Introduction: High kVp techniques, 15% or 10-kVp rules, are well-known dose reduction methods. Traditionally, the use of high tube potential (i.e. increased kVp) is associated with decreased radiographic contrast and overall image quality. Recent studies suggest contrast and image quality are not heavily reliant on kVp with digital systems. This study aims to assess the effects of the high tube potential technique on clinical radiographic image quality when using digital systems, to validate high kVp as a dose saving technique. Methods: A selection of comparable pelvis and lumbar spine radiographs were collected from the hospital's picture archiving and communication system (PACS), with technical factors recorded. All clinical radiographs were assessed by 5 senior radiographers using a 15-point visual grading analysis (VGA) rubric. Results: For 40 AP pelvis radiographs and 40 lateral lumbar spine radiographs, reduction in the dose area product (DAP) with higher kVp is seen. Average pelvis DAP at 75 kVp = 14.06 mGy.cm 2 ; 85 kVp = 7.47 mGy.cm 2. Average lumbar spine DAP at 80 kVp = 15.76 mGy.cm 2 ; 90 kVp = 14.83 mGy.cm 2. Image quality and contrast scores showed no statistically significant difference between the high and low kVp groups (z = 0.06 and 0.12, respectively). Average pelvis VGA score at 75 kVp = 11.26; 85 kVp = 12.55. Average lumbar spine VGA score at 80 kVp = 9.23; 90 kVp = 10.64. Conclusions: The high tube potential techniques allowed for reduced patient radiation doses whilst showing no degradation of diagnostic image quality in a clinical setting. This study successfully validates the high kVp technique as a useful tool for reducing patient radiation doses whilst maintaining high diagnostic image quality for digital pelvis and lumbar spine radiography.

Introduction: Pre-operative templating using digital radiography is an effective method of planning for total hip arthroplasty (THA) and requires a generalised fixed magnification factor (MF) or external calibration markers (ECM). The effect on image magnification when changing source-to-image distance (SID), object-to-image distance (OID) and different imaging conditions is not well described. This study aims to quantify the range of effects manipulation of radiographic parameters can have on image magnification across different body habitus and imaging conditions. Methods: A simple phantom study was performed. A 25 mm ECM was placed at eight different OID values along the anterior-posterior phantom plane at three different SID values and imaging conditions, and X-rays were obtained. On each radiograph, the ECM was measured using a line calliper tool by three radiographers and recorded. The MF was calculated and recorded. Results: The smallest observed image MF was 1.16, for an 8 cm OID, 120 cm SID with the ECM placed within the central ray and the X-ray detector in bucky underneath the X-ray table. The largest image MF was 1.40 for a 15 cm OID, 100 cm SID with the X-ray detector placed underneath an emergency department imaging trolley. Conclusions: Digital pre-operative templating for THA relies on accurate radiographic positioning and is dependent of the patient body habitus, radiographic parameters and imaging conditions selected by the radiographer. The use of appropriately positioned ECMsplaced medially between the patient's internally rotated legs at the level of the greater trochanter, lowers the potential for magnification inaccuracies.

This paper presents the application of carbon dioxide for CT imaging during an endovascular procedure to help characterise unexpected bilateral common iliac artery stenosis utilising an angio-CT system, confirming its application in interventional radiology while maintaining sterility. A 78 year old male was referred to the Radiology Interventional Suite with left lower limb rest pain. On imaging via digital subtraction angiography and CT utilising both iodinated contrast and carbon-dioxide (CO ), endovascular treatment of bilateral CIA stenosis was performed with good clinical result. The case presented demonstrates the advanced imaging techniques possible in suites that have ready access to angiography and conventional CT. CO CT angiography is optimally performed on combined Angio-CT systems where CT and angiography system are integrated into a single room.

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Purpose: Radiation dose to the heart and lung are a concern in accelerated partial breast irradiation (APBI). This work presents an analysis of the metrics inherent to high dose rate APBI using a brachytherapy source. Method and Materials: Five patients receiving APBI brachytherapy, and 4 patients, who were simulated in both supine and prone position for XRT, were contoured. Dose to the heart and lung were calculated for all potential dwell locations within the contoured breast for a range of potential dwell times. Summary volume and dose metrics were calculated for heart and lung as function of minimum distance (dmin) to the normal structures. The distribution of minimum distances was then compared for the prone and supine patients. Results: Dose metrics such as the D10cc were patient specific and not well suited to parameterization. Volume metrics such as V10Gy tend to have similar behavior and may be characterized as a function of dmin. The characterization provides a measure of the normal tissue dose parameters that are achievable as a function of dmin. While prone position shift the distribution of lung to breast distances towards greater value, the distribution of heart to breast distances is shifted to smaller distances. Conclusion: Characteristic curves of the achievable volume metrics as a function of minimum distance from implant to normal structures are presented. These curves may be helpful in the decision to use APBI brachytherapy based on the location of the cavity. The choice of treatment position affects the distribution of breast tissue, though the effect on distance to heart and lung differs.

