The factors and solutions for affecting the image quality of flat panel detector on modified DR / 中国医学装备

Objective:To discuss the factors for affecting image quality of flat panel detector on modified DR and the solution.Methods: We observed disturbed condition of image on display by changing spatial resolution of flat panel detector, grid and display under a certain exposure condition, and observed improvement condition of image quality by changing exposure condition.Results: The variation of spatial resolution of flat panel detector, grid and display could affect image quality directly in DR. The variation of exposure dose could also affect resolution and contrast of image within limits.Conclusion: When taking radiography by flat panel detector, if the spatial resolution of image sections were close, the image would form wave-shape- stripe disturbance with strong regularity and high distinguishability; if the deviation of spatial frequency was large or be in multiple relationship, there would be no wave-shape- stripe on image, or the disturbance was inconspicuous. At the same time, choosing suitable radiography condition also showed certain effect to improve image quality.

Experimental study of correlation between the focus-to-flat panel detector distance and entrance surface dosed in digital radiography of lumbar spine / 中华放射医学与防护杂志

Objective To investigated the correlation between the focus-to-flat panel detector distance and entrance surface dosed in digital radiography of lumbar spine.Methods The spine phantom used for bone mineral density(BMD) calibration was radiographed at different value of FFD (100 ～ 240 cm with the interval 10 cm,totally 15 times) using 70 kV and 90 kV with the automatic exposure control (AEC) mode without anti-scatter grid.The parameters measured by QUART dido 2100K type X-ray dose meter.So record the value parameters of the tube current (mAs) and entrance surface dose (ESD).The relation curve were counted between FFD,ESD,mAs and Exposure index (EI) use excle.Pearson correlation analysis and related coefficient difference analysis were performed using the SPSS 19.0 software (P ＜0.05 for the statistically significant level).The FFD and ESD values of regression equation were obtained with regression analysis.Results (1) When the tube voltage was 70 kV:FFD and ESD were negative correlation (r =-0.922,P ＜ 0.001),FFD and mAs were positive correlation (r =0.991,P ＜0.001),FFD and EI negative correlation (r =-0.938,P ＜ 0.001).(2) When the tube voltage was 90 kV:FFD and ESDwere negative correlation (r=-0.955,P ＜0.001),FFD and mAs were positive correlation (r=0.994,P ＜0.001),FFD and EI showed no significant correlation (r=-0.523,P＞0.05).(3) Different position correlation coefficient analysis of the difference was not statistically significant difference.(4) The regression analysis results:The regression equation of the lumbar anteriorposterior position FFD and the ESD at 70 kV:y=0.805 x + 319.731 (F=74.175,P ＜0.001).The regression equation of the lumbar lateral position FFD and the ESD at 90 kV:y =3.152 x + 457.613 (F =133.524,P ＜ 0.001).Conclusions The FFD and ESD in the lumbar spine X-ray radiography were relevant and highly negative correlation.It can effectively reduce the radiographic ESD of lumbar spine with the increasing of the FFD.

The application of testing DQE in upgrading of DR based on flat panel detector / 中国医学装备

Objective:To discuss the test methods and the application value of detective quantum efficiency (DQE) in upgrading of DR based on flat panel detector(FPD).Methods:Combining the dose of incident X-rays with the image brought by flat panel detector. According to the international electrotechnical commission IEC 62220-1 standard method, the tungsten imaging,and combined with the relationship between the FPD and incident X-ray air kerma, using DQEPro equipment and software to calculate the result of the three different types of FPD.Results: The experiment proves that the basic performance of flat panel detector is known definitely by testing the DQE. DQE can reflect the quality of imaging performance in different types of flat-panel detector.Conclusion: The upgrading of DR based on flat panel detector and the DQE testing can be a better technical basis for DR measurement performance, then it can be ensure the quality of DR upgraded in diagnostic imaging.

Application value of multifunctional dynamic fiat panel X-ray detector in intravenous pyelography / 中国医师进修杂志

Objective To investigate the application value of multifunctional dynamic flat panel X-ray detector in intravenous pyelography.Methods Total 540 patients with intravenous pyelography were divided into multifunctional dynamic flat panel X-ray detector group (300 cases) and conventional flat panel X-ray detector group (240 cases) by random digits table method.Image quality,radiation dosage and examination time were analyzed and compared between the two groups.Results There was no statistical difference between the two groups in image quality (P ＞ 0.05).The examination time and radiation dosage was (25.5 ± 8.2) min and (12.5 ± 6.8) mAs respectively in multifunctional dynamic flat panel X-ray detector group and (39.2 ± 12.1) min and (23.6 ± 7.6) mAs in conventional flat panel X-ray detector group.The differences had statistical significance (P ＜ 0.01).Conclusions Multifunctional dynamic flat panel X-ray detector in intravenous pyelography can provide lower radiation dose,shorter examination time and higher image quality.It has obvious advantages in urography.

