Two-dimensional dose reconstruction using scatter correction of portal images

Context: Electronic portal imaging devices (EPIDs) could potentially be useful for patient setup verification and are also increasingly used for dosimetric verification. The accuracy of EPID for dose verification is dependent on the dose-response characteristics, and without a comprehensive evaluation of dose-response characteristics, EPIDs should not be used clinically. Aims: A scatter correction method is presented which is based on experimental data of a two-dimensional (2D) ion chamber array. An accurate algorithm for 2D dose reconstruction at midplane using portal images for in vivo dose verification has been developed. Subjects and Methods: The procedure of scatter correction and dose reconstruction was based on the application of several corrections for beam attenuation, and off-axis factors, measured using a 2D ion chamber array. 2D dose was reconstructed in slab phantom, OCTAVIUS 4D system, and patient, by back projection of transit dose map at EPID-sensitive layer using percentage depth dose data and inverse square. Verification of the developed algorithm was performed by comparing dose values reconstructed in OCTAVIUS 4D system and with that provided by a treatment planning system. Results: The gamma analysis for dose planes within the OCTAVIUS 4D system showed 98% ±1% passing rate, using a 3%/3 mm pass criteria. Applying the algorithm for dose reconstruction in patient pelvic plans showed gamma passing rate of 96% ±2% using the same pass criteria. Conclusions: An accurate empirical algorithm for 2D patient dose reconstruction has been developed. The algorithm was applied to phantom and patient data sets and is able to calculate dose in the midplane. Results indicate that the EPID dose reconstruction algorithm presented in this work is suitable for clinical implementation

Key technologies in digital breast tomosynthesis system:theory, design, and optimization / 南方医科大学学报

OBJECTIVE@#To develop a digital breast tomosynthesis (DBT) imaging system with optimizes imaging chain.@*METHODS@#Based on 3D tomography and DBT imaging scanning, we analyzed the methods for projection data correction, geometric correction, projection enhancement, filter modulation, and image reconstruction, and established a hardware testing platform. In the experiment, the standard ACR phantom and high-resolution phantom were used to evaluate the system stability and noise level. The patient projection data of commercial equipment was used to test the effect of the imaging algorithm.@*RESULTS@#In the high-resolution phantom study, the line pairs were clear without confusing artifacts in the images reconstructed with the geometric correction parameters. In ACR phantom study, the calcified foci, cysts, and fibrous structures were more clearly defined in the reconstructed images after filtering and modulation. The patient data study showed a high contrast between tissues, and the lesions were more clearly displayed in the reconstructed image.@*CONCLUSIONS@#This DBT imaging system can be used for mammary tomography with an image quality comparable to that of commercial DBT systems to facilitate imaging diagnosis of breast diseases.

The value of HRCT reconstructed with model-based iterative reconstruction algorithm for evaluating early peripheral lung cancers / 实用放射学杂志

Objective To demonstrate the feasibility of high-resolution computed tomography(HRCT)reconstructed with a model-based iterative reconstruction (MBIR)for evaluating early peripheral lung cancer (≤3 cm),by comparing image quality obtained from MBIR,filtered back proj ection reconstruction(FBP)and state of the art adaptive statistical iterative reconstruction(ASIR)algorithm respectively.Methods A total of 30 patients confirmed with lung cancer by postoperative pathology were enrolled in the study.A chest phantom was also used to evaluate image noise,spatial resolution and density resolution.Both patients and chest phantom were received HRCT,and the images were reconstructed using FBP,ASIR(40% ASIR and FBP mix)and MBIR.The objective CT value, standard deviation(SD)and signal noise ratio(SNR)were measured.Two radiologists used a semi-quantitative to rate subjective image quality of lung nodules.Results There was no significant difference in CT value between the three reconstruction algorithms (P>0.05).But significant improvements in objective image noise were observed in MBIR compared with FBP and ASIR (P<0.05):including the SD value in back muscle [(12.63±1.70)with MBIR vs (31.58±5.21)with FBP and (24.55±4.14)with ASIR],and in subcutaneous fat [(12.77±2.53)vs (24.39±5.08)and (19.20±4.11)].Subjective image noise of the three group were also significantly difference:FBP with lowest subjective noise score;and MBIR with highest subjective noise score.The sharpness of small vessels and bronchi and diagnostic acceptability with MBIR were significantly better than with FBP and ASIR (P< 0.05).Conclusion Lung HRCT reconstructed with MBIR provides diagnostically more acceptable images for the detailed analyses of peripheral lung cancer compared with FBP and ASIR.

