Comparison of effects of absolute scatter correction and relative scatter correction on image quality in PET reconstruction / 中华核医学与分子影像杂志

Objective:To study the impact of different scattering correction algorithms in the reconstruction of PET/CT images on image artifacts and the precision of quantitative parameters.Methods:The phantom as described in the National Electrical Manufacturers Association (NEMA) NU2 standard was filled with 18F. The background activity was fixed, and the activity of the solution in the spheres was adjusted to obtain several configurations, including the normal ratio group (4.08∶1) and the extreme ratio group (200∶1). The surface contamination group with the same ratio as the extreme ratio group contained a small radioactive source with different doses of 18F (74, 37, 3.7 and 0.37 MBq) placed at the surface of the phantom. PET/CT images of 30 patients (21 males, 9 females, age: (44.5±10.2) years) from Peking University Cancer Hospital & Institute between July 2012 and December 2021 were retrospectively analyzed, including 10 with normal images ( 18F-FDG) and 20 with abnormal images (10 with dislocation during acquisition, 10 with surface contamination). The images were reconstructed with relative and absolute scattering correction. The phantom was evaluated using the target to background ratio (TBR) and the artifact classification. CV as well as the artifact classification were used to compare the clinical image quality. Mann-Whitney U test and χ2 test were used to analyze data. Results:In the normal ratio group and the extreme ratio group, the TBRs of phantom images reconstructed with relative correction were significantly higher than those with absolute correction (normal ratio group: 3.30(1.94, 4.53) vs 2.72(1.56, 3.56); z=-2.20, P=0.028; extreme ratio group: 105.47(45.62, 162.82) vs 101.36(43.96, 155.57); z=-1.99, P=0.046). In the surface contamination group, with the increase of the activity of the small source, the artifact became more obvious, and the artifact classification score of absolute correction was significantly better than that of relative correction (1.5(1.0, 2.0) vs 2.5(2.0, 3.0); z=-2.00, P=0.046). In the 10 normal 18F-FDG PET/CT patients, the CVliver of the relative correction (9.67%(8.00%, 11.00%)) was significantly lower than that of absolute correction (11.00%(9.00%, 12.00%); z=-2.57, P=0.010), indicating the higher image quality of images with relative correction. In abnormal images, the image quality of absolute correction was significantly higher than that of relative correction with fewer and less severe artifacts (dislocation cases: 9/10 vs 4/10; χ2=5.50, P=0.019; surface contamination cases: 9/10 vs 4/10; χ2=5.50, P=0.019). Conclusions:The relative scattering correction is suitable for normal situations in clinical PET acquisition. However, with dislocation or surface contamination, the absolute scattering correction helps to reduce the artifacts and improve the image quality.

Development of a teledentistry system for the elderly in the context of the covid-19 pandemic: 3d diagnostic models integration in a web platform / Desarrollo de un sistema de teleodontología para adultos mayores en el contexto de la pandemia de covid-19: integración de modelos de diagnóstico 3d en una plataforma web

Objective: To recognize the usefulness of incorporating Three-Dimensional models of standardized humans in electronic health records, in the context of the development of a teledentistry web platform designed for the attention of the elderly population in COVID-19 pandemic context. Material and Methods: A teledentistry web platform designed with different modules for clinical records. Through a new user-computer interface with a standardized virtual 3D phantom, an extraoral physical examination, an intraoral examination section was modeled. A label-associated marker is allowed to record descriptive aspects of the findings. A 3D odontogram represents multiple patient's conditions for each of the 32 dental positions. Results: From a total of 135 patients registered on the platform, 51 markers and 33 photographs associated with the surface of the virtual 3D phantoms were recorded. For the Location parameter: Hard palate 27.6%, inserted gingiva 15.7%, tongue 15.6%. For the Type of lesion parameter (according to the information entered in the pathology selector): unidentified 35.3%, sub-prosthetic stomatitis 23.5%, irritative fibroma 9.8%. Through the registration of the exact location of the finding in the virtual phantom by a 3D marker, the 3D modeling of the oral pathologies contributed to a better diagnosis, improving the remote communication between the attending dentist and specialists. Conclusion: The combination of the 3D modeling and anatomical-referencing in a teledentistry platform can become a powerful tool for the dental practice, due to their utility and specificity.

