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Objective:To explore the effect of the location and size of region of interest (ROI) on the measurement of liver fat by means of quantitative computed tomography (QCT).Methods:A total of 98 subjects who were examined with QCT for bone mineral density examination from December 25, 2019 to January 17, 2020 were recruited continuously from the Department of Health Management of Henan Provincial People′s Hospital. The liver fat content was measured by QCT workstation. The ROI was located respectively in the left lobe, the right anterior lobe and the right posterior lobe of the liver, and it was measured independently by the A measurer and B measurer. The central position of the ROI was fixed and the diameter was increased, and it was measured by the A measurer. In this study, Friedman test was used to compare the differences of measurement results in different positions or sizes of ROI, and intra-class correlation coefficients (ICC) was used to evaluate the repeatability of inter-measurers.Results:There was a significant difference for liver fat content under different positions of ROI (χ2=62.306, P<0.001), but no difference under different seizes of ROI (χ2=1.088, P=0.581). The ICC values of the inter-measurers repeatability analysis of the A measurer and B measurer in the left lobe, right anterior lobe and right posterior lobe of the liver were 0.847, 0.917 and 0.874, all more than 0.75, and the reproducibility was good. Conclusions:When QCT technique is applied to the measurement of liver fat content, the location conditions of ROI may affect results, so it is necessary to select multiple ROI in the whole liver for measurement. The inter-measurers repeatability of QCT in different parts of the liver is good.
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The pathogenesis of Alzheimer's disease (AD), a common neurodegenerative disease, is still unknown. It is difficult to determine the atrophy areas, especially for patients with mild cognitive impairment (MCI) at different stages of AD, which results in a low diagnostic rate. Therefore, an early diagnosis model of AD based on 3-dimensional convolutional neural network (3DCNN) and genetic algorithm (GA) was proposed. Firstly, the 3DCNN was used to train a base classifier for each region of interest (ROI). And then, the optimal combination of the base classifiers was determined with the GA. Finally, the ensemble consisting of the chosen base classifiers was employed to make a diagnosis for a patient and the brain regions with significant classification capability were decided. The experimental results showed that the classification accuracy was 88.6% for AD
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Humans , Alzheimer Disease/diagnosis , Brain/diagnostic imaging , Cognitive Dysfunction/diagnosis , Early Diagnosis , Magnetic Resonance Imaging , Neural Networks, Computer , Neurodegenerative DiseasesABSTRACT
OBJECTIVE: To compare the diagnostic performance and interobserver variability of strain ratio obtained from one or two regions of interest (ROI) on breast elastography.MATERIALS AND METHODS: From April to May 2016, 140 breast masses in 140 patients who underwent conventional ultrasonography (US) with strain elastography followed by US-guided biopsy were evaluated. Three experienced breast radiologists reviewed recorded US and elastography images, measured strain ratios, and categorized them according to the American College of Radiology breast imaging reporting and data system lexicon. Strain ratio was obtained using the 1-ROI method (one ROI drawn on the target mass), and the 2-ROI method (one ROI in the target mass and another in reference fat tissue). The diagnostic performance of the three radiologists among datasets and optimal cut-off values for strain ratios were evaluated. Interobserver variability of strain ratio for each ROI method was assessed using intraclass correlation coefficient values, Bland–Altman plots, and coefficients of variation.RESULTS: Compared to US alone, US combined with the strain ratio measured using either ROI method significantly improved specificity, positive predictive value, accuracy, and area under the receiver operating characteristic curve (AUC) (all p values < 0.05). Strain ratio obtained using the 1-ROI method showed higher interobserver agreement between the three radiologists without a significant difference in AUC for differentiating breast cancer when the optimal strain ratio cut-off value was used, compared with the 2-ROI method (AUC: 0.788 vs. 0.783, 0.693 vs. 0.715, and 0.691 vs. 0.686, respectively, all p values > 0.05).CONCLUSION: Strain ratios obtained using the 1-ROI method showed higher interobserver agreement without a significant difference in AUC, compared to those obtained using the 2-ROI method. Considering that the 1-ROI method can reduce performers' efforts, it could have an important role in improving the diagnostic performance of breast US by enabling consistent management of breast lesions.
