JOURNAL OF NUCLEAR MEDICINE 5:101-111, 1964 Measurement of Pericardial Fluid Correlated with the I'31-Cholografin®and IHSA Heart Scan1'2 David M. Skiaroff, M.D., N. David Charkes, M.D., and Dryden Morse, M.D. Philadelphia INTRODUC1'ION Since its introduction in 1958 by Rejali, Maclntyre and Friedell (1), the radioisotope heart scan has become established as a safe, simple, and useful technique for the diagnosis of pericardial effusion (2,3,4,8). Nevertheless, few studies have been reported concerning quantitative aspects of the method. Early in 1961, the Radioisotope Laboratory of the Albert Einstein Medical Center, Northern Division, instituted a program in conjunction with the Division of Cardiac Surgery designed to evaluate the cardiac photoscan in patients under going open-heart surgery. It was proposed that a preoperative heart scan be per formed and the pericardial contents aspirated and measured in all such patients, and that criteria for heart scanning be established from these figures. To date, 23 operated patients have been so studied. In addition, data was available from post-mortem examination in six other patients, and five patients with pericardial effusion underwent diagnostic pericardiocentesis. An aditional three patients had massive pericardial effusions but were not tapped; these pa tients are also included in the series. Twenty-five other patients with cardiac dis ease, some with pericarditis, are not included in this study because pericardiocen tesis was not performed. ‘Presentedatthe 10thAnnual Meeting,Societyof NuclearMedicine,Montreal,Canada, June26-29,1963. ‘Fromthe Departmentsof Radiology(RadiationTherapy and NuclearMedicine)and ThoracicSurgery,AlbertEinsteinMedicalCenter,NorthernDivision,Philadelphia,Pennsyl vania. 101 102 SKLAROFF, CHARKES AND MORSE From the data obtained from these 37 Patients certain standards have been established.Itappearsthatthe photoscanningtechniquecan be used to detect pericardial effusions of 300 cc or greater, and in individuals with small or normal hearts, of 200 cc. METHOD At first,iodinatedhuman serum albumin-I13'(IHSA) in doses of 4-6 jzc/kg was employed as the scanning agent, as in the original investigations of Rejali et al (1). However, since April, 1961, we have employed I'31@Cholografin®and at present it is used exclusively. Twenty-three of the patients in this series! were scanned with P31-Cholografin and fourteen with IHSA. I'31-Cholografin is extracted from the blood by the polygonal cells of the liver and is then excreted into the biliary tree. The rate of extraction is such that 50 per cent of the initial blood concentration disappears within 4.8 hours' (5). The scan is beg-un 15 minutes after injection at the sternal notch and proceeds caudally, so that by the time the liver is reached (40-60 minutes) about 10-15 per cent of the Cholografin has been removed from the blood. Satisfactory scans have been obtained with doses of P31-Cholografin of 3-7 ,@c/kg and scan speeds of 16-18 cm/mm. Non-radioactive iodine in the form of Organidin® is adminis tered by mouth several hours prior to scanning to block the thyroid uptake of i' -u 1If 0.25 mg. Cholografin is injected. 4 Fig.la (left):Photoscanof cardiacblood pooi of 53 year old white male with mitral stenosis, superimposed on 6.foot, AP, recumbent, split film. 32 cc of pericardial fluid was aspirated at open-heart surgery. Note activity in aorta, pulmonary great vessels, lung fields, and liver. Difference between maximum transverse cardiac diameter of scan and x-ray images is 0.5 cm, ratio 0.97. I―@ChoIo grafin, 300 @c. Fig.lb (right):Cardioscanof30 yearoldwhitefemalewithacutebenignpericarditisand massive effusion. Diameter difference 7.0 cm, ratio 0.63. Note separation of cardiacbloodpoolfrom pulmonaryvasculatureand liver.I―Cholografin, 300 1@c. MEASUREMENT OF PERICARDIAL FLUID 103 The instrument used for thisstudy was the Picker Magnascanner (6), which is equipped with a 3 x 2 inch NaI(TA) crystal and pulse-height analyzer. The maximum count ratevaried somewhat with the dose, blood volume, cardiac size and geometry (4),but was approximatelybetween 6 and 15 cpm/@c (1800-6000 cpm). The count range differential was usually set at 40 to 60 per cent, with background determinedoverthelung fields.Low countrangedifferentialsettings were avoidedsincetheytendtoproduce a smallerimage. The scan was displayedboth on Teledeltospaper and on clearx-rayfilm, but only the latterwas used for diagnosticpurposes (photoscan).Localizing marks were made in the midclavicular lines at approximately the 4th intercostal space and recorded on the photoscan. Lead shots were then placed on the skin marks and two successiveexposuresmade of the chestat a 6-footdistancein the AP projection, the central ray passing through the lead markers alternately. Such splitfilmshave been shown to produce minimal distortionof the cardiacimage (2). The photoscan was then accurately superimposed on the roentgenogram and the maximum transverse cardiac diameters measured. Comparison of these para meters proved to be the best criterion of pericardial effusion. TABLE I CORRELATION OF CARDIAC PHOTOSCAN WITH VOLUME OF PERICARDIAL FLUID ofNumberMean Ratio TransverseDifferenceDiametersPericardialMaximum Fluid*of Diameter, cmBetween sScan PatientsCardiac Diameters, cm (5) X-Ray (X) (X-S)/ 15.4 17.5 2.1 .85 100 cc or less 24 (10.5-21.5)@ (12.0-23.6) (0.5-3.5) (.80-.96) 200 to 300 cc 3 Br—200 cc 1 15.0 19.0 4.0 .79 Hi—200cc 1 14.5 19.8 5.3 .73 Gr—300cc 1 10.0 13.0 3.0 .77 Morethan300cc 10 12.9 18.7 5.8 .69 (10.3-15.6) (13.0-22.0) (4.5-8.7) (.60-.79) *Mcastired by aspiration of pericardial contents at open-heart surgery in 23 patients, at autopsy in 6, and by pericardiocentesis in 5. In 3 patients pericardial effusion was massive but was not measured. XxRa nge. 104 SKLAROFF, CHARKES AND MORSE RESULTS Of the 37 patients, 13 had pericardial effusions of 200 cc or more. The other 24 patients all had severe cardiac disability, with hypertrophy and/or dilatation of one or more chambers. These latter patients, with effusions of 100 cc or less, were compared with the group of 13. Figure la demonstrates an P31-Cholografin photoscan superimposed on a split, 6-foot, AP, recumbent chest film of a patient with mitral stenosis. Thirty two cc of pericardial fluid was found at operation. The blood pools of the heart, aorta, pulmonary great vessels and lung fields are well visualized, and the liver has also been outlined. The cardiac blood pool almost, but not quite completely, fills out the cardiac silhouette on roentgenogram. In the 24 patients with cardiac hypertrophy and/or dilatation with 100 cc or less of pericardial fluid, the mean difference between the maximum transverse cardiac diameters on scan and x-ray was 2.1 cm and was always less than 3.5 cm. The ratio of the two diameters was always greater than .80 (mean .85). There were 13 patients with pericardial effusions of 200 cc or greater and in 11 of these, the difference between the maximum transverse cardiac diameters of scan and x-ray was greater than 4.5 cm. The ratio of the diameters in every case was less than .80 (mean .69). The causes of the pericardial effusions of these 13 patients were: acute myo cardial infarction (1 patient), active rheumatic carditis (2), carcinomatous peri carditis (1), acute benign pericarditis (6), and pericardial effusion of unknown etiology (1). With marked pericardial effusion (Fig. ib) a non-radioctive zone visibly sur rounds the cardiac blood pool, and separation from the pulmonary vasculature and from the liver can be demonstrated. These changes are more obvious when the scan is seen without superimposition on x-ray (Fig. 2). Three patients were found to have effusions of between 200 and 300 cc, Fig. 2.: Same as Figure 1 except that scans are not superimposed on roentgenograms. Note that in pericardial effusion (right) the cardiac blood pool is separated from the liver and pulmonary vasculature. @ — MEASUREMENT OF PERICARDIAL FLUID 105 and in two of these three patients the diagnostic criteria for pericardial effusion were not completely satisfied ( Table I ) . The first of these patients had moderate cardiomegaly ( transverse cardiac scan diameter 15.0 cm ) and was found to have 200 cc of fluid in the pericardial cavity at the time of open-heart surgery for mitral stenosis (Fig. 3). The difference between the maximum transverse cardiac diameters on scan and x-ray was 4.0 cm, which is greater than that of the 22 pa tients with effusions of less than 100 cc, but less than that of 11 patients with effusions of more than 300 cc. This was therefore a borderline result. Similarly, the diameter ratio of 0.79 was also borderline. Thus in the pres ence of cardiomegaly, a 200 cc effusion may not widen the x-ray silhouette enough to satisfy all the criteria for effusion which we have established. In the second patient, with a slightly smaller heart, a routine preoperative scan detected a pericardial effusion (Fig. 4), although there was no clinical evi @ -SI@@ -@-@ - @ ‘@ $T —l--___ - ____ @ Sues @—@ =- - .SI@. S - —-- .@ .___ - — - _. I - @ UI@- -*I@@ SI-@- @—@_p @—@--@-@ @, - @ F -@‘.@-@-@-- -‘— @ 5' @ —@ @—-@-@- -=;=;@ a_I-- ,@. @ — — L --- - - @ —5, -@--@S_ @*-@ -— --- @ @“SSI -@ -@ -e@@ @..-— Fig.3.:Heart scanof 52 year old negro femalewith mitralstenosis.Diameter difference 4.0 cm, ratio 0.79. At operation pericardial cavity contained 200 cc. Note that liver isnot separatedfrom cardiacblood pool.Transversescandiameterof 15.0cm is indicative of cardiomegaly. IHSA, 350 @c. 106 SKLAROFF, CHARKES AND MORSE dence of pericarditis. At open-heart surgery for mitral stenosis 200 cc of sero sanguinous fluid was aspirated from the pericardial cavity, and a fibrinous pen carditis was found.