Objetivo: Reconocer la utilidad de incorporar modelos tridimensionales de humanos estandarizados en registros electrónicos de salud, en el contexto del desarrollo de una plataforma web de teleodontología diseñada para la atención de la población adulta mayor en contexto de pandemia por COVID-19. Material y Métodos: Una plataforma web de teleodontología diseñada con diferentes módulos para historias clínicas. A través de una nueva interfaz usuario-computadora con un fantoma 3D virtual estandarizado, se modeló un examen físico extraoral, una sección de examen intraoral. Se permite un marcador asociado a la etiqueta para registrar aspectos descriptivos de los hallazgos. Un odontograma 3D representa múltiples condiciones del paciente para cada una de las 32 posiciones dentales.Resultados: De un total de 135 pacientes registrados en la plataforma, se registraron 51 marcadores y 33 fotografías asociadas a la superficie de los fantomas virtuales 3D. Para el parámetro Ubicación: Paladar duro 27,6%, encía insertada 15,7%, lengua 15,6%. Para el parámetro Tipo de lesión (según la información ingresada en el selector de patología): no identificado 35,3%, estomatitis subprotésica 23,5%, fibroma irritativo 9,8%. A través del registro de la ubicación exacta del hallazgo en el fantoma virtual mediante un marcador 3D, el modelado 3D de las patologías orales contribuyó a un mejor diagnóstico, mejorando la comunicación remota entre el odontólogo tratante y los especialistas. Conclusión: La combinación del modelado 3D y la referenciación anatómica en una plataforma de teleodontología puede convertirse en una poderosa herramienta para la práctica odontológica, debido a su utilidad y especificidad.

Phantom study in the quality control of low dose solid pulmonary nodule CT based on radiomics analysis / 中华放射学杂志

Objective@#To investigate the value of radiomics in image quality control with low-dose CT examination of solid pulmonary nodules.@*Methods@#Images were acquired on CT750 HD scanner, and chest pulmonary nodules phantom were scanned at different tube voltage and tube current. The radiation dose CTDIvol under different scanning conditions were recorded, as well as CNR and SNR of each scanning sequence. The variation of radiation dose, noise, tube voltage and tube current were analyzed. All data were analyzed by radiomics analysis software. R language statistics software was adopted to analyze the extracted features by principal component analysis (PCA), and the characteristic parameters with the largest contribution rate to image quality were selected for analysis. One-way ANOVA was used to analyze all the important characteristic parameters to reveal the difference of characteristic parameters under different tube voltages. Finally, the post-test method was used to find out the differences among different tube voltage groups.@*Results@#Radiation dose rised linearly with the increase of tube current and tube voltage. Although the overall change trend of SNR and CNR in pulmonary nodules was linearly related to the change of tube voltage and tube current, there was no clear change trend threshold at low dose, which could not accurately evaluate the image quality under low radiation. Both CNR and SNR cannot evaluate the image quality effectively, and have no practiced value for optimizing the low dose scanning parameters. There main components including Uniformity, Voxel Value Sum, and Haralick Correlation extracted by radiomics analysis software were proved to play a critical role in image quality control. The cumulative contribution rate of variance was 89.20% and the eigen values were greater than 1. Uniformity curve of characteristic parameter showed that the trend of change was correlated with the change of tube voltage and tube current, and the stability and consistency were good. Uniformity one-way ANOVA analysis showed that when the tube voltage reduced from 140 to 120 kVp, there was no difference (P=0.117) in the uniformity, while from 120 to 80 kVp, significant differences revealed (P<0.001). Considering tube current, no significant variation was observed in uniformity when current was greater than 90 mA, which indicated that tube current of 90 mA could lead to better image quality.@*Conclusion@#Radiomics analysis can effectively evaluate and control the CT image quality of low dose solid pulmonary nodules.

Low-Dose Abdominal CT Using a Deep Learning-Based Denoising Algorithm: A Comparison with CT Reconstructed with Filtered Back Projection or Iterative Reconstruction Algorithm

