Imaging volumes during COVID-19: A Victorian health service experience.

BACKGROUND: The World Health Organisation declared the coronavirus disease 2019 (COVID-19) a pandemic on March 11, 2020. While globally, the relative caseload has been high, Australia's has been relatively low. During the pandemic, radiology services have seen significant changes in workflow across modalities and a reduction in imaging volumes. AIM: To investigate differences in modality imaging volumes during the COVID-19 pandemic across a large Victorian public health network. METHODS: A retrospective analysis from January 2019 to December 2020 compared imaging volumes across two periods corresponding to the pandemic's first and second waves. Weekly volumes across patient class, modality and mobile imaging were summed for periods: wave 1 (weeks 11 to 16 for 2019; weeks 63 to 68 for 2020) and wave 2 (weeks 28 to 43 for 2019; weeks 80 to 95 for 2020). Microsoft Power Business Intelligence linked to the radiology information system was used to mine all completed examinations. RESULTS: Summed weekly data during the pandemic's first wave showed the greatest decrease of 29.8% in adult outpatient imaging volumes and 46.3% in paediatric emergency department imaging volumes. Adult nuclear medicine demonstrated the greatest decrease of 37.1% for the same period. Paediatric nuclear medicine showed the greatest decrease of 47.8%, with angiography increasing by 50%. The pandemic's second wave demonstrated the greatest decrease of 23.5% in adult outpatient imaging volumes, with an increase of 18.2% in inpatient imaging volumes. The greatest decrease was 28.5% in paediatric emergency department imaging volumes. Nuclear medicine showed the greatest decrease of 37.1% for the same period. Paediatric nuclear medicine showed the greatest decrease of 36.7%. Mobile imaging utilisation increased between 57.8% and 135.1% during the first and second waves. A strong correlation was observed between mobile and non-mobile imaging in the emergency setting (Spearman's correlation coefficient = -0.743, P = 0.000). No correlation was observed in the inpatient setting (Spearman's correlation coefficient = -0.059, P = 0.554). CONCLUSION: Nuclear medicine was most impacted, while computed tomography and angiography were the least affected by the pandemic. The impact was less during the pandemic's second wave. Mobile imaging shows continuous growth during both waves.

Efficacy of model-based iterative reconstruction technique in non-enhanced CT of the renal tracts for ureteric calculi.

The purpose of this study was to assess the efficacy of model-based iterative reconstruction (MBIR), statistical iterative reconstruction (SIR), and filtered back projection (FBP) image reconstruction algorithms in the delineation of ureters and overall image quality on non-enhanced computed tomography of the renal tracts (NECT-KUB). This was a prospective study of 40 adult patients who underwent NECT-KUB for investigation of ureteric colic. Images were reconstructed using FBP, SIR, and MBIR techniques and individually and randomly assessed by two blinded radiologists. Parameters measured were overall image quality, presence of ureteric calculus, presence of hydronephrosis or hydroureters, image quality of each ureteric segment, total length of ureters unable to be visualized, attenuation values of image noise, and retroperitoneal fat content for each patient. There were no diagnostic discrepancies between image reconstruction modalities for urolithiasis. Overall image qualities and for each ureteric segment were superior using MBIR (67.5 % rated as 'Good to Excellent' vs. 25 % in SIR and 2.5 % in FBP). The lengths of non-visualized ureteric segments were shortest using MBIR (55.0 % measured 'less than 5 cm' vs. ASIR 33.8 % and FBP 10 %). MBIR was able to reduce overall image noise by up to 49.36 % over SIR and 71.02 % over FBP. MBIR technique improves overall image quality and visualization of ureters over FBP and SIR.

Orthopaedic and non-orthopaedic applications of a single-energy iterative metal artefact reduction technique and other metal artefact reduction techniques explained.

Metal within the CT field of view causes artefact that degrades the diagnostic quality of the processed images. This is related to the high atomic number of most metals and is due to a combination of beam hardening, scatter, edge effects and photon starvation. Both software and hardware metal artefact reduction (MAR) techniques have been developed. Iterative reconstruction software MAR techniques can be applied on raw CT data sets and show improved image quality in the setting of sparse projection data when compared with filtered back-projection methods. Recently, a novel single-energy iterative metal artefact reduction technique (IMART) was released for use with large orthopaedic devices. The aim of this pictorial essay was to demonstrate the usefulness of IMART in the setting of both orthopaedic and non-orthopaedic metallic objects and devices.

Liver detection algorithm: its efficacy for CT noise reduction in the liver.