Clinical Application of Wireless Flat-panel Detector in X-ray Photography in the Small Joints of the Limbs / 中国医学影像学杂志

Purpose To compare the wireless flat-panel detector with gadolinium oxide coating in X-ray photography in the small joints of the limbs compared with conventional flat panel detector with cesium iodide coating. Materials and Methods Comparison was randomly performed between gadolinium oxide coated sulfur wireless flat-panel detector and cesium iodide coated conventional flat-panel detector for 80 patients who received routine X-ray photography, and scoring data were applied with statistical analysis. Results There was no significant difference between the scoring data from two film-reading people (P>0.05). The resolution of anatomical structure of small joint of limbs and tube current showed no significant difference for two types of imaging systems (P>0.05). Conclusion Wireless flat panel detector sulfur with gadolinium oxide coatings can obtain satisfactory image quality at a reasonable inspection doses in the X-ray photography of small joint of limbs. The imaging quality and inspection doses are similar to conventional flat panel detector device with cesium iodide coating, but the posture is more convenient.

A comparison between magnetic resonance angiography at 3 teslas (time-of-flight and contrast-enhanced) and flat-panel digital subtraction angiography in the assessment of embolized brain aneurysms

PURPOSE: To compare the time-of-flight and contrast-enhanced- magnetic resonance angiography techniques in a 3 Tesla magnetic resonance unit with digital subtraction angiography with the latest flat-panel technology and 3D reconstruction in the evaluation of embolized cerebral aneurysms. INTRODUCTION: Many embolized aneurysms are subject to a recurrence of intra-aneurismal filling. Traditionally, imaging surveillance of coiled aneurysms has consisted of repeated digital subtraction angiography. However, this method has a small but significant risk of neurological complications, and many authors have advocated the use of noninvasive imaging methods for the surveillance of embolized aneurysms. METHODS: Forty-three aneurysms in 30 patients were studied consecutively between November 2009 and May 2010. Two interventional neuroradiologists rated the time-of-flight-magnetic resonance angiography, the contrast-enhanced-magnetic resonance angiography, and finally the digital subtraction angiography, first independently and then in consensus. The status of aneurysm occlusion was assessed according to the Raymond scale, which indicates the level of recanalization according to degrees: Class 1: excluded aneurysm; Class 2: persistence of a residual neck; Class 3: persistence of a residual aneurysm. The agreement among the analyses was assessed by applying the Kappa statistic. RESULTS: Inter-observer agreement was excellent for both methods (K = 0.93; 95 percent CI: 0.84-1). Inter-technical agreement was almost perfect between time-of-flight-magnetic resonance angiography and digital subtraction angiography (K = 0.98; 95 percent CI: 0.93-1) and between time-of-flight-magnetic resonance angiography and contrast-enhanced-magnetic resonance angiography (K = 0.98; 95 percent CI: 0.93-1). Disagreement occurred in only one case (2.3 percent), which was classified as Class I by time-of-flight-magnetic resonance angiography and Class II by digital subtraction angiography. The agreement between contrast-enhanced-magnetic resonance angiography and digital subtraction angiography was perfect (K = 1; 95 percent CI: 1-1). In three patients, in-stent stenosis was identified by magnetic resonance angiography but not confirmed by digital subtraction angiography. CONCLUSION: Digital subtraction angiography and both 3T magnetic resonance angiography techniques have excellent reproducibility for the assessment of aneurysms embolized exclusively with coils. In those cases also treated with stent remodeling, digital subtraction angiography may still be necessary to confirm eventual parent artery stenosis, as identified by magnetic resonance angiography.

Dual-Energy Subtraction Imaging for Diagnosing Vocal Cord Paralysis with Flat Panel Detector Radiography

OBJECTIVE: To investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography. MATERIALS AND METHODS: For 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using kappa statistics and assessing the area under the receiver operating characteristic curve (AUC). RESULTS: Vocal cord delineation scores by DES (mean, 4.2 +/- 0.4) were significantly higher than those by conventional imaging (mean, 3.3 +/- 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (kappa = 0.60, AUC = 0.909) to that by conventional technique (kappa = 0.18, AUC = 0.852) (p = 0.038). CONCLUSION: Dual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

Characteristics of a new cone beam computed tomography / 대한구강악안면방사선학회지

PURPOSE: To determine the physical properties of a newly developed cone beam computed tomography (CBCT). MATERIALS AND METHODS: We measured and compared the imaging properties for the indirect-type flat panel detector (FPD) of a new CBCT and the single detector array (SDA) of conventional helical CT (CHCT). RESULTS: First, the modulation transfer function (MTF) of the CBCT were superior to those of the CHCT. Second, the noise power spectrum (NPS) of the CBCT were worse than those of the CHCT. Third, detective quantum efficiency (DQE) of the indirect-type CBCT were worse than those of the CHCT at lower spatial frequencies, but were better at higher spatial frequencies. Although the comparison of contrast-to-noise ratio (CNR) was estimated in the limited range of tube current, CNR of CBCT were worse than those of CHCT. CONCLUSION: This study shows that the indirect-type FPD system may be useful as a CBCT detector because of high resolution.