OBJECTIVE: To compare the image quality of low-dose (LD) computed tomography (CT) obtained using a deep learning-based denoising algorithm (DLA) with LD CT images reconstructed with a filtered back projection (FBP) and advanced modeled iterative reconstruction (ADMIRE).MATERIALS AND METHODS: One hundred routine-dose (RD) abdominal CT studies reconstructed using FBP were used to train the DLA. Simulated CT images were made at dose levels of 13%, 25%, and 50% of the RD (DLA-1, -2, and -3) and reconstructed using FBP. We trained DLAs using the simulated CT images as input data and the RD CT images as ground truth. To test the DLA, the American College of Radiology CT phantom was used together with 18 patients who underwent abdominal LD CT. LD CT images of the phantom and patients were processed using FBP, ADMIRE, and DLAs (LD-FBP, LD-ADMIRE, and LD-DLA images, respectively). To compare the image quality, we measured the noise power spectrum and modulation transfer function (MTF) of phantom images. For patient data, we measured the mean image noise and performed qualitative image analysis. We evaluated the presence of additional artifacts in the LD-DLA images.RESULTS: LD-DLAs achieved lower noise levels than LD-FBP and LD-ADMIRE for both phantom and patient data (all p < 0.001). LD-DLAs trained with a lower radiation dose showed less image noise. However, the MTFs of the LD-DLAs were lower than those of LD-ADMIRE and LD-FBP (all p < 0.001) and decreased with decreasing training image dose. In the qualitative image analysis, the overall image quality of LD-DLAs was best for DLA-3 (50% simulated radiation dose) and not significantly different from LD-ADMIRE. There were no additional artifacts in LD-DLA images.CONCLUSION: DLAs achieved less noise than FBP and ADMIRE in LD CT images, but did not maintain spatial resolution. The DLA trained with 50% simulated radiation dose showed the best overall image quality.

Influence of different combinations of additional filters and tube voltage and tube current on crib side X-ray image quality and radiation dose / 中华放射医学与防护杂志

Objective To measure the body surface dose under different confinations of additional filters,tube voltage and tube current and discuss the lowest amount of different additional filters,tube voltage and tube current combination for crib side X-ray radiation dose while the quality of the image is guaranteed.Methods Japan Shimadzu wireless tablet mobile DR machine and Dutch Artinis CDRAD 2.0 phantom were used.The tube voltage and tube current for children's crib side X-ray normal work were 50 kV and 1.40 mAs to get the image quality figure inverse (IQFInv),respectively.Totally four filter combinations of 1 mm A1,2 mm A1,1+2 mm A1 and 0.3 mm Cu were added to the opening of collimator system by mobile DR machine.Phantom was shot by respectively combination of 50,66,83 and 100 kV tube voltages and different tube currents.All images to get the IQFInv value,Pearson correlation and regression analysis of the influence of tube voltage and current on IQFInv value were analyzed.The IQFInv value of the additional filter corresponds to the image quality of normal work.The combination of the additional filter with the tube voltage and the tube current was also found.Swedish RTI Barracuda diagnostic level dosimeter was used to measure the entrance surface dose of these combinations after filtration,20 times for each group.Results Comparisons among different filters,tube voltage and tube current combination with quality of daily work images:the tube voltage was positively correlated with IQFInv value in the test range(r=0.49,P＜0.05),and tube current was positively correlated with IQFInv value (r=0.36,P＜0.05).As the additional filters increase,it required greater tube current to acquire the desired value of images.Meanwhile,greater additional filters would increase the difference of IQFInv of tube voltage at each level.Comparisons among different filters,tube voltage and tube current combination with daily shooting dose,and after using additional filters,entrance surface dose changed from (30.58±0.21)to (10.49±0.09) μGy.There is a significant difference between each group (t=-15.306-514.585,P＜0.05).All additional filters effectively reduced entrance surface dose.Meanwhile,as the filter and tube voltage increased,entrance surface dose showed a more significant reduction.However,when the tube voltage exceeded 83 kV,all entrance surface dose of additional filters showed an increasing trend.Conclusions Additional filter is an effective method to reduce the crib side X-ray entrance surface dose.Under the premise of ensuring image quality,additional filter with high atomic number and second high kilovolt tube voltage with paired tube current is the best condition for crib side X-ray.

Clinical application of new type individualized fixation device for radiotherapy of rectal cancer / 中国基层医药

Objective To explore the clinical effect of new type rectal cancer radiotherapy individualized fixation device in the radiotherapy of rectal cancer. Methods From June 2015 to December 2016,60 patients with rectal cancer who accepted the external irradiation in Zhejiang Tumor Hospital were divided into two groups by random number table method. A group(31 cases) received new type rectal cancer radiotherapy position fixation devices with thermoplastic film. B group(29 cases) received simple foam pad with thermoplastic film. Before each treatment,Cone beam CT(CBCT) scan was conducted. The applied CBCT image and the planned reconstruction image were compared in the direction of X(left and right),Y(upper and lower)and Z(front and rear) axis. The setup error was recorded, and the correlation between the two groups was analyzed. Results The average setup error of patients in A group in X (left and right),Y(upper and lower),Z(front and rear) axis were (1. 61 ± 0. 18)mm,(1. 82 ± 0. 13)mm,(1. 91 ± 0. 11)mm,respectively. The average setup error of patients in B group in X(left and right),Y(upper and lower),Z (front and rear) axis were (2. 22 ± 0. 13)mm,(2. 43 ± 0. 14)mm,(2. 36 ± 0. 13)mm,respectively. There were statistically significant differences between the two groups(t=14. 958,17. 501,11. 283,all P＜0. 001). Conclusion The new type of rectal cancer radiotherapy position fixing device is more comfortable than the simple foam pad,and the setting error is smaller than the simple foam pad.

