1976, British Journal of Radiology, 49, 573
Correspondence there a greater opacity in the centre of the balloon compared with the periphery. We have shown both these changes when we repeated these experiments using the same volumes and nominal radiographic factors but changing the concentrations. This we believe is the crux of the matter—that there is an optimal range of concentrations for any given depth of contrast medium (Dure-Smith et al., 1974; Dure-Smith et al, unpublished). The two concentrations (15 and 150 mg/ml. iodine) chosen by Dr. Sherwood happen to fall outside this optimal range. Even within the optimal range changes in film density are small and depend not only on radiographic factors, but also on the characteristics of the film and processing. If the image of the smallest volume or depth appears white, increasing either depth or concentration will produce no discernible effect. Sherwood's illustration using 150 mg/ml. is correct in this respect, but the illustration using 15 mg/ml., apparently also showing no effect, is incorrect as his original radiograph shows, in that the balloons were only just opaque and not white. In this low film-density range a change of concentration X 2-4 or depth (2-5-20 ml. sphere) we would expect to produce a virtually undetectable change in density. We have previously pointed out (Dure-Smith, 1974) that this has a practical application in patients with renal impairment who can achieve only low concentrations of contrast medium in their urine; they are doubly disadvantaged in that they need much larger changes in both depth and concentration of contrast medium to produce a detectable improvement in opacification. This subject has also been confused by the semantics of biological shapes; whether the nephrons or calyces present spheres, ovoids or cylinders to the X-ray beam and the effects which such shapes have on the depth/volume ratio. However, it matters little what the exact shape is providing, as we believe, it is capable of a significant change in depth. We abandoned our biological shaped model because there is so little control over the shape it assumes (and hence depth of contrast medium). Further, the smallest volume (2-5 ml.) chosen by Dr. Sherwood must surely represent a rather hydronephrotic calyx, and its relevance to the normal calyx must be limited in view of the critical depth/concentration relationship. We feel the discussion has moved on since this chapter in Recent Advances was written and the question is not now whether or not there are significant depth changes but what contribution they make to renal opacification for any particular concentration of contrast medium. We are very grateful to Dr. T. Sherwood for allowing us to see one of his original radiographs. We would also like to thank Dr. P. Winstanley, Principal Pharmacist to the Radcliffe Infirmary, for dispensing the correct concentrations of the contrast medium, and to Miss Wendy Hills, D.S.R., for radiographic assistance. Yours, etc., P. DURE-SMITH,
Department of Radiology, Thomas Jefferson University Hospital, Philadelphia 19107, U.S.A. (Visiting Fellow, Wolfson College 1974-75.) G. M. ARDRAN.
Nuffield Institute for Medical Research, University of Oxford, 43 Woodstock Road, Oxford 0X3 6HF. REFERENCES DURE-SMITH, P., SIMENHOFF, N., ZINSKIND, P. O.,
and
KOPROFF, M., 1971. The bolus effect in excretory urography. Radiology, 101, 29-34. DURE-SMITH, P., SIMENHOFF, M., BRODSKY, S., and ZINS-
KIND, P. D., 1972. Opacification of the urinary tract during excretory urography: concentration vs. amount of contrast medium. Investigative Radiology, 7, 407-410. DURE-SMITH, P., ROSEN, R., STERN, A., FRAIMOW, H., and
SIMENHOFF, M., 1974. Physiology of the excretory uro-
gram III. A densitometric and subjective assessment of changes in contrast medium concentration. Investigative Radiology, 9,104-108. DURE-SMITH, P., 1974. Excretion of contrast medium. British Journal of Radiology, 47, 825-826. DURE-SMITH, P., ROSEN, R., FRAIMOW, H., and GALKIN,
B. Physiology of excretory urography V. The role of volumetric changes in urinary tract opacification (unpublished). SHERWOOD, T., 1975. The urinary tract. In Recent Advances in Radiology, 5, edited by T. Lodge and R. E. Steiner, pp.247-262.
THE EDITOR—SIR, MUST RADIOLOGISTS DO ALL THE REPORTING?
