Assessment of colour Doppler sensitivity of a range of early pregnancy ultrasound systems

Abstract

s from the Irish Association of Physicists in Medicine 6th Annual Scientific Meeting Diagnostic Parallel Session A study of the feasibility and reproducibility of measuring blood perfusion in the kidney using MRI without a contrast agent Andrew J. Fagan, Susie Clarke, James F. Meaney. National Centre for Advanced Medical Imaging (CAMI), St. James’s Hospital/ School of Medicine, Trinity College Dublin Introduction: MRI contrast agents are contra-indicated for patients with impaired renal function, and hence there is considerable interest in developing a non-contrast agent techniquewhich can quantify blood perfusion, for example in transplant patients. Pseudo-continuous arterial spin labelling (pCASL) is a new technique which has recently been recommended for use in cerebral perfusion studies; however, its use in the torso/ abdomen regions is severely compounded by artefacts arising from respiratory motion andmagnetic susceptibility inhomogeneities. This study aimed to optimise and assess the reproducibility of pCASL for renal perfusion. Methodology: 15 healthy controls were scanned using a 3T Philips scanner. A high spatial resolution pCASL sequence was optimised through careful tailoring of all acquisition parameters. 16 label/control image pairs were acquired in all cases, with the labelling plane positioned perpendicular to the aorta above the kidneys, and the image plane orientated coronallyoblique. Breath-hold acquisitions were used tominimise respiratorymotion, and B-spline image registration was performed on all images prior to fitting to the standard pCASL perfusion model. Results: Image SNR of 56 ± 3 was achieved in images with: voxel resolution = 2.5 × 2.5 × 6 mm3, receiver bandwidth = 3037 Hz, label duration = 1500 ms, label delay = 1500 ms. Excellent contrast was achieved between medulla and cortex regions, with measured perfusion values of 293 ± 44 and 139 ± 20ml/100 g/min respectively. Excellent intraand intersession reproducibility was noted. Conclusions: It is possible to perform sensitive and reproducible measurements of blood perfusion in the kidney using the pCASL technique, with a spatial resolution sufficiently high to allow for separation of medulla from cortical regions. How to estimate the dose from a dental CT or CBCT scan Anthony Reynolds. IDT Ireland, Kinsale, Co. Cork Cone beam computed tomography (CBCT) scanners are now widely used in dentistry. Under current legislation, dental practitioners must balance the benefit to the patient against the radiation risk. Calculating exact values of dose (and hence risk) is time-consuming and requires specialist knowledge. Thiswork showsa simplemethodof estimating thedosewith sufficient accuracy for the task at hand. We estimate the effective dose from parameters stored in the DICOM header or displayed on the CT or CBCT screen. Database technology interpolates missing or incomplete data, and database tables can be refined as more information becomes available. Most modern equipment displays the Dose Length Product (DLP) or Dose Area Product (DAP). Published data can be used when machines do not provide this information. Multiplying the DLP (expressed in mGy.cm) by 2 for the maxilla or 3 for the mandible gives a rough estimate of the effective dose in microSieverts, within the context of an adult dental CT or CBCT scan. Results are accurate to within a factor of 2, which is sufficient for decisions regarding patientmanagement. Trade-offs between dose and image quality can be complex, and are not always well understood. Selecting a smaller voxel sizemay improve the resolution, at the expense of greater noise, and operators may compensate by increasing the mAs. The additional patient detriment must be justified on the basis of increased diagnostic information. Providing amethod (however rough) of estimating the dose empowers dental practitioners to make an informed decision. Assessment of colour Doppler sensitivity of a range of early pregnancy ultrasound systems Browne JE a, Cournane S b, Fagan AJ c. a School of Physics & Medical Ultrasound Physics & Technology Group, IEO, FOCAS Institute, Dublin Institute of Technology; b Medical Physics and Bioengineering, St James’s Hospital, Ireland; c Centre for Advanced Medical Imaging, St James’s Hospital & Trinity College