Gianfranco Loi - Academia.edu (original) (raw)
Papers by Gianfranco Loi
![Research paper thumbnail of [P200] Deformable Image Registration performances in head and neck patients: Impact of daily imaging quality](https://attachments.academia-assets.com/94150077/thumbnails/1.jpg)
](Physica Medica, 2018
Purpose. Magnetic resonance imaging (MRI) only radiotherapy has in recent years been introduced a... more Purpose. Magnetic resonance imaging (MRI) only radiotherapy has in recent years been introduced as a clinical workflow for prostate cancer patients. MRI only radiotherapy is performed without computed tomography (CT) and instead, a synthetic CT (sCT) is used for treatment planning. With the introduction of new procedures for treatment planning, development of quality assurance (QA) tools must be considered. Today, no such tool has yet been presented. The aim of this study was to develop a clinically feasible QA procedure for sCT using the kV-cone beam CT (CBCT), in an MRI-only workflow for prostate cancer patients. Methods. Three criteria were addressed; 1. Stability in Hounsfield Units (HUs), 2. Deviations in HUs between the CT and CBCT and 3. Validation of the QA procedure. For the two first criteria, phantom measurements were performed. For the third criteria, sCT, CT and CBCT for ten patients were used. Treatment plans were created based on the sCT (MriPlanner TM). CT and CBCT images were registered to the sCT. The treatment plan was recalculated on the CT and CBCT. Dose-volume histogram (DVH) metrics were used to evaluate dosimetric differences between the sCT plan and the recalculated CT and CBCT plans. Well defined errors were artificially introduced in the sCT for one patient to evaluate efficacy of the QA procedure. Results. The kV-CBCT system was stable in HU over time (SD <40 HU). Difference in HUs between CT and CBCT was very small (<60 HU). The differences between sCT-CT and sCT-CBCT dose distributions were below or equal to 1.0%. The highest mean dose difference for the CT and CBCT dose distribution was 0.6%. No statistically significant difference was found between total mean dose deviations from recalculated CT and CBCT plans, except for femoral head. The proposed QA method was found very helpful in identifying the introduced errors. Conclusions. The results in this study indicates that CBCT can be used as a clinically feasible QA tool for MRI-only radiotherapy of prostate cancer patients. The proposed method could easily be integrated in any modern image guided radiotherapy workflow without extensive work.
Scientific Reports, 2020
Radio-induced apoptosis is mediated by the activation of tumor protein p53, Bax and caspases. The... more Radio-induced apoptosis is mediated by the activation of tumor protein p53, Bax and caspases. The purpose of this study was to investigate the early activation of this pathway in men receiving in vivo irradiation immediately before radical prostatectomy for locally advanced prostate cancer. We also investigated cell proliferation index (Ki-67), proto-oncogene (p53) and anti-apoptotic protein (Bcl-2) levels as potential predictive factors. We selected a homogeneous sample of 20 patients with locally advanced prostate cancer and candidate to radical prostatectomy. To assess the apoptotic pathways, Bax, is studied through immunofluorescence assay, before and after 12 Gy single dose intraoperative radiotherapy (IORT) to the prostate, on bioptic samples and on surgical specimens. Moreover, before and after IORT, Bcl-2, p53, and Ki-67 were also detected through immunohistochemistry. A count of positive Bax spots for immunofluorescence was performed on tumor cells, prostatic intraepithelia...
Practical Radiation Oncology, 2019
to CBCT deformable image registration for contour propagation using head & neck patient-based com... more to CBCT deformable image registration for contour propagation using head & neck patient-based computational phantoms: a multicenter study,
Radiotherapy and Oncology, 2019
Radiotherapy and Oncology, 2019
should always be considered for correct staging in these patients. No statistically significant a... more should always be considered for correct staging in these patients. No statistically significant association was found between primary tumor SUVmax values and tumor responses in this study. This may be due to lack of clinical response data with 18 F-FDG PET/CT, which was available only in 16 out of 38 patients.
