Confronting our mistakes: A comprehensive evaluation of radiographic errors in digital chest radiography among adult population in a public sector hospital

Objective: To find out the various types of radiographic errors in digital chest radiography and their effect on image quality leading to image rejection. Material and Methods: This cross-sectional study was carried out in Radiology department of Pakistan Institute of Medical Sciences for a period of One month, September 2019. The study included 1560 digital Chest X-Rays, reaching the Picture Archive and Communication System (PACS), fulfilling the inclusion criteria. All these X-rays were analyzed by two radiology residents for the presence of radiographic errors in them. The various radiographic errors were then classified as: Positioning error, poor collimation, Artifacts, improper exposure, motion blur and mislabeling. The frequency of each radiographic error was measured along with their implication on image quality resulting in three major image categories: ACCEPT, JUST ACCEPTABLE and REJECT. The SPSS was adopted for inferential statistical analysis. Results: The study included 1013 (64.9%) male patients and 547 (35.1%) female patients. The mean age came out to be 36 +/- 15 years. Out of 1560 X-rays, 964 (61.8 %) had radiographic errors in them while 596 (38.2%) were completely devoid of radiographic errors. Positioning error (44.5 percent) was the most frequently encountered error followed by poor collimation (29.8%), artifacts (14.9%), Improper exposure (8%), motion blur (2.2%) and mislabeling (0.5%). The rejection rate came out to be 16.5 %. The major cause of image rejection was anatomy cutoff, especially the cut-off of cardio phrenic (CP) angle. Conclusion: Positioning errors represent the commonest cause of image rejection in chest radiography. The main identified pitfall was lack of radiographer’s education and training in performing an examination and indicates a need to improve their performance. Key words: Digital Radiography, Chest X ray, Radiographic error, Image reject

Analysis of Non-Idealities on CMOS Passive Mixers

In the current state of the art, WiFi-alike standards require achieving a high Image Rejection Ratio (IRR) while having low power consumption. Thus, quadrature structures based on passive ring mixers offer an attractive and widely used solution, as they can achieve a high IRR while being a passive block. However, it is not easy for the designer to know when a simple quadrature scheme is enough and when they should aim for a double quadrature structure approach, as the latter can improve the performance at the cost of requiring more area and complexity. This study focuses on the IRR, which crucially depends on the symmetry between the I and Q branches. Non-idealities (component mismatches, parasitics, etc.) will degrade the ideal balance by affecting the mixer and/or following/previous stages. This paper analyses the effect of imbalances, providing the constraints for obtaining a 40 dB IRR in the case of a conversion from a one-hundred-megahertz signal to the five-gigahertz range (upconversion) and vice versa (downconversion) for simple and double quadrature schemes. All simulations were carried out with complete device models from 65 nm standard CMOS technology and also a post-layout Monte Carlo analysis was included for mismatch analysis. The final section includes guidelines to help designers choose the most adequate scheme for each case.

Design and Analysis of a Reconfigurable Gilbert Mixer for Software-Defined Radios

A reconfigurable gm-boosted, image-rejected downconversion mixer is presented in this paper using the SiGe 8 HP technology. The proposed mixer operates within 0.9–13.5 GHz that is suitable for software-defined radio applications. The conversion mixer comprises of resistive biased radio frequency (RF) section, double balanced Gilbert cell mixer core sections divided as per I and Q stages for image-rejection purpose, inductively peaked gm-boosting section and tunable filter section, respectively. In comparison to previous works in the scientific literature, the design shows enhanced conversion gain (CG), noise figure (NF), and image-rejection ratio (IRR). For the entire band of operation, the mixer attains a good return loss |S11| of <−10 dB. Additionally, the design accomplishes an excellent CG of 22 dB, NF of 2.5 dB, and an image-rejection ratio of 30.2 dB at maximum frequency. Finally, a third-order intercept point (IP3) of −3.28 dBm and 1 dB compression point (CP1) of −13 dBm, respectively, shows moderate linearity performance.