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Editorial |
Following the successful launch of the "Review of the Year" 12 months ago [1], the Editorial Board decided that a similar review should be compiled for 2005. Once again a selection of noteworthy papers on currently important topics has been made by the Honorary and Deputy Editors.
This has been a good year for the Journal with no shortage of suitable papers from which to choose. One of the reasons has been that since the Journal introduced online submission towards the end of 2004, there has been a sharp increase in the number of papers received. Twice as many papers were submitted during the first 6 months of 2005 as for the same period in 2004.
This welcome shift has created some problems. The Editorial Board has been expanded to deal with the increased work-load and refereeing standards have been tightened. In spite of this, the number of papers accepted for publication each month has exceeded the number of pages available in each issue and this has led to an increasing interval between acceptance and publication. We are currently looking at ways to address this problem.
Another important development this year has been the introduction of a Young Investigator Award. This Award is made by the Honorary Editors for the best paper submitted by an author, or first-named author, under 35 years of age at the time of submission. Only papers that are accepted by both referees at the first submission, either without change or with only minimal changes, are eligible for consideration.
18 authors were eligible for the 2005 Award and several of them reached the final short list. The Award is made to Dr T Xiong for his paper entitled "Incidental lesions found on CT colonography: their nature and frequency" [2]. Compilation of this comprehensive, systematic review required careful, painstaking research and provides valuable data on the potential benefits and pitfalls of CT colonography. It is always enlightening to review published research and identify at first hand some of the weaknesses in the published data, despite the eminence of the authors and the reputations of the journals in which they were published. Hopefully the Award and the experience gained by reviewing these data will stimulate Dr Xiong to contribute more to the field of research. A summary of the main findings of the paper appears in the next section.
Diagnostic Radiology and the Young Investigators Award
The difficulty of staying "up to date" in medicine is of concern to most of us in practice, and this has been reinforced this year in the Journal. Whilst our Young Investigator Award winner Dr Xiong was reporting on an analysis of published papers on CT colonography, just 2 months later Jardine et al [3] were perhaps showing us the future of colonography in their report on the potential problems using MR.
Xiong et al [2] identified additional abnormalities reported in almost 40% of patients, with the total number of abnormalities exceeding the number of patients analysed. Furthermore, as would be expected, the number of abnormalities and their potential significance varied dependent on the age of the population studied, and the definition of important abnormality. The examination methodologies also varied, and it would seem reasonable to expect the experts to agree a standardized technique and reporting terminology for the future. A more detailed discussion of the pros and cons of CT colonography may be found in the commentary by Ng and Freeman [4] that accompanied the Award-winning paper. As a practising radiologist, the significance and reliable detection of extracolonic disease may be of critical importance in the future, regarding decisions on who reports these scans. This is a topic of increasing concern for UK based radiologists facing the prospect of the ever increasing use of skill-mix.
Of the many other radiology articles published last year in the BJR, the reader's attention is drawn to the article by Reuben et al [5]. This nicely conducted study on the interpretation of facial trauma images by surgical trainees, managed to justify the use of 3D reconstructions and also suggested that there may still be a role for conventional radiography. 17 trainee faciomaxillary surgeons reviewed plain radiographs, conventional and 3D CT images of facial trauma patients. They were asked to score their ease of interpretation of each type of image. Their results were compared to the "subjective" gold standard of a consultant radiologist and a faciomaxillary surgeon. The trainee surgeons were best at interpreting 3D images, but were less good at interpreting conventional axial CT images compared with plain radiographs.
Finally, in this section on diagnostic radiology, a commentary by Munro [6] is noted. This article, although written as a commentary on a radiotherapy paper, is a "must" for all those radiologists plying their trade in research. This beautifully written piece, with quotations from J K Galbraith and Francis Bacon, explains the need for well-performed observational reporting, and will be a fillip to all those who do not achieve the current research nirvana of a randomized controlled trial.
Computer-aided diagnosis
With the increasing availability of digitized images, computer-aided diagnosis (CAD) is currently a hot topic and this was the subject of one of the two Special Issues of the Journal in 2005. A good review article by Doi entitled "Current status and future potential of computer-aided diagnosis in medical imaging" [7] was supported by six other contributions.