Impact of voxel size on CT radiomics features: A phantom study / 中国医学影像技术

Objective: To investigate the impact of voxel on CT radiomics features. Methods: Catphan 700 phantom was used to perform CT scanning with Siemens definition AS+ 64 row CT scanner on head protocol. The images were reconstructed with different FOV and different thickness, so the ranges of voxel size in these two groups were 0.24-2.38 mm3 and 0.72-2.32 mm3, respectively. ROI was manually sketched using 3D Slicer software, and 108 features were extracted from 7 categories, including shape, first order, gray level dependence matrix, gray level run length matrix, gray level co-occurrence matrix, gray level size zone matrix and neighborhood gray-tone difference matrix. The coefficient of variation (CV) was adapted to evaluate the impact of voxel derived from FOV and slice thickness on CT radiomics features. Results: The voxel had less effect on shape features (CV≤10%), while it had a great impact on most features of other six feature groups (CV>20%). Among them, the dependence entropy, short run emphasis, run entropy, idmn, idn, idm, id and zone entropy were stable (all CV≤10%). Conclusion: The voxel size has a great impact on CT radiomics features. Data preprocessing may be a good way to ensure the stability of features, especially for the application and comparison of multi-centers data.

Influence of Heart Rate and Innovative Motion-Correction Algorithm on Coronary Artery Image Quality and Measurement Accuracy Using 256-Detector Row Computed Tomography Scanner: Phantom Study

OBJECTIVE: To investigate the efficacy of motion-correction algorithm (MCA) in improving coronary artery image quality and measurement accuracy using an anthropomorphic dynamic heart phantom and 256-detector row computed tomography (CT) scanner. MATERIALS AND METHODS: An anthropomorphic dynamic heart phantom was scanned under a static condition and under heart rate (HR) simulation of 50–120 beats per minute (bpm), and the obtained images were reconstructed using conventional algorithm (CA) and MCA. We compared the subjective image quality of coronary arteries using a four-point scale (1, excellent; 2, good; 3, fair; 4, poor) and measurement accuracy using measurement errors of the minimal luminal diameter (MLD) and minimal luminal area (MLA). RESULTS: Compared with CA, MCA significantly improved the subjective image quality at HRs of 110 bpm (1.3 ± 0.3 vs. 1.9 ± 0.8, p = 0.003) and 120 bpm (1.7 ± 0.7 vs. 2.3 ± 0.6, p = 0.006). The measurement error of MLD significantly decreased on using MCA at 110 bpm (11.7 ± 5.9% vs. 18.4 ± 9.4%, p = 0.013) and 120 bpm (10.0 ± 7.3% vs. 25.0 ± 16.5%, p = 0.013). The measurement error of the MLA was also reduced using MCA at 110 bpm (19.2 ± 28.1% vs. 26.4 ± 21.6%, p = 0.028) and 120 bpm (17.9 ± 17.7% vs. 34.8 ± 19.6%, p = 0.018). CONCLUSION: Motion-correction algorithm can improve the coronary artery image quality and measurement accuracy at a high HR using an anthropomorphic dynamic heart phantom and 256-detector row CT scanner.

Technical Report: A Cost-Effective, Easily Available Tofu Model for Training Residents in Ultrasound-Guided Fine Needle Thyroid Nodule Targeting Punctures

OBJECTIVE: To establish a cost-effective and easily available phantom for training residents in ultrasound-guided fine needle thyroid nodule targeting punctures. MATERIALS AND METHODS: Tofu, drinking straws filled with coupling gel, a urine tube, and 21-gauge needles were used to generate a phantom thyroid with nodules for training. Twelve radiology residents were involved in the study. The puncture success rates were recorded and compared before and after phantom training using the Wilcoxon signed-rank test. RESULTS: On ultrasonography, tofu mimicked the texture of the thyroid. Drinking straws filled with coupling gel mimicked vessels. The urine tube filled with air mimicked the trachea, and 21-gauge needles mimicked small nodules in the transverse section. The entire phantom was similar to the structure of the thyroid and surrounding tissues. The puncture success rates of radiology residents were significantly increased from 34.4 ± 14.2% to 66.7 ± 19.5% after training (p = 0.003). The phantom was constructed in approximately 10 minutes and materials cost less than CNY 10 (approximately $ 1.5) at a local store. CONCLUSION: The tofu model was cost-effective, easily attainable, and effective for training residents in ultrasound-guided fine needle thyroid nodule targeting punctures in vitro.