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BACKGROUND: At present, related finite element models have been used to simulate the femoral fracture, and the effects of loading rate, loading angle and cancellous bone on the fracture of hip have been discussed. However, the fracture simulation of trabecula is still lack of relevant research. OBJECTIVE: To simulate the biomechanical process of osteoporotic trabecular compression fracture in ovariectomized rats. METHODS: The right femur of ovariectomized rats was scanned at the distal end of femur by Micro-CT. The microstructure parameters and three-dimensional model of the region of interest of the rat femur were obtained. After geometric optimization in Geomagic Studio, they were pretreated in HyperMesh 14.0, including volume mesh division, setting material property parameters, boundary conditions, setting load of 1 200 N, acting time of 2 ms, and they were calculated in LS-DYNA software. RESULTS AND CONCLUSION: (1) The bone trabeculae in the region of interest showed uneven spatial distribution. (2) The bone trabeculae with small volume and small number first presented deformation fracture, and the plate shape and bone trabeculae with large volume finally demonstrated fracture collapse. (3) The change trend of von Mises stress was roughly the same as that of bone trabeculae fracture collapse. The fracture collapse process of bone trabeculae in the region of interest included vertical collapse and horizontal torsion, in which the degree and rate of horizontal torsion were lower than that of vertical collapse, making the size and rate of cross-section torsion angle less than that of coronal plane angle. (5) The increase and peak value of shear stress of failure unit were smaller than Von-mises stress. (6) These results indicate that fracture collapse of bone trabecula is a complex process, including deformation and angle of different planes.
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Vergence eye movements are the inward and outward rotation of the eyes responsible for binocular coordination. While studies have mapped and investigated the neural substrates of vergence, it is not well understood whether vergence eye movements evoke the blood oxygen level-dependent signal reliably in separate experimental visits. The test-retest reliability of stimulus-induced vergence eye movement tasks during a functional magnetic resonance imaging (fMRI) experiment is important for future randomized clinical trials (RCTs). In this study, we established region of interest (ROI) masks for the vergence neural circuit. Twenty-seven binocularly normal young adults participated in two functional imaging sessions measured on different days on the same 3T Siemens scanner. The fMRI experiments used a block design of sustained visual fixation and rest blocks interleaved between task blocks that stimulated eight or four vergence eye movements. The test-retest reliability of task-activation was assessed using the intraclass correlation coefficient (ICC), and that of spatial extent was assessed using the Dice coefficient. Functional activation during the vergence eye movement task of eight movements compared to rest was repeatable within the primary visual cortex (ICC = 0.8), parietal eye fields (ICC = 0.6), supplementary eye field (ICC = 0.5), frontal eye fields (ICC = 0.5), and oculomotor vermis (ICC = 0.6). The results demonstrate significant test-retest reliability in the ROIs of the vergence neural substrates for functional activation magnitude and spatial extent using the stimulus protocol of a task block stimulating eight vergence eye movements compared to sustained fixation. These ROIs can be used in future longitudinal RCTs to study patient populations with vergence dysfunctions.
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Objective To examine the method of least-square fitting for calibrating the palatal rugae boundary. Methods According to the distribution of the teeth, the feature points were selected; when they were fit, the boundary of the palatal rugae area was created, thereby constructing a mask. The mask was used to remove the part located outside the boundary and filter out the interference. Three samples were utilized for the ex-periments and analyses to come. Results To evaluate the quantitative results of the fitting curves, the correla-tion coefficients(r)of the samples and the relationship between the actual mean value and ideal mean value was obtained through six fitting processes. The differences between the actual mean and ideal mean were found to be significantly small (from 0.2857 to 2.5000) in the six fitting processes, with the range of r close to 1(from 0.9896 to 0.9995). Conclusion The effect of the cubic polynomial fitting method adopted in this study was stable.The proposed boundary calibration method can effectively locate the palatal rugae boundary and remove the interference area, further promoting the practice of forensic identification.
