Choices - indications

When choosing either x-ray, ultrasound, or any other imaging equipment, there are three basic questions which must be fully answered.
1. Who and how many need diagnostic imaging?
2. What types of diagnostic imaging are needed?
3. Where will the imaging be made?

1. Who and how many need diagnostic imaging?

When equipment must be chosen for imaging departments, the task can be either to plan for a large area, such as a city, district, region or country, or to choose for a particular clinic or hospital. It is easier to plan for a region, large or small, because 90% or more of the imaging does not require complex equipment. Most of the inhabitants of the region will need diagnostic imaging because they suffer a fracture, develop a cough, or have an abdominal or pelvic pain. The women will become pregnant. Only a small percentage (probably less than 10%) will need gastrointestinal, cardiovascular, or other advanced studies.

Where money is short, the majority should be properly served first and the few, who will need by far the most expensive equipment, must be given a lower priority.

When the task is to plan imaging services for a particular hospital, attention must be paid to the catchment area, the size of the population, the size of the hospital or clinic, the pattern of referrals, the local disease profile (e.g. heavy industry or rural occupations), the current hospital statistics and future plans, including the special skills of newly appointed specialists who will request specific imaging techniques.

2. What types of diagnostic imaging are needed?

The full list of possible indications for diagnostic imaging is too long to include here, but reference to the chapters or index of this textbook will show the range. It is possible to make a summary, however, because WHO has studied the problem all over the world. The summary is very simple, because everywhere in the world the most common indications for diagnostic imaging are:

Table 2 shows the percentage distribution of examinations at small hospitals and primary care x-ray departments in different parts of the world. About 15 % of the examinations are of children. There is considerable seasonal variation but the overall pattern is consistent everywhere. Over 90% of required examinations are for chest and skeleton. Ultrasound, where available, lowers the number of x-ray examinations of the abdomen.

Table 2. The distribution of radiographic examinations in small x-ray departments, obtained from the records of small hospitals in Sweden, Latin America and Africa

In practice, chest and skeletal examinations are the most important indications for diagnostic imaging in any country and at any clinic or hospital, regardless of size. The majority of these examinations require only "plain radiography" (without fluoroscoy) or general purpose ultrasound. Thus, in small rural or suburban hospitals, plain radiography will account for over 90% of all necessary examinations and ultrasound will satisfy a large part of the other 10%. Indeed, plain radiography or "plain" ultrasound will be all that is necessary for 70-80% of all diagnostic imaging even in a sophisticated university hospital in a big city.

3. Where will the imaging be made?

Imaging should be provided only at those clinics or hospitals where a competent person is available to interpret the results. The request for imaging and the interpretation of the images are the responsibility of physicians. The only exception is that qualified and well trained midwives can do routine antenatal ultrasound examinations, provided they have a physician to whom they can refer when there is a difficult image to interpret.

This means, and WHO recommends, that small hospitals and clinics with at least one doctor (the first referral level) or any large hospital or clinic (the second and third referral levels) all need imaging equipment. The type of equipment increases in complexity and cost as the level of available treatment is raised, but all hospitals will always require good facilities for plain radiography, whatever else may be available.

Patients should be imaged as dose to their home as possible, where they can be treated for all their common ailments by the doctors and nurses whom they know best. Ideally, all images should be taken by a trained radiographer or ultrasonographer and interpreted by a radiologist. Unfortunately, in much of the world this does not happen. If professionals are not available, imaging should be restricted to plain radiography and general ultrasound.

Fluoroscopy or any complex imaging should not be installed, unless there are both radiologists and fully trained technologists to use it. This requirement is equally important for CT, MRI, angiography, nuclear medicine and advanced ultrasound.

Philip E.S. Palmer, Thure Holm and Gerald P. Hanson