Contrast-Enhanced CT with Knowledge-Based Iterative Model Reconstruction for the Evaluation of Parotid Gland Tumors: A Feasibility Study

OBJECTIVE: The purpose of this study was to determine the diagnostic utility of low-dose CT with knowledge-based iterative model reconstruction (IMR) for the evaluation of parotid gland tumors. MATERIALS AND METHODS: This prospective study included 42 consecutive patients who had undergone low-dose contrast-enhanced CT for the evaluation of suspected parotid gland tumors. Prior or subsequent non-low-dose CT scans within 12 months were available in 10 of the participants. Background noise (BN), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were compared between non-low-dose CT images and images generated using filtered back projection (FBP), hybrid iterative reconstruction (iDose⁴; Philips Healthcare), and knowledge-based IMR. Subjective image quality was rated by two radiologists using five-point grading scales to assess the overall image quality, delineation of lesion contour, image sharpness, and noise. RESULTS: With the IMR algorithm, background noise (IMR, 4.24 ± 3.77; iDose⁴, 8.77 ± 3.85; FBP, 11.73 ± 4.06; p = 0.037 [IMR vs. iDose⁴] and p < 0.001 [IMR vs. FBP]) was significantly lower and SNR (IMR, 23.93 ± 7.49; iDose⁴, 10.20 ± 3.29; FBP, 7.33 ± 2.03; p = 0.011 [IMR vs. iDose⁴] and p < 0.001 [IMR vs. FBP]) was significantly higher compared with the other two algorithms. The CNR was also significantly higher with the IMR compared with the FBP (25.76 ± 11.88 vs. 9.02 ± 3.18, p < 0.001). There was no significant difference in BN, SNR, and CNR between low-dose CT with the IMR algorithm and non-low-dose CT. Subjective image analysis revealed that IMR-generated low-dose CT images showed significantly better overall image quality and delineation of lesion contour with lesser noise, compared with those generated using FBP by both reviewers 1 and 2 (4 vs. 3; 4 vs. 3; and 3–4 vs. 2; p < 0.05 for all pairs), although there was no significant difference in subjective image quality scores between IMR-generated low-dose CT and non-low-dose CT images. CONCLUSION: Iterative model reconstruction-generated low-dose CT is an alternative to standard non-low-dose CT without significantly affecting image quality for the evaluation of parotid gland tumors.

Comparison of values of iDose4 iterative reconstruction and filtered back projection reconstruction for coronary CT angiography / 医疗卫生装备

Objective To explore the value of iDose4 iterative reconstruction for coronary CT angiography (CCTA).Methods Totally 124 coronary heart disease patients underwent iDose4 iterative reconstruction and filtered back projection (FBP) reconstruction,of whom,56 ones with BMI not less than 20 kg/m2 were put into No.1 iteration group using 135 kV tube voltage and 68 ones with BMI less than 20 kg/m2 were into No.2 iteration group using 110 kV tube voltage.FBP reconstruction was executed with 110 kV tube voltage.Comparison analyses were carried out on signal noise ratio (SNR),contrast to noise ratio (CNR) and image quality.Results There were significant differences between the values of SNR,radiation dose and image quality in No.1 iteration group and FBP group (P＜0.05).Statistical differences were also found between the values of CNR and radiation dose in No.2 iteration group and FBP group,while there were no obvious differences between the values of SNR and image quality in the above two groups (P＜0.05).Conclusion Low-voltage iDose reconstruction gains advantages in radiation dose and image quality during 64-slice CCTA,and thus is worthy promoting clinically.

Application of reconstruction technique in the CT scan of nasal traumas / 重庆医学

Objective To evaluate the value of the SAFIRE reconstruction technique for the nasal traumatic lesions .Methods Six‐ty‐seven patients with nasal traumas were scanned by the orbital scan and were reconstructed with FBP and SAFIRE (strength grade 1 to 5) respectively .Then a comparative analysis for six kinds of reconstructed images were conducted on the average CT value ,noise ,signal to noise ratio (SNR) ,contrast to noise ratio (CNR) ,subjective scoring and lesion detection .Results Compared with reconstruction by FBP , SAFIRE (strength grade 1 to 5)reconstruction ,for the noise ,decreased to 20 .4% ,31 .4% ,39 .7% ,46 .5% and 57 .2% respectively ;For the SNR ,increased to 33 .3% ,54 .7% ,75 .4% ,87 .4% and 101 .4% respectively ;For the CNR ,it also increased to 23 .0% ,36 .4% ,57 .7% , 87 .4% and 106 .5% respectively ;The difference was statistically significant (P< 0 .05) .For the images of SAFIRE‐1 and SAFIRE‐5 ,the image subjective scoring was lower than that by FBP ;for the images of SAFIRE‐2 and SAFIRE‐4 ,the image subjective scoring was higher than that by FBP ;and SAFIRE‐3 had the highest score .But for the rate of lesion detection ,all the images were the same .Conclusion CT scan combined SAFIRE reconstruction technique can decrease effectively the noise and increase the image quality in the traumatic nasal scan , as well as has a potential effect to decrease the scan dose .

