CT理论与应用研究

A Fast Imaging Method for Grating-based X-ray Phase-contrast Tomosynthesis

XI Yan, ZHAO Jun

2015, 24(4): 475-483. doi: 10.15953/j.1004-4140.2015.24.04.01

Abstract(671) PDF(2)

Abstract:
As an imaging technique with low radiation dose and improved contrast, digital X-ray tomosynthesis is widely used in clinical diagnoses. Based on the superior capability of X-ray phase-contrast imaging(PCI) techniques for imaging low density materials, the combination of X-ray tomosynthesis and PCI could potentially provide higher efficiency in the detection of soft tissues. The goal of this work was to develop a fast and low-dose imaging method for phase-contrast tomosynthesis, called grating-based phase-contrast tomosynthesis(GPC-Tomo), which integrates tomosynthesis with a grating-based PCI technique. During data acquisition with the proposed fast GPC-Tomo, the grating scanning and sample rotation occur at the same time, which is different from the scheme used for conventional GPC-Tomo. Without the phase stepping(PS) technique to extract the differential phase-contrast image at each projection angle for the conventional GPC-Tomo, the data collected by the fast GPC-Tomo is incomplete. Here, we propose a novel reconstruction method called inner-focusing(IF) reconstruction for the proposed fast GPC-Tomo. In the reconstruction stage, measured X-ray intensities from neighboring projection angles that pass through the reconstructed point are utilized to compose a stepping period for signal extraction. The proposed fast GPC-Tomo technique was validated by real experiments. The results demonstrated that the reconstructed images acquired with the fast GPC-Tomo are better than those acquired with conventional GPC-Tomo, and with near-equivalence in radiation dose. Furthermore, since the proposed fast GPC-Tomo employs continuous rotation, its scanning time is much less than the stop-and-go motion of the conventional GPC-Tomo.

Reconstruct Digital Image by Algebraic Reconstruction Technique Based Programming

CHEN Xiong, WANG Cheng-yong, WU Di, WU Fa-en, CHEN Li-cheng

2015, 24(4): 485-493. doi: 10.15953/j.1004-4140.2015.24.04.02

Abstract(991) PDF(4)

Abstract:
Radon transform(line integral) is done on lines along known and unknown digital images, with the same line arrangement each line's integral step is constant. Thus easy to acquire integral approximate value("observed value") of each line on digital image; easy to set up a digital image of unknown linear algebraic equations. Use "Algebraic Reconstruction Technique" addition modified iteration to compile Matlab program, with this program to handle the "measurement vector" data and reconstruct unknown digital image. The relative error between calculated results and known digital image is within 2%. This article is basic research of addition modified iteration ART and provides practical application reference for those who interest in "Algebraic Reconstruction Technique".

Principles and Comparative Study by 320/64 Slice CTA and DSA in Diagnosis of Intracranial Aneurysms

CAO Hua, YANG Ming, CHEN Xin-jian, ZOU Jia-ni, WU Qian

2015, 24(4): 495-502. doi: 10.15953/j.1004-4140.2015.24.04.03

Abstract(722) PDF(3)

Abstract:
Objective: Comparative study the principles and applications of 320 Slice, 64 Slice CTA and rotation 3D DSA in diagnosis of intracranial aneurysms in order to choose the most appropriate inspection ways. Methods: The 86 patients who were highly suspected with intracranial aneurysms were examined by 320 slice CTA, 64 slice spiral CTA and had 3D DSA inspection at the same time. To conduct a comparative study of the characteristics of CTA and 3D DSA image. Results: 86 cases had been confirmed by operation and interventional procedures.92 cases were detected by 320 Slice CTA, 90 cases were detected by 64 slice CTA and 96 cases were detected by 3D DSA respectively, There was no significant difference between 320 slice, 64 slice CTA and 3D DSA(P>0.05). Conclusions: 320 Slice CTA, 64 Slice CTA and 3D DSA examination has their own advantage in the diagnosis of intracranial aneurysms. The 320 Slice CTA is a good method to diagnose aneurysms and is of the advantages including rapidness, noninvasive imaging and high accuracy. CTA are assistant tools for DSA in inspecting intracranial aneurysms. And the re-examination after the surgery still should be the first choice for screening in the patient with aneurysm. And 320 slice CTA is obviously superior to 64 slice CTA, 320-Slice CTA still cannot replace DSA and 3D RA because it may miss very small aneurysm.