Impact of scanning and reconstruction parameters on volume measurement of pulmonary ground glass nodules for phantom study / 中国介入影像与治疗学

Objective: To explore the effect of MSCT scanning and reconstruction parameters on volume measurement of phantom pulmonary ground glass nodules. Methods: Eight pulmonary ground glass nodules were scanned by different tube voltages (80 kV, 100 kV, 120 kV), tube currents (100 mA, 150 mA, 200 mA) by GE VCT. The original data in 150 mA, 80 kV group were reconstructed with different slice thickness (0.625 mm, 1.25 mm), reconstruction algorithm (soft, standard, lung, bone) and field of view (36 cm, 18 cm). The two independent chest radiologists measured the volume of ground glass nodules by lung nodule assessment software. The absolute percentage error (APE)= (|V measurement-V actual|) /Vactual×100% was analyzed statisticall. The consistency of volume measurements was evaluated by intraclass correlation coefficient (ICC). Results: There was great agreement of inter-observers in volume measurement of phantom pulmonary ground glass nodules (ICC=0.98). There was no significant difference in APE value among the nodules under different tube voltages (P>0.05), while the tube current was 150 mA and the APE value was the lowest (P0.05). As the reconstructed field decreased, the APE value decreased (P < 0.05). Different reconstruction algorithms had different effects on the APE value of nodules (P<0.05). The APE value in lung algorithm was smaller than that in the other algorithms. The APE values of low density and small nodules (CT value=-800 HU, diameter=5 mm) were higher than 10 under various conditions. Conclusion: 80 kV, 150 mA of scanning parameters combined with target reconstruction and lung algorithm can reduce the radiation dose and improve the accuracy of volume measurement of ground glass nodules in MSCT, and the pulmonary nodule analysis software is not suitable for the analysis of small ground glass nodules of lung.

A clinical pilot study of jawbone mineral density measured by the newly developed dual-energy cone-beam computed tomography method compared to calibrated multislice computed tomography

PURPOSE: This clinical pilot study was performed to determine the effectiveness of dual-energy cone-beam computed tomography (DE-CBCT) in measuring bone mineral density (BMD).MATERIALS AND METHODS: The BMD values obtained using DE-CBCT were compared to those obtained using calibrated multislice computed tomography (MSCT). After BMD calibration with specially designed phantoms, both DE-CBCT and MSCT scanning were performed in 15 adult dental patients. Three-dimensional (3D) Digital Imaging and Communications in Medicine data were imported into a dental software program, and the defined regions of interest (ROIs) on the 3-dimensional surface-rendered images were identified. The automatically-measured BMD values of the ROIs (g/cm³), the differences in the measured BMD values of the matched ROIs obtained by DE-CBCT and MSCT 3D images, and the correlation between the BMD values obtained by the 2 devices were statistically analyzed.RESULTS: The mean BMD values of the ROIs for the 15 patients as assessed using DE-CBCT and MSCT were 1.09±0.07 g/cm³ and 1.13±0.08 g/cm³, respectively. The mean of the differences between the BMD values of the matched ROIs as assessed using DE-CBCT and calibrated MSCT images was 0.04±0.02 g/cm³. The Pearson correlation coefficient between the BMD values of DE-CBCT and MSCT images was 0.982 (r=0.982, P<0.001).CONCLUSION: The newly developed DE-CBCT technique could be used to measure jaw BMD in dentistry and may soon replace MSCT, which is expensive and requires special facilities.

Quantitative Feasibility Evaluation of ¹¹C-Methionine Positron Emission Tomography Images in Gamma Knife Radiosurgery : Phantom-Based Study and Clinical Application

