Real-time Image Quality Research Articles

Use of Imaging Biomarkers for Regulatory Studies

Imaging often plays an important role in pivotal clinical trials of drugs or devices that have been submitted for approval to regulatory agencies that grant approval for the marketing and sale of these products on the basis of documentation of their safety and efficacy. Imaging biomarkers can help substantiate either or both of these characteristics. This article focuses on how to successfully incorporate imaging biomarkers into clinical trials through a process of careful planning and diligent execution. Planning starts with posing and then answering a number of questions that pertain to the product under study. What will the claimed benefit of the product be? Is there a current standard of care that involves imaging, and will that standard of care help in the documentation of safety and efficacy? Are there relevant novel imaging biomarkers? Are there any relevant guidance documents issued by the regulatory agencies? After imaging biomarkers are identified, their role and benefit must be understood. Will they help diagnose subjects? Will they stratify subjects for enrollment? Will they identify those who are more likely to benefit? Will they help document progression of disease and effectiveness of intervention? Execution must occur in close collaboration with regulatory agencies and with the involvement of imaging experts and imaging core laboratories to ensure attention to key components: imaging charter, investigator training and certification, 21 CFR Part 11 (Part 11 of Title 21 of the U.S. Code of Federal Regulations)-compliant data management, real-time incoming image quality control for eligibility reads and investigator feedback, and centralized image analysis for safety and efficacy by certified readers.

Truly Hybrid Interventional MR/X-Ray System: Investigation of in Vivo Applications

Rationale and Objectives The purpose of this study was to provide in vivo demonstrations of the functionality of a truly hybrid interventional x-ray/magnetic resonance (MR) system. Materials and Methods A digital flat-panel x-ray system (1,024 2 array of 200 μm pixels, 30 frames per second) was integrated into an interventional 0.5-T magnet. The hybrid system is capable of MR and x-ray imaging of the same field of view without patient movement. Two intravascular procedures were performed in a 22-kg porcine model: placement of a transjugular intrahepatic portosystemic shunt (TIPS) (x-ray–guided catheterization of the hepatic vein, MR fluoroscopy–guided portal puncture, and x-ray–guided stent placement) and mock chemoembolization (x-ray–guided subselective catheterization of a renal artery branch and MR evaluation of perfused volume). Results The resolution and frame rate of the x-ray fluoroscopy images were sufficient to visualize and place devices, including nitinol guidewires (0.016–0.035-inch diameter) and stents and a 2.3-F catheter. Fifth-order branches of the renal artery could be seen. The quality of both real-time (3.5 frames per second) and standard MR images was not affected by the x-ray system. During MR-guided TIPS placement, the trocar and the portal vein could be easily visualized, allowing successful puncture from hepatic to portal vein. Conclusion Switching back and forth between x-ray and MR imaging modalities without requiring movement of the patient was demonstrated. The integrated nature of the system could be especially beneficial when x-ray and MR image guidance are used iteratively.

Transmission of real‐time fetal ultrasound images using the IP network vs. ISDN lines

Background: Our group has shown that real-time teleultrasound consultation is not only technically feasible, but also offers diagnostic and management modifications in the clinical setting [1,2]. It helps to bridge the health care gap between the city and the country, where access to subspecialists is usually difficult. Majority of telemedicine work around the world is currently performed with ISDN connection, which is still relatively costly, and is limited to larger centers where ISDN access is available. Rapid evolution of technology has enabled Internet technology to be available to most corners of the world, and the cost of using IP networks is rapidly reducing. Purpose: To compare the quality of real-time ultrasound images transmitted via the IP network vs. ISDN lines. Methods: ISDN and/or IP (broadband wireless local multipoint distribution service, AAPT) connections between three Queensland Hospital sites were established. A standard ultrasound videotape containing fetal images from three different trimesters of pregnancy was played to four experienced observers at random using either ISDN or IP connections at various bandwidths. The observers were blinded to the network or bandwidths used, and evaluated the quality of the images with a standard seven-point scoring sheet on 30 fetal anatomic landmarks. Results: A total of 12 evaluations were performed for various combinations of bandwidths and networks. The intra- and interobserver variations were not significant. The most significant variable affecting the mean score was the bandwidth used. The mean score for transmission using IP was about 0.5 points lower than that using ISDN linkage across all the different bandwidths, but the differences did not reach statistical difference (P = 0.06). Conclusion: IP connection is a reasonable alternative to ISDN linkage for real-time teleultrasound transmission. It has enormous potential to expand telemedicine applications to more remote sites at lower cost, and further explorations as to its reliability and limitations should be performed.

