7 Conclusion

Well, we’ve looked at a wide variety of the imaging systems available in the modern hospital, and there are other more specialized systems that we haven’t even mentioned, such as mammography, dental radiography and magnetic resonance angiography, to mention just a few.

But, perhaps you are asking yourself why there are so many different imaging modalities. Is there not one that will do everything that is required? Well, at the present moment the answer to that question is ‘No’, because each of the systems has its own limitations.

In some cases, risk is an important factor. Risk is complex to assess, and depends on factors such as pregnancy, age and the part of the body which is to be imaged. All of the techniques involving ionizing radiation, that’s X-ray, CT and radionuclide imaging, have an associated risk. But in the vast majority of cases, the benefits of achieving a correct diagnosis far outweigh the risks. However, in the case of the fetus, there is a much higher risk due to ionizing radiation, so ultrasound, which has minimal risk, is the method of choice for repeated examinations.

There is normally little risk associated with MRI, but it is completely unsuitable for some patients, such as those with a heart pacemaker. And then there are limitations on what each technique can do. For example, ultrasound, which is fast, low hazard and very cost-effective, is no use for imaging lungs or bone. This is because of the very high reflections at air tissue and bone tissue interfaces. Radionuclide imaging is excellent for imaging organ function, but gives very low resolution images compared to MRI or CT. CT and MRI, on the other hand, give very high resolution images which can be readily interpreted, but they are comparatively slow and expensive, so they are not suitable for the rapid diagnosis of, let’s say, a broken arm.

So the clinician who is recommending an imaging technique must take all these factors into account and their aim must always be to achieve a correct diagnosis with minimum risk to either the patient or the staff.