JOURNAL OF NUCLEAR MEDICINE 8:411-425, 1967

Modification of a Multi-Isotope Color Scanner forMulti-Purpose Scanning'

Moshe Ben-Porath, Glenn Clayton, and Ervin Kaplan

Hines and Chicago, illinois

In recent publications from our laboratories, a technique using dual pulseheight analyzer count rate systems has been described for electronic subtractionof one gamma photopeak from another allowing unhindered visualization of asecond photopeak. By this method, subtraction of the 198Auphotopeak from the75Se photopeak permits elimination of the liver scan from the pancreaticscan (1-3). Applying similar circuitry to a commercially available color scanner,2

the instrument may be modified to simultaneously scan two isotopes which emitphotons of two different energy levels and display on the recording paper thedistribution of each isotope in a different color. The overlying parts are displayedin intermediate colors or shades of two colors. Combining the “Subtract―andthe “Two-Color―circuits to the color scanner, a variety of modes of operationfor multi-isotope scanning is possible.

THE BLOCK DIAGRAM

The block diagram of the entire system is illustrated in Fig. 1. Thefollowing parts are added to the conventional scanner: input mixing box, a dualchannel analyzer, an output mixing box, two dual ratemeters, a DC-Frequencyconverter and a DC-Isolator. An additional pulse amplifier was wired into the

scanner ratemeter chasses (EXT. PLS.—AMP on Fig. 1), to permit independent

recording on the photo and print systems. The modes of operation of the modi

fied scanner are selected by turning a single 6-deck rotary switch, which is also

‘Fromthe Radioisotope Service, Veterans Administration Hospital, Loyola UniversityStritch School of Medicine, Hines, Illinois, and University of Illinois College of Medicine,Chicago, Illinois.

2Picker Nuclear, Magnascanner V.

411

412 BEN-PORATH,CLAYTON,KAPLAN

shown in Fig. 1. Fig. 2 is a photograph of the modified scanner.' An additionalmodification is the introduction of a “one-waycircuit―to the mechanism of thescanner. This circuit permits the scanner to record while moving in one direction only, returning over the same line at a 200 cm/mm speed. Since scallopingresults from a delay in printout of alternate scan lines due to the factor of timeconstant, this type of scanning eliminates scalloping completely, thus makinghigh-speed, slow time constant scanning possible. The relatively slow time constant (1 see) is necessary mainly for subtract scanning to permit sufficient time forthe subtraction event.

SCANNER SLCTION@ POSITION I —NORMAl. SCANNCN OPERATION

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Fig. 1. A block diagram of the scanner, adjunct equipment and switching arrangementfor various modes of operation.

LOGIC AND PROCEDURE

Position 1

In this position the scanner will function as a conventional color scanner,only the original components of the scanner being included in the circuit.

Position 2

This is the mode of operation previously described in detail (1-3). Pulsesof different energies from two isotopes are discriminated by two pulse heightanalyzers, fed to individual components of a dual ratemeter, subtracted onefrom the second, and fed through a DC to frequency converter, designed andconstructed in our laboratory, to the —@V input of the scanner ratemeter. Thedifference of the pulses may be recorded on both the photo and mechanical

‘InFig. 2, a 4-channel analyzer is shown. Actually only two of the four channels arerequired and used.

413MODIFICATIONOF A MULTI-ISOTOPESCANNER

recording devices. The major application of the mode of scanning appears tous to be for pancreatic scanning. Selenium-75-methionine and colloidal 198Auare administered to the patient simultaneously. Equating the 75Se pulses in apositive mode to the ‘°8Aupulses in a negative mode gives a net picture ‘ofthedistribution of 75Se-methionine outside the liver, the last being subtractedthrough the negative recording of the 198Au pulses. The procedure and resultsof pancreatic scanning by this method have been described and discussed inreferences 1, 2 and 3. Fig. 3 illustrates pancreatic photoscans obtained by thisprocedure. This position is useful also in the scanning of 1251in the presence of131J (or any low-energy gammas in the presence of a higher energy gamma).

Fig. 2. The scanner modified for multiple modes of operation.

414 BEN-PORATH, CLAYTON, KAPLAN

To accomplish this, Channel 2 (ratemeter B) in Fig. 1 is peaked for 125j,Channel 1 (ratemeter A) for iodine-131. An 131J source is placed under thedetector. The settings of the window width of Channel 1 and ratemeter A areselected so that the deflection on ratemeter A equals the deflection on ratemeter B, so that the difference B —A = 0. At this point no 1311counts will berecorded at the output of the subtract circuit, B —A. If an object or organcontaining both 1311and 1251is now placed under the detector, only counts fromthe 1251 will be recorded at the B —A output, as the 131J countrate in ratemeter B will be subtracted by identical countrates from ratemeter A.

