CASE STUDY Regional lung spirometry RPClauss MBChB, MMed (Nuc Med), MD W Pilloy MBChB, MMed (Nuc Med), MD Nuclear Medicine Department, Medical University of Southern Africa Abstract Forty con senti ng patients took part in a study to determine lobar, segmental and regional lung volumes and flows as reflected by changes in lung radioactivity measured by nuclear medicine techniques. Two hundred MBq of the gaseous radioisotope I nXe were injected into are-breathing circuit spirometer with an 8 litre capacity and an equilibrium activity of 25 MBq/litre. A posterior dynamic acquisition of 400 frames at 0.125 seconds per frame for the determination of lung volumes and flows was completed, followed by a gas washout period. The acquisition recorded both tidal breathing and 3-6 cycles of maximal inhalation and exhalation after homogenous mixing of the radioactive Xenon inside the lungs and the spirometer, but before significant diffusion of the tracer into the blood. The conversion from millilitres to counts was accomplished by matching a representative breath cycle on the spirometric graph with the same cycle on the radioactivity curve generated on the processed scintigram of the whole lung. A change in volume was hence matched to a change in radioactivity, and a specific radioactivity per millilitre of lung volume was calculated. A region of interest was drawn on the scintigram over a lung lobe or segment. The regional radioactivity change represented a regional breath cycle in this area, with regional volume and flow changes. Spirometric parameters such as lobar vital capacity, tidal volume, residual volume and forced expiratory volume after 1 second were derived by using the previously calculated radioactivity per millilitre of lung volume. Total lung volumes and flows derived from radioactivity changes were compared to the concurrent volumes and flows measured on the attached spirometer, and a close correlation was found. 21 SA JOU RNAL OF RADIOLOGY. November 1998 Introduction Conventional lung function tests measure the combined volumes and flows of both lungs and compare them to established normal values for the in- vestigated population. This measure- ment is however insensitive to lobar or regional functional changes that may occur with localized pathology. Hamilton et al,l applied a math- ematical model to tidal breathing, us- ing 8lmKr,and Wernly et aF predicted postoperative lung function from preoperative lung function tests by weighting these results according to the preoperative lung distribution of99mTc MAA and 133Xe.Amis et aP calculated a flow/volume ratio for specific lung regions in patients with diaphragmatic paralysis using 81l11Kr and 851111(rconcen- trations at tidal breathing. Holli et al4 and Miërner" used computerised multidetector radiospirometrie meth- ods to determine regional lung func- tion. Kauppinen-Walin et alG used simi- lar techniques to compare I33Xe radiospirometry with Helium spirom- etry and whole-body plethysmography in the determination of functional re- sidual capacity and the effect of body position on this parameter. Seeker-Walker et aF calculated regional lung ventilation from mean functional air exchange in selected lung regions. The above tests measure lung function either indirectly or make us of sp - cialized equipment or isotopes that are not generally available. The aim of this study was to ratify a simple and repro- ducible method to measure lung func- tion by radioisotopes, for application to small lung regions such as lung lob s or segments. Using the radiospirometrie method described below, lung function was derived from gaseous lung 133Xe topage22 Regional lung sp+rorrietrv from page 21 radioactivity, as measured by an Anger gamma camera that is readily available in any nuclear medicine department. The radioactivity was correlated with the actual lung function, as measured on a concurrently generated spiromet- ric volume curve. Method Investigations were performed on 40 consenting patients. Thirty-one were males and nine were females. Ages ranged between 12 and 73 years. Two hundred MBq of 133Xegas was introduced into a lead-shielded, re-breathing circuit bell spirometer, where it was homogeneously mixed with ambient air. The capacity of the spirometer was 8 litres and the activity of its gas mixture was 25 MBq per litre. The patient was connected to the spirometer and proceeded with 5-10 tidal breathing cycles to achieve a dy- namic equilibrium between the lung and spirometer gas concentrations (Figure 1). Four hundred images ofO.I2S sec- onds each were recorded over the lung from a posteriorly positioned Anger gamma camera while the patient continued with tidal breathing, fol- lowed by 3-6 maximal forced inhala- tions and exhalations before the end of the recording. The patient then