• Can image enhancement allow radiation dose to be reduced whilst maintaining the perceived diagnostic image quality required for coronary angiography?

      Joshi, A.; Gislason-Lee, Amber J.; Sivananthan, U.M.; Davies, A.G. (2017-03-03)
      Digital image processing used in modern cardiac interventional x-ray systems may have the potential to enhance image quality such that it allows for lower radiation doses. The aim of this research was to quantify the reduction in radiation dose facilitated by image processing alone for percutaneous coronary intervention (PCI) patient angiograms, without reducing the perceived image quality required to confidently make a diagnosis. Incremental amounts of image noise were added to five PCI patient angiograms, simulating the angiogram having been acquired at corresponding lower dose levels (by 10-89% dose reduction). Sixteen observers with relevant background and experience scored the image quality of these angiograms in three states - with no image processing and with two different modern image processing algorithms applied; these algorithms are used on state-of-the-art and previous generation cardiac interventional x-ray systems. Ordinal regression allowing for random effects and the delta method were used to quantify the dose reduction allowed for by the processing algorithms, for equivalent image quality scores. The dose reductions [with 95% confidence interval] from the state-of-the-art and previous generation image processing relative to no processing were 24.9% [18.8- 31.0%] and 15.6% [9.4-21.9%] respectively. The dose reduction enabled by the state-of-the-art image processing relative to previous generation processing was 10.3% [4.4-16.2%]. This demonstrates that statistically significant dose reduction can be facilitated with no loss in perceived image quality using modern image enhancement; the most recent processing algorithm was more effective in preserving image quality at lower doses.
    • Comparing the supine and erect pelvis radiographic examinations: an evaluation of anatomy, image quality and radiation dose

      Flintham, K.; Alzyoud, K.; England, A.; Hogg, P.; Snaith, Beverly (2021-06)
      Objectives: Pelvis radiographs are usually acquired supine despite standing imaging reflecting functional anatomy. We compared supine and erect radiographic examinations for anatomical features, radiation dose and image quality. Methods: 60 patients underwent pelvis radiography in both supine and erect positions at the same examination appointment. Measures of body mass index and sagittal diameter were obtained. Images were evaluated using visual grading analysis and pelvic tilt was compared. Dose–area product values were recorded and inputted into the CalDose_X software to estimate effective dose (ED). The CalDose_X software allowed comparisons using data from the erect and supine sex-specific phantoms (MAX06 & FAX06). Results: Patient sagittal diameter was greater on standing with an average 20.6% increase at the iliac crest (median 30.0, interquartile range [26.0 to 34.0] cm), in comparison to the supine position [24.0 (22.3 to 28.0) cm; p < 0.001]. 57 (95%) patients had posterior pelvic tilt on weight-bearing. Erect image quality was significantly decreased with median image quality scores of 78% (69 to 85) compared to 87% for the supine position [81 to 91] (p < 0.001). In the erect position, the ED was 47% higher [0.17 (0.13 to 0.33) mSv vs 0.12 (0.08 to 0.18) mSv (p < 0.001)], influenced by the increased sagittal diameter. 42 (70%) patients preferred the standing examination. Conclusion: Patient diameter and pelvic tilt were altered on weightbearing. Erect images demonstrated an overall decrease in image quality with a higher radiation dose. Optimal acquisition parameters are required for erect pelvis radiography as the supine technique is not directly transferable.
    • Comprehensive assessment of patient image quality and radiation dose in latest generation cardiac x-ray equipment for percutaneous coronary interventions

      Gislason-Lee, Amber J.; Keeble, C.; Egleston, D.; Bexon, J.; Kenyelics, S.M.; Davies, A.G. (2017)
      This study aimed to determine whether a reduction in radiation dose was found for percutaneous coronary interventional (PCI) patients using a cardiac interventional x-ray system with state-of-the-art image enhancement and x-ray optimization, compared to the current generation x-ray system, and to determine the corresponding impact on clinical image quality. Patient procedure dose area product (DAP) and fluoroscopy duration of 131 PCI patient cases from each x-ray system were compared using a Wilcoxon test on median values. Significant reductions in patient dose (p ≪ 0.001) were found for the new system with no significant change in fluoroscopy duration (p ¼ 0.2); procedure DAP reduced by 64%, fluoroscopy DAP by 51%, and “cine” acquisition DAP by 76%. The image quality of 15 patient angiograms from each x-ray system (30 total) was scored by 75 clinical professionals on a continuous scale for the ability to determine the presence and severity of stenotic lesions; image quality scores were analyzed using a two-sample t -test. Image quality was reduced by 9% (p ≪ 0.01) for the new x-ray system. This demonstrates a substantial reduction in patient dose, from acquisition more than fluoroscopy imaging, with slightly reduced image quality, for the new x-ray system compared to the current generation system.
    • Does the use of additional x-ray beam filtration during cine acquisition reduce clinical image quality and effective dose in cardiac interventional imaging?

