The purpose of this study is to elucidate the relationship among RR interval (RR), the optimal reconstruction phase, and adequate temporal resolution (TR) to obtain coronary CT angiography images of acceptable quality using 64-MDCT (Aquilion 64) of end-systolic reconstruction in 407 patients with high heart rates. Image quality was classified into 3 groups [rank A (excellent): 161, rank B (acceptable): 207, and rank C (unacceptable): 39 patients]. The optimal absolute phase (OAP) significantly correlated with RR [OAP (ms)=119–0.286RR (ms), r=0.832, p<0.0001], and the optimal relative phase (ORP) also significantly correlated with RR [ORP (%)=62–0.023RR (ms), r=0.656, p<0.0001], and the correlation coefficient of OAP was significantly (p<0.0001) higher than that of ORP. The OAP range (±2SD) in which it is highly possible to get a static image was from [119–0.286RR (ms)–46] to [119–0.286RR (ms)+46]. The TR was significantly different among ranks A (97±22 ms), B (111±31 ms) and C (135±34 ms). The TR significantly correlated with RR in ranks A (TR=–16+0.149RR, r=0.767, p<0.0001), B (TR=–15+0.166RR, r=0.646, p<0.0001), and C (TR=52+0.117RR, r=0.425, p=0.0069). Rank C was distinguished from ranks A or B by linear discriminate analysis (TR=–46+0.21RR), and the discriminate rate was 82.6%. In conclusion, both the OAP and adequate TR depend on RR, and the OAP range (±2SD) can be calculated using the formula [119–0.286RR (ms)–46] to [119–0.286RR (ms)+46], and an adequate TR value would be less than (–46+0.21RR).
To evaluate the detectability of image unsharpness due to a patient's movement, a receiver operating characteristic (ROC) analysis was conducted to compare the diagnostic and preview liquid-crystal displays (LCDs). Phantom images that simulated a patient’s movement were obtained by using a moving metronome and acrylic plates with a computed radiography (CR) system. A total of 104 images were classified into five groups according to the degrees of image unsharpness determined based on the metronome velocity and exposure time. In an ROC observer study (n=6), a 2-megapixel diagnostic monochrome LCD (2M-LCD) and a 1.3-megapixel general color LCD for preview (1.3M-LCD) were compared in terms of the detection of image unsharpness due to the movement. A statistical test was performed using the multi-reader multi-case (MRMC) method. In the results, the average areas under the ROC curve values for the detection of image unsharpness using the 2M-LCD and 1.3M-LCD were 0.952 and 0.850, respectively. The detection of image unsharpness using the 2M-LCD was significantly better than that using the 1.3M-LCD (p<0.05). In addition, some images with slight unsharpness were identified correctly only using the 2M-LCD. The results suggest that the low-resolution LCD (i.e., the 1.3M-LCD for preview) had a limitation in identifying image unsharpness due to the patient's movement. Slight unsharpness could be missed in primary image checks performed on a preview monitor equipped with an imaging system. Therefore, the high-resolution LCD (i.e., a 2M-LCD) is necessary when using radiography for diagnostics.
The purpose of this study is to evaluate the crosstalk effect on spin-echo (SE) images at 1.5 and 3 T MRI. We examined the influence of crosstalk by comparing the full width at half-maximum (FWHM) and slice profile of images of a wedge-shaped phantom for various slice gaps. We also assessed crosstalk effect in the brain by comparing image contrast among healthy volunteers (n=8). Among the subjects, the shapes of the slice profiles at 1.5 T were similar to those at 3 T for long repetition times (TRs); however, at shorter TRs, differences in slice profiles were observed among the subjects and were more apparent at 3 than at 1.5 T. The relative contrast between white matter and gray matter on T1-weighted images was lower at 3 than at 1.5 T. The crosstalk effect was strongest when the TR of the excitation pulse was short. The influence of the adjacent excitation pulse is important in the process of T1 relaxation because T1 values are greater at 3 T. In conclusion, the influence of crosstalk on SE T1-weighted images is greater at 3 than at 1.5 T.
Radiography is used in medical practices based on the principles of justification and optimization. Patients’ exposure doses should be kept as low as still allows for image quality that does not disturb the diagnostic processes. To optimize diagnostic radiological procedures, the international commission on radiological protection (ICRP) advocated the establishment of diagnosis reference levels (DRLs) in the new basic recommendation (Publication 103) in 2007 by stating that “The DRL should be expressed as a readily measurable patient-dose-related quantity for the specified procedure.” In this context, a simple and standardized dosimetric method is needed to verify the adaptability of a radiation dose to the DRLs. As a measuring instrument that has good availability, high accuracy, and easy operability, we adopted the glass badge system, which has been used for individual exposure dose management. We evaluated the accuracy of the system as a tool of simplified dosimetry of diagnostic X-rays by comparing it to the standard dosimetry of an ionization chamber. In an energy range of 50 to 140 kV for X-ray exposure, the glass badge showed values within 7% of or closer to those measured by the standard ionization chamber. Moreover, the glass badge measurement was independent of the rectification modes of the X-ray tubes. In conclusion, glass badge measurement is feasible for verifying diagnostic X-ray doses in relation to DRLs and can be widely used in hospitals and clinics.
A hand hygiene behavior questionnaire and environmental survey were conducted regarding the mobile X-ray system used in the emergency room. As a result, among a total of 22 radiological technologists at this hospital who replied to the questionnaire, 18 wore disposable gloves when performing X-ray imaging using the mobile system. Among those 18, 11 were found to touch computed radiology (CR) consoles and HIS/RIS terminals while still wearing the gloves, thus creating the potential for spreading pathogens to other medical equipment and systems. According to the results of an environmental survey of the emergency imaging preparation room, the highest levels of bacteria were detected on CR consoles and HIS/RIS terminals. A possible reason for this is that these locations are not wiped down and cleaned as a part of routine cleaning and disinfection protocols, thus demonstrating the importance of cleaning and disinfection. Hand hygiene by medical personnel and appropriate cleaning and disinfecting of the working environment are important for preventing the spread of nosocomial infections. Radiological technologists are also required to take effective measures against infections in consideration of the high frequency of contact with both infected patients and patients susceptible to infections.
Color and monochromatic liquid crystal displays (LCDs) were compared in terms of eyestrain by using a new method that uses Landolt rings for a visual perceptional test. In this method, the difference of the nearest distances to distinguish Landolt rings between before and after the usage of LCD monitors was used as the index of eyestrain. When the nearest distance for distinguishing Landolt rings increased, the eyestrain was considered to be severe. A total of 11 observers (2 physicians and 9 radiological technologists) participated to this observer study. In the observer study, the TG18-QC pattern, a standard clinical image of 400 images, and JESRA X-0093 were observed using color and monochromatic LCD monitors for approximately 30 minutes. In addition to the observer study, the noise power spectrum (NPS) of the color and the monochromatic monitors were measured using the NS2002 method. The ratio of the nearest distance after 30 minutes of reading and that of before reading was larger when the color LCD monitor was used than when the monochromatic LCD monitor was used (p<0.05), and thus, the monochromatic LCD monitor was considered to be superior to the color LCD monitor in terms of the degree of eyestrain during image readings. In conclusion, comparing the nearest point for distinguishing Landolt rings measured before and after readings can be used to evaluate eyestrain in diagnostic radiology.