- Email: [email protected]
A computerized scintillation data system for the gamma camera
Compu~. Biol. Med.
Pergamon Press 1972. Vol. 2, pp. 251-256.
Printed in Great Britain.
A Computerized Scintillation Data System for the Gamma Camera MONROE
F. JAHNS, ALFRED L. GARZA and THOMAS P. HAYNIE
University of Texas at Houston, M. D. Anderson Hospital and Tumor Institute, 6723 Bertner Avenue, Houston, Texas 77025, U.S.A. (Received 30 November 1971; revised) Abstract-A computerized scintillation data system for collecting, storing, manipulating, and displaying data obtained by a gamma camera is described, and its operation in a hospital radioisotope laboratory is reviewed. Results of clinical application of the system in image subtraction for pancreas visualization and in a dynamic study of kidney function are presented. The instrument shows considerable potential usefulness as an aid to the collection and analysis of clinical data.
in vivo distribution of radlonuchdes in patients, it is often desirable that the data be in digital form. In this form, the information may be readily manipulated. For the past 12 months, a computerized scintillation data system (Fig. 1) has been used in the M. D. Anderson Hospital and Tumor Institute Radioisotope Laboratory for collecting, storing, manipulating, and displaying data obtained from a gamma camera.(‘) This report describes the system and its operation and presents results of the initial experience with this system in clinical imaging.
IN DETERMININGthe
DESCRIPTION
OF THE SYSTEM
The system has the following performance characteristics : Original data are stored as “frames” in the computer memory and on magnetic tape with essentially no time loss between frames. 2. Frames of data may be redisplayed with varied contrast. 3. Successive frames may be redisplayed for short time intervals. 4. Frames of data taken at different times may be combined to show sums or differences between various distributions. 5. Computer programs may be used to perform arithmetic on data in frames or on designated parts of data frames. 6. Quantitative results of computer manipulation of data may be displayed on a Cathode Ray Tube (CRT) or typed out on a teletype. 7. CRT display of data may be photographed. 8. The system has no effect upon normal operation of the gamma camera. I.
A block diagram of the basic components of the system is shown in Fig. 2. The system may be described as follows: 2.51
252
MONROEF. JAHNS.ALFREDL. GARZA and THOMASP. HAYNIE
CONTROL
~-ELcIYP~]+--I jDsc;s&+
-~1
UNIT
PURPOSE
1
COMP”TE R j
FIG. 2. Block diagram of the data system.
The data system* interface allows connection to existing terminals of a gamma camera.t No modification is required in the camera itself or in the operating procedures. 2. Dual amplifiers amplify both X- and Y-analog address pulses from the gamma camera to a magnitude suitable for analog-to-digital conversion. 3. The digital information from the analog-to-digital converters describing the location of the photon detected by the camera is presented to the system control unit, which causes the data to be stored in the memory of a general purpose computer with an 8192 twelve-bit word memory. Of this memory, two blocks of 1024 data locations each are used alternately to store a 32 b:32 data location matrix. The real time clock is utilized in determining counting time for incoming data which will be accumulated as a “data frame” and also in determining, for data review, how long a data frame will be displayed on the oscilloscope. The system control unit also controls the number of data frames to be accumulated or displayed. 4. As incoming data are stored on one of two data locations matrices in the computer memory, the contents of the other matrix are recorded on a 7-track, high-speed magnetic tape unit. Recording from alternate matrices allows data to be recorded with no dead time between successive frames. Frame times may be as short as 0.2 sec. 5. The computer unit sends and receives commands and prints information through a teletype, paper tape perforator, and perforated paper tape reader unit. The teletype printer also produces hard copy output of quantitative results. 6. The display oscilloscope is used to present partially or fully analyzed camera data during or after the time of data gathering. It is also used for displaying graphs and other computer-derived information. A Polaroid camera is used for making photographs of camera image data or graphs displayed on the oscilloscope in either the storage or nonstorage mode. The system also contains a program loader which transfers computer programs or image data between cassette tapes and the computer’s magnetic core memory. This cassette loading unit transfers 4096 twelve-bit words in less than 60 sec. 1.
* Scintillation Data System A-3, Computer Corporation t Pho Gamma III Nuclear Chicago Corporation.
of America, Houston, Texas.
FIG. 1. Computerized scintillation data system.
CBM facing page 252
Fi(,. 3. Anterior view o f the liver. (a) gamma camera oscilloscope display. (b) data system oscilloscope display with background subtraction. (c) data system display contrast set for best visualization of right lobe. (d) contrast set for best visualization of left lobe.