The basic concept is to provide a computer output as a second opinion to assist image interpretation by radiologists by improving the accuracy and consistency of radiological diagnosis and also by reducing the image reading time. To achieve this goal it is necessary not only to develop suitable algorithms but also to quantify and maximize the effect of computer output on the performance of radiologists. Research and development of CAD has therefore involved a team effort by investigators with different backgrounds – physicists, radiologists, computer scientists, engineers, psychologists and statisticians.
The technique of receiver operator characteristic (ROC) curve analysis can be very helpful in assessing the impact of input from the computer. ROC methodology makes no requirement of the positive/negative decision thresholds of the observer, other than that they remain constant. Results are readily understood "at a glance" – see, for example, Figure 8 in the paper by Doi [7].
Potential clinical applications of CAD considered included: detection of lung nodules on digital chest radiographs; lung nodule detection based on morphology and sequential volume changes in CT images; prompting techniques to assist in the reading of mammograms and their impact; virtual colonoscopy as a screening method for colorectal neoplasia.
The overall conclusion was that since CAD can be applied to all imaging modalities, all body parts and all kinds of examination, it is likely to have a major impact on medical imaging and diagnostic radiology in the 21st century. However, further careful evaluation is required and an awareness of on-going developments is important.
Diagnostic ultrasound and ultrasound measurement
A number of papers have been published during the year on clinical applications of diagnostic ultrasound. Some have illustrated the use of relatively new techniques. For example Gorg et al [8] used quantitative colour Doppler ultrasound to evaluate and characterize arterial supply of chest wall lesions and Dietrich et al [9] used microbubble contrast-enhanced phase inversion ultrasound to differentiate focal nodular hyperplasia and hepatocellular adenoma.
A paper of particular clinical interest was "Ultrasound evaluation of the fibrosis stage in chronic liver disease by the simultaneous use of low and high frequency probes" by Nishiura et al [10]. Those involved in ultrasound will realise that for more than 25 years innumerable attempts have been made at tissue characterization by ultrasound and whilst this article does not claim to do such it seems to give useful clinical help which may reduce the number of invasive liver biopsies required. The authors looked at 103 patients, examining them with two probes, one at 2–5 MHz and another at 5–12 MHz. They used a scoring system evaluating the edge, surface and parenchymal texture of the liver. They found that the high frequency probe was more sensitive for identifying mildly abnormal changes, whereas the low frequency probe was more useful for scoring advanced changes. The accumulated scores of the three parameters was the most reliable with 100% sensitivity for fibrosis stage 4 and results which were almost as impressive in mild disease. The authors do not indicate whether this has had any impact as yet in reducing the number of liver biopsies but the hope must be that it will. They are intending to extend the technique to other hepatic diseases including the potentially more difficult ones seen in children. Let us hope this proves a fruitful field of endeavour.
Given the continuing diversification of the application of diagnostic ultrasound in medicine, the Editorial by Francis Duck entitled "Ultrasound exposure measurement: a hidden science?" [11] was timely. Under the dual pressures of clinical users asking for improved performance and manufacturers competing to gain commercial edge, there is evidence from long-term studies of a general trend towards increased acoustic output. Doppler techniques frequently use outputs that come close to the limits set by the thermal (TI) and mechanical (MI) safety indices [12]. Collapse cavitation of microbubbles, with potentially harmful effects in vivo, can occur at high intensities. In spite of the above, current hospital practice makes little or no attempt to evaluate the ultrasound radiation generated by their equipment and there is little investment in measurement tools or commitment of personnel time to such measurements.
Duck makes two general recommendations. First there is a need for appropriate acoustic measurement devices, suitable for both laboratory-based and field measurements. For example a well-engineered, portable, commercial power meter capable of measuring acoustic power down to 10 mW or less would make available a direct and simple means to confirm the accuracy of the displayed TI for imaging and to identify critical conditions for transducer heating. Similarly an integrated, easy-to-use portable package including hydrophone, positioning, data acquisition and output would enable on-line measurement of pressure wave-form, acoustic frequency, MI, and temporal-averaged intensity, all key quantities for exposure measurement.
Second, there needs to be a culture change in NHS trusts and hospitals. Measurement of ionizing radiation is now part of the scientific ethos of all NHS trusts, who are committed to a regimen of measurement support that is integrated within their risk management policies. A similar commitment to ultrasound measurement is required, thereby ensuring accountability and the ability to respond robustly to the question "What evidence do you have that your ultrasound scanners are safe to use on patients?"