The Multi-domain Seismic Reflection Travel Time Picking Method and Software Design

MA Fei, ZHANG Jian-zhong, ZHAO Tie-hu, SUN Yun-bao

2015, 24(4): 503-515. doi: 10.15953/j.1004-4140.2015.24.04.04

Abstract(606) PDF(1)

Abstract:
Seismic reflection travel time picking is the primary part of reflection travel time tomography. In this paper, we propose a reflection travel time picking method based on multi-domain human-computer interaction, which includes common shot point domain, common receiver point domain, common middle point domain, and common offset domain. By analyzing various characteristics of the seismic data in different domains, we choose to pick reflection travel time in the different domain. In the human-computer interaction environment, the combination of interpreter and computer can help to improve accuracy and efficiency of the picking. Using Qt programming language, we have realized multi-domain display and travel time picking software for seismic data. Both results from synthetic and the field seismic data indicate that the software is flexible and easy to operate, and good results of travel time picking can still be achieved for seismic data acquired in complex areas.

Instantaneous Energy Anomaly Attribute Based on Match Pursuit and its Application in Hydrocarbon Detection of Albertine Graben

ZHANG Shi-xin, DU Xiang-dong, HAN Wen-ming, DUAN Jun, SUN Lin-jie

2015, 24(4): 517-524. doi: 10.15953/j.1004-4140.2015.24.04.05

Abstract(791) PDF(1)

Abstract:
Albertine Graben is one of the hot regain of oil and gas exploration in the world, with the geological features of shallow layer, rapid evolution, and new formation. Cenozoic layer is the primary target, where un-consolidated sandstone is the reservoir type with quite different reservoir parameters. On the effect of porosity and pore-filled fluid, the seismic reflection response of hydrocarbon bearing reservoir has no rules. It is difficult to make hydrocarbon detection in Albertine Graben. The match pursuit algorithm is used to raise the time-frequency resolution in the seismic instantaneous spectral decomposition. With the help of energy absorption analysis method, the instantaneous energy anomaly attribute is proposed based on match pursuit. W oilfield is taken for example in Albertine Graben; we found the rule of hydrocarbon bearing reservoir with low-frequency energy raised and high-frequency energy attenuated. We made hydrocarbon prediction using the instantaneous energy anomaly attribute, which was verified by the drilled well.

SE Obtained Utilizing SNMR Transverse Relaxation Time Methods

YU Lei, LI Zhen-yu, CHEN Shi-yang, HU Wen-guang

2015, 24(4): 525-532. doi: 10.15953/j.1004-4140.2015.24.04.06

Abstract(619) PDF(1)

Abstract:
Spin-echo is an important impulse series of T₂ time measuring which does not affect by magnetic field inhomogeneity when alternating magnetic field boosts signals. The earth magnetic field is relatively stable and this could reduce the influence to NMR signal from earth magnetic field, so we could obtain a real T₂ value and improve the SNR. This is the first time apply spin-echo signal method to the surface nuclear magnetic resonance to calculating T₂ distribution, The article referenced NMR logging multi Index Inversion, utilized singular value decomposition algorithm programming, obtained T₂ distribution and contrast with the results of SNMR inversion software of T₂^*. The research shows that use SE signal to extract T₂ time could reduce the influence of earth magnetic field inhomogeneity to NMR signal, reflect the T₂ distribution more realistically and improve SNR.

Fast-correction of Rotating Center Offset with Part Views Sinogram in 2D CT

LI Zeng-yun, LÜ Dong-hui

2015, 24(4): 533-543. doi: 10.15953/j.1004-4140.2015.24.04.07

Abstract(684) PDF(4)

Abstract:
The existing CT reconstruction algorithms depend on the precise position of the center of rotation. Without the accurate positioning, artifacts will be introduced into the reconstructed image. Sinograms with 180° or 360° views are used to estimate the rotation center. These projection require a long scan time and more computing resources. In this paper, we propose two methods for correcting the rotation center offset of parallel-beam scan and fan-beam scan, both of which only use part views of the projection data. In parallel beam scan, we use the theorem relating to the mass center of the object space and the projection space, to accurately measure the location of the rotation center in the sinogram from the 60° view. In fan beam scan, we realign the fan projection to the parallel projection, rotation center can still be measured accurately in the sonogram from the fan angle plus 60° view.

