Active bone marrow segmentation based on computed tomography imaging in anal cancer patients: A machine-learning-based proof of concept

PURPOSE

Different methods are available to identify haematopoietically active bone marrow (ActBM). However, their use can be challenging for radiotherapy routine treatments, since they require specific equipment and dedicated time. A machine learning (ML) approach, based on radiomic features as inputs to three different classifiers, was applied to computed tomography (CT) images to identify haematopoietically active bone marrow in anal cancer patients.

METHODS

A total of 40 patients was assigned to the construction set (training set + test set). Fluorine-18-Fluorodeoxyglucose Positron Emission Tomography (18FDG-PET) images were used to detect the active part of the pelvic bone marrow (ActPBM) and stored as ground-truth for three subregions: iliac, lower pelvis and lumbosacral bone marrow (ActIBM, ActLPBM, ActLSBM). Three parameters were used for the correspondence analyses between 18FDG-PET and ML classifiers: DICE index, Precision and Recall.

RESULTS

For the 40-patient cohort, median values [min; max] of the Dice index were 0.69 [0.20; 0.84], 0.76 [0.25; 0.89], and 0.36 [0.15; 0.67] for ActIBM, ActLSBM, and ActLPBM, respectively. The Precision/Recall (P/R) ratio median value for the ActLPBM structure was 0.59 [0.20; 1.84] (over segmentation), while for the other two subregions the P/R ratio median has values of 1.249 [0.43; 4.15] for ActIBM and 1.093 [0.24; 1.91] for ActLSBM (under segmentation).

CONCLUSION

A satisfactory degree of overlap compared to 18FDG-PET was found for 2 out of the 3 subregions within pelvic bones. Further optimization and generalization of the process is required before clinical implementation.

Applications of Artificial Intelligence and Radiomics in Molecular Hybrid Imaging and Theragnostics for Neuro-Endocrine Neoplasms (NENs)

Nuclear medicine has acquired a crucial role in the management of patients with neuroendocrine neoplasms (NENs) by improving the accuracy of diagnosis and staging as well as their risk stratification and personalized therapies, including radioligand therapies (RLT). Artificial intelligence (AI) and radiomics can enable physicians to further improve the overall efficiency and accuracy of the use of these tools in both diagnostic and therapeutic settings by improving the prediction of the tumor grade, differential diagnosis from other malignancies, assessment of tumor behavior and aggressiveness, and prediction of treatment response. This systematic review aims to describe the state-of-the-art AI and radiomics applications in the molecular imaging of NENs.

Helical tomotherapy and two types of volumetric modulated arc therapy: dosimetric and clinical comparison for several cancer sites

Radiotherapy accelerators have undergone continuous technological developments. We investigated the differences between Radixact™ and VMAT treatment plans. Sixty patients were included in this study. Dosimetric comparison between the Radixact™ and VMAT plans was performed for six cancer sites: whole-brain, head and neck, lymphoma, lung, prostate, and rectum. The VMAT plans were generated with two Elekta linear accelerators (Synergy^® and Versa HD™). The planning target volume (PTV) coverage, organs-at-risk dose constraints, and four dosimetric indexes were considered. The deliverability of the plans was assessed using quality assurance (gamma index evaluation) measurements; clinical judgment was included in the assessment. The mean AAPM TG218 (3%-2 mm, global normalization) gamma index values were 99.4%, 97.8%, and 96.6% for Radixact™, Versa HD™, and Synergy®, respectively. Radixact™ performed better than Versa HD™ in terms of dosimetric indexes, hippocampi D_100%, spinal cord D_max, rectum V_{38.4  Gy}, bladder V_{30 Gy}, and V_{40 Gy}. Versa HD™ saved more of the (lungs-PTV) V_{5 Gy} and (lungs-PTV) D_mean, heart D_mean, breasts V_{4 Gy}, and bowel V_{45 Gy}. Regarding Synergy^®, the head and neck Radixact™ plan saved more of the parotid gland, oral cavity, and supraglottic larynx. From a clinical point of view, for the head and neck, prostate, and rectal sites, the Radixact™ and Versa HD™ plans were similar; Radixact™ plans were preferable for the head and neck and rectum to Synergy^® plans. The quality of linac plans has improved, and differences with tomotherapy have decreased. However, tomotherapy continues to be an essential add-on in multi-machine departments.