Your Editorial in July asks if radiologists must do all the reporting, and you publish a letter from Dr. Emrys-Roberts. With an increased work-load and a shortage of radiologists, the ideal of reporting on all X-ray examinations is one few of us can accomplish. Indeed, it is foolish to try. It results in reporting at too fast a rate, leading to an increase in errors and distortion of the work pattern as too little time is available for lengthy specialized procedures. Today, many films have to pass through X-ray departments unreported, the type of case varying from hospital to hospital and with the working agreements of the clinicians concerned. We must accept the fact that the ideal of radiologists seeing all films cannot be achieved with the present workload. The answer lies in compromise and probably some combination of the following: 1. The curtailment of the number of investigations depending on the diagnostic yield in a given clinical situation (several papers on this have been published), and the limitation of investigations so they provide only the answers to the questions posed by the clinicians. 2. Getting help from other doctors. This will mean two levels of skill, but this applies to most branches of medicine. A radiologist should be available to help with problems. Off-loading work to community hospitals is a further step which is less secure. The diagnostic yield from examinations undertaken in departments outside the supervisory umbrella of a radiologist will be less and the radiation to the patient probably more. The small department will not be used to capacity, giving a greater cost per examination. 3. Assistance under (2) is likely to be limited, but I believe radiographers could help. With non-contrast studies, suitable radiographers should be able to place films in three categories, "normal", "probably normal" and "abnormal". (I include "probably normal" to avoid the problem of the borderline cases and radiographers exceeding their knowledge to avoid having to put "normal" cases in the "abnormal" category.) The radiographers would issue a "normal" report, signing it themselves. I know this is against the Articles of The Society of Radiographers and has medico-legal implications. With follow-up cases, radiographers should be able to place examinations in three categories, "better", "the same" or "worse" with a view to reporting on those improving and long-term static cases. Even more controversial, but with some advantages, radiographers may prove able to report on some or all casualty patients. These ideas must cause conscientious radiologists concern but some compromise must be reached if radiology is to play its proper part within the present financial limits and shortage of radiologists. Yours, etc., K. R. ABERDOUR.
270, Springfield Road, Chelmsford, Essex CM2 6AS.
573
Correspondence there a greater opacity in the centre of the balloon compared with the periphery. We have shown both these changes when we repeated these experiments using the same volumes and nominal radiographic factors but changing the concentrations. This we believe is the crux of the matter—that there is an optimal range of concentrations for any given depth of contrast medium (Dure-Smith et al., 1974; Dure-Smith et al, unpublished). The two concentrations (15 and 150 mg/ml. iodine) chosen by Dr. Sherwood happen to fall outside this optimal range. Even within the optimal range changes in film density are small and depend not only on radiographic factors, but also on the characteristics of the film and processing. If the image of the smallest volume or depth appears white, increasing either depth or concentration will produce no discernible effect. Sherwood's illustration using 150 mg/ml. is correct in this respect, but the illustration using 15 mg/ml., apparently also showing no effect, is incorrect as his original radiograph shows, in that the balloons were only just opaque and not white. In this low film-density range a change of concentration X 2-4 or depth (2-5-20 ml. sphere) we would expect to produce a virtually undetectable change in density. We have previously pointed out (Dure-Smith, 1974) that this has a practical application in patients with renal impairment who can achieve only low concentrations of contrast medium in their urine; they are doubly disadvantaged in that they need much larger changes in both depth and concentration of contrast medium to produce a detectable improvement in opacification. This subject has also been confused by the semantics of biological shapes; whether the nephrons or calyces present spheres, ovoids or cylinders to the X-ray beam and the effects which such shapes have on the depth/volume ratio. However, it matters little what the exact shape is providing, as we believe, it is capable of a significant change in depth. We abandoned our biological shaped model because there is so little control over the shape it assumes (and hence depth of contrast medium). Further, the smallest volume (2-5 ml.) chosen by Dr. Sherwood must surely represent a rather hydronephrotic calyx, and its relevance to the normal calyx must be limited in view of the critical depth/concentration relationship. We feel the discussion has moved on since this chapter in Recent Advances was written and the question is not now whether or not there are significant depth changes but what contribution they make to renal opacification for any particular concentration of contrast medium. We are very grateful to Dr. T. Sherwood for allowing us to see one of his original radiographs. We would also like to thank Dr. P. Winstanley, Principal Pharmacist to the Radcliffe Infirmary, for dispensing the correct concentrations of the contrast medium, and to Miss Wendy Hills, D.S.R., for radiographic assistance. Yours, etc., P. DURE-SMITH,
Department of Radiology, Thomas Jefferson University Hospital, Philadelphia 19107, U.S.A. (Visiting Fellow, Wolfson College 1974-75.) G. M. ARDRAN.