Radiobiology – low dose risk
The "holy grail" of radiation protection is "what happens at low doses?" and the January issue opened with a fascinating discussion of one of the longest running debates in radiation biology: Is low dose irradiation harmful or protective? [13–17]. This was not simply a rehash of old information. It included the presentation of previously unpublished data from a very large cohort of US workers (28 000) on nuclear powered ships over the period 1980–1988. Their death rates were compared with a similar number of shipyard workers who had not been exposed to abnormal radiation levels and the results were intriguing. The death rate from cancer of the occupationally exposed workers was significantly lower than that of the controls and dramatically lower for non-cancer deaths. This supplements a significant body of epidemiological and radiobiological data supporting the view that low doses may indeed induce protective mechanisms including apoptosis and enhanced immune competence. Counter arguments were also made and while they did not dispute the evidence for a protective effect they relied on the fundamental importance of the double strand break as the dominant DNA lesion and its relationship to dose. It is significant that the linear generation of double strand breaks with dose is not incompatible with mechanisms that enhance apoptosis and immune surveillance. However, the undesirable implications of a change of policy from assuming no safe dose of radiation to one where low doses are desirable, was a compelling argument for maintaining the status quo and the linear no threshold hypothesis seems set to underpin the legislative framework for the foreseeable future. Notwithstanding, there is a genuine scientific debate about mechanisms and risks at low doses, some of which was aired in subsequent issues of the Journal [18–22]. There is a need for the scientific community to maintain a truly open mind on this issue.
Another important outcome of low dose radiation exposure is the delayed expression of chromosomal aberrations as a consequence of genomic instability. This phenomenon was first described 15 years ago [23] and has since been associated with bystander effects [24, 25]. An interesting insight into these processes was reported in the October issue [26]. The study showed that short term repopulating cells in the bone marrow are capable of fully repairing DNA damage, as manifest by chromosome aberrations, within a few cell generations, whereas cells responsible for long term repopulation retain damage in a form that can be expressed as aberrations many months after irradiation. This reinforces the view that radiation induced genomic instability is an early event in multi-step carcinogenesis.
Patient doses and image quality
The subject of patient dosimetry – whether or not we are confident about the risk magnitude – was prominently discussed during the year. A screening programme which involves the irradiation of asymptomatic patients is always subject to particular scrutiny and a comprehensive study of doses received in the UK breast screening programme was reported by Young et al [27]. The radiation dose received by large breasts has been reduced by the use of automatic beam quality selection and large format film. However, this is offset to some extent by an increase in the total dose per woman due to the introduction of two view screening at every visit. The authors call for a revised definition of the standard breast used in the UK to reflect better the exposure factors and doses received in clinical practice.
On the same subject, optically stimulated luminescence was applied in a novel way for in vivo dose measurements in mammography. The presence of the small probes required did not significantly interfere with the diagnostic quality of the images and good agreement with ionization chamber dosimetry was reported [28]. A further novel mammographic technique – near-infrared optical transillumination spectroscopy – has been developed to determine physiological properties of the breast tissue and thus hopefully to quantify differences between women with low and high breast cancer risk [29].
Because of the relatively high effective doses involved, patient dose reduction in CT is a topical issue. Lewis and Edyvean [30] considered the implications of multislice CT scanners, whose ability to utilize long scan lengths and narrow slices can lead to increased doses. Although automatic exposure control and particularly for children and smaller patients, tailoring of tube current to patient size, can lead to dose reductions, the establishment of acceptable levels of image quality for different examination types is the key to dose optimization.
The assessment of image quality raises many scientific issues concerned with the perception and cognition of images and these were outlined in a commentary by Manning et al [31]. Two groups of factors which influence the ability of the observer to interpret image information are those which are image dependent and relate to the visual conspicuity of relevant features and those which are image independent and primarily cognitive. The latter is particularly deserving of further study. Further complications arise because of the introduction of digital image technology, softcopy workstations and the phasing out of hardcopy images. There are countless ways in which images may be processed and manipulated and thus many opportunities to optimize the link between the image and the visual systems of the observers. But how can diagnostic outcomes be measured and compared with hard copy? Computer-aided detection tools may help here. A comparison of full-field digital mammography and film–screen mammography from the point of view of image quality and lesion detection was reported this year [32], demonstrating the superiority of the former.
