E Spezi

Cardiff University, Cardiff, Wales, United Kingdom

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Publications (49)144.92 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This study evaluates the use of sequential I PET/CT for predicting absorbed doses to metastatic lesions in patients with differentiated thyroid cancer undergoing I therapy.
    Clinical Nuclear Medicine 06/2014; · 2.86 Impact Factor
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    ABSTRACT: The use of positron emission tomography (PET) within radiotherapy treatment planning requires the availability of reliable and accurate segmentation tools. PET automatic segmentation (PET-AS) methods have been recommended for the delineation of tumors, but there is still a lack of thorough validation and cross-comparison of such methods using clinically relevant data. In particular, studies validating PET segmentation tools mainly use phantoms with thick plastic walls inserts of simple spherical geometry and have not specifically investigated the effect of the target object geometry on the delineation accuracy. Our work therefore aimed at generating clinically realistic data using nonspherical thin-wall plastic inserts, for the evaluation and comparison of a set of eight promising PET-AS approaches. Sixteen nonspherical inserts were manufactured with a plastic wall of 0.18 mm and scanned within a custom plastic phantom. These included ellipsoids and toroids derived with different volumes, as well as tubes, pear- and drop-shaped inserts with different aspect ratios. A set of six spheres of volumes ranging from 0.5 to 102 ml was used for a baseline study. A selection of eight PET-AS methods, written in house, was applied to the images obtained. The methods represented promising segmentation approaches such as adaptive iterative thresholding, region-growing, clustering and gradient-based schemes. The delineation accuracy was measured in terms of overlap with the computed tomography reference contour, using the dice similarity coefficient (DSC), and error in dimensions. The delineation accuracy was lower for nonspherical inserts than for spheres of the same volume in 88% cases. Slice-by-slice gradient-based methods, showed particularly lower DSC for tori (DSC < 0.5), caused by a failure to recover the object geometry. The region-growing method reached high levels of accuracy for most inserts (DSC > 0.76 except for tori) but showed the largest errors in the recovery of pears and drops dimensions (higher than 10% and 30% of the true length, respectively). Large errors were visible for one of the gradient-based contouring methods when delineating drop-shaped inserts. Low DSC due to systematic underestimation of the volumes was observed for our fuzzy clustering method when using nonspherical inserts. The adaptive iterative thresholding method produced the highest DSC score on our nonspherical dataset (DSC > 0.83, except for tori) and showed robustness to the insert geometry. This study investigated the accuracy of eight PET-AS methods for the delineation of objects with a range of nonspherical geometries. The authors' results confirmed the robustness of some segmentation approaches, but also showed the weaknesses of some of the other methods implemented, which were not observed with spherical inserts. This work therefore highlights the importance of using a variety of thin-wall inserts with complex geometries for the validation of PET-AS methods and provided useful information for further development of the methods tested.
    Medical Physics 02/2014; 41(2):022502. · 3.01 Impact Factor
  • Parham Alaei, Emiliano Spezi, Margaret Reynolds
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    ABSTRACT: Background. With the increasing use of cone beam computed tomography (CBCT) for patient position verification and radiotherapy treatment adaptation, there is an increasing need to develop techniques that can take into account concomitant dose using a personalized approach. Material and methods. A total of 20 patients (10 pelvis and 10 head and neck) who had undergone radiation therapy using intensity modulated radiation therapy (IMRT) were selected and the dose from kV CBCT was retrospectively calculated using a treatment planning system previously commissioned for this purpose. The imaging dose was added to the CT images used for treatment planning and the difference in its addition prior to and after the planning was assessed. Results. The additional isocenter dose as a result of daily CBCT is in the order of 3-4 cGy for 35-fraction head and neck and 23-47 cGy for 25-fraction pelvis cases using the standard head and neck and pelvis image acquisition protocols. The pelvic dose is especially dependent on patient size and body mass index (BMI), being higher for patients with lower BMI. Due to the low energy of the kV CBCT beam, the maximum energy deposition is at or near the surface with the highest dose being on the patient's left side for the head and neck (˜ 7 cGy) and on the posterior for the pelvic cases (˜ 80 cGy). Addition of imaging dose prior to plan optimization resulted in an average reduction of 4% in the plan monitor units and 5% in the number of control points. Conclusion. Dose from daily kV CBCT has been added to patient treatment plans using previously commissioned kV CBCT beams in a treatment planning system. Addition of imaging dose can be included in IMRT treatment plan optimization and would facilitate customization of imaging protocol based on patient anatomy and location of isocenter.
