CT dose reduction using Automatic Exposure Control and iterative reconstruction: A chest paediatric phantoms study

PurposeTo evaluate the impact of Automatic Exposure Control (AEC) on radiation dose and image quality in paediatric chest scans (MDCT), with or without iterative reconstruction (IR).MethodsThree anthropomorphic phantoms representing children aged one, five and 10-year-old were explored using AEC system (CARE Dose 4D) with five modulation strength options. For each phantom, six acquisitions were carried out: one with fixed mAs (without AEC) and five each with different modulation strength. Raw data were reconstructed with Filtered Back Projection (FBP) and with two distinct levels of IR using soft and strong kernels. Dose reduction and image quality indices (Noise, SNR, CNR) were measured in lung and soft tissues. Noise Power Spectrum (NPS) was evaluated with a Catphan 600 phantom.ResultsThe use of AEC produced a significant dose reduction (p < 0.01) for all anthropomorphic sizes employed. According to the modulation strength applied, dose delivered was reduced from 43% to 91%. This pattern led to significantly increased noise (p < 0.01) and reduced SNR and CNR (p < 0.01). However, IR was able to improve these indices. The use of AEC/IR preserved image quality indices with a lower dose delivered. Doses were reduced from 39% to 58% for the one-year-old phantom, from 46% to 63% for the five-year-old phantom, and from 58% to 74% for the 10-year-old phantom. In addition, AEC/IR changed the patterns of NPS curves in amplitude and in spatial frequency.ConclusionsIn chest paediatric MDCT, the use of AEC with IR allows one to obtain a significant dose reduction while maintaining constant image quality indices.     

Simulation of images of CDMAM phantom and the estimation of measurement uncertainties of threshold gold thickness

PurposeTo demonstrate a method of simulating mammography images of the CDMAM phantom and to investigate the coefficient of variation (CoV) in the threshold gold thickness (t_T) measurements associated with use of the phantom.MethodsThe noise and sharpness of Hologic Dimensions and GE Essential mammography systems were characterized to provide data for the simulation. The simulation method was validated by comparing the t_T results of real and simulated images of the CDMAM phantom for three different doses and the two systems. The detection matrices produced from each of 64 images using CDCOM software were randomly resampled to create 512 sets of 8, 16 and 32 images to estimate the CoV of t_T. Sets of simulated images for a range of doses were used to estimate the CoVs for a range of diameters and threshold thicknesses.ResultsNo significant differences were found for t_T or the CoV between real and simulated CDMAM images. It was shown that resampling from 256 images was required for estimating the CoV. The CoV was around 4% using 16 images for most of the phantom but is over double that for details near the edge of the phantom.ConclusionsWe have demonstrated a method to simulate images of the CDMAM phantom for different systems at a range of doses. We provide data for calculating uncertainties in t_T. Any future review of the European guidelines should take into consideration the calculated uncertainties for the 0.1 mm detail.     

Effect of diagnostic cone-beam computed tomography protocols on image quality,patient dose,and lesion detection

ObjectiveTo evaluate the effect of cone-beam computed tomography (CBCT) image acquisition protocols on image quality, lesion detection, delineation, and patient dose.Methods100-patients and a CTDI phantom combined with an electron density phantom were examined using four different CBCT-image acquisition protocols during image-guided transarterial chemoembolization (TACE). Protocol-1 (time: 6 s, tube rotation: 360°), protocol-2 (5 s, 300°), protocol-3 (4 s, 240°) and protocol-4 (3 s, 180°) were used. The protocols were first investigated using a phantom. The protocols that were found to be clinically appropriate in terms of image quality and radiation dose were then assessed on patients. A higher radiation dose and/or a poor image quality were inappropriate for the patient imaging. Patient dose (patient-entrance dose and dose-area product), image quality (Hounsfield Unit, noise, signal-to-noise ratio and contrast-to-noise ratio), and lesion delineation (tumor-liver contrast) were assessed and compared using appropriate statistical tests. Lesion detectability, sensitivity, and predictive values were estimated for CBCT-image data using pre-treatment patient magnetic resonance imaging.ResultsThe estimated patient dose showed no statistical significance (p > 0.05) between protocols-2 and -3; the assessed image quality between these protocols manifested insignificant difference (p > 0.05). Two other phantom protocols were not considered for patient imaging due to significantly higher dose (protocols-1) and poor image quality (protocol-4). Lesion delineation and detection were insignificant (p > 0.05) between protocols-2 and -3. Lesion sensitivities generated were 81–89% (protocol-2) and 81–85% (protocol-3) for different lesion types.ConclusionData acquisition using protocols-2 and -3 provided good image quality, lesion detection and delineation with acceptable patient dose during CBCT-imaging mainly due to similar frame numbers acquired.     