con- tinued with tidal breathing to wash the gas mixture out of the lungs. The whole investigation and wash- out was completed in less than 3 min- utes. Measurements were completed before any significant diffusion of the tracer into the blood. The lung radioactivity graph that was recorded by the gamma camera was compared to the concurrent vol- ume graph that was recorded by the spirometer. A specific radioactivity per unit volume was then calculated: Count/millilitre = Change in lung radioactivity over any breathing cycle Change in lung volume over the same breathing cycle Once a count/lung millilitre was available, a region of interest could be outlined on the lung seinti-image and radioactivity changes in this region could be expressed as volume changes. For instance, if a lung lobe was outlined on the scinti-image, a total volume for GRAPH LESION COUNTS ~, . :..... VOLUME Figure 1: Schematic presentation of the apparatus used for the r33Xe radiospirometry. 22 SAJOURNAL OF RADIOLOGY. November 1998 this lobe could be derived. Similarly any lobar volume changes, for instance lo- bar tidal breathing or maximal inhala- tion and exhalation volumes for lobar vital capacity could be measured. Hence it was possible to derive lobar spirometric parameters (volumes and flows). The following spirometric param- eters were correlated with total lung radioactivity changes: Tidal volume (TV), vital capacity (VC), expiratory reserve volume (ERV), inspiratory ca- pacity (I~) and forced expiratory vol- ume after 1 second (FEVI). Other parameters that were meas- ured but not correlated were: residual capacity, FIV 0.5, FIV I, FIV 3, FEV 0.5 and FEV 3. Results Figure 2 shows the graph of radio- activity changes over both lungs while performing tidal breathing and during a number of maximal inhalation and exhalation cycles in a patient with empyaema. Table I shows the correla- tion of radioactivity to the volume changes in the tested patients. Discussion There is a good correlation between spirometric parameters and lung pa- rameters derived from radioactivity changes. We used the method for determi- nation of regional lung function in vari- ous groups. For instance, we compared the function of the affected lung in patients with unilateral haemo- or pneumothorax, before and after physi- otherapy. A significant improvement in unilateral lung function was de- tected after physiotherapy, while to- tal lung function before and after physiotherapy did not change." This topage23 Regional lung spirornetry frompage22 regional flow/volume loops were generated over the left and the right lungs of one of our patients with bul- lous lung disease. In this patient, air was shunted from the left lung to the right dur- ing an expiratory cy- cle. Such shunting was however not ap- parent on the global (total lung) flow/ volume loop (Fig- ure 3). On the practical side,there are some pitfalls that have to be borne in mind. Xenon is a gas that diffuses from the lung into the bloed." Hence, the longer radio- Xenon is in the lung, the more background activity is present in the blood. This may lead to an over-estimation of the residual volume. As the spirometer is a closed circuit, accumulation of CO 2 could oc- cur; this is however absorbed by soda lime crystals in the cir- cuit. The clinical condition of the patient should allow co-operation during tidal breathing and maximal inspira- tory and expiratory manoeu- vres. Non co-operation may result in leakage of the radio- active gas from the patient's mouth into the surrounding air. When using a bell/fluid spirometer, spillage of water into the spirometer pipes may occur. This results in poor gas mixing and may give mislead- ing results. The piping of the spirometer should therefore be regularly inspected, together with routine calibration. MEt ."c sec Figure 2: Radioactivity curve representing tidal and maximal inhalation and exhalation manoeuvres. Table I: Comparison of total lung radiospirometry and concurrent conventional spirometry (n=40) Parameters Mean Std. dev. Spearman correlation (ml) rr p Tidal '~Xe 605 252 0.905 0.0001 volume Cony. 540 222 Vital I~Xe 1941 860 0.912 0.0001 capacity Cony. 1768 616 Exp. '''Xe 348 218 0.887 0.0001 Reserve Cony. 334 212 Insp. I~Xe 1593 758 0.884 0.0001 Capacity Cony. 1328 498 FEVI 133Xe 1187 551 0.882 O.QOOI Cony. 1081 368 was due to compensation by the healthy lung for the incapacitated lung. We have also applied the method to preoperative empyaema patients to predict postoperative lung function. The determination of regional lung function may be more important than is generally realized. Conventional lung function tests show only global air movements. When the same air move- ments are followed onto a regional level, it appears that there are ongoing dynamic regional changes in