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Aim and Objective: Quantitative analysis of time-activity curve (TAC) derived from 99mTc-pertechnetate salivary glandscintigraphy, used in the evaluation of salivary gland function, is almost always corrected for background count. The objectiveof this study was to: (a) Examine the effect of the alteration of anatomical position of the background region of interest (ROI) onthe (1) semi-quantitative parameters, i.e., upslope (Us) and stimulated downslope (Ds), derived from TAC and (2) on minimumand maximum pixel counts of pixel histogram of background ROI. (b) Examine the effect of minimum and the maximum pixelcounts of the background ROI on the values of Us and Ds.Materials and Methods: In this retrospective study, 16 patients were included who had undergone 99mTc-pertechnetatesalivary scintigraphy for various reasons but had normal salivary scintigraphy reports. Three different sets of background indifferent anatomical positions were chosen: (i) A pair of supraclavicular background ROI, (ii) an isolated central rectangularbackground ROI in brain, and (iii) an isolated suprathyroid ROI. We then calculated two important semi quantitative parameters,i.e., Us and Ds from the TAC of the salivary glands. Individual TAC was generated against each set of the above-mentionedbackgrounds. Individual pixel histogram was also generated against each TAC. Minimum and maximum pixel count of thegenerated background pixel histograms was identified. Comparative studies were made among the afore-mentioned variables.Results and Conclusion: The values of Us and Ds derived from respective background corrected TAC matched well amongeach other irrespective of the altered anatomical positions of the background ROI. The minimum pixel counts per second (CPS)of the background pixel histogram varied with the change in anatomical position of the background ROI but it did not affect thevalues of Us and Ds. In contrast, the maximum pixel CPS of the background pixel histogram varied inversely with the valuesof Ds, although the value of Ds, showed no variation with the change in position of the background ROI.
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Objective To investigate the impact of different ROI and modulus of elasticity in shear wave elastography (SWE) for diagnosis of benign and malignant cervical lymph nodes. Methods Totally 143 enlarged cervical lymph nodes confirmed by puncture biopsy or surgical pathology were examined with routine ultrasound and SWE before operation. Three different ROI, including the small circular ROI (ROI-1) with diameter 2 mm, the maximum circle ROI (ROI-2) not exceeding the edge of the lymph node, and the manual delineation of the entire lymph node-marginal ROI (ROI-3) were used, all containing the hardest region of lymph nodes. The maximum elastic value (Emax), the mean elastic value (Emean) and the elastic standard deviation (SD) were measured and compared, respectively. ROC curve was constructed to obtain the AUC of each elasticity value for the diagnosis of benign and malignant lymph nodes in the neck. Results Emax, Emean and SD measured with 3 ROI in malignant lymph nodes were higher than those in benign lymph nodes (all P0.05), but there was significant difference of Emean and SD (both P0.05). AUC of Emean measured with ROI-1 was higher than those of ROI-2 and ROI-3 (both P0.05). Conclusion SWE could differentiate benign and malignant cervical lymph nodes, but its diagnostic efficacy varies with the choice of ROI and modulus of elasticity. When selecting a smaller ROI, it is recommended to use Emax and Emean, while Emax and SD are recommended when larger ROI is selected.
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Objective: To investigate the repeatability of different ROI seletion methods on histogram analysis parameters of enhanced T1-weighted images of high-grade gliomas (HGGs). Methods: Four ROI selecting methods (small ROI method, contour ROI method, threshold ROI method and volume ROI method) were used to measure the histogram parameters on enhanced T1WI of 45 HGGs patients. The consistency between 2 observers and the differences of histogram parameters were evaluated. Results: The consistent of the mean, standard deviation and kurtosis values measured using volume, contour and threshold ROI methods between 2 observers were good (ICC≥0.80), and of the skewness values were moderate to good (ICC=0.73-0.90). The consistent of histogram characteristic parameters measured using small ROI method between 2 observers were low to medium (ICC=0.30-0.69). Histogram characteristic parameters measured with volume ROI method and contour ROI method had no significant difference (all P>0.05), but the average value, skewness value and kurtosis value measured with threshold ROI method were higher than those with volume and contour ROI method (all P<0.05), and the standard deviation of threshold ROI method was lower than that of volume ROI method and contour ROI method (both P<0.05). Standard deviation measured with small ROI method was lower than that of volume ROI method and contour ROI method (all P<0.05). Conclusion: The consistency of histogram characteristic parameters of HGGs on enhanced T1WI measured with volume ROI method is the highest, and different ROI selection methods have some impact on the measurement results of histogram characteristic parameters of enhanced T1WI.