    Acta oncologica (Stockholm, Sweden) 01/2014; · 2.27 Impact Factor
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    ABSTRACT: Purpose: Commercially available fillable plastic inserts used in positron emission tomography phantoms usually have thick plastic walls, separating their content from the background activity. These "cold" walls can modify the intensity values of neighboring active regions due to the partial volume effect, resulting in errors in the estimation of standardized uptake values. Numerous papers suggest that this is an issue for phantom work simulating tumor tissue, quality control, and calibration work. This study aims to investigate the influence of the cold plastic wall thickness on the quantification of 18F-fluorodeoxyglucose on the image activity recovery and on the performance of advanced automatic segmentation algorithms for the delineation of active regions delimited by plastic walls.Methods: A commercial set of six spheres of different diameters was replicated using a manufacturing technique which achieves a reduction in plastic walls thickness of up to 90%, while keeping the same internal volume. Both sets of thin- and thick-wall inserts were imaged simultaneously in a custom phantom for six different tumor-to-background ratios. Intensity values were compared in terms of mean and maximum standardized uptake values (SUVs) in the spheres and mean SUV of the hottest 1 ml region (SUVmax, SUVmean, and SUVpeak). The recovery coefficient (RC) was also derived for each sphere. The results were compared against the values predicted by a theoretical model of the PET-intensity profiles for the same tumor-to-background ratios (TBRs), sphere sizes, and wall thicknesses. In addition, ten automatic segmentation methods, written in house, were applied to both thin- and thick-wall inserts. The contours obtained were compared to computed tomography derived gold standard ("ground truth"), using five different accuracy metrics.Results: The authors' results showed that thin-wall inserts achieved significantly higher SUVmean, SUVmax, and RC values (up to 25%, 16%, and 25% higher, respectively) compared to thick-wall inserts, which was in agreement with the theory. This effect decreased with increasing sphere size and TBR, and resulted in substantial (>5%) differences between thin- and thick-wall inserts for spheres up to 30 mm diameter and TBR up to 4. Thinner plastic walls were also shown to significantly improve the delineation accuracy for the majority of the segmentation methods tested, by increasing the proportion of lesion voxels detected, although the errors in image quantification remained non-negligible.Conclusions: This study quantified the significant effect of a 90% reduction in the thickness of insert walls on SUV quantification and PET-based boundary detection. Mean SUVs inside the inserts and recovery coefficients were particularly affected by the presence of thick cold walls, as predicted by a theoretical approach. The accuracy of some delineation algorithms was also significantly improved by the introduction of thin wall inserts instead of thick wall inserts. This study demonstrates the risk of errors deriving from the use of cold wall inserts to assess and compare the performance of PET segmentation methods.
    Medical Physics 08/2013; 40(8):082505. · 3.01 Impact Factor
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    ABSTRACT: We developed and validated a Monte-Carlo-based application (RAYDOSE) to generate patient-specific 3D dose maps on the basis of pre-treatment imaging studies. A CT DICOM image is used to model patient geometry, while repeated PET scans are employed to assess radionuclide kinetics and distribution at the voxel level. In this work, we describe the structure of this application and present the tests performed to validate it against reference data and experiments. We used the spheres of a NEMA phantom to calculate S values and total doses. The comparison with reference data from OLINDA/EXM showed an agreement within 2% for a sphere size above 2.8 cm diameter. A custom heterogeneous phantom composed of several layers of Perspex and lung equivalent material was used to compare TLD measurements of gamma radiation from (131)I to Monte Carlo simulations. An agreement within 5% was found. RAYDOSE has been validated against reference data and experimental measurements and can be a useful multi-modality platform for treatment planning and research in MRT.
    Physics in Medicine and Biology 03/2013; 58(8):2491-2508. · 2.92 Impact Factor
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    ABSTRACT: The SCOPE 1 trial closed to recruitment in early 2012 and has demonstrably improved the quality of UK radiotherapy. It has also shown that there is an enthusiastic upper gastrointestinal clinical oncology community that can successfully complete trials and deliver high-quality radiotherapy. Following on from SCOPE 1, this paper, authored by a consensus of leading UK upper gastrointestinal radiotherapy specialists, attempts to define current best practice and the questions to be answered by future clinical studies. The two main roles for chemoradiotherapy (CRT) in the management of potentially curable oesophageal cancer are definitive (dCRT) and neoadjuvant (naCRT). The rates of local failure after dCRT are consistently high, showing the need to evaluate more effective treatments, both in terms of optimal local and systemic therapeutic components. This will be the primary objective of the next planned UK dCRT trial and here we discuss the role of dose escalation and systemic therapeutic options that will form the basis of that trial. The publication of the Dutch 'CROSS' trial of naCRT has shown that this pre-operative approach can both be given safely and offer a significant survival benefit over surgery alone. This has led to the development of the UK NeoSCOPE trial, due to open in 2013. There will be a translational substudy to this trial and currently available data on the role of biomarkers in predicting response to therapy are discussed. Postoperative reporting of the pathology specimen is discussed, with recommendations for the NeoSCOPE trial. Both of these CRT approaches may benefit from recent developments, such as positron emission tomography/computed tomography and four-dimensional computed tomography for target volume delineation, planning techniques such as intensity-modulated radiotherapy and 'type b' algorithms and new treatment verification methods, such as cone-beam computed tomography. These are discussed here and recommendations made for their use.