Physica Medica, 2018
Methods. We applied a mathematical descriptions of GBM proliferation and diffusion, in the frame ... more Methods. We applied a mathematical descriptions of GBM proliferation and diffusion, in the frame of the reaction diffusion theory. We formulated equations capturing of the impact of radiotherapy and heat on GBM in the reaction diffusion equation, including the regrowth induced by stem cells [2]. Results. Our calculated results show that the expected patient survival could be significantly improved by this treatment [3]. For the future, due to the lower power required for a single heating point, a somewhat lower frequency could be hypothesized, without risks of cavitation. This modification would allow the heating of larger tumors in less central regions. Conclusions. The proposed methodology, now limited to a small tumors in a quite central location, can be easily improved in several different respects. These results advocate thorough experiments to validate this very promising theoretical therapeutic benefit. References a ASL5,
Radiotherapy and Oncology, 2017
Radiotherapy and Oncology, 2017
PTV, plans were optimised aiming to obtain V95%>95% D98%>94%, V2%<108%; concerning the rectum, th... more PTV, plans were optimised aiming to obtain V95%>95% D98%>94%, V2%<108%; concerning the rectum, the requirements were: mean<18Gy, V20<35%, V32 <10%, V37<5%,D1%<40Gy while for the bladder, the goal was to keep mean dose <14 Gy and V21 <40%, V33 < 30%, V38 <13%,D1%<40Gy. Routine institutional image-based patient position verification protocols foresaw daily on-line matching by CBCT. The acute and late toxicities were recorded using the RTOG/EORTC scale. Additional data were collected by means of I-PSS e IIEF-5 questionnaires. Biochemical failure was determined using the Phoenix definition. Results The median follow-up duration was 27 months (range: 24 to 36 months). The median age was 74 years (range: 57-80 years). Most dosimetric parameters for the OARs are well within the protocol constraints, with the n otable exception of maximal doses to rectum and bladder (exceeding in about 20% of cases), but we did not find any statistical correlation with late toxicities. Acute GU toxicity of grade 2 (increase in urinary frequency) was observed in 7% patients. The incidence rates of late GI and GU toxicity of any grade were 14.2% and 35.7%, respectively. The late GU toxicity of grade ≥ 2 was 4.7%. No GE late toxicity ≥ 2 was noted. Previous abdominal surgery appeared to be statistically significant (p= 0.004; Fisher's test) for the increase of probability of late GE toxicity. The 3-year local recurrence-free survival rate was 98%, only one patient had clinical abdominal lymph node failure. Among the dosimetric data, only V21 (mean value: 22.1%; range: 8.5-55.2%) revealed to be statistically significant for the late GU (p= 0.035; Wilcoxon Mann Whitney Test). Conclusion Our experience with VMAT-based SBRT in low-and intermediate-risk prostate cancer demonstrates favorable efficacy in tumor control and toxicity profile with no decrease in QOL as determined by I-PSS, IIEF. The general good quality of the clinical outcome and the results concerning GI and GU toxicities seem to confirm the robustness of the dosimetric paradigm adopted. Longer follow-up is needed to investigate complete safety and efficacy of the stereotactic treatments.
Radiotherapy and Oncology, 2016
Conclusion: Our DIR-QA platform demonstrated inter-and intra-operator variability on the order of... more Conclusion: Our DIR-QA platform demonstrated inter-and intra-operator variability on the order of one voxel (1mm by 1mm by 2.5mm). Machine-generated feature points can serve as a measure of the quality of deformable image registration.