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Objective To evaluate the renal peripheral inflow perfusion in patients with liver cirrhosis by region of interest ( ROI) quantification of color Doppler technique . Methods Fifty-eight patients with cirrhosis with normal renal function were selected as the case group ,and classified into A grade ( 10 cases) , B grade (23 cases) and C grade ( 25 cases) according to Child-Pugh classification criteria . Thirty healthy volunteers were selected as the control group .Resistance index ( RI) of interlobar artery and interlobular artery were measured in all groups . The blood flow of renal cortical was analyzed using ROI quantification in the corresponding region ,and vascular index ( VI) ,flow index ( FI) ,vascularization flow index ( VFI) were obtained . Results ① Patients of B grade group and C grade group in the cirrhosis group showed sparser corical blood flow and slender blood vessels . ②No statistical difference were found in the resistance index of the renal interlobaries and interlobular arteries between A grade group and control group ( P ＞0 .05) ,the RI of renal interlobar arteries and interlobular arteries in B grade group and C grade group were significantly higher ( P ＜0 .01) . Compared with the A grade group ,the RI of renal interlobar arteries and interlobular arteries in B grade group and C grade group increased evidently ( P ＜ 0 .01).The RI of renal interlobar arteries and intralobular arteries between B grade groupand C grade group showed no statistical difference (P＞0 .05).③Compared with the control group ,the VI ,FI ,and VFI of A ,B ,and C grade groups declined obviously ( P ＜ 0 .05).With the increase of cirrhosis grade ,VI ,FI and VFI gradually decreased ,and the difference among the three groups were statistically significant ( P ＜ 0 .05 ).Conclusions Patients with cirrhosis have showed a reduction in renal peripheral vascular bed and blood perfusion earlier than laboratory tests for renal dysfunction .ROI quantification of Color Doppler technique can sensitively assess changes of early renal peripheral blood perfusion in patients with cirrhosis .
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Background and purpose: The technique of dynamic contrast-enhanced MRI (DCE-MRI) is widely applied in differential diagnosis between benign and malignant tumor and therapeutic estimation of neoadjuvant chemotherapy in clinic. However, there is no standard quantitative measurement method. This study aimed to assess the variability of different region of interest (ROI) selections for tumor bed of breast cancer using DCE-MRI, and to ascertain the optimal ROI delineation. Methods: We retrospectively analyzed DCE-MRI of 30 patients diagnosed with breast cancer by pathology. The ROIs were delineated by 2 different observers using iCAD software with 4 methods, including whole tumor (Whole), the slice containing the most enhancing voxels (SliceMax), 3 slices centered in SliceMax (Partial) and the 5％ most enhancing contiguous voxels within SliceMax (5Max), to generate the volume transfer constant (Ktrans), the extracellular volume fraction (Ve) and rate constant (Kep). And the reproducibilities of the measurements were assessed using the Bland-Altman method. Results: In the analysis of ROIs delineation, the Ktrans, Ve and Kep reported by different observers were 1.26±0.54 vs 1.25±0.53, 0.75±0.23 vs 0.73±0.22 and 1.93±1.46 vs 1.95±1.51 (P＞0.05) using the method of Whole, and 1.28±0.43 vs 1.26±0.43, 0.74±0.21 vs 0.80±0.27, 1.95±1.53 vs 1.93±1.43 (P＞0.05) using the method of Partial, and 1.30±0.33 vs 1.32±0.33, 0.77±0.20 vs 0.73±0.24, 1.82±1.53 vs 1.87±1.45 (P＞0.05) using the method of SliceMax, and 1.31±0.35 vs 1.35±0.33, 0.77±0.20 vs 0.98±0.25, 1.97±1.36 vs 1.73±1.55 using the method of 5Max (P＜0.05). Using the methods of ROI delineation except 5Max, there was no significant difference between Ktrans, Ve and Kep reported by different observers. The bias vs limits of agreement were 0.002 vs-0.013 to 0.012,-0.003 vs-0.023 to 0.017, 0.006 vs-0.018 to 0.029,-0.035 vs-0.054 to 0.018 measured with Whole method, SliceMax, Partial and 5Max respectively using the Bland-Altman method. Conclusion: It may be reliable to measure functional parameters of primary tumors in breast cancer using DCE-MRI according to the methods of Whole, Partial and SliceMax.