FIG. 4. Data system oscilloscope display of liver and pancreas images. (a) image of rsSe in pancreas and overlying liver. (b) image of 9amTc in liver. (c) computer-derived image of pancreas obtained by subtracting 4b data from 4a data (the spleen also appears on the right in Fig. 4b).
-i J
~1
r~ ~
.,-
~
~
-.--'
t
E'~-E
,
.~ =o~ E=.~ . '~-
O0
0
0
0
0
.~
'
......................
,", ,-. ,-
~0
0
~ ~'.~ .= >~ .~-
= , ~ -~ ._~
==,g~ ~ - ='=-~ --
-
"
-
0
.> .o 'S
, ,...~
.
)
Z..E'= ~ r.
w v
A computerizedscintillationdata systemfor the gammacamera OPERATION
253
OF THE SYSTEM
To prepare the computer for use with the gamma camera, two short programs are entered via the switch registers and the paper tape reader to enable the computer to read from the cassette program loader. This procedure required about 5 min and need be done only once. (To facilitate the use of the computer for other purposes, part of the gamma camera program may be written on the multitrack, high speed magnetic tape, from which it may be rapidly retrieved when required.) The computer is then stopped, the program-starting address is loaded via the switch registers, and the system is ready for use. Gamma camera settings for the pulse-analyzer windows, counts (or time) for data collection, etc., are made in the same manner as if the computer were not interfaced with the camera. To illustrate the simplicity of operation of the data system in data collection, complete instructions for collecting and recording patient data are given here. The magnetic tape is positioned by recalling the last recorded data frame (frame n) i.e. by typing Sn. The typed letter E erases contents of the computer memory, and the typed letter N prepares the system for the next data collection. The number of data frames to be collected and the collection duration for each are set on the control module thumbwheels. When the start button is pressed, the system will then collect the specified number of frames for the specified duration. A typed N on the teletype and a start command on the system control unit are the only manipulations required of the operator between successive studies. Image display
When data are not being collected, data frame n is recalled into computer memory by typing Sn. To display this data frame on the oscilloscope, DD is typed on the teletype. The data recorded as scintillations observed in each of 32 x 32 elements will then be displayed with the oscilloscope display contrast ranging from the element of lowest count content to that of highest count. To display only those elements containing counts between a lower limit 1 and an upper limit u, DI , u is typed on the teletype. This produces a display on the oscilloscope in which the full contrast ranges between the chosen limits. Subsequent displays (typed D) are presented with these contrast limits until new limits are entered via the teletype. Successive frames of image data may be observed in a single computer-controlled pass. To view such a “movie”, the first frame to be viewed is recalled, and the number of frames to be viewed and the display duration are set on the control module thumbwheels. Upon depressing the start button, the magnetic tape will advance through the requested number of frames, each of which will be displayed on the display oscilloscope. Display time per frame may be as short as 0.5 sec. By setting the oscilloscope to the storage mode, successive images can be integrated with preceding ones on the oscilloscope screen. Add-subtract routine
With this program, a composite image may be obtained by taking the sums of or differences between data frames which have been recorded on the magnetic tape. A particular image frame may be added or subtracted any number of times. With this routine it is also possible to display an inverse image by subtracting from an erased (or zero) frame a given frame or a number of frames. This routine is called by typing a J on the teletype. This initiates a dialog between the computer and the operator. The operator responds to repeated “Frame No., Add or Subtract?” questions from the computer to form the desired composite image. After such an
254
MONROE F. JAHNS, ALFRED L. GARZA and THOMAS P. HAYNIE
image has been formed, a printout may be requested. The teletype then prints out a 32 x 32 array of counts in the composite image. Any such image may also be written onto the main magnetic tape.