OBJECTIVE: The functional information of ¹¹C-methionine positron emission tomography (MET-PET) images can be applied for Gamma knife radiosurgery (GKR) and its image quality may affect defining the tumor. This study conducted the phantom-based evaluation for geometric accuracy and functional characteristic of diagnostic MET-PET image co-registered with stereotactic image in Leksell GammaPlan® (LGP) and also investigated clinical application of these images in metastatic brain tumors.METHODS: Two types of cylindrical acrylic phantoms fabricated in-house were used for this study : the phantom with an array-shaped axial rod insert and the phantom with different sized tube indicators. The phantoms were mounted on the stereotactic frame and scanned using computed tomography (CT), magnetic resonance imaging (MRI), and PET system. Three-dimensional coordinate values on co-registered MET-PET images were compared with those on stereotactic CT image in LGP. MET uptake values of different sized indicators inside phantom were evaluated. We also evaluated the CT and MRI co-registered stereotactic MET-PET images with MR-enhancing volume and PET-metabolic tumor volume (MTV) in 14 metastatic brain tumors.RESULTS: Imaging distortion of MET-PET was maintained stable at less than approximately 3% on mean value. There was no statistical difference in the geometric accuracy according to co-registered reference stereotactic images. In functional characteristic study for MET-PET image, the indicator on the lateral side of the phantom exhibited higher uptake than that on the medial side. This effect decreased as the size of the object increased. In 14 metastatic tumors, the median matching percentage between MR-enhancing volume and PET-MTV was 36.8% on PET/MR fusion images and 39.9% on PET/CT fusion images.CONCLUSION: The geometric accuracy of the diagnostic MET-PET co-registered with stereotactic MR in LGP is acceptable on phantom-based study. However, the MET-PET images could the limitations in providing exact stereotactic information in clinical study.

Quantitative Feasibility Evaluation of ¹¹C-Methionine Positron Emission Tomography Images in Gamma Knife Radiosurgery : Phantom-Based Study and Clinical Application

OBJECTIVE: The functional information of ¹¹C-methionine positron emission tomography (MET-PET) images can be applied for Gamma knife radiosurgery (GKR) and its image quality may affect defining the tumor. This study conducted the phantom-based evaluation for geometric accuracy and functional characteristic of diagnostic MET-PET image co-registered with stereotactic image in Leksell GammaPlan® (LGP) and also investigated clinical application of these images in metastatic brain tumors. METHODS: Two types of cylindrical acrylic phantoms fabricated in-house were used for this study : the phantom with an array-shaped axial rod insert and the phantom with different sized tube indicators. The phantoms were mounted on the stereotactic frame and scanned using computed tomography (CT), magnetic resonance imaging (MRI), and PET system. Three-dimensional coordinate values on co-registered MET-PET images were compared with those on stereotactic CT image in LGP. MET uptake values of different sized indicators inside phantom were evaluated. We also evaluated the CT and MRI co-registered stereotactic MET-PET images with MR-enhancing volume and PET-metabolic tumor volume (MTV) in 14 metastatic brain tumors. RESULTS: Imaging distortion of MET-PET was maintained stable at less than approximately 3% on mean value. There was no statistical difference in the geometric accuracy according to co-registered reference stereotactic images. In functional characteristic study for MET-PET image, the indicator on the lateral side of the phantom exhibited higher uptake than that on the medial side. This effect decreased as the size of the object increased. In 14 metastatic tumors, the median matching percentage between MR-enhancing volume and PET-MTV was 36.8% on PET/MR fusion images and 39.9% on PET/CT fusion images. CONCLUSION: The geometric accuracy of the diagnostic MET-PET co-registered with stereotactic MR in LGP is acceptable on phantom-based study. However, the MET-PET images could the limitations in providing exact stereotactic information in clinical study.

Accuracy of Model-Based Iterative Reconstruction for CT Volumetry of Part-Solid Nodules and Solid Nodules in Comparison with Filtered Back Projection and Hybrid Iterative Reconstruction at Various Dose Settings: An Anthropomorphic Chest Phantom Study

