Clinical Radiology (1993) 48, 69-71

Correspondence Letters are published at the discretion of the Editor. Opinions expressed by correspondents are not necessarily those of the Editor. Unduly long letters may be returned to the authors for shortening. Letters in response to a paper may be sent to the author of the paper so that the reply can be published in the same issue.

Letters should be typed double spaced and should be signed by all authors personally. References should be given in the style specified in the Instructions to Authors at the front of the Journal.

ACCESSORY NAVICULAR BONE

S m - I read with interest the paper by Romanowski et al. [1] on the accessory navicular bone. The previously reported histology of this accessory ossicle would appear to correlate well with the authors ' technetium 99m M D P bone scan findings [1].

A study in 1948 [2] reported the histological features present in accessory navicular bones which had been surgically removed from five patients. In all cases the operation had been performed because o f localized pain over the region o f the navicular bone. The specimens removed frequently showed evidence of t rauma in the synchondrosis between the navicular and accessory navicular bone. This was manifest microscopically by areas o f haemorrhage, organizing fibrous tissue which contained osteoclasts or chondroclasts and subchondral repara- tive tissue which resembled callus. These appearances are similar to the situation in Osgood-Schlatter disease with repetitive strain on the tibial tubercle [3].

It is likely that the increased uptake of technetium 99m M D P in the region of symptomatic accessory navicular bones is due to the traumatized fibrocartilage seen histologically.

R. F A R R O W Department of Radiology Derriford Hospital

Plymouth PL6 8DH

References

1 Romanowski CA J, Barrington NA. The accessory n a v i c u l a r - a n important cause of medial foot pain. Clinical Radiology 1992; 46:261- 264.

2 Zadek I, Gold AM. The accessory tarsal scaphoid. Journal of Bone and Joint Surgery 1948;4:957 968.

3 Uhry E. Osgood-Schlatter disease. Archives of Surgery 1944;48:406- 414.

SIR We are grateful for the opportunity to reply to Dr Farrow's letter and agree with his comment that the increased uptake of technetium 99m M D P seen in the region of the symptomatic accessory navicular bones is likely to be due to traumatized fibrocartilage and adjacent bone. In the one case in our series where histology was available this showed reactive high turnover bone with increased osteoblastic and osteoclastic activity and large numbers of inflammatory cells. These features are strongly suggestive of a chronic stress reaction. The histological features in this case are similar to the cases reported by Lawson et al. [l ] who also showed this to be a similar histological pattern to that seen in the healing phases o f experimental epiphyseal separation as demonstrated by Salter and Harris [2].

We therefore agree that our finding of increased activity on bone scans of these symptomatic patients is due to chronically-traumatized fibrocartilage and adjacent bone.

C. A. J. R O M A N O W S K I N. A. B A R R I N G T O N

References

Department of Radiology Royal Hallamshire Hospital

Glossop Road Sheffield SIO 2JF

1 Lawson JP, Ogden JA, Sella E, Barwick KW. The painful accessory navicular. Skeletal Radiology 1984;12:250 262.

2 SalterRB, HarrisWR. Injuriesinvolvingtheepiphysealplate. Journal of Bone and Joint Surgery (American) 1963;45;587.

STAGING PROSTATIC CANCER

S i n - T h e review, Staging Prostate Cancer, by Drs Clements and Griffiths and Mr Peeling provides an excellent overview of recent

developments but largely concentrates on investigation of men prior to radical prostatectomy [1]. While use o f the most accurate staging methods for local disease is essential for surgical candidates, the operation is not universally practised in the U K nor suitable for every patient with clinically and radiologically localized disease. When radiotherapy is the preferred form of radical therapy the requirements of the staging test differ; simply stated the radiotherapist needs to know whether there is disease extending beyond the usual treatment margins and whether the extent o f demonstrable lymphatic metastasis renders radical treatment futile. In our own unit about 1 in 10 candidates for radical radiotherapy examined by CT, after exclusion of skeletal metastases, have evidence of lymphadenopathy with a similar propor- tion having significantly more extensive local disease than clinically palpable [2].

There are strong arguments for using CT to stage candidates for radical radiotherapy, in additon to its use in planning treatment [3]. Certainly CT is inferior to MRI or T R U S for detection o f early capsular breach but it is reliable at detecting greater degrees of local extension which would modify or contraindicate radiotherapy. In the largest published comparative trial of CT and MRI involving 46 men who had radical surgery, all understaging failures of CT involved lack of detection of microscopic capsular breach or invasion of normal sized seminal vesicles [4]. Whilst radiotherapy fields usually include a margin of 1 to 2 cm around the prostate gland - according to the likelihood of capsular invasion treatment volume may not encompass the seminal vesicles in order to reduce the dose to the rectum. The ability to identify tumour in the seminal vesicles is thus a clear advantage of MRI. Its utility is still uncertain for radiotherapy planning and more work is required to assess the role of MRI and also transrectal ul t rasound in the staging and planning of candidates for radiotherapy.