We leave this subject by reflecting that after many years of reporting patient dose measurements the point has been reached where we need to think carefully whether further data add to our overall understanding. This means that the Journal will be more selective in the studies accepted for publication and will favour work which takes into account all aspects of the imaging process (of which dose is only one component). As Martin stated in his Editorial this year [33] "...finding the appropriate level of image quality is the most important objective. Keeping the dose low should always be secondary".
Image quality, as noted above, is an often ill-defined feature of the imaging process. In the November edition, an international collaborative study [34] described a comparison of conventional X-ray imaging of mice and rabbit lungs with two types of phase-contrast imaging. Phase contrast techniques highlight lung boundaries and provide enhanced lung visibility compared with conventional X-ray imaging, although the wider clinical applications at present remain uncertain.
Procedures for the radiation protection of staff working with X-rays are well understood, even if, at low doses, the resultant risks are not. In general, the regulatory requirements for safe practice in this field are not too inhibiting. Unfortunately, the same may not be the case for MRI, at least in the European Union. Impending legislation on electromagnetic field exposure to staff may cause serious problems in the provision of clinical services, as gradient field limits will inhibit work close to the magnet bore during imaging. This has particularly serious consequences for interventional MR procedures [35]. We hope that the sparse evidence for deleterious effects will prompt a future UKRC debate on the motion "There is no risk to health at low current densities".
Radiotherapy and Oncology – adverse effects of radiation treatment
This was a year for reminding us, if we needed reminding, of the fundamental paradox that underlies clinical radiotherapy. We treat a dread disease with an intervention that is, itself, dangerous. Shakespeare was, as so often, there before us:
"......, and wish
To jump a body with a dangerous physic,
That's sure of death without it"
(Coriolanus: Act 3, Scene 1).
Two papers early in the year reminded us of the late consequences of treatment [36, 37]. In the first Rowland Payne et al [36] investigated the efficacy and tolerability of the hyfrecator (Conmed, Utica, NY), a versatile office-based electrosurgical instrument, as a treatment for radiation-induced telangiectasia. The treatment was well tolerated and generally resulted in a substantial reduction in telangiectasia with a concomitant improvement in quality of life. In the second, Power [37] reviewed the proceedings of a meeting held at the BIR in May 2004 to discuss issues regarding the recording and analysis of late effects of radiotherapy treatments. The outcome was that data on late effects are essential to assess the therapeutic effect of treatment, but there is a need for international consensus as to the best methods of data collection – which should be validated, sensitive, reproducible and user-friendly. In addition to these two papers, the BJR Supplement on "Radiation-induced multi-organ involvement and failure" [38] provided an excellent overview for practising oncologists – keeping in mind that, with the threat of terrorists bearing dirty bombs, we might be called upon to deal with the casualties following the use of such a weapon.
On the more hopeful side, the paper by Amemiya et al [39] was reassuring, showing once again, that the benefits offered by radiotherapy – treatment of early squamous cell carcinoma of the head and neck in this work – usually far outweigh the disadvantages (radiation-induced second cancers in this study). Cominos et al [40] showed that radiotherapeutic technique is important in avoiding the adverse consequences of treatment. Using a four-field technique for treating oesophageal cancer significantly reduced the dose to the heart. Finally, in a careful meta-analysis of clinical trials Dayes et al [41] showed that there was no evidence to support the use of nitroimidazoles as hypoxic cell sensitizers in patients treated with radiotherapy for carcinoma of the cervix but there was a significant increase in the rate of neurotoxicity.
In view of the severe, and largely unexpected adverse late effects of neutrons, two papers by Jones and others on particle therapy deserve mention [42, 43]. The role that particle therapy can, and should, play in the management of cancer is a matter of some debate. We hope that, in the coming months, the BJR will make a useful and authoritative contribution to this debate. We need informed discussions, based on facts. We cannot afford to let the agenda be hijacked for political or commercial reasons. To do so would be to fail in our scientific obligations and more importantly, to fail in our duty of care to patients with cancer.
References
This article has been cited by other articles:
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  Editorial. Br. J. Radiol., July 1, 2006; 79(943): viii - viii. [Full Text] [PDF]
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