A case report of long-term successful stereotactic arrhythmia radioablation in a cardiac contractility modulation device carrier with giant left atrium, including a detailed dosimetric analysis

Introduction

Catheter ablation (CA) is the current standard of care for patients suffering drug-refractory monomorphic ventricular tachycardias (MMVTs). Yet, despite significant technological improvements, recurrences remain common, leading to increased morbidity and mortality. Stereotactic arrhythmia radioablation (STAR) is increasingly being adopted to overcome the limitations of conventional CA, but its safety and efficacy are still under evaluation.

Case presentation

We hereby present the case of a 73-year-old patient implanted with a mitral valve prosthesis, a cardiac resynchronization therapy-defibrillator, and a cardiac contractility modulation device, who was successfully treated with STAR for recurrent drug and CA-resistant MMVT in the setting of advanced heart failure and a giant left atrium. We report a 2-year follow-up and a detailed dosimetric analysis.

Conclusion

Our case report supports the early as well as the long-term efficacy of 25 Gy single-session STAR. Despite the concomitant severe heart failure, with an overall heart minus planned target volume mean dosage below 5 Gy, no major detrimental cardiac side effects were detected. To the best of our knowledge, our dosimetric analysis is the most accurate reported so far in the setting of STAR, particularly for what concerns cardiac substructures and coronary arteries. A shared dosimetric planning among centers performing STAR will be crucial in the next future to fully disclose its safety profile.

Prognostic value of whole-body PET volumetric parameters extracted from 68Ga-DOTATOC-PET/CT in well-differentiated neuroendocrine tumors

Aim: To evaluate the prognostic value of somatostatin receptor tumor burden (SRTB) at ⁶⁸Ga-DOTATOC positron emission tomography/computed tomography (PET/CT) in patients with well-differentiated neuroendocrine tumors (WD-NETs). Methods: We retrospectively analyzed ⁶⁸Ga-DOTATOC-PET/CT of 84 patients with histologically confirmed WD-NETs (51 G1, 30 G2 and 3 G3). For each PET/CT, all DOTATOC-avid lesions were independently segmented by 2 operators using a customized threshold based on the healthy liver maximum standardized uptake value (SUV_max) using LIFEx 5.1. Somatostatin receptor expressing tumor volume (SRETV) and total lesion somatostatin receptor expression (TLSRE=SRETV*SUVmean) were extracted for each lesion and then whole-body SRETV and TLSRE (SRETVwb and TLSREwb) were defined as the sum of SRETV and TLSRE of all segmented lesions in each patient, respectively. Time to progression (TTP) was defined as the combination of disease-free-survival in patients undergoing curative surgery (n = 10) and progression-free survival for patients with unresectable/metastatic disease (n = 74). TTP and overall survival (OS) were calculated by Kaplan-Meier analysis, log-rank test, and Cox's proportional hazard model. Results: After a median follow-up period of 15.5 months disease progression was confirmed in 35 patients (41.7%) and 14 patients died. Higher SRETVwb (>39.1ml) and TLSREwb (>306.8g) were significantly correlated with shorter median TTP (TTP = 12months vs not reached; p<0.001). In multivariate analysis, SRETVwb (P = 0.005) was the only independent predictor of TTP regardless of histopathologic grade and TNM staging. Conclusion: According to our results, SRETVwb and TLSREwb extracted from ⁶⁸Ga-DOTATOC-PET/CT could predict TTP/OS and might have an important clinical utility in the management of in patients with WD-NETs.

The influence of basic plan parameters on calculated small field output factors - A multicenter study

PURPOSE

The influence of basic plan parameters such as slice thickness, grid resolution, algorithm type and field size on calculated small field output factors (OFs) was evaluated in a multicentric study.

METHODS AND MATERIALS

Three computational homogeneous water phantoms with slice thicknesses (ST) 1, 2 and 3 mm were shared among twenty-one centers to calculate OFs for 1x1, 2x2 and 3x3 cm² field sizes (FSs) (normalized to 10x10 cm² FS), with their own treatment planning system (TPS) and the energy clinically used for stereotactic body radiation therapy delivery. OFs were calculated for each combination of grid resolution (GR) (1, 2 and 3 mm) and ST and finally compared with the OFs measured for the TPS commissioning. A multivariate analysis was performed to test the effect of basic plan parameters on calculated OFs.