It seems likely that radical prostatectomy will become more prevalent in the UK. We would caution against undue optimism for the ability of body coil MRI to predict early capsular breach. Early reports of accuracies of 70 to 80% from premier centres in the USA [4,5] mus t be contrasted with the findings of the much larger cooperative multicentre R D O G study using similar equipment which reported only 57% accuracy for staging localized disease [6] and an even more sceptical report indicating body coil MRI to be no better than pre-operative prostate-specific antigen assay for prediction of extracapsular disease [7]. This appears to be an intrinsic limitation o f available technology as there was no variation in performance of the various centres in the R D O G study [6]. As indicated in the review, early results of endorectal coil MRI appear very promising with a reported 16% improvement over body coil M RI [8]. Increased accuracy of pre-surgical assessment is only achieved with an escalation in cost and invasiveness and this develop- ment is not available for some systens in current use in the UK. Preliminary results of a multicentre RDOG assessment o f endorectal coil imaging have failed to show such an impressive improvement over body coil imaging (M. D. Rifkin, RSNA 1992).

Whilst accurate assessment of lymph node status is important to both forms of radical therapy, its evaluation has received scant attention in the MRI literature. In the largest reported study (185 men with pelvic node sampling), only 4% of involved nodes were detected pre- operatively by MRI, suggesting room for improvement [6]. There has never been such a large study comparing CT and M RI for nodal staging. In our own experience very high resolution MRI techniques allow confident identification of very small pelvic nodes. New guidelines are required to set the threshold of normality for size, site and number of nodes in patients who have not only cancer but potentially transurethral surgery, biopsy and infection as additonal nodal stimulants. Only centres performing lymphadenectomy or pelvioscopy are in a position to address these important questions and it is imperative that radiolo- gists privileged to receive this valuable feedback concerning surgical pathology construct prospective studies to shed more light on the significance of pelvic nodes, reactive or neoplastic, enlarged or small.

J. SPENCER Churchill Hospital S. G O L D I N G Oxford OX3 7LJ D. COLE

70 CLINICAL RADIOLOGY

References

1 Clements R, Griffiths G J, Peeling WB. Staging prostate cancer. Clinical Radiology 1992;36:225 231.

2 Spencer J, Golding S. CT evaluation of lymph node status at presentation of prostatic carcinoma. British Journal of Radiology 1992;65:199-201.

3 Dobbs H J, Husband JE. The role of CT in the staging and radiotherapy planning of prostatic tumours. British Journal of Radiology 1985;58:429-436.

4 Hricak H, Dooms GC, Jeffrey RB, Avallone A, Jacobs D, Benton W K et al. Prostatic carcinoma: staging by clinical assessment, CT, and M R imaging. Radiology 1987;162:331-336.

5 Bezzi M, Kressel HY, Allen KS, Schiebler ML, Al tman HG, Wein AJ et al. Prostatic carcinoma: staging with M R imaging at 1.5T. Radiology 1988;169:339~346.

6 Rifkin MD,,Zerhouni EA, Gatsonis CA, Quint LE, Paushter DM, Epstein JI et al. Compar ison of magnetic resonance imaging and ul trasonography in staging early prostate cancer. New England Journal of Medicine 1992;323:621-626.

7 Schiebler ML, Yankaskas BC, Tempany C, Holtz P, Zerhouni E. Investigative Radiology 1992;27:575-577.

8 Schnall MD, Yutaka I, Tomaszewski J, Pollack HM, Lenkinski RE, Kressel HY. Prostate cancer: tocal staging with endorectal surface coil M R imaging. Radiology 1991;178:797-802.

Reference

1 Hous ton JG, Morris AD, Howie CA, Ried JL, McMillan N. Technical report: quantitative assessment of diaphragmatic move- ment - a reproducible method using ultrasound. Clinical Radiology 1992; 46:504-407.

SIR - - We would like to thank Dr Husien for his interest in our work. Our study was performed entirely in accordance with guidelines set out by our local Research and Ethical Committee which has extensive experience in reviewing clinical research projects. All patients gave informed consent and 'ill patients ' were not subjected to tests, let alone repeated tests. As Clinicians working in acute medicine, we believe that it is entirely appropriate to use patients to evaluate a non-invasive simple test which may prove useful in the evaluation of such patients in clinical practice.

J. G. H O U S T O N Department of Medicine and Therapeutics Gardiner Institute Western Infirmary Glasgow Gl l 6NT

CLINICO-RADIOLOGICAL MEETINGS

SIR - The operation of radical prostatectomy provides a pathological specimen that can be extremely carefully examined, enabling correlation of histopathological~and imaging data. It is this precise correlation which has developed our understanding of the limitations of imaging techniques of the prostate, and it is only natural that a review article on the staging of prostatic cancer should concentrate on published work based on such patients rather than on patients receiving radiotherapy where the histopathologicat correlation is absent.