    Clinical Oncology 03/2013; · 2.83 Impact Factor
  • The British journal of radiology 02/2013; · 2.11 Impact Factor
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    ABSTRACT: Aim: The aim of this work was the evaluation of the usefulness of 124I PET/CT sequential scans to predict absorbed doses to metastatic thyroid cancer in patients undergoing 131I therapy. Methods: From July 2011 until April 2012 8 patients affected by metastatic thyroid cancer were enrolled. Each patient underwent 4 PET/CT scans at 4, 24, 48, 72 h after the administration of about 74 MBq of 124I. Blood samples and whole body exposure measurements were obtained to calculate blood and red marrow doses. Activity concentrations and lesion volumes obtained from PET/CT images were used to evaluate tumour doses with MIRD formalism and spheres model. The average administered 131I therapeutic activity was 6475 MBq (range: 3700-9250 MBq). Results: 124I PET/CT images showed, with a very good resolution, all 131I avid lesions detected by post therapy whole body scans. The average dose rates for blood, red marrow and lesions were respectively: 6.58E-02±1.64E-02 mGy/MBq, 5.73E-02±1.57E-02 mGy/MBq, 2.22E+01±1.62E+01 mGy/MBq. Three out of eight patients did not show any uptake of 124I in all PET/CT scans, despite high level of TSH and CT detectable lesions. Post-therapy 131I whole body scan confirmed the absence of focal iodine uptake. Conclusion: Negative 124I PET/CT images probably could be used as predictive of real absence of iodine avidity, avoiding all toxicity from useless 131I therapy. A higher number of patients is necessary to validate these preliminary results and a project is ongoing to compare MIRD results to voxel dosimetry based on Monte Carlo simulation.
    The quarterly journal of nuclear medicine and molecular imaging: official publication of the Italian Association of Nuclear Medicine (AIMN) [and] the International Association of Radiopharmacology (IAR), [and] Section of the Society of... 12/2012; 56(6):509-14. · 1.72 Impact Factor
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    ABSTRACT: To evaluate different conformity indices (CIs) for use in the analysis of outlining consistency within the pretrial quality assurance (Radiotherapy Trials Quality Assurance [RTTQA]) program of a multicenter chemoradiation trial of esophageal cancer and to make recommendations for their use in future trials. The National Cancer Research Institute SCOPE 1 trial is an ongoing Cancer Research UK-funded phase II/III randomized controlled trial of chemoradiation with capecitabine and cisplatin with or without cetuximab for esophageal cancer. The pretrial RTTQA program included a detailed radiotherapy protocol, an educational package, and a single mid-esophageal tumor test case that were sent to each investigator to outline. Investigator gross tumor volumes (GTVs) were received from 50 investigators in 34 UK centers, and CERR (Computational Environment for Radiotherapy Research) was used to perform an assessment of each investigator GTV against a predefined gold-standard GTV using different CIs. A new metric, the local conformity index (l-CI), that can localize areas of maximal discordance was developed. The median Jaccard conformity index (JCI) was 0.69 (interquartile range, 0.62-0.70), with 14 of 50 investigators (28%) achieving a JCI of 0.7 or greater. The median geographical miss index was 0.09 (interquartile range, 0.06-0.16), and the mean discordance index was 0.27 (95% confidence interval, 0.25-0.30). The l-CI was highest in the middle section of the volume, where the tumor was bulky and more easily definable, and identified 4 slices where fewer than 20% of investigators achieved an l-CI of 0.7 or greater. The available CIs analyze different aspects of a gold standard-observer variation, with JCI being the most useful as a single metric. Additional information is provided by the l-CI and can focus the efforts of the RTTQA team in these areas, possibly leading to semi-automated outlining assessment.