OBJECTIVES: This study was performed to evaluate the efficacy of a novel computed tomography (CT) liver detection algorithm (LDA), which allows for targeted increase of radiation dose to the upper abdomen, on image quality of the liver. METHODS: We retrospectively evaluated the LDA by comparing 40 consecutive patients who had portal venous CT abdomen performed without use of the algorithm, to 40 patients in whom the algorithm was used. Image quality was assessed objectively by comparing the standard deviation (SD) of attenuation values in Hounsfield units (HU) of the abdominal organs. Qualitative analysis was performed by two blinded radiologists who independently graded the image quality of abdominal organs RESULTS: There was significant noise reduction in the liver (P < 0.001) and spleen (P < 0.001) in the LDA group compared to the conventional group. There was also a significant improvement in image quality of the liver (P < 0.001), kidney (P < 0.001), spleen (P < 0.001), pancreas (P < 0.001), and psoas (P = 0.005) in the LDA group compared to the conventional group. Overall dose between the two groups was similar. CONCLUSIONS: This liver detection algorithm improves the subjective image quality of upper abdominal organs, in particular the liver, without increasing overall radiation dose.

Efficacy of 'fine' focal spot imaging in CT abdominal angiography.

OBJECTIVES: To assess the efficacy of fine focal spot imaging in calcification beam-hardening artefact reduction and vessel clarity on CT abdominal angiography (CTAA). METHODS: Adult patients of any age and gender who presented for CTAA were included. Thirty-nine patients were examined with a standard focal spot size (SFSS) of 1 × 1 mm in the first 3 months while 31 consecutive patients were examined with a fine focal spot size (FFSS) of 1 × 0.5 mm in the following 3 months. Vessel clarity and calcification beam-hardening artefacts of the abdominal aorta, celiac axis, superior mesenteric artery, inferior mesenteric artery, renal arteries, and iliac arteries were assessed using a 5-point grading scale by two blinded radiologists randomly. RESULTS: Cohen's Kappa test indicated that on average, there was substantial agreement among reviewers for vessel wall clarity and calcification artefact grading. Mann-Whitney test showed that there was a significant difference between the two groups, with FFSS performing significantly better for vessel clarity (U, 6481.50; p < 0.001; r, 0.73) and calcification artefact reduction (U, 1916; p < 0.001; r, 0.77). CONCLUSION: Fine focus CT angiography produces images with better vessel wall clarity and less vessel calcification beam-hardening artefact. KEY POINTS: Focal spot size affects the spatial resolution of a CT system. Fine focus CTAA produces images with improved vessel wall clarity. Fine focus CTAA is associated with fewer calcification beam-hardening artefacts. Fine focus CTAA may improve accuracy in assessment of luminal stenosis.

Effects of electrocardiogram gating on CT pulmonary angiography image quality.

INTRODUCTION: Pulmonary embolism (PE) is the third most common cause of death from cardiovascular disease. Computed-tomographic pulmonary angiography (CTPA) is an accurate and safe test for diagnosing PE. The aim of this retrospective analysis was to evaluate the effects on image quality (IQ) of electrocardiogram (ECG) gating during CTPA. METHODS: Fifty consecutive patients presenting for CTPA were included in the study. A single acquisition was performed, resulting in two reconstructions: one at 75% of the R-R interval and the other without ECG influence. IQ evaluation was undertaken by two radiologists, focusing on respiratory and cardiac motion, image noise, low-contrast resolution, vessel and lung clarity, contrast media opacification and artefacts. Various regions of the lungs and vasculature were evaluated, and IQ scores were statistically compared. RESULTS: For the ECG-tagged reconstructions, IQ was noted to be better overall with regard to vessel clarity (P < 0.05) and cardiac motion (P < 0.05), while lung clarity was better only in the left lower zone (P < 0.05). IQ was better with regard to image noise (P < 0.05) and low-contrast resolution (P < 0.05) in the non-ECG-tagged reconstructions. No statistical IQ difference between the two types of reconstruction was noted with regard to respiratory motion, contrast media opacification or presence of artefacts. CONCLUSION: The two types of reconstruction provide complementary information for evaluating CTPA results.

Efficacy of 'breath holding at ease' during CT pulmonary angiography in the improvement of contrast enhancement in pulmonary arteries.