B (1311) — A (“I) = 0

A (1251) = 0B (1251) —A (1251) = B (1251)

Therefore [B(1311) + B('251)] — [A(131I) + A(125)] = B(1251)

Position 3

In this position, two isotopes emitting photons of different energy levels maybe scanned simultaneously and a color display of the distribution of each of theisotopes in a different color obtained. The overlying parts will appear on thescan in intermediate shades of the two colors. Pulses from the preamplifier arefed into a dual channel analyzer. The outputs of the two channels are split, feeding a dual ratemeter and a mixing circuit consisting of two diodes to preventfeedback from one channel to the other. The pulses from the mixing circuit arefed through the scanner ratemeter and drive the stylus. The ratemeter outputs

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Fig. 3. A pancreatic scan obtained by subtraction of the liver image allowing unimpededvisualization of the pancreas. (Reprinted')

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415MODIFICATION OF A MULTI-ISOTOPE SCANNER

are subtracted one from the other by a built-in circuit.1 The difference, whichmay be positive or negative, used to subtract one isotope from the other maynow display the subtracted isotope in one color and the positive in anothercolor by driving the scanner's color control through a DC isolator designed andconstructed in this laboratory. This isolator is essential, as the DC output of thesubtractor and the DC input of the color drive are isolated. The DC isolatorschematic diagram is shown in Fig. 4. In operation, the DC output of the subtract circuit is connected to a #6977 Amperex light source. Any change in theDC output, positive or negative, will alter the light intensity of this lamp. Thelight output is measured by a CdS cell; the DC output of the CdS cell drivesthe color controL This output is proportional to the light output and thusproportional to the relative output from the two ratemeters.

The standard color tape of the scanner consists of seven usable colors, withblack at one extreme and dark red at the other; purple, blue, green, orange anda light red are intermediate colors. The color tape has been modified using onlytwo colors—blueand red, and four shades of each, diminishing in darkness fromthe extremes to the center. The range of color is controlled by the scanner“colorcalibrate―potentiometer control and by the resistor switch in Fig. 4.The center color is set by the potentiometer in Fig. 4.

The dual ratemeter is set in test postition. Both range scales are at 10K. Atthese settings, the difference of the two outputs is zero, and the center coloris selected by means of the DC isolator potentiometer in Fig. 4. The range ofcolor (or shades) is established, with the aid of the above mentioned resistorswitch and “colorcalibrate―potentiometer by setting one ratemeter range to3K and the second to 30K scales, to provide maximum differences. This step

1Picker-Nuclear Dual Ratemeter Model #5846.

Fig. 4. Wiring diagram of the “colorcalibrate―circuitry.

416 BEN-PORATH,CLAYTON,KAPLAN

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417

is then repeated, inverting the settings of the two ratemeters to obtain deflectionof the color tape in the opposite direction. The ratemeter is reset to normalposition. The patient is then scanned manually and the ratemeter scales determined. The scales should be set so that the maximum deflections (not countrates) on each meter are of an equal magnitude. This condition can be achievedby selecting proper scale ranges for each meter and, if necessary, by altering thechannel width on the corresponding analyzers. This procedure could best beaccomplished by a balancing circuit between the two meters.

The patient and the instrument are now set for energy-color scanning. Ifonly pulses of energy A are detected, the color band will be deflected to oneextreme and the pulses will be recorded in color A. If only pulses of energy Bare detected, the color band will be deflected in the opposite direction and onlycolor B will be printed. If pulses of both energies are detected, the color bandwill move between the extremes printing out intermediate shades of the twocolors. If A is greate@ than B, the lighter shades of color A will be printed, thedarker shades indicating the magnitude of the difference. If A is less than B,shades of color B will be printed. The intensity of the counts is indicated by thedensity of impulses printed, which is controlled by the sum of A + B.

Figure 5 shows the energy-color scan of a phantom, consisting of 50 ,LC 198Auin a Marinelli Beaker and 50,@CT5Sein a cylindrical container inserted %into thehollow part of the beaker. The gold is printed out in black, the selenium inred, and the overlapping part in the intermediate colors. Figure 6 is a scan ofthe liver containing T5Seand ‘98Aushown in blue and the pancreas containing75Se in red. In Figure 7, the liver (198Au, black) overlies most of the right kid

MODIFICATION OF A MULTI-ISOTOPE SCANNER

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Fig. 9. (right) The two color display in conjunction with the subtract mode is usedto visualize @MAuin the liver and 75Se in the pancreas.