Application of Image Enhancement in X-ray Medical Image

CAO Yan, CHEN Wei

2015, 24(4): 545-551. doi: 10.15953/j.1004-4140.2015.24.04.08

Abstract(683) PDF(4)

Abstract:
Objective: To Enhance the X-ray image. Method: Apply multiple complementary method on image enhancement. First of all, using the Laplacian method to highlight image details, and then using the gradient method projecting edge. Then using the smoothed gradient image masks Laplacian image, through the high increase filter obtains sharpen image. And then, the dynamic gray level range of the image sharpening is increased by the gray level transformation. Finally, comparing the results of traditional algorithm with the algorithm proposed in this paper. The algorithm proposed in this paper enhanced the X-ray medical image significantly, has the great advantage compared to the traditional algorithm. The detail of the enhanced image is clearer, the implementation effect is better than any kind traditional algorithm. Conclusion: The algorithm proposed in this paper has certain theoretical and practical applied value on X-ray medical image.

A CT Number Conversion Method of Cone Beam CT

CHEN Yun-bin, WANG Yuan, LIU Qing-hua

2015, 24(4): 553-561. doi: 10.15953/j.1004-4140.2015.24.04.09

Abstract(851) PDF(7)

Abstract:
As a necessary composition of medical CT image, in some cases, CT number has been an aid when doctors diagnose diseases, such as measurement of bone density, image segmentation and recognition. This paper described a CT number conversion method of cone beam CT. On the base of Sedentex CT phantom, standard CT numbers and reconstructed attenuation coefficients of five analyzed materials were obtained respectively. The conversion equation between CT number and reconstructed attenuation coefficient was established by linear fitting. After CT number transformation, the numerical changes of contrast to noise ratio and uniform deviation were analyzed in the end.

The CT and MRI Features of Hepatic Epithelioid Hemangioendothelioma with the Correlation of Pathology

ZHAO Yue, LONG Shi-liang, TIAN Zhi-nan, DENG Ying-ying, LIU Duan-cai, ZHENG Qi-wen, YANG Chun-yu, SHEN Bi-xian

2015, 24(4): 563-569. doi: 10.15953/j.1004-4140.2015.24.04.10

Abstract(628) PDF(1)

Abstract:
Purpose: To analyze the CT and MRI features of hepatic epithelioid hemangioendothelioma(HEHE) with the correlation of pathology. Materials and Methords: CT and MRI data of ten cases with HEHE comfirmed by surgery and pathology were retrospectively analyzed. Results the lesions of six cases were multiple and mostly located adjacent to the hepatic capsule, the "capsular retraction" sign was found in eight cases, the "halo" sign was found in six cases, the "lollipop" sign was found in two cases, the "tumor vessel"sign was found in eight cases. After contrast administration, mild to moderate peripheral enhancement was assessed in arterial phase, and progressive enhancement in portal venous phase and delay phase in eight cases, mild peripheral enhancement was assessed in arterial phase, but no significant alteration in portal venous phase and delay phase in two cases. Conclusion: multiple nodules under liver capsule, the capsular retraction sign, the halo sign, the lollipop sign and the tumor vessel sign were characteristic imaging features of HEHE, the lollipop sign and the tumor vessel sign have specificity in the diagnosis and differential diagnosis.

Analysis of the Imaging of Carpal Dislocations and Fracture-dislocations

LI Ming-qiu, CHEN Xing-ming, FANG Ting-song, YIN Ling, PENG Guo-yi

2015, 24(4): 571-579. doi: 10.15953/j.1004-4140.2015.24.04.11

Abstract(678) PDF(3)

Abstract:
Objective: To analyze the imaging manifestations of carpal dislocations and fracture-dislocations, to discuss the propagation of forces in wrist. Methods: 129 cases of carpal dislocation underwent the X-ray plain films and the MSCT, analysis of carpal dislocation or fracture-dislocation type. Results: 32 cases of lunate dislocation, 2 cases of central carpal dislocations, 95 cases of perilunate fracture-dislocations: 50 cases of transscaphoid perilunate dislocation, 23 cases of transradial styloid perilunate dislocation, 4 cases of transcapitate perilunate dislocation, 7 cases of transtriquetrum perilunate dislocation,11 cases of transulnar styloid perilunate dislocation. The diagnosis of transscaphoid and transradial styloid were correctly detected on X-ray plain film, the remaining 56 cases with fracture of other carpal bones which X-ray missed 6 cases were usually detected on MSCT and reconstruct technology at last. The pure perilunate dislocation is poor(only 3 cases), there were 5 cases of X-ray diagnosis of pure perilunate dislocation which tiny fracture can be found in MSCT. Conclusion: X-ray plain film may underestimates the full extent of the original injury,accurate and intuitive diagnosis can be made by MSCT. To analyze the propagation of forces in carpal dislocations and fracture-dislocations has an important value for imaging diagnosis.