RESULTS

A total of 509 data points were collected. Calculated OFs are slightly higher than measured ones. The multivariate analysis showed that Center, GR, algorithm type, and FS are predictive variables of the difference between calculated and measured OFs (p < 0.001). As FS decreases, the spread in the difference between calculated and measured OFs became larger when increasing the GR. Monte Carlo and Analytical Anisotropic Algorithms, presented a dependence on GR (p < 0.01), while Collapsed Cone Convolution and Acuros did not. The effect of the ST was found to be negligible.

CONCLUSIONS

Modern TPSs slightly overestimate the calculated small field OFs compared with measured ones. Grid resolution, algorithm, center number and field size influence the calculation of small field OFs.

Impact of segmentation and discretization on radiomic features in 68Ga-DOTA-TOC PET/CT images of neuroendocrine tumor

OBJECTIVE

To identify the impact of segmentation methods and intensity discretization on radiomic features (RFs) extraction from 68Ga-DOTA-TOC PET images in patients with neuroendocrine tumors.

METHODS

Forty-nine patients were retrospectively analyzed. Tumor contouring was performed manually by four different operators and with a semi-automatic edge-based segmentation (SAEB) algorithm. Three SUVmax fixed thresholds (20, 30, 40%) were applied. Fifty-one RFs were extracted applying two different intensity rescale factors for gray-level discretization: one absolute (AR60 = SUV from 0 to 60) and one relative (RR = min-max of the VOI SUV). Dice similarity coefficient (DSC) was calculated to quantify segmentation agreement between different segmentation methods. The impact of segmentation and discretization on RFs was assessed by intra-class correlation coefficients (ICC) and the coefficient of variance (COVL). The RFs' correlation with volume and SUVmax was analyzed by calculating Pearson's correlation coefficients.

RESULTS

DSC mean value was 0.75 ± 0.11 (0.45-0.92) between SAEB and operators and 0.78 ± 0.09 (0.36-0.97), among the four manual segmentations. The study showed high robustness (ICC > 0.9): (a) in 64.7% of RFs for segmentation methods using AR60, improved by applying SUVmax threshold of 40% (86.5%); (b) in 50.9% of RFs for different SUVmax thresholds using AR60; and (c) in 37% of RFs for discretization settings using different segmentation methods. Several RFs were not correlated with volume and SUVmax.

CONCLUSIONS

RFs robustness to manual segmentation resulted higher in NET 68Ga-DOTA-TOC images compared to 18F-FDG PET/CT images. Forty percent SUVmax thresholds yield superior RFs stability among operators, however leading to a possible loss of biological information. SAEB segmentation appears to be an optimal alternative to manual segmentation, but further validations are needed. Finally, discretization settings highly impacted on RFs robustness and should always be stated.

68Ga-DOTATOC PET/CT-Based Radiomic Analysis and PRRT Outcome: A Preliminary Evaluation Based on an Exploratory Radiomic Analysis on Two Patients

Aim: This work aims to evaluate whether the radiomic features extracted by 68Ga-DOTATOC-PET/CT of two patients are associated with the response to peptide receptor radionuclide therapy (PRRT) in patients affected by neuroendocrine tumor (NET).

Methods: This is a pilot report in two NET patients who experienced a discordant response to PRRT (responder vs. non-responder) according to RECIST1.1. The patients presented with liver metastasis from the rectum and pancreas G3-NET, respectively. Whole-body total-lesion somatostatin receptor-expression (TLSREwb-50) and somatostatin receptor-expressing tumor volume (SRETV wb-50) were obtained in pre- and post-PRRT PET/CT. Radiomic analysis was performed, extracting 38 radiomic features (RFs) from the patients' lesions. The Mann–Whitney test was used to compare RFs in the responder patient vs. the non-responder patient. Pearson correlation and principal component analysis (PCA) were used to evaluate the correlation and independence of the different RFs.