INTRODUCTION: The aim of this study is to assess whether breath-hold at ease by patients during the CT pulmonary angiography (CTPA) will improve contrast enhancement in pulmonary arteries. METHODS: Retrospective review was conducted on 51 consecutive CTPA studies undertaken in the traditional method of patients taking deep inspiration and breath-hold immediately prior to scanning, and subsequently 75 consecutive CTPA studies with patients breathing-holding at ease immediately prior to and during the scanning. Attenuation values in pulmonary arteries of different anatomical levels in both groups were measured in Hounsfield unit (HU). Results were compared between the two groups. RESULTS: The mean attenuation value in pulmonary arteries including pulmonary trunk, main and proximal pulmonary arteries calculated in HU in the 'deep inspiration and breath-hold' group was 327 HU (95% confidence interval: 315 to 339 HU). The mean attenuation value in pulmonary arteries in the 'breath hold at ease' group was calculated to be 390 HU (95% confidence interval: 381 to 399 HU); that is, an overall 17.95% increase (P-value < 0.0001) in attenuation value in this group. CONCLUSIONS: By asking patients to breath-hold at ease instead of taking deep inspiration and breath hold prior to CTPA scan can effectively improve contrast enhancement in pulmonary arteries, therefore producing a higher-quality CT pulmonary angiography scan.

Radiation dose reduction using a neck detection algorithm for single spiral brain and cervical spine CT acquisition in the trauma setting.

Cervical spine injuries occur in 4-8 % of adults with head trauma. Dual acquisition technique has been traditionally used for the CT scanning of brain and cervical spine. The purpose of this study was to determine the efficacy of radiation dose reduction by using a single acquisition technique that incorporated both anatomical regions with a dedicated neck detection algorithm. Thirty trauma patients for brain and cervical spine CT were included and were scanned with the single acquisition technique. The radiation doses from the single CT acquisition technique with the neck detection algorithm, which allowed appropriate independent dose administration relevant to brain and cervical spine regions, were recorded. Comparison was made both to the doses calculated from the simulation of the traditional dual acquisitions with matching parameters, and to the doses of retrospective dual acquisition legacy technique with the same sample size. The mean simulated dose for the traditional dual acquisition technique was 3.99 mSv, comparable to the average dose of 4.2 mSv from 30 previous patients who had CT of brain and cervical spine as dual acquisitions. The mean dose from the single acquisition technique was 3.35 mSv, resulting in a 16 % overall dose reduction. The images from the single acquisition technique were of excellent diagnostic quality. The new single acquisition CT technique incorporating the neck detection algorithm for brain and cervical spine significantly reduces the overall radiation dose by eliminating the unavoidable overlapping range between 2 anatomical regions which occurs with the traditional dual acquisition technique.

Efficacy of patient questionnaire in predicting renal dysfunction in outpatients older than 60 years of age prior to contrast-enhanced computed tomography.

INTRODUCTION: Contrast-induced nephropathy (CIN), a common iatrogenic cause of acute renal failure, is preventable. Identification of impaired renal function prior to intravenous contrast is important. Questionnaire screening has been useful to negate the need for cumbersome and costly renal function testing on all patients prior to contrast-enhanced CT (CECT). The Royal Australian and New Zealand College of Radiologists guidelines include age older than 60 as a risk marker requiring renal function testing. The aim of this retrospective study is to assess the efficacy of the pre-CT questionnaire in identifying patients with pre-existing renal impairment even in this older than 60 age group. METHODS: All outpatients were given questionnaires containing 11 CIN risk markers prior to CECT. Radiographers documented age, gender, serum creatinine and/or estimated glomerulofiltration rate (eGFR mL/min/1.72 m(2) ) within 3 months of CT. Questionnaires of all patients older than 60 years were collated. The data was tabulated and analyzed. Incomplete questionnaires were excluded. RESULTS: 134/171 (78.4%) patients had eGFR ≥ 60 and 37/171 (21.6%) had eGFR < 60, with 31/171 (18.1%) having eGFR between 30 and 60 and 3/171 (1.8%) having eGFR < 30. 47/171 (27.5%) circled 'no' to all risk markers. Percentage for sensitivity is 81.1% (95% confidence interval (CI) 64.8-92%), for specificity 29.9% (95% CI 22.3-38.4%), for positive predictive value 24.2% (95% CI 17-32.7%) and for negative predictive value 85.1% (95%CI 71.7-93.8%). Kidney disease, anaemia, myeloma and vasculitis seem to be statistically significant risk factors (P < 0.05). All three true-positive patients with eGFR < 30 indicated known kidney disease. Seven false-negative patients had eGFR 30-60, with 4/7 (57.1%) having CIN risk markers in their medical records. CONCLUSION: Questionnaire screening for CIN risk has a high negative predictive value (85.1%) even in patients older than 60 years.