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Objective To determine the consistency of spectral CT parameters in advanced gastric cancer using different region of interests (ROIs) and their relationship with tumor micro-vessel density (MVD).Methods Thirty patients with histologically proven gastric cancer were prospectively enrolled.All the patients were examined using spectral-dual-phase-abdominal CT and treated successfully with radical surgery within 2 weeks after CT scanning.Two observers independently acquired iodine concentration(IC), normalized IC(nIC),and CT value at workstation using three different ROI protocols:10 mm2 circular ROI near tumor border where enhanced obviously,30 mm2 near the tumor center and the freehand outline ROI. The Data of the two observers were tested with interclass correlation coefficient (ICC) and Bland-Altman plot.The mean value of each parameter was documented as the final result.Differences of each group of ROI data were compared using ANOVA test. All the specimen were pathologically examined and MVD was counted. The relationship of each parameter to tumor MVD was analyzed by Pearson correlation. Results All of the IC,nIC and CT values obtained by the 2 observers using three ROI measurements were consistent well,and the ROI-outline had the highest ICC than that of smaller circular ROIs(ICC:0.991 to 0.997).The 95% differences confident interval of nIC-AP and nIC-VP using freehand outline ROI by two observers were-0.003 to 0.002 and -0.001 to 0.012, respectively. The outline-ROI method had better inter-observer accuracy. There were significant differences between the means of the all parameters with three ROI protocols (P<0.05). Values of ROI-10 mm2 were highest, while the values of ROI-outline were lowest (P<0.05).The mean counts of tumor MVD was(29.0±8.4)/high magnification.The nIC in venous phase(VP)had good correlations with intra-tumoral MVD, especially the ROI-outline (r=0.670, P<0.01), within different ROI measurements.Conclusions The different ROI selection in tumor has significant impact on the final CT parameters. Outlined ROI protocol improves inter-observer consistency and nIC-VP obtained by this method can indirectly reflect the condition of tumor angiogenesis.
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Objective To investigate the application of Computed tomography perfusion imaging (CTP) in superficial temporal artery-middle cerebral artery bypass(STA-MAC) treated moyamoya disease (MMD).Methods The clinical data of 21 patients with MMD who received STA-MAC surgery were collected.CTP was performed before and after the surgery for all the patients included.We routinely delimited the corresponding position as regions of interest (ROI) and obtained value of the cerebral blood flow(CBF),cerebral blood volume(CBV),the mean transittime(MTT),time to peak(TTP).The deviations of rCBF,rCBV,rMTT,rTTP between the affected side and corresponding area were analysed and the paired t test was performed.Results Unobstructed blood flow was observed in all patients received STA-MAC surgery after DSA examination.Increased CBF was observed in 100％ patients and increased CBV in 80.95％ patients,shortened MMT in 80.95 ％ patients,shortened TTP in 85.71％ patients.Difference of CBF,CBV,MTT,r-CBF,rMTT between pre-and post-Operation had statistical significance (P ＜ 0.05).Conclusion CTP is important in elucidating the hemodynamic changes before and after STA-MCA bypass,which indicts a crucial role in evaluating therapeutic effect of surgical treatment for MMD.
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Objective To analyze the differences between calculated and actual volumes of regions of interest ( ROIs) in three treatment planning systems ( TPSs):PrecisePlan, Xio, and Oncentra, to transfer different ROIs and compare their calculated volume between the three TPSs, and to provide a basis for clinical application. Methods Different sizes of ROIs were delineated on 5 sets of computed tomography ( CT) images with different slice thickness. Square and round regions with different slice numbers were contoured in a homogeneous phantom. Three groups of patients ( n=5) with head and neck tumor, chest and abdomen tumor, and pelvic tumor, respectively, were enrolled as subjects. All the ROIs were independently transferred back and forth between three TPSs and different workstations with the same system in DICOM RT format. The changes in actual and calculated ROI volumes were evaluated after back and forth transfer. Results There was a significant positive linear correlation between the calculated volume, slice thickness, slice number, and actual volume of ROI in each TPS ( PrecisePlan:R2=0. 994, P<0. 01;Xio:R2=0. 997, P<0. 01;Oncentra:R2=0. 995, P<0. 01) . There were significant differences in all calculated ROI volumes of the head, chest and abdomen between the three TPS ( P<0. 05) except for the calculated ROI volumes of the chest and abdomen between Oncentra and Xio ( P=0. 114 ) . Conclusions The variations in volume calculation algorithm and slice thickness are the main causes of differences in calculated ROI volume. Particularly, small?volume ROIs have the greatest variation in calculated volume. To avoid a secondary reconstruction of ROI volume, it is recommended to transfer ROI back and forth between dose calculation workstations with the same TPS.