Radiotherapy and Oncology, 2015
Purpose/Objective: Radiotherapy induced xerostomia (RIX) is the most common permanent side effect... more Purpose/Objective: Radiotherapy induced xerostomia (RIX) is the most common permanent side effect of radiotherapy (RT) to the head and neck (H&N) with no effective treatment. LMS-611 is a mimetic of a natural lamellar body which has been shown to have the potential to reduce the 'stickiness' of oral cavity secretions following RT. Our pre-clinical study was designed as an ex vivo, efficacy, proof of concept study as a preparatory step towards our clinical study of LMS-611 in RIX. Materials and Methods: Patients with H&N cancer who were booked for RT or chemoRT (CRT) as primary treatment were recruited. Patient reported xerostomia scores were collected using the Groningen RIX (GRIX) questionnaire at baseline, weeks 2, 4 and 6 of radiotherapy. Saliva samples were also collected and adhesiveness and viscosity tested by assessing time taken to travel 5cm on an inclined plane (IP). LMS-611 was added to saliva samples and IP test repeated. Results: 30 patients were enrolled. All patients had a pathologically confirmed diagnosis of squamous cell carcinoma (SCC) oropharynx. Mean age 54.8 years, range 42-67. 80% were male and the majority stage III and IV disease (96.6%). 90% received CRT. The mean IP test results (seconds) are as follows baseline 31.3; week 2 49.7; week 4 51.1; week 6 55.7 indicating increasing saliva adhesiveness and viscosity as RT progresses. The increase was significant from baseline to week 2 with only moderate increases from week 2 to 4 and week 4 to 6. Wide inter-patient variability was seen at baseline. GRIX scores increased as RT progressed, figure 1. Differences between GRIX scores at weeks 2, 4 and 6 were statistically significant when compared with pre-treatment scores. Modest variability in GRIX scores was seen at baseline and this remained constant.
Radiotherapy and Oncology, 2010
Purpose: Magnetic Resonance Spectroscopy (MRS) of Prostate Cancer (PC) is a relative new approach... more Purpose: Magnetic Resonance Spectroscopy (MRS) of Prostate Cancer (PC) is a relative new approach that holds great promise for target localization in radiotherapy treatment planning and for evaluation of therapy response and cancer recurrence. An accurate definition of the extent of tumour tissue could allow boost therapy doses using intensity-modulated external beam radiotherapy (IMRT). Moreover, according to recent studies there is likely to be a strong correlation between MRS and biopsy findings. In the present work the feasibility of an MRS protocol applied to radiotherapy treatment planning in a clinical routine is studied. When available, the obtained MRS results were compared with histological or PET-CT examinations. Materials: MR examinations were performed on a 1.5 T Philips Achieva scanner. For all the patients included in the study axial T2-weighted images of prostate were acquired. Chemical shift imaging (CSI) and single voxel (SV) spectroscopy sequences were then performed. An external phased array coil was used. Antispastic drug was given before examination to reduce pelvic organs motion. In PC the relevant detectable metabolites are Choline (Cho), Creatine (Cr) and Citrate (Cit). In order to obtain metabolite maps, different post-processing elaboration techniques were evaluated; optimal parameters for filtering, spectrum phase adjustment and residual water suppression were found. Spectra quality was evaluated by calculating the height of metabolite peaks in relation to background noise. Results: SV and CSI spectroscopy results were compared with data available in literature. The possibility of considering absolute Cho or (Cho+Cr) area or Cho/Cit or (Cho+Cr)/Cit area ratio was discussed for every patient taking into account the spectrum quality and, if any, the duration of hormone-deprivation therapy. Metabolite maps, with superimposed T2-weigthed images, were generated (fig.1) and implemented in a treatment planning system (TPS) for targeting purpose. When available, metabolite maps were compared with PET-CT images obtaining a good agreement between the technique. Conclusions: Slice specific contrast based segmentation shows promise as a method of reproducibility delineating PET target volumes with good accuracy and robustness.
