 weeks after the end of CRT (postMRI). Cancer volumes (Vpre, Vmid, Vpost) were drawn manually and the reduction rate calculated (ΔVmid, ΔVpost). According to Rödel's pathological tumour regression grade (TRG), patients were considered non-responders (NR; TRG0-2), partial responders (PR; TRG3), and complete responders (CR; TRG4). Multivariate regression analysis was performed to identify the best MRI predictors of NR, PR, and CR.
Twenty-five patients were considered PR (52%), 13 CR (27%), and 10 NR (22%). Tumour shrinkage mainly occurred shortly after CRT (ΔVmid: CR: 80±10% versus PR: 56±19% versus NR: 28±22%, p=2.2×10−16). Vmid, Vpost, ΔVmid, and ΔVpost correlated with TRG (p<0.001). At multivariate analysis, the combined assessment of Vmid and ΔVmid was selected as the best predictor of response to CRT, in that it distinguishes CR, PR, and NR early and accurately (81.5%).
MidMRI allows final response assessment to neoadjuvant CRT earlier and better than the MRI performed after the end of CRT. MRI findings at midMRI may be useful to tailor patient treatment.
•An additional MRI performed during CRT may be useful in the early evaluation of response to CRT.•TRG correlated slightly better with ΔVmid (ρ=0.713, p<0.001) than ΔVpost (ρ=0.645, p<0.001).•MidMRI might be potentially useful to tailor patient’s treatment in relation to tumour shrinkage.
•Dosimetric predictors of skin toxicities after IMRT for HN cancer are lacking.•Data of 70 HN patients (Tomotherapy SIB, 54/66 Gy) were available.•DVHs of skin layers (SL, 2 mm thick) were ...recovered.•SL DVHs (V53Gy-V68Gy) predict CTCAEv4.0 G2/G3 acute toxicity.•Constraining V64 < 3 cc, should keep the risk of G3 toxicities below 10%.
To explore the association between planning skin dose-volume data and acute cutaneous toxicity after Radio–chemotherapy for Head and Neck (HN) cancer patients.
Seventy HN patients were treated with Helical Tomotherapy (HT) with radical intent (SIB technique: 54/66 Gy to PTV1/PTV2 in 30fr) ± chemotherapy superficial body layer 2 mm thick (SL2) was delineated on planning CT. CTCAE v4.0 acute skin toxicity data were available. Absolute average Dose-Volume Histograms (DVH) of SL2 were calculated for patients with severe (G3) and severe/moderate (G3/G2) skin acute toxicities.
Differences against patients with none/mild toxicity (G0/G1) were analyzed to define the most discriminative regions of SL2 DVH; univariable and multivariable logistic analyses were performed on DVH values, CTV volume, age, sex, chemotherapy.
Sixty-one % of patients experienced G2/G3 toxicity (rate of G3 = 19%). Differences in skin DVHs were significant in the range 53-68Gy (p-values: 0.005–0.01). V56/V64 were the most predictive parameters for G2/G3 (OR = 1.12, 95%CI = 1.03–1.21, p = 0.001) and G3 (OR = 1.13, 95%CI = 1.01–1.26, p = 0.027) with best cut-off of 7.7cc and 2.7cc respectively. The logistic model for V56 was well calibrated being both, slope and R2, close to 1. Average V64 were 2.2cc and 6cc for the two groups (G3 vs G0-G2 toxicity); the logistic model for V64 was quite well calibrated, with a slope close to 1 and R2 equal to 0.60.
SL2 DVH is associated with the risk of acute skin toxicity. Constraining V64 < 3cc (equivalent to a 4x4cm2 skin surface) should keep the risk of G3 toxicity below or around 10%.
Highlights • A method for planning CT-to-MVCT deformable image registration (DIR) was investigated. • The feasibility and the dosimetric accuracy of the DIR method was investigated. • Local dose ...differences and gamma distributions was evaluated with good results. • The proposed CT-MVCT DIR method could allow the dose of the day computation. • The suggested method is sufficiently reliable to be used for adaptive strategies.
Purpose
The value of FDG PET-derived parameters in predicting overall survival (OS), local relapse-free survival (LRFS) and distant relapse-free survival (DRFS) in treated patients with malignant ...pleural mesothelioma (MPM) was evaluated.
Methods
This retrospective evaluation included 55 MPM patients treated between March 2006 and February 2015 with FDG PET/CT-guided salvage helical tomotherapy (HTT) after previous surgery plus chemotherapy. Univariate Cox regression analysis was performed to assess the impact of the following FDG PET-derived parameters: biological target volume (BTV), mean and maximum standardized uptake values (SUV
mean/max
), metabolic tumour volume (MTV) and total lesion glycolysis (TLG), measured using different uptake thresholds (40%, 50% and 60%). Logistic regression was then performed to identify the best FDG PET-derived parameters for selecting patients with poorer survival.
Results
The median OS was 9.1 months (range 0.0 – 69.6 months) after the end of HTT; 54/55 patients were dead at the last follow-up. BTV and TLG40, TLG50 and TLG60 were the most significant predictors of OS (
p
< 0.005). The median OS was 4.8 months in patients with MTV60 >5 cm
3
and TLG40 >334.4, compared with 13.8 months and 16.1 months in patients with smaller values, respectively. The median LRFS and DRFS were 6.2 months (range 1.2 – 39.4 months) and 6.5 months (0.0 – 66.4 months), respectively. TLG40, TLG50 and TLG60 were significantly correlated with LRFS (
p
< 0.015). Median DRFS was 6.4 months in patients with MTV40 >39.6 cm
3
and 6.2 months in patients with TLG40 >334.4, compared with 17 months and 18.8 months in patients with smaller values. BTV, TLG40 and MTV40 were also found to be good predictors in patients with poor OS/LRFS/DRFS (median survival times less than the median values).
Conclusion
FDG PET-derived parameters effectively discriminated patients with a poor prognosis and may be helpful in the selection of MPM patients for salvage HTT.
We developed an efficient technique to auto-propagate parotid gland contours from planning kVCT to daily MVCT images of head-and-neck cancer patients treated with helical tomotherapy. The method ...deformed a 3D surface mesh constructed from manual kVCT contours by B-spline free-form deformation to generate optimal and smooth contours. Deformation was calculated by elastic image registration between kVCT and MVCT images. Data from ten head-and-neck cancer patients were considered and manual contours by three observers were included in both kVCT and MVCT images. A preliminary inter-observer variability analysis demonstrated the importance of contour propagation in tomotherapy application: a high variability was reported in MVCT parotid volume estimation (p = 0.0176, ANOVA test) and a larger uncertainty of MVCT contouring compared with kVCT was demonstrated by DICE and volume variability indices (Wilcoxon signed rank test, p < 10(-4) for both indices). The performance analysis of our method showed no significant differences between automatic and manual contours in terms of volumes (p > 0.05, in a multiple comparison Tukey test), center-of-mass distances (p = 0.3043, ANOVA test), DICE values (p = 0.1672, Wilcoxon signed rank test) and average and maximum symmetric distances (p = 0.2043, p = 0.8228 Wilcoxon signed rank tests). Results suggested that our contour propagation method could successfully substitute human contouring on MVCT images.
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