Comparaison entre les modes d’acquisition 2D et 3D en TEP au FDG

AimSome positron emission tomography (PET) cameras offer the possibility of choosing between the 2D and 3D acquisition modes. Due to the lack of comparative and objective data in the litterature between the two modes in clinical routine conditions, we have performed a comparative study based on the assessment of qualitative and quantitative parameters.Materials and methodsA series of 33 FDG PET studies has been prospectively selected in the nuclear medicine department. All studies have been performed with a Discovery ST^® camera (GE healthcare) first in the 2D or 3D mode according to the usual criteria of the department. Then a new single step was acquired on a pathological region using the other mode. The same single slice was chosen and analyzed in the two modes (blindly and in random order) by seven nuclear physicians in terms of qualitative and quantitative parameters.ResultsThe 2D mode is significantly better than 3D concerning the overall image quality for patients with a body mass index (BMI) > 27.5 (p = 0.006) and concerning the confidence in lesion reporting for patients with a BMI > 25 (p = 0.01). The mean number of detected lesions is not affected by the acquisition mode but it is significantly correlated with the image quality and the confidence in lesion reporting (p = 0.07 and p = 0.013, respectively).ConclusionWith the Discovery ST PET-CT, the 2D mode gives better results than 3D for overweight and obese patients in terms of image quality and confidence in lesion reporting.     

Optimization of the exposure parameters in digital mammography using contrast-detail metrics

PurposeOptimization studies in digital mammography aid to assure the image quality and radiological protection of the patient. The aim of this work is to test effectiveness and applicability of a method based on a Figure of Merit (FOM = (IQF_inv)²/AGD) to improve all the exposure parameters (Target/Filter combination, kVp and mAs) in order to improve the image acquisition technique that will provide the best compromise between image quality and the average glandular dose (AGD).MethodsA contrast-detail analysis, employing the test object CDMAM, was carried out for the digital mammography unit manufactured by Lorad Hologic – model Selenia. We simulated two breast thicknesses using phantoms and a Figure of Merit as optimization tool, which includes an indicator of image quality, the IQF_inv and the average glandular dose. Images of the ACR and TORMAM phantoms were obtained with both, automatic and optimized exposure parameters. In order to compare the image quality, the SNR (Signal to Noise Ratio) was measured in each image.ResultsIn the two phantoms, for both 4.5 and 7.5 cm thicknesses, the AGDs obtained with the optimized parameters show a reduction. In addition, the images obtained with the optimized exposure parameters, had the same or a better image quality when compared to the images obtained using the automatic mode.ConclusionsThe proposed optimization methodology proved to be an effective tool to improve the digital mammography unit, due to the use of objective metrics for evaluation and validation of the results.     

The optimal balance between quality and efficiency in proton radiography imaging technique at various proton beam energies: A Monte Carlo study

Proton radiography is a novel imaging modality that allows direct measurement of the proton energy loss in various tissues. Currently, due to the conversion of so-called Hounsfield units from X-ray Computed Tomography (CT) into relative proton stopping powers (RPSP), the uncertainties of RPSP are 3–5% or higher, which need to be minimized down to 1% to make the proton treatment plans more accurate.In this work, we simulated a proton radiography system, with position-sensitive detectors (PSDs) and a residual energy detector (RED). The simulations were built using Geant4, a Monte Carlo simulation toolkit. A phantom, consisting of several materials was placed between the PSDs of various Water Equivalent Thicknesses (WET), corresponding to an ideal detector, a gaseous detector, silicon and plastic scintillator detectors. The energy loss radiograph and the scattering angle distributions of the protons were studied for proton beam energies of 150 MeV, 190 MeV and 230 MeV. To improve the image quality deteriorated by the multiple Coulomb scattering (MCS), protons with small angles were selected. Two ways of calculating a scattering angle were considered using the proton’s direction and position.A scattering angle cut of 8.7 mrad was applied giving an optimal balance between quality and efficiency of the radiographic image. For the three proton beam energies, the number of protons used in image reconstruction with the direction method was half the number of protons kept using the position method.     