Results: TLSREwb-50 and SRETVwb-50 modifications correlate with RECIST1.1 response. A total of 28 RFs extracted on pre-therapy PET/CT showed significant differences between the two patients in the Mann–Whitney test (p < 0.05). A total of seven second-order features, with poor correlation with SUVmax and PET volume, were identified by the Pearson correlation matrix. Finally, the first two PCA principal components explain 83.8% of total variance.

Conclusion: TLSREwb-50 and SRETVwb-50 are parameters that might be used to predict and to assess the PET response to PRRT. RFs might have a role in defining inter-patient heterogeneity and in the prediction of therapy response. It is important to implement future studies with larger and more homogeneous patient populations to confirm the efficacy of these biomarkers.

Adoption of Expansion Margins to Reduce the Dose Received by the Coronary Arteries and the Risk of Cardiovascular Events in Lymphoma Patients

PURPOSE

Mediastinal radiation therapy (RT) in patients with lymphoma implies involuntary coronary artery (CA) exposure, resulting in an increased risk of coronary artery disease (CAD). Accurate delineation of CAs may spare them from higher RT doses. However, heart motion affects the estimation of the dose received by CAs. An expansion margin (planning organ at risk volume [PRV]), encompassing the nearby area where CAs displace, may compensate for these uncertainties, reducing CA dose and CAD risk. Our study aimed to evaluate if a planning process optimized on CA-specific PRVs, rather than just on CAs, could provide any dosimetric or clinical benefit.

METHODS AND MATERIALS

Forty patients receiving RT for mediastinal lymphomas were included. We contoured left main trunk, left anterior descending, left circumflex, and right coronary arteries. An isotropic PRV was then applied to all CAs, in accordance with literature data. A comparison was then performed by optimizing treatment plans either on CAs or on PRVs, to detect any difference in CA sparing in terms of maximum (D_max), median (D_med), and mean (D_mean) dose. We then investigated, through risk modeling, if any dosimetric benefit obtained with the PRV-related optimization process could translate to a lower risk of ischemic complications.

RESULTS

Plan optimization on PRVs demonstrated a significant dose reduction (range, 7%-9%) in D_max, D_med, and D_mean for the whole coronary tree, and even higher dose reductions when vessels were located 5- to 20-mm from PTV (range, 13%-15%), especially for left main trunk and left circumflex (range, 16%-21%). This translated to a mean risk reduction of developing CAD of 12% (P < .01), which increased to 17% when CAs were located 5- to 20-mm from PTV.

CONCLUSIONS

Integration of CA-related PRVs in the optimization process reduces the dose received by CAs and translates to a meaningful prevention of CAD risk in patients with lymphoma treated with mediastinal RT.

18F-FDG Pet Parameters and Radiomics Features Analysis in Advanced Nsclc Treated with Immunotherapy as Predictors of Therapy Response and Survival

Objectives: (1.1) to evaluate the association between baseline 18F-FDG PET/CT semi-quantitative parameters of the primary lesion with progression free survival (PFS), overall survival (OS) and response to immunotherapy, in advanced non-small cell lung carcinoma (NSCLC) patients eligible for immunotherapy; (1.2) to evaluate the application of radiomics analysis of the primary lesion to identify features predictive of response to immunotherapy; (1.3) to evaluate if tumor burden assessed by 18F-FDG PET/CT (N and M factors) is associated with PFS and OS. Materials and Methods: we retrospectively analyzed clinical records of advanced NCSLC patients (stage IIIb/c or stage IV) candidate to immunotherapy who performed 18F-FDG PET/CT before treatment to stage the disease. Fifty-seven (57) patients were included in the analysis (F:M 17:40; median age = 69 years old). Notably, 38/57 of patients had adenocarcinoma (AC), 10/57 squamous cell carcinoma (SCC) and 9/57 were not otherwise specified (NOS). Overall, 47.4% patients were stage IVA, 42.1% IVB and 8.8% IIIB. Immunotherapy was performed as front-line therapy in 42/57 patients and as second line therapy after chemotherapy platinum-based in 15/57. The median follow up after starting immunotherapy was 10 months (range: 1.5–68.6). Therapy response was assessed by RECIST 1.1 criteria (CT evaluation every 4 cycles of therapy) in 48/57 patients or when not feasible by clinical and laboratory data (fast disease progression or worsening of patient clinical condition in nine patients). Radiomics analysis was performed by applying regions of interest (ROIs) of the primary tumor delineated manually by two operators and semi-automatically applying a threshold at 40% of SUVmax. Results: (1.1) metabolic tumor volume (MTV) (p = 0.028) and total lesion glycolysis (TLG) (p = 0.035) were significantly associated with progressive vs. non-progressive disease status. Patients with higher values of MTV and TLG had higher probability of disease progression, compared to those patients presenting with lower values. SUVmax did not show correlation with PD status, PFS and OS. MTV (p = 0.027) and TLG (p = 0.022) also resulted in being significantly different among PR, SD and PD groups, while SUVmax was confirmed to not be associated with response to therapy (p = 0.427). (1.2) We observed the association of several radiomics features with PD status. Namely, patients with high tumor volume, TLG and heterogeneity expressed by “skewness” and “kurtosis” had a higher probability of failing immunotherapy. (1.3) M status at 18F-FDG PET/CT was significantly associated with PFS (p = 0.002) and OS (p = 0.049). No significant associations were observed for N status. Conclusions: 18F-FDG PET/CT performed before the start of immunotherapy might be an important prognostic tool able to predict the disease progression and response to immunotherapy in patients with advanced NSCLC, since MTV, TLG and radiomics features (volume and heterogeneity) are associated with disease progression.