418 BEN-PORATH,CLAYTON,KAPLAN

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ney (‘9THg,red); nevertheless both organs are individually visualized by intermediate colors. Figure 8 is a lung (R1311SA Macroaggregate) and liver (‘°8Aucollodial) - scan. The patient was suspected of a right subdiaphragmatic abscess (4). The scan excludes this possibility, as the overlying part of the liverand right lung lobe are outlined in the intermediate shades. The pathologyindicated in the upper and medial left lung were confirmed by radiologicalfindings.

Position 4 -

In this position, both the subtract and the two color circuits are activated.The net output of the subtract is fed from the DC-frequency converter to oneof the two ratemeters of the color control dual ratemeter and to the input of the

I TWO ISOTOPE SCAN

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Fig. 15. Circuit diagram of one way one isotope scanner modification.

MODIFICATION OF A MULTI-ISOTOPE SCANNER 421

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422 BEN-PORATH, CLAYTON, KAPLAN

output mixer box. In this setting scanning two isotopes, one will be displayedin one color and the “subtract―of the two in a second color. This factor isparticularly useful if, for instance, the pancreas and the liver are to be displayed.Then the 198Auwill be displayed in one color and the extrahepatic T5Se minus‘98Aupulses in the second color ( Fig. 9). The usefulness of this position isdemonstrated in the following case:

A pancreas scan by the subtract method was performed on a patient withsuspected malignant involvement of the pancreas ( Fig. 10). It was difficult todetermine the meaning of the large mass of selenium concentration demonstrated in this scan. An energy-color scan was subsequently performed (Fig.11 ). This scan showed the selenium mass to be in the liver. A liver scanutilizing the 198Aualready in the liver was performed (Fig. 12) and revealeda “cold―area, interpreted as a space occupying lesion at the identical locationof the selenium mass visualized in Fig 11.

Fifty-two days after these scans were performed, a necropsy revealed ahepatoma and severe chronic pancreatitis. A massive tumor was found in theliver ( Fig. ha ), precisely at the location revealed by the scan. Tumor cells werespread throughout the entire liver with several nodules of various sizes. Fivegram specimens of various organs were obtained and the T5Se concentrationwas determined (Table I) and revealed to be equal in both liver and hepatomaat 52-days post administration. No information is available concerning relativeconcentration at the time of scanning. Assuming equal concentration at the timeof scanning, the T5Sein the hepatoma would still be visualized by this methodas ‘98Audid not concentrate in the tumor allowing the nonsubtracted “Seinthe hepatoma to be visualized as a separate color.

Another application of position four is demonstrated in Figure 13A, the“@Ithyroid scan visualizing a hot nodule in the left lobe. The patient then wasgiven 10 units of TSH followed in 24 hours by iodine-131. The 131!scan of thesame thyroid in 13B indicates the right lobe is considerably intensified, comparedto Figure 13A. Figure 13C is a position four scan of the thyroid after TSH. Theblue area represents the 125! concentration, the Orange-Red area the 131! concentration, where-ever no 125!is present in the gland. Thus, this area shows thepart of the thyroid stimulated by TSH, which was “cold―prior to the TSHtreatment. The thyroid uptake of the patient was 22% before and 50% afterTSH. This mode of scanning was employed to simultaneously visualize thechambers of the heart with R1251SAand the lungs with “Ialbumin macroaggregate in separate colors. A normal chest (Fig. 14A) may be compared withthe scan of a patient with pericarditis (Fig. 14B). In the second patient thepericardial effusion is demonstrated as a non-colored space at the cardiac margin,proved by pericardial tap and having a water bottle heart on chest x-ray.

Position 5

It is possible to simultaneously visualize two organs in separate color onpaper and the subtract scan demonstrating a single organ with the other subtracted on film. This technique is useful in two-color scanning of liver and

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MODIFICATION OF A MULTI-ISOTOPE SCANNER 423

pancreas with a simultaneous black and white subtraction scan of the pancreas.This condition is accomplished by feeding the DC-Frequency converter outputinto the external pulse amplifier, which then drives the photorecording system,while the DC isolator output drives the color system and the sum of the pulsesof both isotopes drive the stylus.

Position 6

In this mode of operation, two isotopes drive the color control andstylus as described in position 3, while the pulses of a third are fed throughthe scanner pulse height analyzer, bypassing the stylus mechanism through theexternal pulse amplifier and recorded on the film. This procedure permitssimultaneous recording of three organs as, for instance, the liver (198Au), spleen(203Hg) and kidneys (‘97Hg).

TABLE I

75Se concentration in different organs 52 days following 250 pC 71Se.methionine administration. (Single case.)

