Observation and interpretation

To understand and interpret medical images, an individual needs an understanding of the process by which the images were created. Almost all medical imaging in the UK is now in digital format, be that the output from the image intensifier in fluoroscopy, static images in fluorography, computed radiography (CR) images, direct digital radiography (DR), computed tomography (CT), magnetic resonance (MR) imaging, radionuclide imaging (RNI) and ultrasound (US).

Digital format has several advantages (e.g. the potential for manipulation of the image after it has been captured); however, the uninitiated may simulate or mask/obscure pathology by incorrect manipulation of images. Transfer of images in digital format is also simplified; no longer does the reporting professional have to wait for ‘hard copy’ images or carry around stacks of photographic film. Electronic digital image files can now be transferred to image reporting stations within (and outside) the healthcare facility in which they are acquired.

It is important to acknowledge that image reporting workstations have specific requirements for monitor quality. Three megapixel monitors are used for reporting in medical imaging departments, but satellite facilities on hospital wards or outpatient clinics may not have such high resolution monitors (often standard computer displays are utilized) and it must be recognized that abnormalities may go undetected if healthcare professionals use these to try to interpret and diagnose from medical images.

Building on the basic understanding of medical images, the next skill required is to understand how pathological/disease processes affect imaging appearances. Although much of this can be learned in the classroom on a theoretical basis, there is no substitute for actual/real clinical experience and all taught courses in the UK have embedded such clinical perspective within them.

Many healthcare professionals learning the skills of medical image reporting start off using a technique known as ‘pattern recognition’. This involves subconsciously matching the viewed image against a preconceived pattern or ‘template’, such that matches and mismatches are recognized immediately by the viewer. This process is integral to human perception (a full discussion of how this works is beyond the scope of this chapter) due to the way image information is built up within separate areas of the brain and finally brought together into a recognizable form.

Patterns can be built up over a period of time so that specific pathological findings are immediately recognized without conscious thought because they had been experienced in the past. The radiological community has adopted the term ‘Aunt Minnie’ type pattern recognition for this and there is a commercial website named after the phenomenon (auntminnie.com) which also promotes educational activities.

Although pattern recognition has its uses, there are potential downfalls to relying on the process. For instance, if a pattern demonstrated is not one that the viewer has seen before, or is not one they are completely familiar with, it may not be recognized. In such cases, even quite obvious abnormalities may be ignored as the individual is only looking for ‘what they know’. To overcome this limitation, the trainee reporting practitioner is taught to review medical images systematically, interrogating the whole image sequentially, looking at all parts of an image and all images within each particular examination or study. This may be quite challenging since with multidetector CT examinations (MDCT) and multisequence MR studies, there may be 300–500 individual images in a single study (Fishman, no date). When, therefore, it is not possible to scrutinize each image in detail, pattern recognition remains the primary method of review. This process may be facilitated by computer-assisted detection (CAD) software, application specific programs being commonplace for virtual colonoscopy (VC) for instance, to highlight potential pathology.

It is also important that personnel involved in image interpretation and reporting understand the clinical information provided by the referring clinician (The Royal College of Radiologists, 2006). In the UK, there is a legal requirement that this is sufficient to enable the radiologist or radiographer to ‘justify’ the examination with respect to the ionizing radiations (medical imaging) regulations (IR(ME)R 2000) (Department of Health, 2000). Clinical information in the referral should convey any relevant signs and symptoms elicited from the patient’s medical history, physical examination and laboratory tests and should give a provisional diagnosis or suggest differentials. The referral is often expressed in terms of a ‘clinical question’, for instance, a patient with unexplained iron deficiency anemia may be referred for a range of diagnostic tests such as initial esophago-gastroduodenoscopy (OGD) and subsequent DCBE or colonoscopy to confirm or refute the presence of a colonic source of bleeding such as a cecal tumor.

Reporting style and structure

Report styles vary across institutions, the range including simple ‘normal/abnormal’ flag systems (such as red dot), informal commenting systems and definitive free text reporting.

The definitive report is the permanent legal record of the medical imaging examination. This is now typically stored electronically within a radiology information system (RIS) with a paper or electronic copy in the individual patient record (clinical or medical notes).

Most medical imaging reporters use a free text type report, although alternatives include a pre-defined proforma style, where specific questions are answered or pre-coded standard phrases selected (Naik et al., 2001). Each style has its own strengths but the recommended structure expected of medical imaging reports is defined by the The Royal College of Radiologists (2006). Initially, a report should contain patient identifying information to ensure that a specific report can be related to a specific patient on a specific occasion, as misidentification can have significant, potentially serious adverse consequences.

Next, procedural information should be included. Often this is part of the electronic patient record, but it is important to check that the planned examination did actually happen; for instance, if a request for a DCBE was made but the patient was not fit enough to participate in the full/complete examination, a less demanding, but less diagnostically sensitive test such as a single contrast barium enema may have been performed. The significance of altering/modifying the requested examination must be made clear to the referrer in the report. Similarly, it is important to acknowledge limitations within the report when the findings are based upon sub-optimal images.

Since medical imaging examinations are usually performed to answer a specific clinical question, the clinical question is also usually included within the main body of the report.

Next should follow a description of the imaging findings (The Royal College of Radiologists, 2006) in terms of size, shape, outline contour, position and radiographic characteristics. The overall radiological findings must then be related to the presence or absence of pathology. Comments can be made on normal findings where this refutes the clinical question or where there is a variance of normal anatomy, e.g. malrotation of the colon or situs inversus.

Communication