Radiation therapy for oligometastatic oropharyngeal cancer

At presentation, isolated metastasis from oropharyngeal squamous cell carcinoma is rare. Liver is a relatively uncommon first site of failure, especially in the absence of other distant metastases, particularly without diagnosis of lung metastases. We report on a case of HPV-related oropharyngeal squamous cell carcinoma with synchronous liver metastasis treated with radiation therapy. This condition, defined as "oligometastatic state," describes a subset of patients with limited volume metastatic disease in whom favorable outcomes were reported with the use of local ablative therapies on both the primary tumor and metastatic sites. As a definitive treatment, we offered the patient, ineligible for other therapeutic approaches, exclusive radiation treatment on the head and neck region and a stereotactic ablative approach targeted to the liver metastasis.

Dose to Pelvic Bone Marrow Defined with FDG-PET Predicts for Hematologic Nadirs in Anal Cancer Patients Treated with Concurrent Chemo-radiation

PURPOSE

To investigate whether irradiated volume of pelvic active bone marrow (^ACTBM) may predict decreased blood cells nadirs in anal cancer patients undergoing concurrent chemo-radiation.

METHODS

Forty-four patients were analyzed and pelvic active bone marrow (^ACTBM) was characterized employing ¹⁸FDG-PET. Dosimetric parameters on dose-volume histograms were correlated to nadirs with generalized linear modeling.

RESULTS

^ACTBM mean dose was significantly correlated to white blood cell (β = -1.338; 95%CI: -2.455/-0.221; p = 0.020), absolute neutrophil count (β = -1.651; 95%CI: -3.284/-0.183; p = 0.048), and platelets (β = -0.031; 95%CI: -0.057/-0.004; p = 0.024) nadirs. Other dosimetric parameters were found to be correlated (^ACTBM-V_10,-V_20,-V₃₀and-V₄₀).

CONCLUSIONS

¹⁸FDG-PET is able to define active bone marrow and may predict for decreased blood cells count nadirs.

Variability of clinical target volume delineation for rectal cancer patients planned for neoadjuvant radiotherapy with the aid of the platform Anatom-e

Objective

Delineation of treatment volumes is a major source of uncertainties in radiotherapy (RT). This is also true for rectal cancer patients undergoing neoadjuvant RT, with a potential impact on treatment quality. We investigated the role of the digital platform Anatom-e (Anatom-e Information Sytems Ltd., Houston, Texas) in increasing the compliance to follow a specific treatment protocol in a multicentric setting.

Materials and methods

Two clinical cases of locally advanced rectal cancer were chosen. Participants were instructed to follow the 2009 Radiation Therapy Oncology Group consensus atlas and asked to manually segment clinical target volumes (CTVs), for both patient 1 and 2, on day 1 with and without the use of Anatom-e. After one week (day 2), the same radiation oncologist contoured again, with and without Anatom-e, the same CT series. Intraobserver (Intra-OV) and interobserver (Inter-OV) variability were evaluated with the Dice similarity coefficient (DSC), the Hausdorff distance (HD) and mean distance to agreement (MDA).