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Purpose To assess the feasibility of measuring maximal density of a region of interest (ROI) with contrast-enhanced CT in quantifying degrees of intestinal ischemia in patients with intestinal obstruction.Materials and Methods Abdominal CT images and reports of 160 patients with intestinal obstruction were retrospectively studied.All the data were reviewed by CT visual evaluation method and measuring maximal density of ROI respectively.The CT visual evaluation took the way of accumulated points,and divided the degrees of intestinal ischemia into five categories.The measuring maximal density of ROI quantified the degrees of bowel enhancement with a bar histogram on CT workstation.The results were compared with the pathological examination.The sensitivity,specificity,positive and negative predictive values and accuracy of the two methods were calculated respectively,and compared.Results The sensitivity,specificity,positive and negative predictive values and accuracy of CT visual evaluation method were 96.7％,72.9％,82.1％,94.4％ and 86.2％,respectively.The sensitivity,specificity,positive and negative predictive values and accuracy of the measuring maximal density of ROI were 68.8％,100.0％,100.0％,71.4％,82.5％,respectively.By measuring the area under the ROC curve,the ROI method (0.995) was more accurate than CT visual evaluation method (0.908) in the diagnosis of bowel ischemia.Conclusion Measuring the maximal density of ROI can quantize bowel wall enhancement.It is a reliable and useful method in the diagnosis of intestinal ischemia,and in accordance with pathological results.
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Objective To explore the influence of ROI size on the diagnostic performance of shear wave elstography (SWE) of breast masses.Methods A total of 225 consecutive patients with 239 solid breast masses underwent SWE before surgery,and then quantitative SWE parameters,including the maximum stiffness (Emax),mean stiffness (Emean),ratio of stiffness of the mass to stiffness of surrounding fat (Eratio) and standard deviation (SD),were measured by two methods,one method was using larger ROI to include the largest part of a mass,and the other was placing fixed ROI=2 mm over the stiffest part of the lesion to measure.The diagnostic performance of the two methods were evaluated by ROC curve,and the cut-off value,sensitivity and specificity of each SWE parameter were obtained.Results There were no statistically significant differences between the performance of Emax,Emean and SD from the two different methods (all P＞ 0.05),the performance of Eratio of the two methods showed significant difference (P=0.046).The significantly higher specificity of Emax and Emean in the larger ROI were found,and the significantly higher sensitivity of SD and Eratio in the ROI=2 mm was found.Furthermore,the diagnostic performance of combination of SWE and BI-RADS were not greatly affected by the ROI size,the difference had no statistical significance (all P＞0.05).Conclusion The ROI size only affects the diagnostic performance of Eratio,and donot affect the diagnostic performance of the quantitative SWE parameters (Emax,Emean,SD) and combination of SWE and BI-RADS.
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Objective To investigate the effects of spine region of interest (ROI),tracking range,and real-time image contrast ratio on the positioning errors of cyberknife.Methods The LTT dynamic phantom was used to develop a spine tracking plan and perform treatment,and the target positioning system was used to preset the phantom and obtain real-time preset image and positioning error.Based on the realtime preset image,spine ROI,tracking range,and real-time image contrast ratio were changed to observe the changes in positioning error and related parameters.Pearson correlation analysis was performed.Results The change in tracking range did not change the positioning error in spine tracking,and tracking range was not correlated with positioning error (R =0,P =1).The changes in ROI and image contrast ratio did not affect the translation error,but affected the rotation error,especially the rotation error in left-right direction (r =0.533 and 0.693,P=0.002 and 0.026).The image contrast ratio had the most obvious effect,with an amplitude of variation up to 2.2°.Conclusions The change in tracking range does not affect the positioning errors in spinal tracking,but the changes in ROI and image contrast ratio can cause varying degrees of changes in positioning errors,which should be taken seriously in cyberknife treatment.