air flows and pressures. For example, while most segments decrease their volumes dur- ing expiration, there are some segments that may actually increase their volume. However, these small paradoxical dis- crepancies cannot be seen on conven- tional spirometric curves. For example, 23 SA JOURNAL OF RADIOLOGY· November 1998 Another aspect that appears to in- fluence the spirometric curves is the inertia of the spirometer bell. The ra- dioactivity changes and curve edges are sharper and better defined than those on the spirometric graph. Volume changes and the rate of volume change may be under-estimated by conven- tional spirometry. The smallest lung region size that could be reasonably evaluated by the above method was approximately 20 ml. In smaller regions, there is a problem of insufficient count statistics. We are at the moment modifying our techniques to obtain list mode c. Posterior lung image showing the flow-volume loop of both lungs (excluding trachea). to page 24 Regional lung sp irorrtetrv trom page 23 rather than frame mode acquisitions, so that framing time can be chosen by the processing operator after com- pletion of the radiospirometry. This helps in the smoothing of curves and in the selection of the activity peaks that are used for determination of lung parameters. Conclusion The above method is practical and can be applied in any nuclear medicine department. There is a good correla- tion between conventional spirometry and J33Xe radiospirometry. There should be further exploration of paradoxic lobar and segmental air move- ments and investigation into possible local lung reflexes. Regional inca-ordi- nation of such air movements may in- fluence respiratory disease. References 1. Hamilton 0, Godfrey KR, Causer DA McIntosh JA. Regional specific mean expiratory gas flow from RI"Kr equilibrium inhalation data. Eur J Nucl Med 1985; 10:321-331. Wernly JA, DeMeester TR, Kirchner PT, Myerowitz P, Oxford DE, Golomb HM. Clinical value of quantitative ventilation-perfusion lung scans in the surgical management of bronchogenic carcinoma. J Thorac Cardiollasc Surg 1980;80:535-543. AmisTC, Ciofetta G, HughesJMB, Loh L. Regional lung function in bilateral diaphragmatic paralysis. Clinical Science 1980;59:485-492. 4. Holli H, Muittart A, Paakkala T, Poyhonen L, Seppanen A, Uusitalo A. Comparison between conventional examinations and radiospirometry measured by computerized multidetector unit- Kefut Bl 1200 in evaluations of regional lung function pre-operatively and after cobalt therapy. Radioaki Isop Klin Forsell 1976; 12:23. 5. Miërner G. "'Xe Radiospirometry: A clinical method for studying lung function. Scand J Respir Dis 1968;SuppI64: 17-43. 6. Kauppinen-Walin K, Sovijarui ARA, Muittari A, Uusitalo A. Determination of residual capacity with 111Xenonradiospirometry. Comparison with whole body plethysmography and Helium spirometry. Effect of body position. Scand J Clin Lab invest 1980;40:347-354. 7. Secker-Walker RH, Hili RI, Markharn J, Baker l,Wilhelm J,Alderson PO, Potehen EJ. The measurement of regional ventilation in man: A new method of quantification. J NucMed 1973;14:725-731. 8. Mji M, Clauss RI'.The efTects of expiratory and incentive expiratory spirometry on young males with traumatic haemo-pneumo-thorax. MEDUNSA abstracts 1991;12th academic day. 9. Ahmad M, Perrillo RP, Sunwoo YC, Donati RM. Xenon-I ~3 retenlion in hepatic steatosis - correlation with liver biopsl in 45 patients: concise communication. JNM 1979;20l5):397-401. frampage 15 2 A mini rev ievv of paragangliornas vvitl : presentation of tvvo cases Surgical cure rates of 66-85 % have been reported with a 5-10 % recur- rence rate.2,3 The five year survival is 80-95 % with surgery, and less than 50 % in malignant disease.v" The hy- pertension cure rate is 75 % if total tumour excision is accomplished. In 25 % of cases the hypertension per- sists either due to unmasking of pri- mary hypertension, intraoperative re- nal ischaemia, damage to the renal vessels, or catecholamine-induced vas- cular damage. Conclusion Paragangliomas are rare tumours that are potentially lethal if undiag- nosed or discovered incidentally. Their early diagnosis requires a high index of suspicion and appropriate biochemical tests. Accurate radiological localisation of the tumour is best accomplished using MRI as a first line investigation with MIBG scans being reserved for cases of recurrence, multicentricity, metastatic disease or equivocal MRI. Where the tumour is biochemically inactive, MR! scanning is the best op- tion. Octreotide is emerging as a prom- ising agent, but its long-term perform- ance remains to be fully evaluated. Appropriate and early intervention car- ries a favourable prognosis in an other- wise dangerous tumour. 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