Radiotherapy and Oncology, 2013
Medical Physics, 2015
ABSTRACT To investigate the accuracy of various algorithms for deformable image registration (DIR... more ABSTRACT To investigate the accuracy of various algorithms for deformable image registration (DIR), to propagate regions of interest (ROIs) in computational phantoms based on patient images using different commercial systems. This work is part of an Italian multi-institutional study to test on common datasets the accuracy, reproducibility and safety of DIR applications in Adaptive Radiotherapy. Eleven institutions with three available commercial solutions provided data to assess the agreement of DIR-propagated ROIs with automatically drown ROIs considered as ground-truth for the comparison. The DIR algorithms were tested on real patient data from three different anatomical districts: head and neck, thorax and pelvis. For every dataset two specific Deformation Vector Fields (DVFs) provided by ImSimQA software were applied to the reference data set. Three different commercial software were used in this study: RayStation, Velocity and Mirada. The DIR-mapped ROIs were then compared with the reference ROIs using the Jaccard Conformity Index (JCI). More than 600 DIR-mapped ROIs were analyzed. Putting together all JCI data of all institutions for the first DVF, the mean JCI was 0.87 ± 0.7 (1 SD) while for the second DVF JCI was 0.8 ± 0.13 (1 SD). Several considerations on different structures are available from collected data: the standard deviation among different institutions on specific structure raise as the larger is the applied DVF. The higher value is 10% for bladder. Although the complexity of deformation of human body is very difficult to model, this work illustrates some clinical scenarios with well-known DVFs provided by specific software. CI parameter gives the inter-user variability and may put in evidence the need of improving the working protocol in order to reduce the inter-institution JCI variability.
Radiotherapy and Oncology, 2015
Radiotherapy and Oncology, 2018
Physics in Medicine and Biology, 2017
Over the years, many efforts have been made to develop radiation detectors to handle the complex ... more Over the years, many efforts have been made to develop radiation detectors to handle the complex issues of small field dosimetry and achieve the increasing accuracy, precision and in vivo dose monitoring required by the new advanced treatment modalities. In this context, interest has surged in the development of sensors based on scintillating optical fibres. In this paper, the near-infrared radioluminescence and dosimetric properties of Yb-doped silica optical fibres, coupled with a laboratory prototype based on an avalanche photodiode, were studied by irradiating the fibres with photons and electron beams generated by a Varian Trilogy accelerator. The performance of the system in standard and small field sizes has also been investigated, comparing the output factor, percentage depth dose and off-axis ratio measurements of the prototypal detector with other commercial sensors, including the Exradin W1 scintillator. The results of this study demonstrate that the drawback due to the stem effect in Yb-doped silica optical fibres can be managed in a simple but effective way by optical filtering. The robustness of the system in complex dosimetric scenarios and the accuracy and precision achieved by Yb-doped fibres in relative dose assessments suggest an effective use of the system for real-time in vivo dosimetry applications.
Physica Medica, 2016
A project dedicated to stereotactic body radiotherapy (SBRT) dosimetric aspects started in the fr... more A project dedicated to stereotactic body radiotherapy (SBRT) dosimetric aspects started in the framework of the Italian Association of Medical Physics (AIFM) SBRT working group. Its main objectives are manifold but sharing the knowledge between different clinics is the one of the most important. More than 30 centres, equipped with Varian, Elekta, Siemens or CyberKnife linac were enrolled. The project was divided in several work-packages, the first one evaluated the relative measurements with detectors routinely used by individual centers and in the following different detectors run in various centre. Each centre in the same work-package performed dose profile of field size ranging from 0.6 × 0.6 cm 2 to 5.0 × 5.0 cm 2 , and relative output factors (ROF) measurements with a diamond or silicon diode or scintillator detector. In workpackage-1 ROF values measured in the first phase were compared with the ones measured with a microdiamond showing a higher inter-center consistency with this dosimeter compared to routine detectors. In workpackage-2 a silicon diode of new generation was used also to develop a mathematical relation from multicentric experimental data, which describes and predicts the ROF as a function of effective field size for TrueBeam Varian and Elekta linacs. Workpackage-3 used a plastic scintillator for TPR20, 10 and ROF; the latter showed a greater variability. Workpackage-4 used diamond and plastic scintillator with Cyberknife beams, to evaluate if microDiamond could be a suitable alternative to silicon diodes for OF determination and to validate the feasibility of using the scintillator as a reference detector in consideration of the CerenkovLightRatio and experimental uncertainties. The results of the study for all the detectors emphasized the usefulness of a multi-center validation over a single center approach.