Results

For clinical case 1, no significant difference was found for Intra-OV and Inter-OV. For clinical case 2, no significant difference was found for Intra-OV but a statistically significant difference was found for Inter-OV in DSC when using or not the platform. Mean DCS was 0.65 (SD: ±0.64; range: 0.58-0.79) for day 1 vs reference volume without Anatom-e and 0.72 (SD: ±0.39; range: 0.67-0.77) (p = 0.03) with it. Mean MDA was lower with Anatom-e (3.61; SD: ±1.33; range: 2.85-4.78) than without (4.14; SD: ±2.97; range: 2.18-5.21), with no statistical significance (p = 0.21) The use of Anatom-e decreased the SD from 2.97 to 1.33. Mean HD was lower with Anatom-e (26.06; SD: ±2.05; range: 24.08-32.62), with no statistical significance (p = 0.14) compared to that without (31.39; SD: ±1.31; range: 26.14-48.72).

Conclusions

The use of Anatom-e decreased the Inter-OV in the CTV delineation process for locally advanced rectal cancer with complex disease presentation planned for neoadjuvant RT. This system may be potentially helpful in increasing the compliance to follow shared guidelines and protocols.

Evaluation of a commercial automatic treatment planning system for liver stereotactic body radiation therapy treatments

PURPOSE

Automated treatment planning is a new frontier in radiotherapy. The Auto-Planning module of the Pinnacle³ treatment planning system (TPS) was evaluated for liver stereotactic body radiation therapy treatments.

METHODS

Ten cases were included in the study. Six plans were generated for each case by four medical physics experts. The first two planned with Pinnacle TPS, both with manual module (MP) and Auto-Planning one (AP). The other two physicists generated two plans with Monaco TPS (VM). Treatment plan comparisons were then carried on the various dosimetric parameters of target and organs at risk, monitor units, number of segments, plan complexity metrics and human resource planning time. The user dependency of Auto-Planning was also tested and the plans were evaluated by a trained physician.

RESULTS

Statistically significant differences (Anova test) were observed for spinal cord doses, plan average beam irregularity, number of segments, monitor units and human planning time. The Fisher-Hayter test applied to these parameters showed significant statistical differences between AP e MP for spinal cord doses and human planning time; between MP and VM for monitor units, number of segments and plan irregularity; for all those between AP and VM. The two plans created by different planners with AP were similar to each other.

CONCLUSIONS

The plans created with Auto-Planning were comparable to the manually generated plans. The time saved in planning enables the planner to commit more resources to more complex cases. The independence of the planner enables to standardize plan quality.

Dose to specific subregions of pelvic bone marrow defined with FDG-PET as a predictor of hematologic nadirs during concomitant chemoradiation in anal cancer patients

To test the hypothesis that irradiated volume of specific subregions of pelvic active bone marrow as detected by (18)FDG-PET may be a predictor of decreased blood cells nadirs in anal cancer patients undergoing concurrent chemoradiation, we analyzed 44 patients submitted to IMRT and concurrent chemotherapy. Several bony structures were defined: pelvic and lumbar-sacral (LSBM), lower pelvis (LPBM) and iliac (IBM) bone marrow. Active BM was characterized employing (18)FDG-PET and characterized in all subregions as the volume having standard uptake values (SUVs) higher than SUVmean. All other regions were defined as inactive BM. On dose-volume histograms, dosimetric parameters were taken. Endpoints included white blood cell count (WBC), absolute neutrophil count (ANC), hemoglobin (Hb) and platelet (Plt) nadirs. Generalized linear modeling was used to find correlations between dosimetric variables and blood cells nadirs. WBC nadir was significantly correlated with LSBM mean dose (β = -1.852; 95 % CI -3.205/-0.500; p = 0.009), V10 (β = -2.153; 95 % CI -4.263/-0.721; p = 0.002), V20 (β = -2.081; 95 % CI -4.880/-0.112; p = 0.003), V30 (β = -1.971; 95 % CI -4.748/-0.090; p = 0.023) and IBM V10 (β = -0.073; 95 % CI -0.106/-0.023; p = 0.016). ANC nadir found to be significantly associated with LSBM V10 (β = -1.878; 95 % CI -4.799/-0.643; p = 0.025), V20 (β = -1.765; 95 % CI -4.050/-0.613; p = 0.030) and IBM V10 (β = -0.039; 95 % CI -0.066/-0.010; p = 0.027). Borderline significance was found for correlation between Plt nadir and LSBM V30 (β = -0.056; 95 % CI -2.748/-0.187; p = 0.060), V40 (β = -0.059; 95 % CI -3.112/-0.150; p = 0.060) and IBM V30 (β = -0.028; 95 % CI -0.074/-0.023; p = 0.056). No inactive BM subsites were found to be correlated with any blood cell nadir. (18)FDG-PET is able to define active bone marrow within pelvic osseous structures. LSBM is the strongest predictor of decreased blood cells nadirs in anal cancer patients undergoing concurrent chemoradiation.

