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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Optimizing the reconstruction filter in cone-beam CT to improve periodontal ligament space visualization: An in vitro study

PURPOSE: Evaluation of alveolar bone is important in the diagnosis of dental diseases. The periodontal ligament space is difficult to clearly depict in cone-beam computed tomography images because the reconstruction filter conditions during image processing cause image blurring, resulting in decreased spatial resolution. We examined different reconstruction filters to assess their ability to improve spatial resolution and allow for a clearer visualization of the periodontal ligament space. MATERIALS AND METHODS: Cone-beam computed tomography projections of 2 skull phantoms were reconstructed using 6 reconstruction conditions and then compared using the Thurstone paired comparison method. Physical evaluations, including the modulation transfer function and the Wiener spectrum, as well as an assessment of space visibility, were undertaken using experimental phantoms. RESULTS: Image reconstruction using a modified Shepp-Logan filter resulted in better sensory, physical, and quantitative evaluations. The reconstruction conditions substantially improved the spatial resolution and visualization of the periodontal ligament space. The difference in sensitivity was obtained by altering the reconstruction filter. CONCLUSION: Modifying the characteristics of a reconstruction filter can generate significant improvement in assessments of the periodontal ligament space. A high-frequency enhancement filter improves the visualization of thin structures and will be useful when accurate assessment of the periodontal ligament space is necessary.

Influence of B₁-Inhomogeneity on Pharmacokinetic Modeling of Dynamic Contrast-Enhanced MRI: A Simulation Study

OBJECTIVE: To simulate the B₁-inhomogeneity-induced variation of pharmacokinetic parameters on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). MATERIALS AND METHODS: B₁-inhomogeneity-induced flip angle (FA) variation was estimated in a phantom study. Monte Carlo simulation was performed to assess the FA-deviation-induced measurement error of the pre-contrast R₁, contrast-enhancement ratio, Gd-concentration, and two-compartment pharmacokinetic parameters (K(trans), v(e), and v(p)). RESULTS: B₁-inhomogeneity resulted in −23–5% fluctuations (95% confidence interval [CI] of % error) of FA. The 95% CIs of FA-dependent % errors in the gray matter and blood were as follows: −16.7–61.8% and −16.7–61.8% for the pre-contrast R₁, −1.0–0.3% and −5.2–1.3% for the contrast-enhancement ratio, and −14.2–58.1% and −14.1–57.8% for the Gd-concentration, respectively. These resulted in −43.1–48.4% error for K(trans), −32.3–48.6% error for the v(e), and −43.2–48.6% error for v(p). The pre-contrast R₁ was more vulnerable to FA error than the contrast-enhancement ratio, and was therefore a significant cause of the Gd-concentration error. For example, a −10% FA error led to a 23.6% deviation in the pre-contrast R₁, −0.4% in the contrast-enhancement ratio, and 23.6% in the Gd-concentration. In a simulated condition with a 3% FA error in a target lesion and a −10% FA error in a feeding vessel, the % errors of the pharmacokinetic parameters were −23.7% for K(trans), −23.7% for v(e), and −23.7% for v(p). CONCLUSION: Even a small degree of B₁-inhomogeneity can cause a significant error in the measurement of pharmacokinetic parameters on DCE-MRI, while the vulnerability of the pre-contrast R₁ calculations to FA deviations is a significant cause of the miscalculation.

Relationship between the peripheral dose and radioactive counts of 125I seeds detected by SPECT/CT / 中华核医学与分子影像杂志

Objective To explore the relationship between the peripheral dose and radioactive counts of 125I seeds detected by SPECT/CT.Methods Six 125I seeds(1.48×107 Bq, 1.85×107 Bq, 2.22×107 Bq, 2.59×107 Bq, 2.96×107 Bq, 3.33×107 Bq) were put into the solid water phantoms respectively. SPECT/CT was applied to scan the seeds. The radioactive counts (x) at the distance of 1-15 mm from the center of seeds were recorded respectively, while the corresponding doses (y, cGy) were calculated. SPSS 18.0 was used to analyze the relationship between the radioactive counts and peripheral dose. Results There was an exponential relationship between the peripheral dose of 125I seeds and the radioactive counts. The formula was as follow: y=507.849×1.004x. Conclusion SPECT/CT can visualize the peripheral dose of 125I seed, which may provide a method for dosimetric verification after brachytherapy.

Evaluation of factors influencing arterial Doppler waveforms in an in vitro flow phantom

PURPOSE: The aim of this study was to investigate factors that influence arterial Doppler waveforms in an in vitro phantom to provide a more accurate and comprehensive explanation of the Doppler signal. METHODS: A flow model was created using a pulsatile artificial heart, rubber or polyethylene tubes, a water tank, and a glass tube. Spectral Doppler tracings were obtained in multiple combinations of compliance, resistance, and pulse rate. Peak systolic velocity, minimum diastolic velocity, resistive index (RI), pulsatility index, early systolic acceleration time, and acceleration index were measured. On the basis of these measurements, the influences of the variables on the Doppler waveforms were analyzed. RESULTS: With increasing distal resistance, the RI increased in a relatively linear relationship. With increasing proximal resistance, the RI decreased. The pulsus tardus and parvus phenomenon was observed with a small acceleration index in the model with a higher grade of stenosis. An increase in the distal resistance masked the pulsus tardus and parvus phenomenon by increasing the acceleration index. Although this phenomenon occurred independently of compliance, changes in the compliance of proximal or distal tubes caused significant changes in the Doppler waveform. There was a reverse relationship between the RI and the pulse rate. CONCLUSION: Resistance and compliance can alter the Doppler waveforms independently. The pulse rate is an extrinsic factor that also influences the RI. The compliance and distal resistance, as well as proximal resistance, influence the pulsus tardus and parvus phenomenon.