The Application of MRI in the Diagnosis of Cervical Cancer

WU Hui-qin, QIAN Chun-mei

2015, 24(4): 581-586. doi: 10.15953/j.1004-4140.2015.24.04.12

Abstract(673) PDF(1)

Abstract:
Objective: To analyze the MRI performance of large sample cases of cervical patients and explore different histological types and classification of cervical tumor by MRI performance characteristics and their corresponding pathological histology and then evaluate the value of MRI in diagnose of cervical benign and malignant lesions. Methods: We randomly selected 620 cases of cervical cancer patients that were pathology confirmed and received surgery in our hospital, accounted for 655 lesions. All cases were performed MR scan, dynamic enhance, diffusion weighted imaging in order to explore the distribution of cervical malignant and benign lesions; Analyzed the diagnostic sensitivity and specificity of MR on invasive and non-invasive cervical cancer and made comparisons between contrast-enhanced ultrasonography and MRI in the diagnosis of tumor size infiltration depth Near the palace infiltration, lymph node metastasis and clinical staging accuracy. Results: There can be found 405 malignant cervical lesions and 250 benign cervical lesions. The benign lesions were in a diameter of 1.50 cm, malignant lesions were in a diameter of 2.32 cm; the benign lesions were in the median age of 40.42 years old and the malignant lesions were in the median age of 46.57 years old; The cervical MR effectiveness for the diagnosis of invasive cervical cancer(sensitivity and specificity) was higher than non-invasive cervical cancer(P<0.05); The accuracy of MRI in the diagnosis of palace next to the infiltration was 92.3%, the accuracy of MRI in the diagnosis of lymph node metastasis was 93.4%, the accuracy of MRI in the diagnosis of clinical stage was 95.2%, the accuracy of MRI were higher than ultrasound imaging accuracy(P<0.05). Conclusions: The MRI effectiveness for the diagnosis of invasive cervical cancer(sensitivity and specificity) was higher than non-invasive cervical cancer(P<0.05); the accuracy of MRI in the diagnosis of palace next to the infiltration, lymph node metastasis and clinical stage were higher than ultrasound imaging accuracy(P<0.05). Studies have shown that MRI played an important role in cervical cancer diagnosis, skilled and improvement of MRI techniques could improve the correct rate of diagnosing of cervical cancer.

Signature Analysis of Dynamic Enhanced CT for Gastrointestinal Carcinoid

CUI Run-he, LIU Hui, ZHAO Lei

2015, 24(4): 587-594. doi: 10.15953/j.1004-4140.2015.24.04.13

Abstract(613) PDF(2)

Abstract:
Objective: To characterize the imaging findings of dynamic enhanced CT for gastrointestinal carcinoid, in order to improve the diognosis. Method: 11 patients with gastrointestinal carcinoid were retrospectively analyzed. The pathological changes of the cavity wall thickness, margin, morphology, adjacent structure, density and dynamic enhanced CT feature on three phases image were to evaluate. The ROC curve was used for finding prognostic factor of metastasis. Result: The attenuation of lesions in the plain scan was(33.54 ± 6.96)HU(range 26 - 48 HU),(62.72 ± 19.35)HU(range 33 - 87 HU) in the arterial phase, 56 - 100 HU(range 56 - 100 HU) in the venous phase,(60.09 ± 12.69)HU(range 43 - 78 HU) in the lag period. The lesions slowly enhanced, the density was to the peak in portal vein phase. The lesions density in delay phase was to lower, forming a plateau. Lesions in the cavity wall thickness had certain value in predicting carcinoid tumor distant metastasis(AUC = 0.917, P<0.05). Conclusion: Dynamic enhanced CT had clinical application value in diagnosis of gastrointestinal carcinoid.