Dosimetric commissioning and quality assurance of scanned ion beams at the Italian National Center for Oncological Hadrontherapy

PURPOSE

To describe the dosimetric commissioning and quality assurance (QA) of the actively scanned proton and carbon ion beams at the Italian National Center for Oncological Hadrontherapy.

METHODS

The laterally integrated depth-dose-distributions (IDDs) were acquired with the PTW Peakfinder, a variable depth water column, equipped with two Bragg peak ionization chambers. fluka Monte Carlo code was used to generate the energy libraries, the IDDs in water, and the fragment spectra for carbon beams. EBT3 films were used for spot size measurements, beam position over the scan field, and homogeneity in 2D-fields. Beam monitor calibration was performed in terms of number of particles per monitor unit using both a Farmer-type and an Advanced Markus ionization chamber. The beam position at the isocenter, beam monitor calibration curve, dose constancy in the center of the spread-out-Bragg-peak, dose homogeneity in 2D-fields, beam energy, spot size, and spot position over the scan field are all checked on a daily basis for both protons and carbon ions and on all beam lines.

RESULTS

The simulated IDDs showed an excellent agreement with the measured experimental curves. The measured full width at half maximum (FWHM) of the pencil beam in air at the isocenter was energy-dependent for both particle species: in particular, for protons, the spot size ranged from 0.7 to 2.2 cm. For carbon ions, two sets of spot size are available: FWHM ranged from 0.4 to 0.8 cm (for the smaller spot size) and from 0.8 to 1.1 cm (for the larger one). The spot position was accurate to within ± 1 mm over the whole 20 × 20 cm(2) scan field; homogeneity in a uniform squared field was within ± 5% for both particle types at any energy. QA results exceeding tolerance levels were rarely found. In the reporting period, the machine downtime was around 6%, of which 4.5% was due to planned maintenance shutdowns.

CONCLUSIONS

After successful dosimetric beam commissioning, quality assurance measurements performed during a 24-month period show very stable beam characteristics, which are therefore suitable for performing safe and accurate patient treatments.

A GPU Simulation Tool for Training and Optimisation in 2D Digital X-Ray Imaging

Conventional radiology is performed by means of digital detectors, with various types of technology and different performance in terms of efficiency and image quality. Following the arrival of a new digital detector in a radiology department, all the staff involved should adapt the procedure parameters to the properties of the detector, in order to achieve an optimal result in terms of correct diagnostic information and minimum radiation risks for the patient. The aim of this study was to develop and validate a software capable of simulating a digital X-ray imaging system, using graphics processing unit computing. All radiological image components were implemented in this application: an X-ray tube with primary beam, a virtual patient, noise, scatter radiation, a grid and a digital detector. Three different digital detectors (two digital radiography and a computed radiography systems) were implemented. In order to validate the software, we carried out a quantitative comparison of geometrical and anthropomorphic phantom simulated images with those acquired. In terms of average pixel values, the maximum differences were below 15%, while the noise values were in agreement with a maximum difference of 20%. The relative trends of contrast to noise ratio versus beam energy and intensity were well simulated. Total calculation times were below 3 seconds for clinical images with pixel size of actual dimensions less than 0.2 mm. The application proved to be efficient and realistic. Short calculation times and the accuracy of the results obtained make this software a useful tool for training operators and dose optimisation studies.