Physica Medica, 2018
Purpose. Magnetic resonance imaging (MRI) only radiotherapy has in recent years been introduced a... more Purpose. Magnetic resonance imaging (MRI) only radiotherapy has in recent years been introduced as a clinical workflow for prostate cancer patients. MRI only radiotherapy is performed without computed tomography (CT) and instead, a synthetic CT (sCT) is used for treatment planning. With the introduction of new procedures for treatment planning, development of quality assurance (QA) tools must be considered. Today, no such tool has yet been presented. The aim of this study was to develop a clinically feasible QA procedure for sCT using the kV-cone beam CT (CBCT), in an MRI-only workflow for prostate cancer patients. Methods. Three criteria were addressed; 1. Stability in Hounsfield Units (HUs), 2. Deviations in HUs between the CT and CBCT and 3. Validation of the QA procedure. For the two first criteria, phantom measurements were performed. For the third criteria, sCT, CT and CBCT for ten patients were used. Treatment plans were created based on the sCT (MriPlanner TM). CT and CBCT images were registered to the sCT. The treatment plan was recalculated on the CT and CBCT. Dose-volume histogram (DVH) metrics were used to evaluate dosimetric differences between the sCT plan and the recalculated CT and CBCT plans. Well defined errors were artificially introduced in the sCT for one patient to evaluate efficacy of the QA procedure. Results. The kV-CBCT system was stable in HU over time (SD <40 HU). Difference in HUs between CT and CBCT was very small (<60 HU). The differences between sCT-CT and sCT-CBCT dose distributions were below or equal to 1.0%. The highest mean dose difference for the CT and CBCT dose distribution was 0.6%. No statistically significant difference was found between total mean dose deviations from recalculated CT and CBCT plans, except for femoral head. The proposed QA method was found very helpful in identifying the introduced errors. Conclusions. The results in this study indicates that CBCT can be used as a clinically feasible QA tool for MRI-only radiotherapy of prostate cancer patients. The proposed method could easily be integrated in any modern image guided radiotherapy workflow without extensive work.
Scientific Reports, 2020
Radio-induced apoptosis is mediated by the activation of tumor protein p53, Bax and caspases. The... more Radio-induced apoptosis is mediated by the activation of tumor protein p53, Bax and caspases. The purpose of this study was to investigate the early activation of this pathway in men receiving in vivo irradiation immediately before radical prostatectomy for locally advanced prostate cancer. We also investigated cell proliferation index (Ki-67), proto-oncogene (p53) and anti-apoptotic protein (Bcl-2) levels as potential predictive factors. We selected a homogeneous sample of 20 patients with locally advanced prostate cancer and candidate to radical prostatectomy. To assess the apoptotic pathways, Bax, is studied through immunofluorescence assay, before and after 12 Gy single dose intraoperative radiotherapy (IORT) to the prostate, on bioptic samples and on surgical specimens. Moreover, before and after IORT, Bcl-2, p53, and Ki-67 were also detected through immunohistochemistry. A count of positive Bax spots for immunofluorescence was performed on tumor cells, prostatic intraepithelia...
Practical Radiation Oncology, 2019
to CBCT deformable image registration for contour propagation using head & neck patient-based com... more to CBCT deformable image registration for contour propagation using head & neck patient-based computational phantoms: a multicenter study,
Radiotherapy and Oncology, 2019
Radiotherapy and Oncology, 2019
should always be considered for correct staging in these patients. No statistically significant a... more should always be considered for correct staging in these patients. No statistically significant association was found between primary tumor SUVmax values and tumor responses in this study. This may be due to lack of clinical response data with 18 F-FDG PET/CT, which was available only in 16 out of 38 patients.
