Computed Tomography Urography: Comparison of Image Quality and Radiation Dose between Single- and Split-Bolus Techniques

<p><b>INTRODUCTION</b>In this study, we aimed to compare the split-bolus and single-bolus computerised tomography (CT) urography and determine if this offers a reduction in radiation dose without compromising image quality.</p><p><b>MATERIALS AND METHODS</b>A retrospective evaluation was performed on 88 patients undergoing split-bolus CT urography and this was compared to a control group of 101 consecutive patients undergoing single-bolus CT urography. A radiation dose analysis was performed on each subject. Subjects with urinary bladder lesions, hydronephrosis, renal masses or cysts >3 cm in diameter were excluded. All images were classified according to image quality by 2 consultant radiologists.</p><p><b>RESULTS</b>Opacification of  the renal parenchyma, pelvicalyceal system, proximal ureters and urinary bladder were comparable between the 2 techniques, whilst image quality of the middle and distal third of the ureters was better using the split-bolus technique. The mean dose length product (DLP) for the single-bolus technique was 1324.1 mGy-cm, whilst that of  the split-bolus technique was 885.7 mGy-cm. The mean effective dose reduction was calculated to be 31.1% between the 2 groups.</p><p><b>CONCLUSION</b>The split-bolus technique gives a reduced radiation dose without compromising image quality. The associated reduction in images is beneficial for data storage and reporting efficiency. As such, our department will adopt the split-bolus technique for young, low-risk patients.</p>

Clinics in diagnostic imaging (182). Acute descending aortic dissection with aortic root retrograde extension

A 77-year-old man presented with acute-onset severe chest pain radiating to the back and elevated blood pressure. Multiphasic computed tomography of the aorta revealed an intimal tear in the descending thoracic aorta which extended both retrograde to the aortic root and antegrade to the infra-renal abdominal aorta. The initial impression, that the images showed a Stanford type B aortic dissection, was because the portion of the false lumen that extended beyond the aortic arch remained unopacified even on delayed phases, making it challenging to assess the extent of the dissection flap. Bedside transthoracic echocardiography revealed a pericardial effusion. Cardiac tamponade ensued and the patient passed away shortly after presentation. This case highlights the need for early and accurate imaging assessment of acute aortic dissection, including accurate identification of the site of intimal tear and the extent of the dissection flap.