Feasibility study of low tube voltage technique and low concentration of contrast in CT pulmonary angiography by filtered back projection reconstruction / 中华放射医学与防护杂志

Objective To investigate the feasibility of CT pulmonary angiography (CTPA) with 80 kVp and contrast agent of iodixanol (270 mg I/ml) by filtered back projection(FBP) reconstruction.Methods In total,52 patients who underwent CTPA were randomly divided into two equally-sized groups,control group and experimental group.The volume computed tomography dose index (CTDIvol) and dose-length product (DLP)were recorded,and the weighted computed tomography dose index (CTDIw) and effective dose (E) were calculated.The image quality was visually evaluated and measured,and statistical analyses were performed on the image quality and the radiation dose.Results The sex,age,height,weight and body mass index (BMI) had no statistical difference between two groups (P ＞ 0.05).The average iodine dosage decreased by 22.9％ in the experimental group compared with the control group.Compared with the control group,the CTDIvol,DLP,CTDIw and E decreased by 73.5％,75.1％,73.5％ and 75.8％,respectively.The differences were statistically significant (t =＜0.001,30.5,＜ 0.001,-28.7,P ＜ 0.05).The image quality of the two groups met the requirement of diagnosis and there were no significant statistic differences between visually evaluating and objectively measuring the image quality (P ＞ 0.05).Conclusions Using 80 kVp and iodixanol for CTPA,FBP reconstruction image quality can meet diagnostic requirements.At the same time the radiation dose,the contrast agent dose and the X-ray tube wastage are reduced respectively.

Quantitative Analysis of the Effect of Iterative Reconstruction Using a Phantom: Determining the Appropriate Blending Percentage

PURPOSE: To investigate the optimal blending percentage of adaptive statistical iterative reconstruction (ASIR) in a reduced radiation dose while preserving a degree of image quality and texture that is similar to that of standard-dose computed tomography (CT). MATERIALS AND METHODS: The CT performance phantom was scanned with standard and dose reduction protocols including reduced mAs or kVp. Image quality parameters including noise, spatial, and low-contrast resolution, as well as image texture, were quantitatively evaluated after applying various blending percentages of ASIR. The optimal blending percentage of ASIR that preserved image quality and texture compared to standard dose CT was investigated in each radiation dose reduction protocol. RESULTS: As the percentage of ASIR increased, noise and spatial-resolution decreased, whereas low-contrast resolution increased. In the texture analysis, an increasing percentage of ASIR resulted in an increase of angular second moment, inverse difference moment, and correlation and in a decrease of contrast and entropy. The 20% and 40% dose reduction protocols with 20% and 40% ASIR blending, respectively, resulted in an optimal quality of images with preservation of the image texture. CONCLUSION: Blending the 40% ASIR to the 40% reduced tube-current product can maximize radiation dose reduction and preserve adequate image quality and texture.

The Simulation of CT Filtering Projection Reconstruction Using Computer / 中国医学物理学杂志

Objective: So far, CT back projection technology is already quite mature, this article is a basic research for CT back projection technology, which uses software method to realize back-projection technology, so that you can have a better under-standing of CT back-projection technology. It uses computer soflware programming to realize computer simulation of CT back-projection reconstruction: algorithm is CT back projection algorithm. While realizing back-projection reconstruction, we can choose a suitable faltering function to process received image data in finquency domain, so as to achieve the purpose of the elimination of simple back-projection arising from star-shaped artifact. Methods: The programming environment uses VC soft-ware platform integrated development environment ODE). It bases on the CT filtering back-projection reconstruction algorithm and develops a PC software of graphic user interface. By choosing the value of the various parameters related to the back-pro-jection, we can obtain different effect of back-projection reconstruction image, so that we can compare the result of different pa-rameters to get important factors which effects CT filter back-projection most. Results: We realize the simulation of image re-construction of standard phantom. The interface is easy, so makes it very convenient for deeper understanding of back-projec-tion reconstruction, at the same time the filtering function based on the frequency domain also partly eliminates the star artifact caused by reconstruction process. The reconstruction image of the standard phantom achieves the desired effect. Conclusions: The software simulation of the back-projectiun reconstruction can show the process of recoustruction clearly. By change the val-ue of the parameters, we can have a better understanding of the reconstruction algorithm, so that we can find more suitable fil-tering function.

Method of electron tomography three-dimensional reconstruction / 医疗卫生装备

This paper introduces the method of electron tomography three-dimensional reconstruction,which is widely applied in structural biology field and summarizes its advantages and disadvantages.The aim is to provide a reference for the application of the method.