Area(s) of interest routine With this program the counts in designated portions of each of a consecutive series of data frames are obtained. To define areas for the computer, the lower left corner of the display is defined as the origin, the variable X ranges from 1 (left edge) to 32 (right edge), and Y ranges from 1 (lower edge) to 32 (upper edge). This routine is called by typing A on the teletype. The teletype asks: number of areas?; X, AX, Y, AY, for each area (these define a rectangle between X and X+AX and between Y and Y -tAY); number of frames to be reviewed; and first frame number. The computer then causes the indicated frames to be reviewed and determines the number of counts recorded within each area of interest for each data frame. At the conclusion of the review, the teletype prints for each area of interest the maximum counts within that area for any of the data frames reviewed. At this time, an analog graph for each area of interest, showing the counts within that area vs. the frame number, is displayed on the oscilloscope. Following oscilloscope display, the computer will cause the total count within each area of interest to be typed out for each frame reviewed. Teletype analog graphs similar to those displayed on the oscilloscope may be obtained at this time. To obtain such typed graphs, a routine is read into the computer memory from the cassette tape program loader. CLINICAL RESULTS Contrast enhancement Figure 3 demonstrates how contrast control can enhance various portions of a display. An anterior view of the liver in a patient injected with 3 mCi of technetium-99m sulfur colloid is shown. In 3a, a photo from the gamma camera oscilloscope is shown. The photo in 3b is from the data system oscilloscope. This display shows all elements whose contents are above background. In 3c, the display contrast has been set for best visualization of the right lobe of the liver, where activity is generally high. In 3d, contrast has been set for best visualization of the left lobe of the liver. Subtraction of images Figure 4 shows an example of the usefulness of the Add-Subtract routine. This image of the pancreas has been obtained by a procedure in which a liver image is subtracted from a liver plus pancreas image.t2v3) ggmTc sulfur colloid injected in a patient localizes in the liver and will yield image data which define the extent of the liver. After such image data are recorded, 75Se-selenomethionine is injected with the patient in the same position. This compound localizes in both the liver and pancreas, and emitted radiation will yield image data which define both of these organs. (The ggmTc is injected and imaged first because the radiation from primary radiation from g8mT~ lies within the energy band of Compton 75Se. Since the primary radiation from ?%e is of higher energy, it can be readily measured in the presence of ggmTc.) Figure 4a shows an image of the radioactivity emitted from ‘%e in a pancreas and an overlying liver. An image of radioactivity from the liver alone is seen in 4b. Figure 4c shows an image of pancreatic radioactivity alone derived by the computer by subtracting the image data of 4b from that of 4a. (The intense activity on the right in 4b is from the spleen.)
A computerizedscintillationdata systemfor the gammacamera
255
Area-of-interest sequencing An example of this technique is a renal study obtained with the system. Figure 5a is a posterior view of the midlumbar region of a patient who had been injected with 200 mCi of 1311-hippuran. This image is the sum of 60 successive +-min frames begun immediately after injection of the hippuran. (A computer-generated grid has been projected over the image to assist in defining the areas of interest.) The two regions of interest, the patient’s kidneys, show intense activity in this view. Counts in the areas of interest are then summed for each of the 60 frames. Figure 5b is a photograph of such an oscilloscope display. These curves, commonly called renograms, c4v5)show the concentration of radionuclide within each kidney as a function of time. Figure 5c shows typed graphs for each area of interest for the frames reviewed. Here the teletype has printed the numeral 1 for points on the curve for area of interest number 1, etc. The numerals have been connected by hand-drawn lines to improve clarity. The largest count found in either area of interest on any frame is shown as 100 per cent and all other counts are “normalized” to this value. In Fig. 5d, the counts are normalized separately for each area, i.e. so each curve has one point plotted as 100 per cent.
DISCUSSION In determining the in viva distribution of radionuclides in patients for diagnostic purposes, the radioactivity is usually displayed as an analog image. The interpreting physician may study anterior, posterior, lateral, or other views to evaluate the distribution. The shape, size, and relative concentrations of various portions of the image are studied, and the size of abnormalities and their location relative to anatomical landmarks are noted. Generally, a localized increase (or decrease) in concentration of radioactivity is indicative of a lesion. For example, a decrease of concentration (“cold area”) in the liver is usually caused by decreased reticuloendothelial function at the site of the lesion. In a second category of studies, the desired information is the time rate of change of radioactivity distribution. An example of this type of study is determination of accumulation and elimination of radioactivity in each kidney after radioactive 1311-hippuran has been injected into the patient. As shown in the examples given above, by collecting and presenting the image data in digital as well as analog form, the data obtained can be manipulated and subjected to various displays to obtain additional information or to confirm subjective conclusions. The contrast and brightness in the image may be varied to give optimum viewing characteristics for each region of the display. Quantitative differences may then be obtained between various areas suggested by the analog display. Also, it is useful to compare the relative activity between paired organs such as the kidneys or lungs. By collecting data over a series of successive, short-time intervals, change of radioactivity concentration with time may be plotted, composite Images formed, or one image subtracted from another. Many of the systems designed for data analysis process the data on-line or afterwards in real time. On-line analysis requires that factors controlling the display be preselected. If this selection is not satisfactory, the procedure must be repeated. Systems which allow a “replay” in real time are time-consuming. The system described here overcomes many of these difficulties and lends itself to practical use in our laboratory. We are continuing to expand our experience to assess its over-all usefulness in clinical diagnosis.