Physica Medica, 2018
Methods. We applied a mathematical descriptions of GBM proliferation and diffusion, in the frame ... more Methods. We applied a mathematical descriptions of GBM proliferation and diffusion, in the frame of the reaction diffusion theory. We formulated equations capturing of the impact of radiotherapy and heat on GBM in the reaction diffusion equation, including the regrowth induced by stem cells [2]. Results. Our calculated results show that the expected patient survival could be significantly improved by this treatment [3]. For the future, due to the lower power required for a single heating point, a somewhat lower frequency could be hypothesized, without risks of cavitation. This modification would allow the heating of larger tumors in less central regions. Conclusions. The proposed methodology, now limited to a small tumors in a quite central location, can be easily improved in several different respects. These results advocate thorough experiments to validate this very promising theoretical therapeutic benefit. References a ASL5,
Radiotherapy and Oncology, 2017
Radiotherapy and Oncology, 2017
PTV, plans were optimised aiming to obtain V95%>95% D98%>94%, V2%<108%; concerning the rectum, th... more PTV, plans were optimised aiming to obtain V95%>95% D98%>94%, V2%<108%; concerning the rectum, the requirements were: mean<18Gy, V20<35%, V32 <10%, V37<5%,D1%<40Gy while for the bladder, the goal was to keep mean dose <14 Gy and V21 <40%, V33 < 30%, V38 <13%,D1%<40Gy. Routine institutional image-based patient position verification protocols foresaw daily on-line matching by CBCT. The acute and late toxicities were recorded using the RTOG/EORTC scale. Additional data were collected by means of I-PSS e IIEF-5 questionnaires. Biochemical failure was determined using the Phoenix definition. Results The median follow-up duration was 27 months (range: 24 to 36 months). The median age was 74 years (range: 57-80 years). Most dosimetric parameters for the OARs are well within the protocol constraints, with the n otable exception of maximal doses to rectum and bladder (exceeding in about 20% of cases), but we did not find any statistical correlation with late toxicities. Acute GU toxicity of grade 2 (increase in urinary frequency) was observed in 7% patients. The incidence rates of late GI and GU toxicity of any grade were 14.2% and 35.7%, respectively. The late GU toxicity of grade ≥ 2 was 4.7%. No GE late toxicity ≥ 2 was noted. Previous abdominal surgery appeared to be statistically significant (p= 0.004; Fisher's test) for the increase of probability of late GE toxicity. The 3-year local recurrence-free survival rate was 98%, only one patient had clinical abdominal lymph node failure. Among the dosimetric data, only V21 (mean value: 22.1%; range: 8.5-55.2%) revealed to be statistically significant for the late GU (p= 0.035; Wilcoxon Mann Whitney Test). Conclusion Our experience with VMAT-based SBRT in low-and intermediate-risk prostate cancer demonstrates favorable efficacy in tumor control and toxicity profile with no decrease in QOL as determined by I-PSS, IIEF. The general good quality of the clinical outcome and the results concerning GI and GU toxicities seem to confirm the robustness of the dosimetric paradigm adopted. Longer follow-up is needed to investigate complete safety and efficacy of the stereotactic treatments.
Radiotherapy and Oncology, 2016
Conclusion: Our DIR-QA platform demonstrated inter-and intra-operator variability on the order of... more Conclusion: Our DIR-QA platform demonstrated inter-and intra-operator variability on the order of one voxel (1mm by 1mm by 2.5mm). Machine-generated feature points can serve as a measure of the quality of deformable image registration.
