Errors in radiographic image annotation by radiographers could potentially lead to misdiagnoses by radiologists and wrong side surgery by surgeons. Such medical negligence has dire medico-legal consequences . It was hypothesized that image annotation with newer technology of CR and direct digital radiography (DDR) would potentially lead to a change in practice with subsequent reduction in annotation errors . Following installation of computed tomography, a modality with electronic image annotation, the hypothesis was investigated in our study centre. The choice of study centre was due to its reputation of being well-equipped with different radiological modalities as well as being well-staffed with both quality and quantity of radiation personnel (Figs. 3, 4, and 5).
Findings from our study showed considerable reduction in annotation errors between FSR (4.6%) and CR (0.6%). That was a 670% decrease in error when FSR is compared with CR. Our 0.6% error rate in CR is closely similar to that of Platt and Strudwck , who recorded zero error in CR images. However, Barry et al.  recorded higher values of error (5.8%) in similar study in Australia. The possible reason for the variation may be attributable to the methodology. While our study evaluated CR images in a general imaging department acquired over several weeks, that of Barry et al. (2016) evaluated images generated over a period of 48 h in a paediatric department. It is therefore our opinion that CR and DDR images could reduce or completely eliminate errors in image annotations in medical imaging. Anecdotal evidence from observation of radiographers at work in the study centre revealed their meticulous efforts to eliminate error from radiographic procedures. Errors which inadvertently crept in were mainly due to marker burnout from overexposure, and cone-off, due to ambitious collimation.
It was reported that zero error level was possible if a checklist used in the quality control room contains presence or absence of anatomic side maker as a fundamental item. Our study showed that 43% of the marker positions were in the umbra region of the radiation similar to other studies that recorded 25–32% placement in the same region [1, 6]. This is however contrary to the recommendations of Platt and Strudwick  and Bontrager and Lampignano  who advocated 100% marker placement in the umbra region of the radiation beam. An earlier study in our centre almost aligned with the recommendation, as 89% of markers was placed in umbra region . That study evaluated only FSR in contrast to the present study which evaluated both FSR and CR. The CR was a probable cause of reduction in errors.
We observed that marker placement within umbra of the x-ray beam, aside from being a practice of precedent, did not appear to offer any superior advantage to markers placed within the penumbra. A growing global tendency of radiographic image annotation within penumbra calls for a re-evaluation of the old order . In view of the evidence from our present study and from literature, we suggest that the best practice of ASM should be guided primarily by legibility and sparing of essential anatomy and secondly by aesthetics.
Although ASM error of 0.6% was observed with CR in comparison to 4.51% of FSR in our study, the more reliable result ought to be from FSR. This is because FSR involves pre-exposure marker placement, rather than post-exposure where there is possibility of marker position modifications. Adding markers during post-processing is considered a sloppy method which only encourages error . Notwithstanding, it is reported that in ASM error analysis, a higher error rate is to be expected from FSR than with CR . Since no study has shown zero error rate with FSR, the observation that incorrect use of pre-exposure ASMs is one of the major sources of error in radiography could be justified . The 2% error rate in FSR of an earlier study  and 4.6% (FSR) of the present study is in the same range of 2.4% reported by Aakre and Johnson (2006) .
Annotation error, however, increased in the present study by 126%. The difference may be due to sampling technique applied in the studies. Whereas, simple random sampling (n = 623) was adopted in the older study, complete enumeration (N = 4726) was adopted in the current study. Error rate would be more accurate with complete enumeration since every data would benefit from analysis. The fact that higher error persisted with FSR in the centre calls for further research with anthropomorphic phantoms in order to perfect pre-exposure marker placement. The authors are of the strong opinion that consistent practice with anthropomorphic phantoms, rather than patients, is a necessary first step in eliminating errors in imaging, especially where students are being trained.
Following installation of CR and acquisition of additional equipment, there was consequent increase in the number of personnel by as much as 62.3%. This appeared to be an administrative strategy to ensure that resources were appropriately managed. Experienced radiographers however, decreased from ≤ 18 to ≤ 12 while interns who were their mentees increased from ≤ 10 to ≥ 45 (350%). Radiography Interns, after a month or less of orientation, are usually in the frontline of image generation. An investigation of radiographic image annotation with ASMs by hospitals that train interns is indirectly a quality control of the practice of those interns, and directly an assessment of the effectiveness of supervision by senior radiographers. Although the overall 0.6% error rate in CR appears commendable, a zero error rate should be the goal. This is likely if interns are not left to work unsupervised soon after assumption of duty. They ought to acclimatize with equipment and accessories to reduce marker burnout and cone-off which constituted the errors at the centre.
As has been observed both from our work and in the literature, error rate was higher in FSR than in computed radiography. There are plausible explanations for this. Whereas FSR and CR always undergo pre-exposure marking, only CR enjoys the privilege of another round of post-exposure marking. Post-exposure marking on FSR is a patently slobby practice that should be discouraged and is often counted as error during marker audits . The higher error rate in FSR may be due to the ease with which pre-exposure markers are identifiable from post-exposure markers using aesthetics. Post-exposure marking in FSR is not as aesthetic as in pre-exposure. If re-irradiation is used, re-exposed area will appear darker than surrounding areas of the image due to further activation of silver halide and deposition of black metallic silver in the film emulsion. If scratching or pen marking is used, it will appear on, and not, in the image. In CR however, radiographers can easily mask errors of absence of marker by revisiting previous images. The authors are therefore of the opinion that the most reliable error rate in any marker audit are those from FSR where error masking is easily detectable.
From anecdotal experience, in busy departments with very few radiopaque markers, radiographers tend to use radiopaque object such as syringe needles to indicate an anatomical side with the intention of later using an electronic marker to mask it. Many times, such needles fall off, are displaced outside radiation beam or become illegible due to beam attenuation by obese patients. Solution to marker errors should incorporate anthropomorphic phantoms and abundance of radiopaque markers in the department. While a single anthropomorphic phantom may be adequate for the whole department, each radiographer should possibly own a personal marker. Furthermore, pre-exposure markers become illegible when obese patients attenuate radiation beam. Imaging of the obese patient presents diagnostic challenges that have appeared insurmountable over the years . The fixed nature of detector casing sizes makes this problem difficult to address. The largest size of detector casing in use in our country is 14 in × 17 in (35 cm × 43 cm). Abdomen and pelvis for some obese patients extend beyond the edges of this size of casing and provide no free space for marker placement. The solution may lie with cassette manufacturers. If they will produce obese-specific detector casing sizes, illegibility and cone-off of markers may reduce.
Our work had some limitations. Due to the retrospective nature of data collection, it was not possible to ascertain if the 0.6% error rate in computed radiography actually represented excellent pre-exposure ASM placement or post-exposure annotation ‘excellence’ at workstation. A prospective work to clearly ascertain this is therefore envisaged in the near future.