Digital Chest Radiography with an Amorphous Silicon Flat-Panel-Detector Versus a Storage-Phosphor System: Comparison of Soft-Copy Images

PURPOSE: We compared the soft-copy images produced by an amorphous silicon flat-panel-detector system with the images produced by a storage-phosphor radiography system for their ability to visualize anatomic regions of the chest. MATERIALS AND METHODS: Two chest radiologists independently analyzed 234 posteroanterior chest radiographs obtained from 78 patients on high-resolution liquid crystal display monitors (2560x2048x8 bits). In each patient, one radiograph was obtained with a storage-phosphor system, and two radiographs were obtained via amorphous silicon flat-panel-detector radiography with and without spatial frequency filtering. After randomizing the 234 images, the interpreters rated the visibility and radiographic quality of 11 different anatomic regions. Each image was ranked on a five-point scale (1 = not visualized, 2 = poor visualization, 3 = fair visualization, 4 = good visualization, and 5 = excellent visualization). The statistical difference between each system was determined using the Wilcoxon's signed rank test. RESULTS: The visibility of three anatomic regions (hilum, heart border and ribs), as determined by the chest radiologist with 14 years experience (p<0.05) and the visibility of the thoracic spine, as determined by the chest radiologist with 8 years experience (p=0.036), on the amorphous silicon flat-panel-detector radiography prior to spatial frequency filtering were significantly superior to that on the storage-phosphor radiography. The visibility of 11 anatomic regions, as determined by the chest radiologist with 14 years experience (p<0.0001) and the visibility of five anatomic regions (unobscured lung, rib, proximal airway, thoracic spine and overall appearance), as determined by the chest radiologist with 8 years experience (p<0.05), on the amorphous silicon flat-panel-detector radiography after spatial frequency filtering were significantly superior to that on the storage-phosphor radiography. CONCLUSION: The amorphous silicon flat-panel-detector system depicted the anatomic structures on chest radiographs comparably or significantly better as compared to the storage-phosphor system. The superiority of the amorphous silicon flat-panel-detector system compared to the storage-phosphor system was more obvious after performing spatial frequency filtering.

The Effect of Dose Reduction on Image Quality in Digital Radiography Using a Flat-panel Detector: Experimental Study in Rabbits

PURPOSE: To evaluate the effect of dose reduction on image quality in digital radiography using a flat-panel detector. MATERIALS AND METHODS: Digital radiographs of 30 rabbits were obtained at two different dose levels (33.23 µGy for the standard dose group and 20.09 µGy for the reduced dose group). The amorphous selenium-based flat-panel detector system had a panel size of 7x8.5 inches, a matrix of 1280x1536 (pixels?), and a pixel pitch of 138 µm. Four observers evaluated the soft-copy images on a high-resolution video monitor (2560x2048x8 bits) in random order. The observers rated the visibility of 13 different anatomic structures on a 5-point scale, viz. the retrocardiac lung, subdiaphragmatic lung, heart border, diaphragmatic border, proximal airway, unobscured lung, liver border, kidney border, bowel gas, flank stripe, ribs, and vertebrae in the mediastinal and abdominal regions. Statistical significance was determined using Wilcoxon's signed rank test. RESULTS: There was no statistically significant difference in the visibility of the anatomic structures on digital radiography between the standard and reduced dose groups. CONCLUSION: Digital radiography using an amorphous selenium-based flat-panel detector can preserve the image quality, even though the does is reduced to 40% of the standard level.

Quality Assurance of DR System Refitted from Common X-ray Machine / 医疗卫生装备

This paper suggests how to ensure the production quality when the common X-ray machine is refitted to DR system,and describes that a suitable X-ray machine and an aptitude company are necessary to refit DR system.It also introduces some methods on how to refit,inspect and practise in order to ensure the refitted DR system a reliable quality,stable performance and clear image.

To analyze reasons of discarding as useless of ?-Se direct conversion digital flat panel detector / 医疗卫生装备

Objective To analyze the reasons of discarding as useless of ?-Se direct conversion digital flat panel detector (?-Se FPD). Methods (1) E-COM DR-2000CTM chest system, with high frequency X-ray machine made by CPI company of Canada, the X-ray tube made by VARIAN company of America and Direct Ray-1000 ?-Se FPD made by DRC company of America. (2) 50 cases were collected rondomizedly, each had 4 pieces of chest image and were analyzed by two experienced radiologists and two technicians. Results After about 14 months with 30,000 times exposure efficacious, some damage lines and points appeared in the detector. After about 34 months with 70,000 times exposure efficacious, a damage region (area is 6.7in*0.95in ) existed, this reduced the images' quality and at the end the detector was discarded as useless. Conclusion The ?-Se FPD needs maintenance and monitoring working circumstance.