OBJECTIVE: To investigate the accuracy of model-based iterative reconstruction (MIR) for volume measurement of part-solid nodules (PSNs) and solid nodules (SNs) in comparison with filtered back projection (FBP) or hybrid iterative reconstruction (HIR) at various radiation dose settings. MATERIALS AND METHODS: CT scanning was performed for eight different diameters of PSNs and SNs placed in the phantom at five radiation dose levels (120 kVp/100 mAs, 120 kVp/50 mAs, 120 kVp/20 mAs, 120 kVp/10 mAs, and 80 kVp/10 mAs). Each CT scan was reconstructed using FBP, HIR, or MIR with three different image definitions (body routine level 1 [IMR-R1], body soft tissue level 1 [IMR-ST1], and sharp plus level 1 [IMR-SP1]; Philips Healthcare). The SN and PSN volumes including each solid/ground-glass opacity portion were measured semi-automatically, after which absolute percentage measurement errors (APEs) of the measured volumes were calculated. Image noise was calculated to assess the image quality. RESULTS: Across all nodules and dose settings, the APEs were significantly lower in MIR than in FBP and HIR (all p < 0.01). The APEs of the smallest inner solid portion of the PSNs (3 mm) and SNs (3 mm) were the lowest when MIR (IMR-R1 and IMR-ST1) was used for reconstruction for all radiation dose settings. (IMR-R1 and IMR-ST1 at 120 kVp/100 mAs, 1.06 ± 1.36 and 8.75 ± 3.96, p < 0.001; at 120 kVp/50 mAs, 1.95 ± 1.56 and 5.61 ± 0.85, p = 0.002; at 120 kVp/20 mAs, 2.88 ± 3.68 and 5.75 ± 1.95, p = 0.001; at 120 kVp/10 mAs, 5.57 ± 6.26 and 6.32 ± 2.91, p = 0.091; at 80 kVp/10 mAs, 5.84 ± 1.96 and 6.90 ± 3.31, p = 0.632). Image noise was significantly lower in MIR than in FBP and HIR for all radiation dose settings (120 kVp/100 mAs, 3.22 ± 0.66; 120 kVp/50 mAs, 4.19 ± 1.37; 120 kVp/20 mAs, 5.49 ± 1.16; 120 kVp/10 mAs, 6.88 ± 1.91; 80 kVp/10 mAs, 12.49 ± 6.14; all p < 0.001). CONCLUSION: MIR was the most accurate algorithm for volume measurements of both PSNs and SNs in comparison with FBP and HIR at low-dose as well as standard-dose settings. Specifically, MIR was effective in the volume measurement of the smallest PSNs and SNs.

Construcción, reparación y mantenimiento de simuladores de paciente (fantomas) de ecografía / Construction, Repair and Maintenance of Ultrasound Fantoms

El uso de simuladores "fantomas" o fantoms ha demostrado ser de utilidad para la enseñanza de ultrasonido y particularmente para la enseñanza de técnicas de intervencionismo guiado por ecografía. Los fantomas se pueden conseguir comercialmente, aunque son costosos, o se pueden construir utilizando gelatina, lo cual es más económico. Construimos fantomas de gelatina para la instrucción de técnicas de intervencionismo y, como es natural, estos se deterioraron ostensiblemente con el uso debido a la falta de experiencia de los estudiantes. Por lo tanto, desarrollamos técnicas de reparación para rupturas grandes de la superficie, para el deterioro por el uso de agujas en repetidas ocasiones y finalmente para el deterioro ocasionado por crecimiento de microorganismos.

Ultrasound phantoms are useful for teaching ultrasound and particularly in the instruction of ultrasound guided techniques. They are commercially available, being expensive, or they can be inexpensively built using gelatin. We built gelatin phantoms for the instruction of ultrasound guided techniques and during the practice they deteriorated due to the apprentices lack of experience. We developed repair techniques for gross ruptures in the surface, for small dents resulting from multiple punctures and finally for the growth of microorganisms.

High resolution reconstruction for optimization of imaging quality of GE Discovery CT 750 HD / 中国介入影像与治疗学

Objective To explore the value of high resolution reconstruction for optimization of imaging quality of GE Discovery CT 750 HD based on phantom pilot.Methods CT scanning with large (50 cm) and small (32 cm) scanning field of view (SFOV) was performed for a Catphan 500 phantom with or without high resolution on GE Discovery CT 750 HD.All raw data acquired by volumetric CT scan were reconstructed as the same size of a small DFOV (25 cm) with STAND algorithm.Then the images were divided into four groups,including large SFOV without high resolution (group A),large SFOV with high resolution (group B),small SFOV without high resolution (group C) and small SFOV with high resolution (group D).The spatial-resolution (SR),density-resolution (DR),noise (N),CNR,SNR and CT dose index volumes (CTDI) were measured and compared among 4 groups.Results The overall differences of SR,DR,N,CNR,SNR and CTDI were statistically significant among four groups (all P＜0.05).Compared with group A,the average N increased in group C (P＜0.01),SR increased in group B and the average CNR and SNR decreased in group D,while N increased in group D (all P＜0.01).Conclusion Large SFOV combined with high resolution reconstruction may ensure CNR and SNR,and improve SR.