Evaluation of automatic image quality assessment in chest CT – A human cadaver study

PurposeThe evaluation of clinical image quality (IQ) is important to optimize CT protocols and to keep patient doses as low as reasonably achievable. Considering the significant amount of effort needed for human observer studies, automatic IQ tools are a promising alternative. The purpose of this study was to evaluate automatic IQ assessment in chest CT using Thiel embalmed cadavers.MethodsChest CT’s of Thiel embalmed cadavers were acquired at different exposures. Clinical IQ was determined by performing a visual grading analysis. Physical-technical IQ (noise, contrast-to-noise and contrast-detail) was assessed in a Catphan phantom. Soft and sharp reconstructions were made with filtered back projection and two strengths of iterative reconstruction. In addition to the classical IQ metrics, an automatic algorithm was used to calculate image quality scores (IQs). To be able to compare datasets reconstructed with different kernels, the IQs values were normalized.ResultsGood correlations were found between IQs and the measured physical-technical image quality: noise (ρ = −1.00), contrast-to-noise (ρ = 1.00) and contrast-detail (ρ = 0.96). The correlation coefficients between IQs and the observed clinical image quality of soft and sharp reconstructions were 0.88 and 0.93, respectively.ConclusionsThe automatic scoring algorithm is a promising tool for the evaluation of thoracic CT scans in daily clinical practice. It allows monitoring of the image quality of a chest protocol over time, without human intervention. Different reconstruction kernels can be compared after normalization of the IQs.     

Few-view CT reconstruction via a novel non-local means algorithm

PurposeNon-local means (NLM) based reconstruction method is a promising algorithm for few-view computed tomography (CT) reconstruction, but often suffers from over-smoothed image edges. To address this problem, an adaptive NLM reconstruction method based on rotational invariance (ART-RIANLM) is proposed.MethodsThe method consists of four steps: 1) Initializing parameters; 2) ART reconstruction using raw data; 3) Positivity constraint of the reconstructed image; 4) Image updating by RIANLM filtering. In RIANLM, two kinds of rotational invariance measures which are average gradient (AG) and region homogeneity (RH) are proposed to calculate the distance between two patches and a novel NLM filter is developed to avoid over-smoothed image. Moreover, the parameter h in RIANLM which controls the decay of the weights is adaptive to avoid over-smoothness, while it is constant in NLM during the whole reconstruction process. The proposed method is validated on two digital phantoms and real projection data.ResultsIn our experiments, the searching neighborhood size is set as 15 × 15 and the similarity window is set as 3 × 3. For the simulated case of Shepp-Logan phantom, ART-RIANLM produces higher SNR (36.23 dB > 24.00 dB) and lower MAE (0.0006 < 0.0024) reconstructed images than ART-NLM. The visual inspection demonstrated that the proposed method could suppress artifacts or noises more effectively and recover image edges better. The result of real data case is also consistent with the simulation result.ConclusionsA RIANLM based reconstruction method for few-view CT is presented. Compared to the traditional ART-NLM method, SNR and MAE from ART-RIANLM increases 51% and decreases 75%, respectively.     

Évaluation par la TEMP–TDM des lésions classées indéterminées en scintigraphie osseuse chez les patients de cancérologie