Nuffield Institute for Medical Research, University of Oxford, 43 Woodstock Road, Oxford 0X3 6HF. REFERENCES DURE-SMITH, P., SIMENHOFF, N., ZINSKIND, P. O.,
and
KOPROFF, M., 1971. The bolus effect in excretory urography. Radiology, 101, 29-34. DURE-SMITH, P., SIMENHOFF, M., BRODSKY, S., and ZINS-
KIND, P. D., 1972. Opacification of the urinary tract during excretory urography: concentration vs. amount of contrast medium. Investigative Radiology, 7, 407-410. DURE-SMITH, P., ROSEN, R., STERN, A., FRAIMOW, H., and
SIMENHOFF, M., 1974. Physiology of the excretory uro-
gram III. A densitometric and subjective assessment of changes in contrast medium concentration. Investigative Radiology, 9,104-108. DURE-SMITH, P., 1974. Excretion of contrast medium. British Journal of Radiology, 47, 825-826. DURE-SMITH, P., ROSEN, R., FRAIMOW, H., and GALKIN,
B. Physiology of excretory urography V. The role of volumetric changes in urinary tract opacification (unpublished). SHERWOOD, T., 1975. The urinary tract. In Recent Advances in Radiology, 5, edited by T. Lodge and R. E. Steiner, pp.247-262.
THE EDITOR—SIR, MUST RADIOLOGISTS DO ALL THE REPORTING?
Your Editorial in July asks if radiologists must do all the reporting, and you publish a letter from Dr. Emrys-Roberts. With an increased work-load and a shortage of radiologists, the ideal of reporting on all X-ray examinations is one few of us can accomplish. Indeed, it is foolish to try. It results in reporting at too fast a rate, leading to an increase in errors and distortion of the work pattern as too little time is available for lengthy specialized procedures. Today, many films have to pass through X-ray departments unreported, the type of case varying from hospital to hospital and with the working agreements of the clinicians concerned. We must accept the fact that the ideal of radiologists seeing all films cannot be achieved with the present workload. The answer lies in compromise and probably some combination of the following: 1. The curtailment of the number of investigations depending on the diagnostic yield in a given clinical situation (several papers on this have been published), and the limitation of investigations so they provide only the answers to the questions posed by the clinicians. 2. Getting help from other doctors. This will mean two levels of skill, but this applies to most branches of medicine. A radiologist should be available to help with problems. Off-loading work to community hospitals is a further step which is less secure. The diagnostic yield from examinations undertaken in departments outside the supervisory umbrella of a radiologist will be less and the radiation to the patient probably more. The small department will not be used to capacity, giving a greater cost per examination. 3. Assistance under (2) is likely to be limited, but I believe radiographers could help. With non-contrast studies, suitable radiographers should be able to place films in three categories, "normal", "probably normal" and "abnormal". (I include "probably normal" to avoid the problem of the borderline cases and radiographers exceeding their knowledge to avoid having to put "normal" cases in the "abnormal" category.) The radiographers would issue a "normal" report, signing it themselves. I know this is against the Articles of The Society of Radiographers and has medico-legal implications. With follow-up cases, radiographers should be able to place examinations in three categories, "better", "the same" or "worse" with a view to reporting on those improving and long-term static cases. Even more controversial, but with some advantages, radiographers may prove able to report on some or all casualty patients. These ideas must cause conscientious radiologists concern but some compromise must be reached if radiology is to play its proper part within the present financial limits and shortage of radiologists. Yours, etc., K. R. ABERDOUR.
270, Springfield Road, Chelmsford, Essex CM2 6AS.
573