      Davies, A.G.; Gislason-Lee, Amber J.; Cowen, A.R.; Kengyelics, S.M.; Lupton, M.; Moore, J.; Sivananthan, M. (2014-12)
      The impact of spectral filtration in digital (‘cine’) acquisition was investigated using a flat panel cardiac interventional X-ray imaging system. A 0.1-mm copper (Cu) and 1.0-mm aluminium (Al) filter added to the standard acquisition mode created the filtered mode for comparison. Image sequences of 35 patients were acquired, a double-blind subjective image quality assessment was completed and dose–area product (DAP) rates were calculated. Entrance surface dose (ESD) and effective dose (E) rates were determined for 20- and 30-cm phantoms. Phantom ESD fell by 28 and 41 % and E by 1 and 0.7 %, for the 20- and 30-cm phantoms, respectively, when using the filtration. Patient DAP rates fell by 43 % with no statistically significant difference in clinical image quality. Adding 0.1-mm Cu and 1.0-mm Al filtration in acquisition substantially reduces patient ESD and DAP, with no significant change in E or clinical image quality.
    • An Evaluation of Image Acquisition Techniques, Radiographic Practice, and Technical Quality in Neonatal Chest Radiography

      Pedersen, C.C.E.; Hardy, Maryann L.; Blankholm, A.D. (2018-09)
      Background Neonatal chest radiography is a frequently performed diagnostic examination, particularly in preterm infants where anatomical and/or biochemical immaturity impacts on respiratory function. However, the quality of neonatal radiographic images has been criticized internationally and a prevailing concern has been that radiographers (radiologic technologists) fail to appreciate the unique nature of neonatal and infant anatomical proportions. The aim of this study was to undertake a retrospective evaluation of neonatal chest radiography image acquisition techniques against key technical criteria. Methods Hundred neonatal chest radiographs, randomly selected from all those acquired in 2014, were retrospectively evaluated. Inclusion criteria for radiographs acquisition were as follows: anterior-posterior supine; within 30 days of birth; and with all preprocessed collimation boundaries visible. Image evaluation was systematically undertaken using an image assessment tool. To test for statistical significance, Student's t-test, χ2 test, and logistic regression were undertaken. Results Only 47% of the radiographs were considered straight in both upper and lower thoraces. The cranial collimation border extended beyond the upper border of the third cervical vertebra in 30% of cases, and the caudal border extended below the lower border of the first lumbar vertebra in 20% of cases, suggesting high possibility of neonatal overirradiation. Upper thorax rotation was significantly associated with head position (χ2 = 10.907; P < .001) as has been stated in many published textbooks internationally, but arm position had no apparent influence on rotation of the upper thorax (χ2 = 5.1260; P = .275). Birth weight was associated with accurate midline centering of central ray (logistic regression; OR = 1.0005; P = .009; CI, 1.00139–1.000957) with greater accuracy observed in images of neonates with higher birth weight. Conclusion This study has highlighted areas for neonatal chest radiography improvement. Importantly, the findings bring into question commonly advocated radiographic techniques relating to arm positioning and assessment of rotation while confirming the importance of other technical factors. These findings begin the work toward developing the evidence base to underpin neonatal chest radiograph acquisition, but further prospective work and multicenter/multinational data comparison are required to confirm the findings.
    • Image quality based x-ray dose control in cardiac imaging