The aim of the present study was to investigate the contribution of the single photon emission computed tomography/computed tomography (SPECT/CT) in cancer patients and to evaluate its ability to correctly classify indeterminate lesions on planar bone scintigraphy (PBS).MethodsFrom November 2006 to August 2007, all patients with confirmed malignancy, whose PBS showed indeterminate lesions, underwent without delay a SPECT/CT. The study included 120 patients (67 men, 53 women), with a mean age of 69 ± 12 years (range 42–96 years). The patients with obvious metastases, important pains or who did not accept the examination were excluded from the study. The location of the lesions was described either as precise, probable or indeterminate. The lesions were classified either as definitely malignant, definitely benign or indeterminate.ResultsBreast, prostate, lung and kidney neoplasms represented approximately 80% of all cancers. The PBS highlighted 267 lesions of location either as precise (n = 29), probable (n = 129) or indeterminate (n = 109), classified either as definitely malignant (n = 28), definitely benign (n = 27) or indeterminate (n = 212). The SPECT/CT revealed 440 lesions, of location either as precise (n = 353), likely (n = 39) or indeterminate (n = 48), classified either as definitely malignant (n = 84), definitely benign (n = 305) or indeterminate (n = 51). Thoracic and lumbar spine and pelvis were the locations of 79% of the scintigraphic lesions and of 88% of the osseous metastases. SPECT/CT modified the final report of 80 patients, by excluding from metastases (n = 2), by showing metastases (n = 23) and by showing the benign character of indeterminate lesions (n = 55). Moreover, 69 patients out of 120 (> 57%) had an evolution confirmed with 35 true positives, 31 true negatives, one false negative and two patients with indeterminate lesions on SPECT/CT, without osseous metastasis.ConclusionThe assessment of the indeterminate scintigraphic lesions of oncologic patients benefits from the SPECT/CT. The lesion-based analysis showed that the SPECT/CT detected more lesions (+64%) and correctly classified 88% of the detected lesions. The patient-based analysis highlighted that SPECT/CT modified the final report for more than 66% of the patients. The follow-up showed that SPECT/CT correctly classified for more than 95% of the patients.     

Megavoltage 2D topographic imaging: An attractive alternative to megavoltage CT for the localization of breast cancer patients treated with TomoDirect

PurposeTo show the usefulness of topographic 2D megavoltage images (MV2D) for the localization of breast cancer patients treated with TomoDirect (TD), a radiotherapy treatment technique with fixed-angle beams performed on a TomoTherapy system.MethodsA method was developed to quickly localize breast cancer patients treated with TD by registering the MV2D images produced before a TD treatment with reference images reconstructed from a kilovoltage CT simulation scanner and by using the projection of the beam-eye-view TD treatment field. Dose and image quality measurements were performed to determine the optimal parameters for acquiring MV2D images. A TD treatment was simulated on a chest phantom equipped with a breast attachment. MVCT and MV2D images were performed for 7 different shifted positions of the phantom and registered by 10 different operators with the simulation kilovoltage CT images.ResultsCompared to MVCT, MV2D imaging reduces the dose by a factor of up to 45 and the acquisition time by a factor of up to 49. Comparing the registration shift values obtained for the phantom images obtained with MVCT in the coarse mode to those obtained with MV2D, the mean difference is 1.0 ± 1.1 mm, −1.1 mm ± 1.1, and −0.1 ± 2.2 mm, respectively, in the lateral, longitudinal, and vertical directions.ConclusionsWith dual advantages (very fast imaging and a potentially reduced dose to the heart and contralateral organs), MV2D topographic images may be an attractive alternative to MVCT for the localization of breast cancer patients treated with TomoDirect.     

Measurement of stray neutron doses inside the treatment room from a proton pencil beam scanning system

PurposeTo measure the environmental doses from stray neutrons in the vicinity of a solid slab phantom as a function of beam energy, field size and modulation width, using the proton pencil beam scanning (PBS) technique.MethodMeasurements were carried out using two extended range WENDI-II rem-counters and three tissue equivalent proportional counters. Detectors were suitably placed at different distances around the RW3 slab phantom. Beam irradiation parameters were varied to cover the clinical ranges of proton beam energies (100–220 MeV), field sizes ((2 × 2)–(20 × 20) cm²) and modulation widths (0–15 cm).ResultsFor pristine proton peak irradiations, large variations of neutron H¹(10)/D were observed with changes in beam energy and field size, while these were less dependent on modulation widths. H¹(10)/D for pristine proton pencil beams varied between 0.04 μSv Gy⁻¹ at beam energy 100 MeV and a (2 × 2) cm² field at 2.25 m distance and 90° angle with respect to the beam axis, and 72.3 μSv Gy⁻¹ at beam energy 200 MeV and a (20 × 20) cm² field at 1 m distance along the beam axis.ConclusionsThe obtained results will be useful in benchmarking Monte Carlo calculations of proton radiotherapy in PBS mode and in estimating the exposure to stray radiation of the patient. Such estimates may be facilitated by the obtained best-fitted simple analytical formulae relating the stray neutron doses at points of interest with beam irradiation parameters.     