Radiotherapy and Oncology, 2015
Purpose/Objective: Radiotherapy induced xerostomia (RIX) is the most common permanent side effect... more Purpose/Objective: Radiotherapy induced xerostomia (RIX) is the most common permanent side effect of radiotherapy (RT) to the head and neck (H&N) with no effective treatment. LMS-611 is a mimetic of a natural lamellar body which has been shown to have the potential to reduce the 'stickiness' of oral cavity secretions following RT. Our pre-clinical study was designed as an ex vivo, efficacy, proof of concept study as a preparatory step towards our clinical study of LMS-611 in RIX. Materials and Methods: Patients with H&N cancer who were booked for RT or chemoRT (CRT) as primary treatment were recruited. Patient reported xerostomia scores were collected using the Groningen RIX (GRIX) questionnaire at baseline, weeks 2, 4 and 6 of radiotherapy. Saliva samples were also collected and adhesiveness and viscosity tested by assessing time taken to travel 5cm on an inclined plane (IP). LMS-611 was added to saliva samples and IP test repeated. Results: 30 patients were enrolled. All patients had a pathologically confirmed diagnosis of squamous cell carcinoma (SCC) oropharynx. Mean age 54.8 years, range 42-67. 80% were male and the majority stage III and IV disease (96.6%). 90% received CRT. The mean IP test results (seconds) are as follows baseline 31.3; week 2 49.7; week 4 51.1; week 6 55.7 indicating increasing saliva adhesiveness and viscosity as RT progresses. The increase was significant from baseline to week 2 with only moderate increases from week 2 to 4 and week 4 to 6. Wide inter-patient variability was seen at baseline. GRIX scores increased as RT progressed, figure 1. Differences between GRIX scores at weeks 2, 4 and 6 were statistically significant when compared with pre-treatment scores. Modest variability in GRIX scores was seen at baseline and this remained constant.
Radiotherapy and Oncology, 2010
Purpose: Magnetic Resonance Spectroscopy (MRS) of Prostate Cancer (PC) is a relative new approach... more Purpose: Magnetic Resonance Spectroscopy (MRS) of Prostate Cancer (PC) is a relative new approach that holds great promise for target localization in radiotherapy treatment planning and for evaluation of therapy response and cancer recurrence. An accurate definition of the extent of tumour tissue could allow boost therapy doses using intensity-modulated external beam radiotherapy (IMRT). Moreover, according to recent studies there is likely to be a strong correlation between MRS and biopsy findings. In the present work the feasibility of an MRS protocol applied to radiotherapy treatment planning in a clinical routine is studied. When available, the obtained MRS results were compared with histological or PET-CT examinations. Materials: MR examinations were performed on a 1.5 T Philips Achieva scanner. For all the patients included in the study axial T2-weighted images of prostate were acquired. Chemical shift imaging (CSI) and single voxel (SV) spectroscopy sequences were then performed. An external phased array coil was used. Antispastic drug was given before examination to reduce pelvic organs motion. In PC the relevant detectable metabolites are Choline (Cho), Creatine (Cr) and Citrate (Cit). In order to obtain metabolite maps, different post-processing elaboration techniques were evaluated; optimal parameters for filtering, spectrum phase adjustment and residual water suppression were found. Spectra quality was evaluated by calculating the height of metabolite peaks in relation to background noise. Results: SV and CSI spectroscopy results were compared with data available in literature. The possibility of considering absolute Cho or (Cho+Cr) area or Cho/Cit or (Cho+Cr)/Cit area ratio was discussed for every patient taking into account the spectrum quality and, if any, the duration of hormone-deprivation therapy. Metabolite maps, with superimposed T2-weigthed images, were generated (fig.1) and implemented in a treatment planning system (TPS) for targeting purpose. When available, metabolite maps were compared with PET-CT images obtaining a good agreement between the technique. Conclusions: Slice specific contrast based segmentation shows promise as a method of reproducibility delineating PET target volumes with good accuracy and robustness.
