High Contrast Dose Research Articles

An Example of the Application of the Contrast-Dose Diagram to Medical Radiographs

AbstractIn our previous paper, contrast-dose diagram was proposed for evaluating the relationship between radiographic contrast and patient dose. In this paper, the diagram is applied to radiographs of Sella Turcica in which the pituitary gland exists at the centre of skull.Radiographs of Sella Turcica are made, ivith and without an anti-scatter grid, varying irradiation field area. Several observers decided the threshold contrast, whether or not each image needed to be retaken because of its poor contrast. The mAs values needed to make the images which have higher contrast than the threshold disperse in a wide range. By using the contrast-dose diagram, patient dose can be reduced to about 1/3 if narrow fields are available. Exposure conditions can be determined, balancing high image contrast and tow patient dose, if the diagram and the threshold contrast are known.

Update

In the last decade, i.v. contrast media use in magnetic resonance imaging (MRI) of the central nervous system has become well established. Three agents are currently available in the United States: gadopentetate dimeglumine (Magnevist), gadodiamide (Omniscan), and gadoteridol (ProHance). At a dose of 0.1 mmol/kg, for which all three agents are approved, the contrast effect is equivalent. The agents differ on the basis of stability in vivo, osmolality, and charge. A single agent (ProHance) is approved for high-dose administration (0.3 mmol/kg). The basis of this approval is due in part to the high stability of the agent and thus lower potential for toxicity from long-term heavy metal deposition. Clinical experience, combined with new developments in MR technology, continue to expand applications for these agents. Improved detection of metastatic disease to the brain has been demonstrated in multiple clinical trials with high-dose contrast administration. High dose may also play an important role in brain infection and infarction, providing improved recognition of blood-brain barrier disruption and thus disease activity. First-pass studies make possible the evaluation of regional cerebral blood volume with high intrinsic spatial resolution. The availability of new instrumentation, together with the use of high contrast dose, have improved the quality and clinical utility of these studies. Research is ongoing in the development of new agents, both with greater tissue selectivity and improved safety profile. Chelates of dysprosium, in addition to gadolinium, are receiving attention for potential clinical application in first-pass imaging.

Digital angiography--myth and reality.

SUMMARYIV‐DSA has a place in modern angiography but it is a high contrast dose examination and rather unsuitable for many of the patients currently selected for it. Claims that it is non‐invasive, quick, simple and safe are also open to question. Intra‐arterial DSA, however, appears to possess many of the merits claimed for IV‐DSA. The conclusion to draw is not that there is no place for IV‐DSA but, rather, that we should be considerably more discriminating in our choice of patients to undergo the procedure.ABSTRACTThe parameters determining image quality in digital subtraction angiography (DSA) are outlined and a discussion of the relative merits of intravenous and intra‐arterial DSA is presented.