Analysis of translational errors in frame-based and frameless cranial radiosurgery using an anthropomorphic phantom / Análise dos erros de posicionamento translacionais em radiocirurgia craniana frame e frameless com uso de objeto simulador antropomórfico

Abstract Objective: To evaluate three-dimensional translational setup errors and residual errors in image-guided radiosurgery, comparing frameless and frame-based techniques, using an anthropomorphic phantom. Materials and Methods: We initially used specific phantoms for the calibration and quality control of the image-guided system. For the hidden target test, we used an Alderson Radiation Therapy (ART)-210 anthropomorphic head phantom, into which we inserted four 5mm metal balls to simulate target treatment volumes. Computed tomography images were the taken with the head phantom properly positioned for frameless and frame-based radiosurgery. Results: For the frameless technique, the mean error magnitude was 0.22 ± 0.04 mm for setup errors and 0.14 ± 0.02 mm for residual errors, the combined uncertainty being 0.28 mm and 0.16 mm, respectively. For the frame-based technique, the mean error magnitude was 0.73 ± 0.14 mm for setup errors and 0.31 ± 0.04 mm for residual errors, the combined uncertainty being 1.15 mm and 0.63 mm, respectively. Conclusion: The mean values, standard deviations, and combined uncertainties showed no evidence of a significant differences between the two techniques when the head phantom ART-210 was used.

Resumo Objetivo: Comparar os erros de posicionamento e erros residuais translacionais tridimensionais de uma radiocirurgia guiada por imagem, frame versus frameless, com uso de um objeto simulador antropomórfico. Materiais e Métodos: Para a calibração e qualidade do sistema de imagem foram utilizados objetos simuladores específicos. Para o teste hidden target foi utilizado o crânio do objeto simulador antropomórfico Alderson Radiation Therapy (ART)-210, dentro do qual foram inseridas quatro esferas metálicas de 5 mm de diâmetro como volumes alvos de tratamento. Imagens tomográficas foram realizadas com o ART-210 devidamente posicionado para ambos os métodos de imobilização. Resultados: Para o método frameless, a média foi 0,22 ± 0,04 mm para os erros setup e 0,14 ± 0,02 mm para os erros residuais, apresentando uma incerteza combinada de 0,28 mm e 0,16 mm, respectivamente. Para o método frame, a média foi 0,73 ± 0,14 mm para os erros setup e 0,31 ± 0,04 mm para os erros residuais, apresentando uma incerteza combinada de 1,15 mm e 0,63 mm, respectivamente. Conclusão: Com base nas médias, desvios-padrão e incertezas combinadas, os resultados mostraram não haver evidências de diferença significativa entre as técnicas em questão quando utilizado um objeto simulador antropomórfico craniano ART-210.

Contrast reference values in panoramic radiographic images using an arch-form phantom stand

PURPOSE: The purpose of this study was to investigate appropriate contrast reference values (CRVs) by comparing the contrast in phantom and clinical images. MATERIALS AND METHODS: Phantom contrast was measured using two methods: (1) counting the number of visible pits of different depths in an aluminum plate, and (2) obtaining the contrast-to-noise ratio (CNR) for 5 tissue-equivalent materials (porcelain, aluminum, polytetrafluoroethylene [PTFE], polyoxymethylene [POM], and polymethylmethacrylate [PMMA]). Four panoramic radiographs of the contrast phantom, embedded in the 4 different regions of the arch-form stand, and 1 real skull phantom image were obtained, post-processed, and compared. The clinical image quality evaluation chart was used to obtain the cut-off values of the phantom CRV corresponding to the criterion of being adequate for diagnosis. RESULTS: The CRVs were obtained using 4 aluminum pits in the incisor and premolar region, 5 aluminum pits in the molar region, and 2 aluminum pits in the temporomandibular joint (TMJ) region. The CRVs obtained based on the CNR measured in the anterior region were: porcelain, 13.95; aluminum, 9.68; PTFE, 6.71; and POM, 1.79. The corresponding values in the premolar region were: porcelain, 14.22; aluminum, 8.82; PTFE, 5.95; and POM, 2.30. In the molar region, the following values were obtained: porcelain, 7.40; aluminum, 3.68; PTFE, 1.27; and POM, - 0.18. The CRVs for the TMJ region were: porcelain, 3.60; aluminum, 2.04; PTFE, 0.48; and POM, - 0.43. CONCLUSION: CRVs were determined for each part of the jaw using the CNR value and the number of pits observed in phantom images.

