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

Communication of the report to the referrer is of paramount importance as the report is the end result of the imaging examination (The Royal College of Radiologists, 2007). It is important that the referrer can understand the report and that it is written in plain language, devoid of jargon and obscure terminology.

The distinction between a ‘descriptive report’ offered by an allied healthcare professional and a ‘medical report’ offered by a clinical radiologist is one that should be made on the grounds of authorship (Robinson, 1996b). Only a medical practitioner can provide a ‘medical report’, anything else is considered a ‘descriptive report’ regardless of content, thus the authorship and professional status of the reporter should be stated in the report somewhere (Dimond, 2002).

Where there are urgent or unexpected abnormal findings, e.g. obstructing tumor, these should be communicated rapidly to the referring clinician and this procedure documented (The Royal College of Radiologists, 2006). To ensure that the referrer is aware of the situation, direct communication, such as face-to-face or telephone conversation is always best, as a written note, memo, letter, fax, e-mail or voice mail may be ignored, lost, erased in error, or its urgency or significance may not be appreciated if it is received by an inappropriate member of the healthcare team.

In recognition of this issue, the National Patient Safety Agency (NPSA, 2007) reported a number of incidents which had led to patient fatalities and significant long-term harm when there had been failures to follow up on medical imaging reports.

It is unusual for patients to be told the results of a medical imaging investigation at the time of the investigation. This is because the referrer will be the person with all the relevant information pertaining to the range of clinical, laboratory and imaging investigations and how the results of these all fit together to inform the care or treatment plan for the individual patient. It is often frustrating for patients to be told that they must see the referring clinician again for the results, but allied healthcare professionals (AHPs) must be trained to deal with such delicate situations. There are some situations where AHPs do give results (e.g. in obstetric ultrasound) but this is only after specific training has been undertaken and is within the remit of an agreed protocol which outlines their responsibility and scope of practice (Simpson, 2001).

Terminology

The terminology used in imaging reports (and of course in the clinical history provided by the referrer) is important; all parties involved need to understand the terms and phrases used. It is very easy to use abbreviations, acronyms and technical or professional jargon, which are perfectly reasonable in context, but are open to misinterpretation. Some examples of terms with multiple meanings are shown in the Table 19.1.

Table 19.1 Standard abbreviations and their multiple clinical meanings

Adapted from GlobalRPh.com 2007.

In the same way, use of ambiguous reporting terminology is to be discouraged when describing medical imaging findings. Although conventions are important, key stakeholders need to know what the conventions are. For instance, diverticulosis, seen on a DCBE, may be described as mild, moderate or severe, but it is important to ensure that there is consistency between individual reporting personnel so that the referrer knows just what degree of disease is implied when each term is used. If one observer states that disease is moderate while another calls it severe and a third observer calls it moderately severe, the clinician will find it unhelpful. To avoid this, a local agreement/consensus should be reached, for example, mild diverticulosis might be defined as ‘some scattered diverticula’, moderate disease as more concentrated in a particular segment and includes circular muscle thickening, and the term severe reserved for cases where the disease interferes with confidence of diagnosis or exclusion within a particular segment. Such agreement must involve all interested parties, i.e. referrers and reporters.

Inconsistency may also exist in the way that the reporter states that the imaging investigation shows no evidence of active disease. Phrases in common use include: NAD (no abnormality detected), normal, completely normal, within normal limits, no significant abnormality, no definite abnormality. All these statements indicate lack of pathology to a greater or lesser degree, although the intent of the reporter and the understanding of the report recipient may be discrepant. The reporter thus needs to be aware of the connotations of the language used in their reports and choose words and phrases carefully.

As in any specialty, specialized language is often used in relation to specific imaging techniques such as ‘signal intensity’, ‘enhancement pattern’ or ‘echogenicity’ but, wherever possible, ‘jargon’ terms should be kept to a minimum unless the reporter is sure that the intended recipient (referrer) will understand the terms used. Where there is evidence of a pathological process, this should be commented upon and interpreted as either significant findings (related to the current signs and symptoms) and thus requiring some intervention, or be categorized/classified as insignificant findings where incidental findings such as degenerative disease, inactive colitis or diverticulosis are not considered to be responsible for the patient’s current presentation. Significant findings must be analyzed to suggest a diagnosis or list of differentials. Occasionally, specific findings cannot be attributed to a single pathological process. For example, extrinsic compression of the colon noted at DCBE can have a range of causes which produce the same imaging appearances (Blakeborough et al., 2001). In such cases, the differential list should start with the most likely possibility. Wherever possible, the report should contain a recommendation as to any further investigations that might be suitable for clarifying such a diagnostic dilemma; in the aforementioned example, this might include abdominal and pelvic CT to characterize the nature of an extrinsic mass.

Some indication of the diagnostic certainty should be included in the report. This can be expressed in terms of the language used such as ‘there is’ rather than ‘there may be’ or ‘this represents’ rather than ‘appearances are compatible with’.

Where findings are equivocal, ‘don’t know’ might be an appropriate answer to the clinical question. In such cases, it is important to include a recommendation for further investigation. For instance, it may not be possible to tell during a DCBE whether a particular filling defect is due to residual feces, a mucosal fold or if it represents a true polyp, in such a case it is appropriate to suggest that endoscopy would be a useful adjunct.

Clinical coding systems, such as READ or SNOMED CT are used in administration systems to ensure compatibility and standardization across institutions/electronic recording systems (NHS, 2007), but are not used in the generation of medical imaging reports at the time of writing. Hypothetically, this might be a future development with computerized reporting systems in medical imaging departments linking electronic/voice recognition reporting with the applications codes to keep the report as an integral part of the image file.

When static images are available for a particular examination, a ‘double reporting’ process is recommended in some areas of medical imaging. Such practice is routine in mammographic breast screening, as it is more cost effective in terms of reducing the number of ‘false positive’ recalls for further assessment than single reading and it increases the cancer detection rate (Brown et al., 1996). Double reporting has been recommended for use in DCBE as it increases the sensitivity but inevitably decreases specificity of the examination (Markus et al., 1990; Anderson et al., 1991). However, where the examination images are dynamic, such as in ultrasound or videofluoroscopy, double reporting is problematic unless the entire study is stored and available for review on a separate workstation. This was not realistically feasible before the advent of PACS (picture archiving and communication system) due to the large data storage requirements and the time constraints of second real-time review of a dynamic study, i.e. at least the same length of time as taken to perform the original study. However, the benefits of being able to review dynamic studies digitally and frame by frame or in slow motion should not be underestimated.