Radiotherapy and Oncology, 2013
Medical Physics, 2015
ABSTRACT To investigate the accuracy of various algorithms for deformable image registration (DIR... more ABSTRACT To investigate the accuracy of various algorithms for deformable image registration (DIR), to propagate regions of interest (ROIs) in computational phantoms based on patient images using different commercial systems. This work is part of an Italian multi-institutional study to test on common datasets the accuracy, reproducibility and safety of DIR applications in Adaptive Radiotherapy. Eleven institutions with three available commercial solutions provided data to assess the agreement of DIR-propagated ROIs with automatically drown ROIs considered as ground-truth for the comparison. The DIR algorithms were tested on real patient data from three different anatomical districts: head and neck, thorax and pelvis. For every dataset two specific Deformation Vector Fields (DVFs) provided by ImSimQA software were applied to the reference data set. Three different commercial software were used in this study: RayStation, Velocity and Mirada. The DIR-mapped ROIs were then compared with the reference ROIs using the Jaccard Conformity Index (JCI). More than 600 DIR-mapped ROIs were analyzed. Putting together all JCI data of all institutions for the first DVF, the mean JCI was 0.87 ± 0.7 (1 SD) while for the second DVF JCI was 0.8 ± 0.13 (1 SD). Several considerations on different structures are available from collected data: the standard deviation among different institutions on specific structure raise as the larger is the applied DVF. The higher value is 10% for bladder. Although the complexity of deformation of human body is very difficult to model, this work illustrates some clinical scenarios with well-known DVFs provided by specific software. CI parameter gives the inter-user variability and may put in evidence the need of improving the working protocol in order to reduce the inter-institution JCI variability.
Radiotherapy and Oncology, 2015
Radiotherapy and Oncology, 2018
Physics in Medicine and Biology, 2017
Over the years, many efforts have been made to develop radiation detectors to handle the complex ... more Over the years, many efforts have been made to develop radiation detectors to handle the complex issues of small field dosimetry and achieve the increasing accuracy, precision and in vivo dose monitoring required by the new advanced treatment modalities. In this context, interest has surged in the development of sensors based on scintillating optical fibres. In this paper, the near-infrared radioluminescence and dosimetric properties of Yb-doped silica optical fibres, coupled with a laboratory prototype based on an avalanche photodiode, were studied by irradiating the fibres with photons and electron beams generated by a Varian Trilogy accelerator. The performance of the system in standard and small field sizes has also been investigated, comparing the output factor, percentage depth dose and off-axis ratio measurements of the prototypal detector with other commercial sensors, including the Exradin W1 scintillator. The results of this study demonstrate that the drawback due to the stem effect in Yb-doped silica optical fibres can be managed in a simple but effective way by optical filtering. The robustness of the system in complex dosimetric scenarios and the accuracy and precision achieved by Yb-doped fibres in relative dose assessments suggest an effective use of the system for real-time in vivo dosimetry applications.
Physica Medica, 2016
A project dedicated to stereotactic body radiotherapy (SBRT) dosimetric aspects started in the fr... more A project dedicated to stereotactic body radiotherapy (SBRT) dosimetric aspects started in the framework of the Italian Association of Medical Physics (AIFM) SBRT working group. Its main objectives are manifold but sharing the knowledge between different clinics is the one of the most important. More than 30 centres, equipped with Varian, Elekta, Siemens or CyberKnife linac were enrolled. The project was divided in several work-packages, the first one evaluated the relative measurements with detectors routinely used by individual centers and in the following different detectors run in various centre. Each centre in the same work-package performed dose profile of field size ranging from 0.6 × 0.6 cm 2 to 5.0 × 5.0 cm 2 , and relative output factors (ROF) measurements with a diamond or silicon diode or scintillator detector. In workpackage-1 ROF values measured in the first phase were compared with the ones measured with a microdiamond showing a higher inter-center consistency with this dosimeter compared to routine detectors. In workpackage-2 a silicon diode of new generation was used also to develop a mathematical relation from multicentric experimental data, which describes and predicts the ROF as a function of effective field size for TrueBeam Varian and Elekta linacs. Workpackage-3 used a plastic scintillator for TPR20, 10 and ROF; the latter showed a greater variability. Workpackage-4 used diamond and plastic scintillator with Cyberknife beams, to evaluate if microDiamond could be a suitable alternative to silicon diodes for OF determination and to validate the feasibility of using the scintillator as a reference detector in consideration of the CerenkovLightRatio and experimental uncertainties. The results of the study for all the detectors emphasized the usefulness of a multi-center validation over a single center approach.