Position 7

(Not described in Fig. 1.1) Position seven enables the visualization of thesubtraction of two isotopes on film, while mechanically recording a third isotope.This procedure is important for some cases of pancreatic scans in which thekidneys concentrate a fair amount of 75Se-methionine and are visualized on thepancreas scan. To determine whether this activity recorded is actually due tokidney concentration, ‘9THgNeohydrin is administered and a kidney scan isobtained simultaneously with the pancreas scan done by subtraction technique.

1One additional switching position “7―is required, (see Fig. 1), in which the followingloops are added to pin #7 on each deck: 1:7-blank; °°:7-1;111:7-6; IV:7-2; V:7-6; VI:7-indicator light.

424 BEN-PORATH,CLAYTON,KAPLAN

As indicated, current technical modification eliminates scalloping by printingwhile scanning in one direction the detector return at high speed without printing. Further modification has resulted in significant simplification of the circuitryseen in the block diagram (Fig. 15). Despite the prolongation of scanning timeusing this method, the quality of the scan is improved and the cost of the modification is considerably reduced, compared to the circuitry initially described in thispaper. The standard color scanner is altered by addition of a single channel pulseheight analyzer and a two-contact relay. In operation the probe, when movingfrom left to right, trips the carriage limit (probe reverse) micro switch at theend of a scan line. In addition to reversing scan direction, a relay is activatedpermitting only pulses from PHA1, set for isotope A, to be recorded in color A

in the following line. At the end of that line, the second carriage limit microswitch activates PHA2 set for isotope B to be recorded in color B in the subsequent line. The two sequences alternate throughout the scan. Thus, oneisotope will be recorded in a specific color while the probe is scanning in onedirection and the second isotope in a different color, while the probe is scanningin the opposite direction. To prevent loss of space density, one-half of normalspacing should be employed, so that each isotope will be scanned at normalspacing. (e.g. If the normal spacing for liver and pancreas scanning is 4 mm,a spacing of 2 mm is used with this method. Scalloping is also eliminatedusing this technique, as each isotope is scanned in one direction. Displacementof the images in each color occurs relative to each other. Being a function ofscanning speed and time constant, it can be calculated:

D=TxSwhere D = displacement in cm

T = Time constant in secondsS = Scanning speed in cm/second

(e.g. If T = 0.1 second, S = 1 cm/second, D = 0.1 X 1 0.1 cm in eachdirection, which is negligible.)

The subtract circuit previously described by the authors (2) may also beused with this method, allowing the “subtract scan― to be visualized in onecolor and one of the two isotopes in a second color. A representative scan of aliver and pancreas in a normal individual and one with carcinoma of the pancreasis seen in Fig. 16a and b. To accomplish the subtract mode, a mode switch orDC to AC converter and a dual rate meter are added to the circuitry (Fig. 15).

SUMMARY

A simple method is described by which a standard color scanner may beconverted into a multi-isotope scanner. The distribution of each isotope may berecorded in either positive or negative modes or combinations of the two. Up tothree isotopes may be scanned simultaneously. Various clinical applications ofthis system are demonstrated.

MODIFICATION OF A MULTI-ISOTOPE SCANNER 425

ACKNOWLEDGMENT

We wish to acknowledge the cooperation in this study of Picker NuclearDivision of Picker X-Ray Corporation and Dr. Paul Numerof of E. R. Squibband Sons.

BIBLIOGRAPHY

1. KAPLAN, E., B@-Poiwni, M., FINK, S., CLAYTON, C. and JACOBSON,B., A DualChannel Technique for Elimination of the Liver Image from Selenomethionine Pancreas OrganScans. Progress in Biomedical Engineering, Books, Inc., Washington, D.C., 1966.

2. BEN-Pon@m, M., CLAYTON, G. and KAPLAN, E., Selective Visualization of thePancreas by Subtractive Double Radioisotope Scanning Technique. Transactions of theAmerican Nuclear Society, 9:76, 1966.

3. KAPLAN, E., BEN-P0IiAm, M. FINK, S., CLAYTON, G. and JACOBSON, B., Elimination

of Liver Interference from the Selenomethione Pancreas Scan, Journal of Nuclear Medicine,7:807-816, 1966.

4. BROWN,D. W., Lung-Liver Radioisotope Scans in the Diagnosis of SubdiaphragmaticAbscess. JAMA, 197:728, 1966.

Announcement to Authors

Preliminary Notes

Space will be reserved in each issue of THE JOURNAL OF NUCLEAR MEDICINE for the publication of one preliminary note concerning new original work that isan important contribution in Nuclear Medicine.

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