      Davies, A.G.; Kengyelics, S.M.; Gislason-Lee, Amber J. (2015-03)
      An automated closed-loop dose control system balances the radiation dose delivered to patients and the quality of images produced in cardiac x-ray imaging systems. Using computer simulations, this study compared two designs of automatic x-ray dose control in terms of the radiation dose and quality of images produced. The first design, commonly in x-ray systems today, maintained a constant dose rate at the image receptor. The second design maintained a constant image quality in the output images. A computer model represented patients as a polymethylmetacrylate phantom (which has similar x-ray attenuation to soft tissue), containing a detail representative of an artery filled with contrast medium. The model predicted the entrance surface dose to the phantom and contrast to noise ratio of the detail as an index of image quality. Results showed that for the constant dose control system, phantom dose increased substantially with phantom size (x5 increase between 20 cm and 30 cm thick phantom), yet the image quality decreased by 43% for the same thicknesses. For the constant quality control, phantom dose increased at a greater rate with phantom thickness (>x10 increase between 20 cm and 30 cm phantom). Image quality based dose control could tailor the x-ray output to just achieve the quality required, which would reduce dose to patients where the current dose control produces images of too high quality. However, maintaining higher levels of image quality for large patients would result in a significant dose increase over current practice.
    • Impact of body part thickness on AP pelvis radiographic image quality and effective dose

      Alzyoud, K.; Hogg, P.; Snaith, Beverly; Flintham, K.; England, A. (2018-10-03)
      Introduction: Within medical imaging variations in patient size can generate challenges, especially when selecting appropriate acquisition parameters. This experiment sought to evaluate the impact of increasing body part thickness on image quality (IQ) and effective dose (E) and identify optimum exposure parameters. Methods: An anthropomorphic pelvis phantom was imaged with additional layers (1e15 cm) of animal fat as a proxy for increasing body thickness. Acquisitions used the automatic exposure control (AEC), 100 cm source to image distance (SID) and a range of tube potentials (70e110 kVp). IQ was evaluated physically and perceptually. E was estimated using PCXMC software. Results: For all tube potentials, signal to noise ratio (SNR) and contrast to noise ratio (CNR) deceased as body part thickness increased. 70 kVp produced the highest SNR (46.6e22.6); CNR (42.8e17.6). Visual grading showed that the highest IQ scores were achieved using 70 and 75 kVp. As thickness increases, E increased exponentially (r ¼ 0.96; p < 0.001). Correlations were found between visual and physical IQ (SNR r ¼ 0.97, p < 0.001; CNR r ¼ 0.98, p < 0.001). Conclusion: To achieve an optimal IQ across the range of thicknesses, lower kVp settings were most effective. This is at variance with professional practice as there is a tendency for radiographers to increase kVp as thickness increases. Dose reductions were experienced at higher kVp settings and are a valid method for optimisation when imaging larger patients.
    • Impact of latest generation cardiac interventional X-ray equipment on patient image quality and radiation dose for trans-catheter aortic valve implantations

      Gislason-Lee, Amber J.; Keeble, C.; Malkin, C.J.; Egleston, D.; Bexon, J.; Kengyelics, S.M.; Blackman, D.; Davies, A.G. (2016)
      Objectives: This study aimed to determine the impact on radiation dose and image quality of a new cardiac interventional X-ray system for trans-catheter aortic valve implantation (TAVI) patients compared to the previously-used cardiac X-ray system. Methods: Patient dose and image data were retrospectively collected from a Philips AlluraClarity (new) and Siemens Axion Artis (reference) X-ray system. Patient dose area product (DAP) and fluoroscopy duration of 41 patient cases from each X-ray system were compared using a Wilcoxon test. Ten patient aortograms from each X-ray system were scored by 32 observers on a continuous scale to assess the clinical image quality at the given phase of the TAVI procedure. Scores were dichotomised by acceptability and analysed using a Chi-squared test. Results: Significant reductions in patient dose (p<<0.001) were found for the new system with no significant change in fluoroscopy duration (p=0.052); procedure DAP reduced by 55%, fluoroscopy DAP by 48% and “cine” acquisition DAP by 61%. There was no significant difference between image quality scores of the two X-ray systems (p=0.06). Conclusions: The new cardiac X-ray system demonstrated a very significant reduction in patient dose with no loss of clinical image quality. Advances in Knowledge: The huge growth of TAVI may impact on the radiation exposure of cardiac patients and particularly on operators including anaesthetists; cumulative exposure of interventional cardiologists performing high volume TAVI over 30-40 years may be harmful. The Phillips Clarity upgrade including improved image enhancement and optimised X-ray settings significantly reduced radiation without reducing clinically acceptable image quality.