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OBJECTIVES: With the increased use of computed tomography (CT) in clinics, dose reduction is the most important feature people seek when considering new CT techniques or applications. We developed an intensity-weighted region-of-interest (IWROI) imaging method in an exact half-fan geometry to reduce the imaging radiation dose to patients in cone-beam CT (CBCT) for image-guided radiation therapy (IGRT). While dose reduction is highly desirable, preserving the high-quality images of the ROI is also important for target localization in IGRT. METHODS: An intensity-weighting (IW) filter made of copper was mounted in place of a bowtie filter on the X-ray tube unit of an on-board imager (OBI) system such that the filter can substantially reduce radiation exposure to the outer ROI. In addition to mounting the IW filter, the lead-blade collimation of the OBI was adjusted to produce an exact half-fan scanning geometry for a further reduction of the radiation dose. The chord-based rebinned backprojection-filtration (BPF) algorithm in circular CBCT was implemented for image reconstruction, and a humanoid pelvis phantom was used for the IWROI imaging experiment. RESULTS: The IWROI image of the phantom was successfully reconstructed after beam-quality correction, and it was registered to the reference image within an acceptable level of tolerance. Dosimetric measurements revealed that the dose is reduced by approximately 61% in the inner ROI and by 73% in the outer ROI compared to the conventional bowtie filter-based half-fan scan. CONCLUSIONS: The IWROI method substantially reduces the imaging radiation dose and provides reconstructed images with an acceptable level of quality for patient setup and target localization. The proposed half-fan-based IWROI imaging technique can add a valuable option to CBCT in IGRT applications.
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Humans , Cone-Beam Computed Tomography , Copper , Image Processing, Computer-Assisted , Methods , Pelvis , Radiation Exposure , Radiotherapy, Image-GuidedABSTRACT
Purpose To propose a novel compression method for region of interest (ROI) based on Curvelet transform and SPIHT algorithm. Materials and Methods The ROI was firstly extracted without compression, and Curvelet transform was applied for the background regions. The Curvelet coefifcients were coded using SPIHT algorithm. Then the images after compression are obtained by inverse Curvelet transform. The ROI and the background were ifnally overlapped to get the full compressed image. Effect of ROI compression and overall compression were compared, as well as the Curvelet transform and wavelet transform, based on peak signal noise ratio. Results The ROI compression highlighted the region of interest and the visual effect was superior to the overall compression. The peak signal to noise of Curvelet transform was higher than that of wavelet transforms, and the compressed images were more clear for the same proportion. Conclusion ROI compression based on Curvelet transform and SPIHT algorithm can achieve efficient compression images without losing important diagnostic information, which complies with the requirement of high precision and high quality of medical image compression.
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Objective To observe the spatiotemporal characteristics of the micro-structural injury in a rat model of diffuse axonal injury (DAI) and quantitatively assess the axonal injury severity in the vulnerable areas. Methods The 7.0 T MRI was performed in rats in DAI group (n =20) and control group ( n = 15 ) to synthesize the diffusion tensor imaging ( DTI) parameter map and calculate the parameter value of the vulnerable areas. Immunohistochemistry was used to detect β-APP expression in the vulnerable areas and the IPP software to quantitatively assess the axonal injury severity. Results Compared with the control group, FA and AD maps showed local signal defection or reduction in the corpus callosum and their values decreased significantly in the brain stem and corpus callosum in the DAI group (P ＜0.01 ). The integrated optical density (IOD) value of the vulnerable areas in the DAI group was significantly higher than that of the control group ( P ＜ 0. 01 ) , with the highest level in the brain stem (P＜0.05). The normalized FA, AD and ADC in the vulnerable areas were correlated negatively with the IOD (P ＜ 0.05). Conclusion DTI can detect invisible micro-structural injury in the vulnerable areas and quantitatively assess the axonal injury severity in vivo in the early stage.