Quantification and monitoring of PET/CT data in multicentre trials: The Swiss SAKK 56/07 trial experience

AimTo outline the importance of continuous monitoring of quantitative positron emission tomography (PET) data in multicentre trials to minimize quantitative bias in longitudinal intra-patient PET studies in light of the multicentre SAKK 56/07 experience in quantification and monitoring ¹⁸F-FDG PET/CT data.Patients and methodsWe collected 64 uniform phantom ¹⁸F-FDG PET acquisitions periodically at the enrolling centres (12 European institutions). A core-laboratory analysed them for standard uptake value (SUV) accuracy (desired 1.00 ± 10%) and acceptable image noise was defined by a coefficient of variation (COV) less than 15%. In total, 151 patients ¹⁸F-FDG PET acquisitions (baseline and follow-up) were also collected and analysed to verify longitudinal coherence of main acquisition/reconstruction parameters (DICOM tags verification) and patient preparation, in particular the uptake time (desired uptake time [UT] = 60 ± 10 min).ResultsUniform phantom PET acquisition satisfied the inclusion criteria in 58/64 (89%) examinations. All PET scanner exhibited comparable SUV quantification, but we found large dispersion in terms of noise, with COV ranging 3–15%. Only 1 phantom PET acquisition was out of range with COV = 21.5%. Patient data exhibited important variation in uptake time with UT = 65 ± 10 min (mean ± SD), with only 111/151 (74%) patients’ examinations satisfying inclusion criteria while 26% were out of range.ConclusionsRegular monitoring of PET data in multicentre trials is capital to ensure longitudinal intra-patient PET data consistence and minimize quantitative bias while it helps to spread the culture of quality in participating centre. Recent EARL (EANM Research Ltd) standardization and unification of procedures is a welcome step in this direction.     

Risk factors associated with human papillomavirus prevalence and cervical neoplasia among Cameroonian women

BackgroundThis study used community-based cervical cancer screening for high-risk human-papillomavirus (HPV) to determine demographic and lifestyle factors associated with HPV prevalence and cervical intraepithelial neoplasia grade 2 or worse (CIN2+).MethodsWomen (n = 838) aged 25–65 years were recruited in two sequential studies in Cameroon. Demographic and historical data were obtained from participants and specimens were self-collected for HPV-testing using real-time PCR. HPV-positive women underwent biopsy and endocervical curettage. Associations were determined using bivariate analysis and logistic regression.ResultsHPV and self-reported HIV prevalence were 39.0% and 9.2%, respectively. Eighteen (9.3%) CIN2+ lesions were found among HPV-positive women. Housewives had a higher risk of being HPV infected (OR = 1.60, p = 0.010). HIV co-infection (aOR = 3.44, p < 0.001) and hormonal contraception (aOR = 1.97, p = 0.007) were associated with increased HPV prevalence. HPV-positive women who used condoms during sexual intercourse were at lower risk of CIN2+ (aOR = 0.15, p = 0.029). CIN2–3 lesions were found in women younger than 50 years, with a median age of 36 years (31–44). HPV-16/18-positive women had a 4.65-fold increased risk of CIN2+ (p = 0.015).ConclusionsYoung, single women and housewives were at higher risk of HPV infection. Preventive strategies for cervical cancer in low-resource settings should target women aged 30–50 years for HPV screening, and should focus treatment and follow-up on HPV-16/18-positive women. Further studies are needed to clarify if other risk factors require attention.     