VQEG Evaluation of Objective Methods of Video Quality Assessment

This paper briefly discusses objective and subjective methods for video quality assessment by focusing on the current work plan and schedule of the Video Quality Experts Group (VQEG). Subjective assessment methods have been used reliably for many years to evaluate video image quality, yet, some issues arise with subjective assessment including the cost of conducting the evaluations and the fact that these methods cannot easily be used to monitor video image quality in realtime. Traditional analog objective measurements, while still necessary, are not sufficient to measure the quality of digitally compressed video systems. Thus, there is a need to develop new objective methods utilizing the characteristics of the human visual system. While several new objective methods have been developed, there is no internationally standardized method. The VQEG is comprised of experts from various fields and organizations working on the evaluation and standardization of methods for video quality assessment. The first and current task of VQEG is the evaluation of objective model performance against subjective results for video quality in the bit rate range of 768 kbits/sec to 50 Mbits/sec.

The imaging quality of angiodynography in the ilio-femoral tract

The imaging quality of angiodynography (Quantum; Philips) in the ilio-femoral tract was compared with uniplanar angiography. One hundred ilio-femoral tracts were investigated with both translumbar conventional angiography and angiodynography. The ilio-femoral tract was divided into five parts; proximal and distal common iliac, proximal and distal external iliac and common femoral. Stenosis was scored from 0-24, 25-49, 50-74, 75-99 and 100% and the lengths of those of 25% or more were measured in centimeters. Because the thickness of the subcutaneous fat layer decreases the depth range (normally 11.5 cm) of the 5.0 MHz transducer it was also measured in centimetres. The results showed that a significantly larger number of vessels were not seen (especially the common iliac) with an increasing thickness of the subcutaneous fat. The results based on the real-time imaging quality alone of angiodynography showed a reasonable accuracy of 83.9% when detecting stenoses graded from 0-24, 25-49, 50-74, 75-99 up to 100%. The clinically more important discrimination between a haemodynamically important stenosis of more than 50% showed a sensitivity of 88% and specificity of 98% on visual information alone. By integrating the peak velocity measurements to the results, this sensitivity rose to 95% and the specificity became 99%. The correlation in length was within a range of 1 cm in 94% and within 1-2 cm in 6% of the stenoses. In conclusion, angiodynography is a reliable technique for investigating the ilio-femoral tract.

Evaluation of image quality of ultrasound scanners in medical diagnostics.

The evaluation of the properties of ultrasound diagnostic scanners has not yet been standardized. Because the image itself is the basis of diagnostic decisions, it should also be the basis of evaluation of the capabilities of scanners. This study is aimed to help the standardization work by suggesting a procedure for testing the image quality of the scanners. The image quality depends on the tissue resolution, which is difficult to determine without real tissue studies. Therefore, the presented testing procedure consists of two parts: first, lateral and longitudinal resolution, image uniformity, sensitivity, and cyst and tumor imaging are determined by phantom tests; second, imaging experiments of formalin-fixed tissue samples are used to give information on the imaging capability of selected tissue details and boundaries. The procedure has been carried out by an experimental comparative test of 30 scanner and transducer combinations. The role of real tissue tests is important. A reliable whole-body phantom, including liquids flowing in veins, would be a breakthrough in testing real-time image quality.