Development of a new ball-type phantom for evaluation of the image layer of panoramic radiography

PURPOSE: This study proposes a new ball-type phantom for evaluation of the image layer of panoramic radiography. MATERIALS AND METHODS: The arch shape of an acrylic resin phantom was derived from average data on the lower dental arch in Korean adult males. Metal balls with a 2-mm diameter were placed along the center line of the phantom at a 4-mm mesiodistal interval. Additional metal balls were placed along the 22 arch-shaped lines that ran parallel to the center line at 2-mm buccolingual intervals. The height of each ball in the horizontal plane was spaced by 2.5 mm, and consequently, the balls appeared oblique when viewed from the side. The resulting phantom was named the Panorama phantom. The distortion rate of the balls in the acquired image was measured by automatically calculating the difference between the vertical and horizontal length using MATLAB®. Image layer boundaries were obtained by applying various distortion rate thresholds. RESULTS: Most areas containing metal balls (91.5%) were included in the image layer with a 50% distortion rate threshold. When a 5% distortion rate threshold was applied, the image layer was formed with a small buccolingual width along the arch-shaped center line. However, it was medially located in the temporomandibular joint region. CONCLUSION: The Panorama phantom could be used to evaluate the image layer of panoramic radiography, including all mesiodistal areas with large buccolingual width.

Metal artifact production and reduction in CBCT with different numbers of basis images

PURPOSE: To evaluate the effect of different numbers of basis images and the use of metal artifact reduction (MAR) on the production and reduction of artifacts in cone-beam computed tomography images. MATERIALS AND METHODS: An acrylic resin phantom with a metal alloy sample was scanned, with 450 or 720 basis images and with or without MAR. Standard deviation values for the test areas (around the metal object) were obtained as a way of measuring artifact production. Two-way analysis of variance was used with a 5% significance level. RESULTS: There was no significant difference in artifact production among the images obtained with different numbers of basis images without MAR (P=.985). MAR significantly reduced artifact production in the test areas only in the protocol using 720 basis images (P=.017). The protocol using 450 basis images with MAR showed no significant difference in artifact production when compared to the protocol using 720 basis images with MAR (P=.579). CONCLUSION: Protocols with a smaller number of basis images and with MAR activated are preferable for minimizing artifact production in tomographic images without exposing the patient to a greater radiation dose.

Phantoms for diffusion-weighted imaging and diffusion tensor imaging quality control: a review and new perspectives

Abstract: Introduction Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) combine magnetic resonance imaging (MRI) techniques and diffusion measures. In DWI, the contrast is defined by microscopic motion of water protons. Nowadays, DWI has become important for early diagnostic of acute stroke. DTI images are calculated from DWI images acquired in at least six directions, which give information of diffusion directionality, making it possible to reconstruct axonal or muscle fiber images. Both techniques have been applied to study body structures in healthy and pathological conditions. Currently, it is known that these images and derived parameters are quite sensitive to factors related to acquisition and processing. Magnetic field inhomogeneity, susceptibility, chemical shift, radiofrequency (RF) interference, eddy currents and low signal-to-noise ratio (SNR) can have a more harmful effect in diffusion data than in T1- or T2-weighted image data. However, even today there are not reference phantoms and guidelines for DWI or DTI quality control (QC). Review Proposals for construction and use of DWI and DTI QC phantoms can be found in literature. DWI have been evaluated using containers filled by gel or liquid with tissue-like MRI properties, as well as using microfabricated devices. DTI acquisitions also have been checked with these devices or using natural or artificial fiber structures. The head phantom from American College of Radiology (ACR) is also pointed out as an alternative for DTI QC. This article brings a discussion about proposed DWI and DTI phantoms, challenges involved and future perspectives for standardization of DWI and DTI QC.

Realistic deformable 3D numeric phantom for transcutaneous ultrasound

Abstract Introduction Numerical phantoms are important tools to design, calibrate and evaluate several methods in various image-processing applications, such as echocardiography and mammography. We present a framework for creating ultrasound numerical deformable phantoms based on Finite Element Method (FEM), Linear Isomorphism and Field II. The proposed method considers that the scatterers map is a property of the tissue; therefore, the scatterers should move according to the tissue strain. Methods First, a volume representing the target tissue is loaded. Second, parameter values, such as Young’s Modulus, scatterers density, attenuation and scattering amplitudes are inserted for each different regions of the phantom. Then, other parameters related to the ultrasound equipment, such as ultrasound frequency and number of transducer elements, are also defined in order to perform the ultrasound acquisition using Field II. Third, the size and position of the transducer and the pressures that are applied against the tissue are defined. Subsequently, FEM is executed and deformation is computed. Next, 3D linear isomorphism is performed to displace the scatterers according to the deformation. Finally, Field II is carried out to generate the non-deformed and deformed ultrasound data. Results The framework is evaluated by comparing strain values obtained the numerical simulation and from the physical phantom from CIRS. The mean difference between both phantoms is lesser than 10%. Conclusion The acoustic and deformation outcomes are similar to those obtained using a physical phantom. This framework led to a tool, which is available online and free of charges for educational and research purposes.