Évaluation des paramètres et méthode de contrôle de qualité de la correction d’atténuation en tomographie par émission de positons

ObjectiveThe aim of this study is to evaluate the performance of the Computed Tomography based Attenuation Correction (CTAC) for Positron Emission Tomography (PET) data. Attenuation maps containing linear attenuation coefficients at 511 keV (LAC_511 keV) are calculated by trilinear conversion of Hounsfield Units (HU) obtained from CT slices after matrix size-reduction and gaussian filtering. Our work focusses on this trilinear conversion.Materials and methodsCT slices of an electron density phantom, composed of 17 cylindrical inserts made of different tissue-equivalent materials, were acquired using a Discovery ST4^® PET-CT. Data were processed with a customized version of CT quality control software, giving automatically the experimental conversion function: LAC_511 keV = f(HU). Furthermore, data from patient datasets were assessed using both smoothed CT slices and attenuation maps.ResultsLAC_511 keV extracted from phantom data are in good correlation with the expected theoretical values, except for the standard 10 mm diameter dense bone insert, where the obtained CTAC values are underestimated. Assuming a sample size issue, similar acquisitions were performed with a special 30 mm-diameter dense bone insert, confirming the underestimation as a consequence of the sample size. This effect, caused partly by a too smooth Gaussian filter of the CT images, could be limited by reducing the strength of the filter. Measurements from patients’ data showed the same underestimation of CAL_511 keV for high-density tissues.ConclusionWe assessed an underestimation of the CTAC obtained-values related to the sample size of the insert. A quality control was developed to this effect.     

Virtual patient 3D dose reconstruction using in air EPID measurements and a back-projection algorithm for IMRT and VMAT treatments

PurposeAt our institute, a transit back-projection algorithm is used clinically to reconstruct in vivo patient and in phantom 3D dose distributions using EPID measurements behind a patient or a polystyrene slab phantom, respectively. In this study, an extension to this algorithm is presented whereby in air EPID measurements are used in combination with CT data to reconstruct ‘virtual’ 3D dose distributions. By combining virtual and in vivo patient verification data for the same treatment, patient-related errors can be separated from machine, planning and model errors.Methods and materialsThe virtual back-projection algorithm is described and verified against the transit algorithm with measurements made behind a slab phantom, against dose measurements made with an ionization chamber and with the OCTAVIUS 4D system, as well as against TPS patient data. Virtual and in vivo patient dose verification results are also compared.ResultsVirtual dose reconstructions agree within 1% with ionization chamber measurements. The average γ-pass rate values (3% global dose/3 mm) in the 3D dose comparison with the OCTAVIUS 4D system and the TPS patient data are 98.5 ± 1.9%(1SD) and 97.1 ± 2.9%(1SD), respectively. For virtual patient dose reconstructions, the differences with the TPS in median dose to the PTV remain within 4%.ConclusionsVirtual patient dose reconstruction makes pre-treatment verification based on deviations of DVH parameters feasible and eliminates the need for phantom positioning and re-planning. Virtual patient dose reconstructions have additional value in the inspection of in vivo deviations, particularly in situations where CBCT data is not available (or not conclusive).     

Optimization of 18F-Choline PET/CT acquisition in prostate cancer: Preliminary results concerning the length of the acquisition

ObjectiveFCH-PET/CT protocol for prostate cancer assessment consists of an early and late acquisition. Concerning the early acquisition, this study compares contrast-to-noise ratio of tumoral lesions between 5 and 10 minutes post-injection in order to shorten the time of this early acquisition.Materials and methodsPatients with proven prostate cancer referred for initial staging or recurrence were prospectively included. Patients underwent 10 minutes of pelvic dynamic acquisition for the early phase and late phase was performed at 60 minutes post-injection. Contrast-to-noise of lesions at 5 and 10 min post-injection were compared.ResultsForty-nine patients with 77 lesions were analyzed. No significant difference of prostatic lesions contrast-to-noise ratio was found between 5 min and 10 min post-injection (median contrast-to-noise ratio was respectively 38 and 42, P = 0.128).ConclusionThese results could have an impact on clinical practice with FCH-PET/CT early acquisition shortened to 5 min post-injection for patients with prostate cancer.     