As Dr Spencer and colleagues admit, CT is an inferior examination for staging of prostatic cancer; as we stressed in our article, the opt imum imaging technique on the basis o f current published experience is MRI. It is unfortunate that M R facilities are so limited in the U K and 1 would hope that readers would accept the need to advocate wider availability of the better technique. In Newport at present we only perform M R on the relatively few of our patients being considered for radical prostatec- tomy. We do stage other patients with C T when required but in the knowledge that it is the more available but less accurate technique.

The correlation of imaging data with histopathological specimens has greatly enhanced our understanding o f the staging of the primary tumour within the prostate and I completely endorse the call for correlative studies to shed more light on pelvic nodal involvement in patients with prostatic cancer.

R. CLEMENTS Department of Clinical Radiology Royal Gwent Hospital

Newport Gwent NP9 2UB

IS IT ETHICAL TO USE PATIENTS T O DETERMINE N O R M A L FINDINGS?

SIR - I read with interest the paper by Hous ton et al. [1] and wish to congratulate them on this original work. I would, however, like to make a point on the ethical basis o f the study. The aim was ' to determine normal range o f excursion' of the diaphragm. Yet, they used '55patients on a general medical ward', with a mean age of 59 years, some of whom had to undergo the test more than once. The aim of the study could have been equally fulfilled by using healthy volunteers instead of subjecting ill people to a test which had nothing to do with their management . If the reason for usingpatients was to assess their tolerance for the test, a small number o f them would have sufficed. The rest of the study should have been conducted on healthy volunteers. There is no shortage of healthy people who would be happy to act as 'guinea pigs' in a safe medical research and who are ideal for an ul t rasound study to establish a normal range.

A. M. A. HUSIEN X-ray Department Kettering General Hospital

Kettering Northants NN16 8UZ

SIR - - Mr Leung's and Dr Dixon 's paper [1] costing ' some aspects o f the benefits' of clinico-radiological meetings disturbs me by its selective approach. Supposing that it were useful to assign a mean cost to management decisions and altered diagnoses in this way, their method appears too simple to achieve a figure with real meaning. For one thing no assessment is attempted o f the cost of making (or not making) radiologicaUy-driven decisions without meetings; in describing them as 'good buys" do the authors assume that none of them would otherwise have been reached? In a hospital with little use o f clinico-radiological meetings, advice may be obtained by a clinician visiting or telephoning the X-ray department, which is cheaper in terms of salaried staff time; indeed the radiologists are more likely to include management sugges- tions in their written reports - cheaper still. Fur thermore this method of deriving a cost rests on the assumption that meetings occur within the defined working week, whereas many are held before 9 am or between 1-2 pm, so that technically we are not being paid for them!

These quibbles may seem silly, but the whole issue o f the value of clinico-radiological meetings is too complex and important to be subjected to a costing of part of their function. Through such administrative exercises we risk losing sight of the advantages of open discussion. Meetings are a forum for peer review and the modification of clinical practice by consensus, giving other clinicians a chance to comment on their colleague's problem and learn from the radiologist 's response which is lost if only the two individuals discuss it. Similarly junior medical staff and radiology trainees alike are provided in meetings with a wider pool of experience than that available to them from their own cases, and they appreciate this benefit. The need of radiologists to keep up with clinical progress and of clinicians with developments in imaging technology is also most readily met through their weekly encounters.

More subtle imponderables are also significant. Meetings are essential to the nurtur ing o f happy and productive working relationships. Having trained as a radiologist in eight different hospitals which embrace the gamut of attitudes towards clinico-radiological meetings, I am in a position to observe that without them the radiologists tend to feel out of touch with clinical practice and relatively impotent to influence it. (Whether the clinicians are happier managing their patients without undue radiological interference, I am less certain.) And there is no doubt that meetings offer a basis for teaching radiology to medical students which is too often missing from their formal curriculum. If we were able to assess the effectiveness with which imaging is used in different hospitals, I am sure that a relationship with the amoun t o f their juniors ' exposure to discussion in meetings would emerge. This kind of educational value can hardly be costed.

Leung and Dixon presume that their clinicians brought their most puzzling cases, yet deemed 31% of them 'routine'. Perhaps the most efficient use of meeting time should be debated. The form which a meeting takes need not be fossilized by long tradition but can be redesigned by mutual agreement: I have seen this done with surprisingly creative results. Experiments with an integral teaching session, bringing the medical students to front row involvement rather than dozing off at the back, proved sufficiently popular with their consultants for them to forego their opportunity to leave and linger on the fringe, while working wonders for the radiologists' boredom levels. In one hospital, teaching