    International journal of radiation oncology, biology, physics 08/2012; 84(4):1037-42. · 4.59 Impact Factor
  • P Alaei, E Spezi, M Reynolds
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    ABSTRACT: Purpose: To assess the dose from kilovoltage cone beam CT from two image acquisition protocols, pelvis and head and neck, by addition of the dose to the patient treatment plans. Methods: A total of 20 patients (10 pelvis and 10 head and neck) undergoing radiation therapy were selected and the dose from kV CBCT was calculated using a treatment planning system previously commissioned for this purpose. The imaging dose was added to the CT images used for treatment planning. Daily shifts as a Result of imaging were recorded and applied to imaging beam whenever the sum of the shifts exceeded 0.5 cm. The kV CBCT dose can also be computed prior to planning, in case of IMRT treatments, and used during optimization. Results: The additional dose as a Result of daily CBCT is in the order of few cGy for head and neck and up to 90 cGy for the pelvis cases using the standard head and neck and pelvis protocols. The pelvic dose is especially dependent on patient size, being higher for smaller patients. Due to the low energy of the kV CBCT beam, the maximum energy deposition is at or near the surface with the highest dose being on the patient's left side for the head and neck and on the posterior for the pelvic cases. Conclusions: Dose from daily kilovoltage CBCT can be added to patient treatment plans using previously commissioned kV CBCT beams in a treatment planning system. In the case of IMRT planning, optimization can be done accounting for kV CBCT dose.
    Medical Physics 06/2012; 39(6):3655. · 3.01 Impact Factor
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    ABSTRACT: The global move towards more conformal radiotherapy for rectal cancer requires better imaging modalities that both visualise the disease accurately and are reproducible; to reduce interobserver variation. This review explores the advances in imaging modalities used in target volume delineation, with a view to make recommendations for current clinical practice and to propose future directions for research. A systematic review was conducted using MEDLINE and EMBASE. Articles considered relevant by the authors were included. Planning with orthogonal films is being replaced by computed tomography (CT) simulation. This is now considered the 'gold standard' and allows conformal three-dimensional planning. Magnetic resonance imaging (MRI) has been shown to overcome some of the limitations of CT and can be used either as a diagnostic image to visually aid planning, or as a 'planning' MRI carried out in the treatment position and co-registered with the planning CT. The latter approach has been shown to change the treated volumes compared with CT and in prostate cancer patients has been shown to reduce interobserver variation. There are remaining issues with four-dimensional motion that are yet to be fully appreciated or overcome. 2-[18F] fluoro-2-deoxy-d-glucose positron emission tomography/CT co-registered with planning CT results in smaller volumes than CT alone and also reduces interobserver variation, but requires further validation before routine implementation. Experimental work utilising novel positron emission tomography tracers and diffusion-weighted MRI shows promise and requires further evaluation. Rigorous quality assurance is important with processing of newer imaging modalities. Further work needs to be conducted into both interobserver variation and the formal evaluation of the clinical benefits of newer imaging modalities. Developments in image-guided radiotherapy are also required to ensure that improvements in target definition at the planning stage are reproducible throughout treatment.
    Clinical Oncology 02/2012; 24(1):52-63. · 2.83 Impact Factor
  • Parham Alaei, Emiliano Spezi
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    ABSTRACT: The feasibility of accounting of the dose from kilovoltage cone-beam CT in treatment planning has been discussed previously for a single cone-beam CT (CBCT) beam from one manufacturer. Modeling the beams and computing the dose from the full set of beams produced by a kilovoltage cone-beam CT system requires extensive beam data collection and verification, and is the purpose of this work. The beams generated by Elekta X-ray volume imaging (XVI) kilovoltage CBCT (kV CBCT) system for various cassettes and filters have been modeled in the Philips Pinnacle treatment planning system (TPS) and used to compute dose to stack and anthropomorphic phantoms. The results were then compared to measurements made using thermoluminescent dosimeters (TLDs) and Monte Carlo (MC) simulations. The agreement between modeled and measured depth-dose and cross profiles is within 2% at depths beyond 1 cm for depth-dose curves, and for regions within the beam (excluding penumbra) for cross profiles. The agreements between TPS-calculated doses, TLD measurements, and Monte Carlo simulations are generally within 5% in the stack phantom and 10% in the anthropomorphic phantom, with larger variations observed for some of the measurement/calculation points. Dose computation using modeled beams is reasonably accurate, except for regions that include bony anatomy. Inclusion of this dose in treatment plans can lead to more accurate dose prediction, especially when the doses to organs at risk are of importance.