The Imaging Findings of Primary Chondrosarcoma of Ribs

MU Hua-guo, SANG Ling, WU De-hong, WEI Wan-qing, FU Chuan-ming, CHEN Lun-gang, CHEN Ping-you

2015, 24(4): 595-602. doi: 10.15953/j.1004-4140.2015.24.04.14

Abstract(666) PDF(2)

Abstract:
Objective: To explore the imaging characteristics of primary chondrosarcoma of ribs. Methods: Collected pathologically confirmed 12 cases of primary chondrosarcoma of ribs, retrospectively analyzed the X-ray, CT and MRI. Results: 12 cases of primary chondrosarcoma of ribs with 6 cases of male and female 6 cases. 12 cases of primary chondrosarcoma of ribs located in Costa rib cartilage junction 7 cases, rib bones is located near thoracic vertebra in 4 cases, rib axillary segment in 1 cases, X-ray examination showed for the realm of clear/uniform density of breast lumps(left side in 7 cases and 5 cases of right) and adjacent rib bone structure fuzzy variable. CT scan lesions were osteolytic and expansive bone destruction, local soft tissue mass with clear edge accompanied by the strip, nodular and annular calcification, enhanced CT scan which the lesions(11 cases) no obvious enhancement, adjacent vertebral body and appendix performance for bone erosion damage. 10 cases of primary chondrosarcoma of ribs received MRI examination, Lesions showed as clear boundary long T1 and long T2 mixed signal mass, which enhanced orbicular heterogeneous enhancement. Conclusion: Calcification is the characteristic of primary chondrosarcoma of ribs, boundary clear mass lesion is vital signs, ring strengthen for their enhanced CT/MRI performance characteristics, perfect imaging examination can significantly improve the accuracy of diagnosis and guide the clinical surgery.

The Application Value of 3D CE-MRA in Diagnosis on Lower Extremity Atherosclerosis Disease

HUANG Yao-bin, LIANG Zong-hui

2015, 24(4): 603-610. doi: 10.15953/j.1004-4140.2015.24.04.15

Abstract(664) PDF(1)

Abstract:
Objective: To investigate the application value of 3D CE-MRA in diagnosis of atherosclerosis occlusive disease of lower extremity. Methods: 64 patients which were diagnosed as LEASD by clinic underwent both 3D CE-MRA and DSA examination of bilateral arteries of lower extremity, and were analyzed if there were any difference between the results. Results: Taken DSA as the golden standard, the detection rate and grade of 3D CE-MRA in lower extremity artery stenosis and occlusion was compared with DSA. The value of Kappa 0.84 ≥ 0.75 and showed a good consistency with no statistical significance(P>0.05). However, diagnosis of 3D CE-MRA in lower extremity artery stenosis and occlusion had over-estimation and under-estimation to some extent. The rate of over-estimation for slight stenosis, moderate stenosis, sever stenosis were respectively 3.3%(11/332), 4.0%(5/125), 4.5%(5/112). The rate of under-estimation for moderate stenosis, sever stenosis, occlusion were respectively 9.6%(12/125), 4.0%(5/112), 15%(20/132). Taken DSA as the standard, the sensitivity, specificity and positive predictive value and negative predictive value of 3D CE-MRA in lower extremity artery stenosis and occlusion were 93.7%(701/753), 93.1%(563/605), 95.1%(701/737), 94.9%(563/599). Conclusion: 3D CE-MRA of lower extremity artery is a nontraumatic, nonradioactive and effective vascular examination. It could be the optimizing examination for LEASD.

CT and MRI Manifestations of Autoimmune Pancreatitis

WU De-hong, CHEN Shao-bo, MU Hua-guo, GONG Xiao-hong, FU Chuan-ming, CHEN Wen

2015, 24(4): 611-619. doi: 10.15953/j.1004-4140.2015.24.04.16

Abstract(620) PDF(1)

