CORRESPONDENCE 3 No attempt has been made to compare the distribution of the abnormalities on CT scanning with the extent of the disease as demonstrated by bronchography in the two patients who had a full examination. 4 The poor tolerance of bronchography which is valuable in confirming the diagnosis of OB might be overcome by using an alternative contrast medium to Dionosil suspension. We have recently reported the tolerance and suitability of using a water soluble non-ionic dimer (Iotrolan, Schering AG) in selective bronchography via the fibreoptic br0nchoscope (Morcos et al., 1989). The effects on spirometry and oxygen saturation (SaO2) were significantly less than those reported with Dionosil (Goldman et al., 1987). Iotrolan can be injected directly into the suction channel o f the bronchoscope, it does not obscure bronchoscopic vision nor does it interfere with further bronchoscopic procedures such as trans-bronchial biopsy which can be used to confirm the diagnosis of OB histologically. S. K. MORCOS
Department of Diagnostic Radiology Northern General Hospital Sheffield $5 7A U
al., 1987). There is currently no evidence to suggest that poor tolerance ofbronchography in our patients might be overcome by use of Iotrolan. Geddes et al. (1977) reported that the airways obstruction in OB was wide spread and patchy and in their patients could only be confirmed histologically after 'painstaking post-mortem examination'. Even in disorders with diffuse pareuchymal involvement, e.g. sarcoidosis, transbronchial biopsy may only provide diagnostic specimens in approximately 60% of cases. This diagnostic yield would probably be greatly diminished in patchy asymmetrical disease such as OB, in which the risk of pneumothorax is potentially extremely hazardous. 5 It is perhaps appropriate to indicate that thick section (10 mm) CT with a lung algorithm was used to scan our patients rather than our usual method, i.e. high resolution CT using a bone algorithm as the former is more sensitive to density changes and our study was not primarily concerned with the very subtle structural changes which may have been present. M. SWEATMAN
Mount Vernon Hospital Northwood Middlesex HA6 2 R N
Breatnach, E & Kerr, I (1982). The radiology of cryptogenic obliterative bronchiolitis. Clinical Radiology, 33, 657 661. Dark, J & Corris, PA (1989). The current state of lung transplantation. Thorax, 44, 689-692. Goldman, JM, Currie, DC, Morgan, AD & Collins, JV (1987). Arterial oxygen saturation during bronchography via the fibreoptic bronchoscope. Thorax, 42, 694 695. Morcos, SK, Baudouin, SV, Anderson, PB, Beedie, R & Bury, RW (1989). Iotrolan in selective bronchography via the fibreoptic bronchoseope. British Journal of Radiology, 62, 383 385. Sweatman, MC, Millar, AB, Strickland, B & Turner-Warwick, M (1990). Computed tomography in adult obliterative bronchiolitis. Clinical Radiology, 41, 116-119.
Geddes, DM, Corrin, B, Brewerton, DA, Davies, RJ & TurnerWarwick, M (1977). Progressive airways obliteration in adults and its association with rheumatoid disease. Quarterly Journal of Medicine, 46, 427-444.
SIR We were appreciative of Dr Moreos' interest in our paper and would like to make the following points in response to his remarks: 1 Heart-lung transplantation was included in our submitted manuscript as a cause of OB and remains referenced (Burke et al., 1984) in the published version; regrettably an error of proof reading occurred and I am grateful for the opportunity of making this correction. The paper on lung transplantation (Dark and Corris, 1989) was published after submission of our manuscript and thus did not appear among the references. 2 CT was considerably more successful in revealing extensive abnormalities than either the chest radiograph or bronchogram within the patient group studiedalthough Dr Morcos was correct in understanding that the limitation of bronchography was solely due to poor patient tolerance. This is an important and clinically practical point, since the better sensitivity of bronchography becomes irrelevant in a context within which this investigation cannot be used (as in many patients with OB). The major advantage of CT is that it is a non-invasive, well tolerated procedure which can be performed (if necessary serially) in every patient with OB. The principal stated aim o f our paper was to compare CT with the plain chest radiograph in the assessment of patients with OB in which respect it is worthwhile observing that the sensitivity of the latter was only 77% compared with CT, certainly supporting the contention that CT may be a more effective investigation in patients with OB. In those patients who underwent both bronchography and CT, both investigations were abnormal indicating respective sensitivities of 100%. 3 In the two patients undergoing, full bronchograms and CT, the extent of disease demonstrated by CT was equivalent to the bronchogram in one patient but greater in the other revealing previously Undetected right upper lobar involvement. 4 Goldman et al. (1987) did indeed demonstrate that the use of l)ionosil could provoke severe arterial oxygen desaturation in patients with bronchiectasis undergoing selective bronchography via the fibreoptic bronchoscope, although they could not discriminate causally between the physical presence of the instrument or the properties of the aqueous contrast medium. They recommended that bilateral bronchophy should be avoided in patients with pre-operative hypoxaemia. orcos et al. (1989) reported the tolerance and suitability of Iotrolan in Patients with bronchiectasis (8), solitary pulmonary nodule (2) and recurrent left upper lobar collapse (1) but speeifically exeludedpatients ~Vith poor respiratory function; these are not comparable with our Patients in the context o f whose extremely poor lung function bronehography should evidently be avoided were possible (Goldman et
STARTING F R O M S C R A T C H - S O M E P R O B L E M S WITH FORREST S1R - The Editorial by P. B. Guyer (1990) voiced many problems with regard to the national breast screening programme (Forrest, 1986). It states that in order to comply with the Pritehard double reading recommendation (Pritchard, 1987), two extra radiologist sessions per week would be required in a unit screening 70 patients daily. We carried out a survey of the 48 screening units operational by midNovember 1989 to determine the number o f centres that were doublereading and also the number of centres routinely carrying out two view studies in the prevalence round. Of the 43 replies received (90%), 29 centres (67%) had doublereading, and 14 centres (33%) had single-reading. It is particularly interesting to note that 41% of the double-reading centres routinely performed two view mammography in the prevalence round. Only 21% of the single-reading centres routinely performed two view studies. The variation in practice between centres is probably influenced by financial constraints, but we find it surprising that single-reading centres perform only half as many two view studies as double-reading centres. When statistics are being reviewed for the purpose of audit, results from centres where radiologists are single-reading single view studies, should not be compared with centres where radiologists are doublereading two view studies. A. O ' D O H E R T Y P. D O N A G H Y
Northern Ireland Screening Programmes 12 22)Linenhall Street Belfast BT2 8BS
References Forrest, P (1986). Breast Cancer Screening. HMSO, London. Guyer, PB (1990). Starting from scratch - some problems with Forrest. Clinical Radiology, 41, 1 2. Pritchard, J (1987). Guidelines on the Establishment of a Quality Assurance System for the Radiologieal Aspects o f Mammography used for Breast Screening. Report o f a Sub-Committee of the Radiological Advisory Committee of the Chief Medical Officer at the Department of Health and Social Security. p. 1.
INHALATION OF CARBEX I read the letter by Dr Mills (1990) on inhalation of Carbex with some interest, as this is a problem I think we must all have met at some stage during training. As Dr Mills implies, swallowing the dry granules is difficult for nervous or elderly patients and those with dysphagia. Indeed, having tried it myself, they are difficult to swallow easily when (relatively) young, fit and healthy! The dry granules rarely pass smoothly down the oesophagus and the liquid chaser usually starts fizzing in the mouth and pharynx from contact with retained powder. My own solution to this practical problem in radiology, is to dissolve the