    Journal of Applied Clinical Medical Physics 01/2012; 13(6):3971. · 1.11 Impact Factor
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    ABSTRACT: The purpose of the present study was to quantify the concomitant dose received by patients undergoing cone beam computed tomography (CBCT) scanning in different clinical scenarios as a part of image-guided radiotherapy (IGRT) procedures. We calculated the three-dimensional concomitant dose received as a result of CBCT scans in 6 patients representing different clinical scenarios: two pelvis, two head and neck, and two chest. We assessed the effect that a daily on-line IGRT strategy would have on the patient dose distribution, assuming 40 CBCT scans throughout the treatment course. The additional dose to the planning target volume margin region was also estimated. In the pelvis, a single CBCT scan delivered a mean dose to the femoral heads of 2-6 cGy and the rectum of 1-2 cGy. An additional dose to the planning target volume was within 1-3 cGy. In the chest, the mean dose to the planning target volume varied from 2.5 to 5 cGy. The lung and spinal cord planning organ at risk volume received ≤4 cGy and ≤5 cGy, respectively. In the head and neck, a single CBCT scan delivered a mean dose of 0.3 cGy, with bony structures receiving 0.5-0.8 cGy. The femoral heads received an additional dose of 1.5-2.5 Gy. A reduction of 20-30% in the mean dose to the organs at risk was achieved using bowtie filtration. In the head and neck, the dose to the eyes and brainstem was eliminated by decreasing the craniocaudal field size. The additional dose from on-line IGRT procedures can be clinically relevant. The organ dose can be significantly reduced with the use of appropriate patient-specific settings. The concomitant dose from CBCT should be accounted for and the acquisition settings optimized for optimal IGRT strategies on a patient basis.
    International journal of radiation oncology, biology, physics 10/2011; 83(1):419-26. · 4.59 Impact Factor
  • Fuel and Energy Abstracts 10/2011; 81(2).
  • E Spezi, W Volken, D Frei, M K Fix
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    ABSTRACT: The purpose of this investigation was to study the source characteristics of a clinical kilo-voltage cone beam CT unit and to develop and validate a virtual source model that could be used for treatment planning purposes. We used a previously commissioned full Monte Carlo model and new bespoke software to study the source characteristics of a clinical kilo-voltage cone beam CT (CBCT) unit. We identified the main particle sources, their spatial, energy and angular distribution for all the image acquisition presets currently used in our clinical practice. This includes a combination of two energies (100 and 120 kVp), two filters (neutral and bowtie), and eight different x-ray beam apertures. We subsequently built a virtual source model which we validated against full Monte Carlo calculations. We found that the radiation output of the clinical kilo-voltage cone beam CT unit investigated in this study could be reproduced with a virtual model comprising of two sources (target and filtration cone) or three sources (target, filtration cone and bowtie filter) when additional filtration was used. With this model, we accounted for more than 97% of the photons exiting the unit. Each source in our model was characterised by a origin distribution in both X and Y directions, a fluence map, a single energy spectrum for unfiltered beams and a two dimensional energy spectrum for bowtie filtered beams. The percentage dose difference between full Monte Carlo and virtual source model based dose distributions was well within the statistical uncertainty associated with the calculations ( ± 2%, one standard deviation) in all cases studied. The virtual source that we developed is accurate in calculating the dose delivered from a commercial kilo-voltage cone beam CT unit operating with routine clinical image acquisition settings. Our data have also shown that target, filtration cone, and bowtie filter sources needed to be all included in the model in order to accurately replicate the dose distribution from the clinical radiation beam.
    Medical Physics 09/2011; 38(9):5254-63. · 3.01 Impact Factor
  • E. Spezi, P. Downes, E. Radu
    Radiotherapy and Oncology 05/2011; 99. · 4.86 Impact Factor
  • Radiotherapy and Oncology 05/2011; 99. · 4.86 Impact Factor
  • E. Spezi, M. Fix, W. Volken, D. Frei
    Radiotherapy and Oncology 05/2011; 99. · 4.86 Impact Factor
  • Radiotherapy and Oncology 05/2011; 99. · 4.86 Impact Factor
  • Clinical Oncology 04/2011; 23(3). · 2.83 Impact Factor

Publication Stats

438 Citations
144.92 Total Impact Points


  • 2009–2013
    • Cardiff University
      • School of Chemistry
      Cardiff, Wales, United Kingdom
  • 2012
    • University of Minnesota Twin Cities
      Minneapolis, Minnesota, United States
  • 2010–2011
    • The Bracton Centre, Oxleas NHS Trust
      Дартфорде, England, United Kingdom
  • 2006–2008
    • Policlinico S.Orsola-Malpighi
      Bolonia, Emilia-Romagna, Italy