Preclinical evaluation of acoustic radiation force impulse measurements in regions of heterogeneous elasticity

PURPOSE: The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes. METHODS: Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex 4C1 probe and the linear 9L4 probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively). RESULTS: The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the 9L4 probe than in the case of the 4C1 probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050). CONCLUSION: Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures.

A Comparison of Two Commercial Volumetry Software Programs in the Analysis of Pulmonary Ground-Glass Nodules: Segmentation Capability and Measurement Accuracy

OBJECTIVE: To compare the segmentation capability of the 2 currently available commercial volumetry software programs with specific segmentation algorithms for pulmonary ground-glass nodules (GGNs) and to assess their measurement accuracy. MATERIALS AND METHODS: In this study, 55 patients with 66 GGNs underwent unenhanced low-dose CT. GGN segmentation was performed by using 2 volumetry software programs (LungCARE, Siemens Healthcare; LungVCAR, GE Healthcare). Successful nodule segmentation was assessed visually and morphologic features of GGNs were evaluated to determine factors affecting segmentation by both types of software. In addition, the measurement accuracy of the software programs was investigated by using an anthropomorphic chest phantom containing simulated GGNs. RESULTS: The successful nodule segmentation rate was significantly higher in LungCARE (90.9%) than in LungVCAR (72.7%) (p = 0.012). Vascular attachment was a negatively influencing morphologic feature of nodule segmentation for both software programs. As for measurement accuracy, mean relative volume measurement errors in nodules > or = 10 mm were 14.89% with LungCARE and 19.96% with LungVCAR. The mean relative attenuation measurement errors in nodules > or = 10 mm were 3.03% with LungCARE and 5.12% with LungVCAR. CONCLUSION: LungCARE shows significantly higher segmentation success rates than LungVCAR. Measurement accuracy of volume and attenuation of GGNs is acceptable in GGNs > or = 10 mm by both software programs.

Biopsy guided by real-time virtual navigation system using computed tomography imaging data:a phantom study / 中华超声影像学杂志

ObjectiveTo verify the feasibility and the accuracy for the biopsy of targets not visible on sonography but shown on CT in a phantom by using real-time virtual navigation system(RVS).Methods The tissue mimicking phantom,made of gel,contained 30 red spheres which were 10 mm in diameter,randomly placed.These spheres were invisible on sonography,but visible on CT.A junior operator and a senior operator performed the biopsy respectively,and each sphere was biopsied once guide by both RVS and conventional ultrasound for each operator.The red dye in thebiopsied sample meant successful performance.The success rate of biopsy and the length of the red dyed sample were recorded.Results There was no statistically difference between the performance results of the two operators.The success rate and the median length of red dyed sample biopsy of RVS were respectively 96.7％ (58/60) and 7.5 mm (rang,6-9 mm) which were statistically higher and longer than that of conventional ultrasound,43.3％(26/60) and 0 mm(rang,0 - 5 mm) ( P ＜0.05).ConclusionsBiopsy guided by RVS for the target invisible to ultrasound is a feasible and accuracy method,which will be a new guided method for interventional ultrasound.

The measurement of organic radiation dose of multi-slice CT scanning by using the Chinese anthropomorphic chest phantom / 中华放射学杂志

Objective Using the Chinese anthropomorphic chest phantom to measure the absorbed dose of various tissues and organs under different noise index, and to assess the radiation dose of MSCT chest scanning with the effective dose(ED). Methods The equivalence of the Chinese anthropomorphic chest phantom(CDP-1C) and the adult chest on CT sectional anatomy and X-ray attenuation was demonstrated. The absorbed doses of various tissues and organs under different noise index were measured by laying thermoluminescent dosimeters(TLD) inside the phantom, and the corresponding dose-length products(DLP) were recorded. Both of them were later converted into ED and comparison was conducted to analyze the dose levels of chest CT scanning with automatic tube current modulation (ATCM) under different noise index. Student t-test was applied using SPSS 12.0 statistical software. Results The Phantom was similar to the human body on CT sectional anatomy. The average CT value of phantom are -788.04 HU in lung,45.64 HU in heart,65.84 HU in liver,254.32 HU in spine and the deviations are 0.10%,3.04%, 4.49% and 4.36% respectively compared to humans. The difference of average CT value of liver was statistically significant(t=-8.705,P＜0.05),while the differences of average CT values of lung, heart and spine were not significant(t value were -0.752,-1.219,-1.138,respectively and P＞0.05).As the noise index increased from 8.5 to 22.5, the DLP decreased from 393.57 mGy·cm to 78.75 mGy·cm and the organs dose declined. For example, the average absorbed dose decreased from 22.38 mGy to 3.66 mGy in lung. Compared to ED calculating by absorbed dose, the ED calculating by DLP was lower. The ED values of the two methods were 6.69 mSv and 8.77 mSv when the noise index was set at 8.5. Conclusions Application of the Chinese anthropomorphic chest phantom to carry out CT dose assessment is more accurate. The noise index should be set more than 8.5 during the chest CT scanning based on ATCM technique.