Abstract:
Objective: To explore the CT and MRI manifestation features of Autoimmune pancreatitis(AIP), deepen the understanding to this rare disease, and improve the diagnosis level of AIP. Methods: The CT and MRI imaging data of 11 cases confirmed as AIP by operation and clinic were retrospectively analyzed, summarize the imaging features. All the 11 cases took CT examination, including 7 cases of MRI examination at the same time. Results: 7 cases of AIP were characterized by diffuse enlargement in pancreas, and the other 4 cases localized enlargement. Diseased pancreas appeared isodensity and low density on CT scanning. The signal intensity of pancreas on T1 WI was lower, and slight elevated on T2 WI. The enhancement decreased during enhanced scanning in arterial phase, and the enhancement became progressive and evenly in portal venous phase and delayed phase. Capsular ring can be seen in six cases on MRI, and 4 cases of capsular ring showed on CT, CT cannot display stenosis of the pancreatic duct. 4 cases of stenosis showed on MRCP. The manifestations of related organs and tissues outside the pancreas are mainly presented as follows: bile duct wall thickening and luminal stenosis in 5 cases, splenic vessels embedding became thinner in 4 cases, renal involvement in 3 cases, and retroperitoneal lymph node enlargement in 6 cases. The fibrosis around mesenteric blood vessels in 1 case and retroperitoneal fibrosis in 1 case after treatment with steroids, imaging review showed that internal and external pancreatic lesions both have different degree of improvement. Conclusion: The internal and external CT and MRI manifestation of AIP presents some specific characteristics. With its imaging manifestation in combination with effective steroid hormone therapy, correct diagnosis can be made, and unnecessary surgical treatment for patients can be avoided.

The Application of Combination of Transthoracic Echocardiography and 64-slice Spiral CT Angicardiography in Diagnosis on Tetralogy of Fallot

GAO Wei-hua, ZHAO Li, CAI Qin, WANG Yang, MOU Jian-jun

2015, 24(4): 621-628. doi: 10.15953/j.1004-4140.2015.24.04.17

Abstract(602) PDF(1)

Abstract:
Objective: To compare the diagnostic accuracy in pulmonary stenosis, the main pulmonary artery, left, right pulmonary artery, the right ventricular outflow tract inner diameter and pulmonary vascular development situation between Transthoracic Echocardiography(ECG) and the combination of Transthoracic Echocardiography and 64-slice Spiral CT Angicardiography(ACG), analyze the closely correlation between ECG and 64-slice Spiral CT ACG in left and right heart chamber indexes by correlation analysis so that we can illustrate the important value in the application of the combination of ECG and 64-slice Spiral CT ACG in TOF diagnosis accuracy. Methods: ECG and ECG combined with 64-slice Spiral CT ACG were used to diagnose the pulmonary stenosis area and evaluate pulmonary vascular development situation, and then made comparison with the actual diagnosis after surgery; ECG and ECG combined with 64-slice Spiral CT ACG were used to measure the main pulmonary artery, left, right pulmonary artery and the right ventricular outflow tract inner diameter, and then made comparison with the actual diagnosis after surgery; Correlation analysis was used to analyze the correlation between ECG and 64-slice Spiral CT ACG in left and right heart chamber indexes. Results: The diagnostic accuracy in pulmonary stenosis in ECG combined with 64-slice Spiral CT ACG group was 91.5%, which was higher than ECG group's 68.1%(P<0.05); There were no significant differences in Me Goon index, Nakata index, the main pulmonary artery, left, right pulmonary artery, the right ventricular outflow tract inner diameter between ECG combined with 64-slice Spiral CT ACG group and actual diagnosis after surgery group(P>0.05); There was closely correlation between ECG and 64-slice Spiral CT ACG in left and right heart chamber indexes by correlation analysis(r>0.7, P<0.05). Conclusions: There was closely correlation between ECG and 64-slice Spiral CT ACG in diagnosis of TOF, the diagnostic accuracy of TOF is higher in ECG combined with 64-slice Spiral CT ACG group than the ECG group which provides a new train of thought in tetralogy of TOF.

Proposals of Revise on the Current National Standards of Industrial Computed Tomography

ZHANG Chao-zong, XIAO Yong-shun

2015, 24(4): 629-635. doi: 10.15953/j.1004-4140.2015.24.04.18

Abstract(625) PDF(4)

Abstract:
Since 2012 a set of National Standards on Industrial Computed Tomography has been issued in China. Although they have taken some active effect, a lot of obvious deficiency is exposed. In this paper some proposals of revise about definition of technical terms, testing condition of spatial resolution, contrast resolution, low-contrast spatial resolution, study of testing using disk phantom, measure of transmission to scattering ratio etc. are presented.

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2015 Vol. 24, No. 4