Variable angle stereo imaging for rapid patient position correction in an in-house real-time position monitoring system

PurposeTo develop and validate a variable angle stereo image based position correction methodology in an X-ray based in-house online position monitoring system.Materials and methodsA stereo imaging module that enables 3D position determination and couch correction of the patient based on images acquired at any arbitrary angle and arbitrary angular separation was developed and incorporated to the in-house SeedTracker real-time position monitoring system. The accuracy of the developed system was studied by imaging an anthropomorphic phantom implanted with radiopaque markers set to known offset positions from its reference position in an Elekta linear accelerator (LA) and associated XVI imaging system. The accuracy of the system was further validated using CBCT data set from 10 prostate SBRT patients. The time gains achieved with the stereo image based position correction was compared with the manual matching of seed positions in Digitally Reconstructed Radiographs (DRRs) and kV images in the Mosaiq record and verify system.ResultsBased on phantom and patient CBCT dataset study stereo imaging module implemented in the SeedTracker shown to have an accuracy of 0.1(σ = 0.5) mm in detecting the 3D position offset. The time comparison study showed that stereo image based methodology implemented in SeedTracker was a minimum of 80(4) s faster than the manual method implemented in Mosaiq R&V system with a maximum time saving of 146(6) s.ConclusionThe variable angle stereo image based position correction method was shown to be accurate and faster than the standard manual DRR–kV image based correction approach, leading to more efficient treatment.     

Comparison between new-generation SiPM-based and conventional PMT-based TOF-PET/CT

PurposeThis study aimed to determine whether the SiPM-PET/CT, Discovery MI (DMI) performs better than the PMT-PET/CT system, Discovery 710 (D710).MethodsThe physical performance of both systems was evaluated using NEMA NU 2 standards. Contrast (%), uniformity and image noise (%) are criteria proposed by the Japanese Society of Nuclear Medicine (JSNM) for phantom tests and were determined in images acquired from Hoffman and uniform phantoms using the DMI and D710. Brain and whole-body [¹⁸F]FDG images were also acquired from a healthy male using the DMI and D710.ResultsThe spatial resolution at 1.0 cm off-center in the DMI and D710 was 3.91 and 4.52 mm, respectively. The sensitivity of the DMI and D710 was 12.62 and 7.50 cps/kBq, respectively. The observed peak noise-equivalent count rates were 185.6 kcps at 22.5 kBq/mL and 137.0 kcps at 29.0 kBq/mL, and the scatter fractions were 42.1% and 37.9% in the DMI and D710, respectively. The D710 had better contrast recovery and lower background variability. Contrast, uniformity and image noise in the DMI were 61.0%, 0.0225, and 7.85%, respectively. These outcomes were better than those derived from the D710 and satisfied the JSNM criteria. Brain images acquired by the DMI had better grey-to-white matter contrast and lower image noise at the edge of axial field of view.ConclusionsThe DMI offers better sensitivity, performance under conditions of high count rates and image quality than the conventional PMT-PET/CT system, D710.     

Analyse comparative de 3 logiciels de reconstruction itérative de tomoscintigraphie monophotonique myocardique

ObjectiveThis study makes a comparative analysis of the quality reconstruction of three software: 2D ordered subset expectation maximisation (2D OSEM), 3D ordered subsets expectation maximisation (Flash 3D) and Wallis.Patients and methodsThe data from myocardial scintigraphy acquisitions of 50 patients (38 men and 12 women; average age 61 ± 9 years) were successively reconstructed using three myocardial perfusion SPECT algorithms (Flash 3D, OSEM 2D and Wallis). Different combinations of iterations and subsets were considered. For Wallis, only the cut-off frequency was considered. The image's quality was assessed by determining the maximum contrast and the signal to noise ratio.ResultsThe Wallis software provided a higher signal to noise ratio compared to Flash 3D and OSEM 2D at stress and rest. The Wallis signal to noise ratio increased by a factor 1.93 (P = 0.0010) and 2.28 at stress (P = 0.0009); 1.50 (P = 0.0011) and 2.84 at rest (P = 0.0024) compared to respectively Flash 3D and OSEM 2D. Flash 3D provided better signal to noise ratio than OSEM 2D at stress and at rest. The difference in medians and interquartile ranges of the signal-to-noise ratio in post-stress were 22 % and 54 %, respectively between Flash 3D and OSEM 2D. At rest, the difference between the two methods in signal to noise ratio was 32 % ± 0.,29.ConclusionWallis algorithm was improve image quality with better signal to noise ratio compared to the reference method of Siemens Flash 3D. For both Flash 3D and OSEM 2D methods, the combination with 8 subsets and 12 iterations provided the best contrast and signal to noise ratio.