IntroductionThe various problems that are managed with circular external fixation (e.g. deformity, complex fractures) also typically require serial plain x-ray imaging.One of the challenges here is that the relatively radio-opaque components of the circular external fixator (e.g. the rings) can obscure the view of the area of interest (e.g. osteotomy site, fracture site).In this presentation we describe how the geometry of the x-ray beam affects the produced image and how we can use knowledge of this to our advantage.Whilst this can be applied to any long bone, we have focused on the tibia, given that it's the most common long bone that is treated by circular external fixation.Materials & MethodsIn the first part of the presentation we describe the known attributes (geometry) of the x-ray beam and postulate what effect it would have when we x-ray a long bone that is surrounded by a circular external fixator.In the second part we demonstrate this in practice using a tibia and a 3 ring circular external fixator. Differing x-ray beam orientations are used to demonstrate both how the geometry of the beam affects the produced image and how we can use this to our advantage to better visualise part of the bone.ResultsThe practical part of the study confirmed the theoretical part.ConclusionsKnowledge of the beam geometry can be used to minimise the obscuring nature of the circular fixator. This technique is simple and can be easily taught to the radiographer. It is a useful adjunct for the limb reconstruction surgeon.

Background:Conventional radiography remains part of the diagnosis of axial spondyloarthritis and determines qualification for biologic disease modifying anti-rheumatic drugs in many countries. The standard anteroposterior radiograph (XR) incompletely images the complex sacroiliac joint with recognised unacceptably low levels of agreement between readers. Digital tomosynthesis (DTS) uses conventional radiographic projections to create a three-dimensional image and is a potential alternative for the initial radiographic detection and grading of sacroiliitis.Objectives:To compare the level of agreement between two radiologists when reporting sacroiliac joint imaging with digital tomosynthesis versus conventional radiography, as well as to compare the diagnostic accuracy of each imaging modality.Methods:229 consecutive patients that had radiography and digital tomosynthesis performed at Footscray Hospital, Melbourne, Australia were included. Two blinded radiologists independently re-reported all images according to the modified New York criteria, or listed an alternative diagnosis. An overall assessment of each image as inflammatory sacroiliitis, normal or non-inflammatory disease was also recorded. Demographic and clinical data were extracted from medical records. Agreement between and within readers was evaluated using kappa (κ) statistic. Diagnostic accuracy was calculated by comparing each reader’s overall assessment against 2 reference standard comparators: most recent rheumatologist diagnosis and fulfillment of ASAS criteria at any time point.Results:The intra-reader agreement of reader 1 was almost perfect for the left, right and overall sacroiliac joint assessments (κ 0.77 - 0.94), with DTS outperforming XR. Reader 2 agreement was mostly moderate (κ 0.39 - 0.69), with DTS and XR better on the left and right sacroiliac joint respectively, but XR having better overall assessment. The inter-reader agreement of DTS for all patients was moderate and better than XR as shown in the Table. When excluding non-spondyloarthritis patients, inter-reader agreement improved (κ 0.50 to 0.58) but there was no significant difference between DTS and XR. Using reader 1, the sensitivity of DTS (64.8 - 66.7%) was better than XR (54.9 - 60.7%) but low, in keeping with what is known about radiographic sacroiliitis and axial spondyloarthritis. The specificity of XR (78.5 – 80.3%) was better than DTS (72.3 – 73.1%). There were no significant differences when fulfillment of modified New York Criteria was used as a reader’s positive test.Table.Inter-rater reliability between the readersAll patients(N=229)*Inflammatory sacroiliitis & normal patients (N=164)**Inflammatory sacroiliitis patients (N=92)**XR Right0.360.520.56DTS Right0.390.500.51XR Left0.340.550.56DTS Left0.420.550.58XR Overall0.40DTS Overall0.45*Non-weighted kappa statistic**Weighted kappa statisticConclusion:DTS demonstrated moderate reliability for assessment of sacroiliitis, marginally better than conventional radiography. Overall levels of agreement for both imaging modalities were however lower than radiography in previous studies, with several possible contributing factors. A prospective study in a selected spondyloarthritis cohort may better determine any benefit of DTS.References:[1]Christiansen AA, Hendricks O, Kuettel D, Horslev-Petersen K, Jurik AG, Nielsen S, et al. Limited Reliability of Radiographic Assessment of Sacroiliac Joints in Patients with Suspected Early Spondyloarthritis. The Journal of rheumatology. 2017;44(1):70-7.[2]van Tubergen A, Heuft-Dorenbosch L, Schulpen G, Landewe R, Wijers R, van der Heijde D, et al. Radiographic assessment of sacroiliitis by radiologists and rheumatologists: does training improve quality? Annals of the rheumatic diseases. 2003;62(6):519-25.Disclosure of Interests:None declared