256
MONROEF. JAHNS,ALFREDL. GARZA and THOMASP. HAYNIE
SUMMARY
AND CONCLUSIONS
We have described the characteristics and performance of a scintillation data system that makes possible the manipulation and quantification of data obtained with a gamma camera. In prelimary studies the system has demonstrated considerable potential usefulness. Specifically, it has made possible enhancement of images, subtraction scanning, and area of interest sequencing. We are applying these techniques to liver, pancreas, and renal studies with success. Application of this system to other problems in the radioisotope laboratory is being explored. REFERENCES 1. H. 0. ANGER, Gamma-ray and positron scintillation camera, Nucleonics 21(10), 56-59 (1963). 2. P. C. BLANQLJET, C. R. BECK, J. FLEURY and C. J. PALAIS, Pancreas scanning with “Se and losAu using digital-data-processing techniques, J. Nucl. Med. 9, 486-488 (1968). 3. E. KAPLAN, M. BEN PORATH,S. FINK, G. D. CLAYTONand B. JACOBSON,Elimination of liver interference from the selenomethionine pancreas scan, J. Nucl. Med. 7, 807-816 (1966). 4. B. H. STEWARTand T. P. HAYNIE, Critical appraisal of the renogram in renal vascular disease, J.A.M.A. 180,454-459 (1962). 5. G. V. TAPLIN, 0. M. MEREDITH,Jr., H. KADE and C. C. WINTER, The radioisotope renogram, J. Lab. & Clin. Med. 48, 886-901 (1956).
Pergamon Press 1972. Vol. 2, pp. 251-256.
Printed in Great Britain.
A Computerized Scintillation Data System for the Gamma Camera MONROE
F. JAHNS, ALFRED L. GARZA and THOMAS P. HAYNIE
University of Texas at Houston, M. D. Anderson Hospital and Tumor Institute, 6723 Bertner Avenue, Houston, Texas 77025, U.S.A. (Received 30 November 1971; revised) Abstract-A computerized scintillation data system for collecting, storing, manipulating, and displaying data obtained by a gamma camera is described, and its operation in a hospital radioisotope laboratory is reviewed. Results of clinical application of the system in image subtraction for pancreas visualization and in a dynamic study of kidney function are presented. The instrument shows considerable potential usefulness as an aid to the collection and analysis of clinical data.
in vivo distribution of radlonuchdes in patients, it is often desirable that the data be in digital form. In this form, the information may be readily manipulated. For the past 12 months, a computerized scintillation data system (Fig. 1) has been used in the M. D. Anderson Hospital and Tumor Institute Radioisotope Laboratory for collecting, storing, manipulating, and displaying data obtained from a gamma camera.(‘) This report describes the system and its operation and presents results of the initial experience with this system in clinical imaging.
IN DETERMININGthe
DESCRIPTION
OF THE SYSTEM
The system has the following performance characteristics : Original data are stored as “frames” in the computer memory and on magnetic tape with essentially no time loss between frames. 2. Frames of data may be redisplayed with varied contrast. 3. Successive frames may be redisplayed for short time intervals. 4. Frames of data taken at different times may be combined to show sums or differences between various distributions. 5. Computer programs may be used to perform arithmetic on data in frames or on designated parts of data frames. 6. Quantitative results of computer manipulation of data may be displayed on a Cathode Ray Tube (CRT) or typed out on a teletype. 7. CRT display of data may be photographed. 8. The system has no effect upon normal operation of the gamma camera. I.
A block diagram of the basic components of the system is shown in Fig. 2. The system may be described as follows: 2.51
252
MONROEF. JAHNS.ALFREDL. GARZA and THOMASP. HAYNIE
CONTROL
~-ELcIYP~]+--I jDsc;s&+
-~1
UNIT
PURPOSE
1
COMP”TE R j
FIG. 2. Block diagram of the data system.
The data system* interface allows connection to existing terminals of a gamma camera.t No modification is required in the camera itself or in the operating procedures. 2. Dual amplifiers amplify both X- and Y-analog address pulses from the gamma camera to a magnitude suitable for analog-to-digital conversion. 3. The digital information from the analog-to-digital converters describing the location of the photon detected by the camera is presented to the system control unit, which causes the data to be stored in the memory of a general purpose computer with an 8192 twelve-bit word memory. Of this memory, two blocks of 1024 data locations each are used alternately to store a 32 b:32 data location matrix. The real time clock is utilized in determining counting time for incoming data which will be accumulated as a “data frame” and also in determining, for data review, how long a data frame will be displayed on the oscilloscope. The system control unit also controls the number of data frames to be accumulated or displayed. 4. As incoming data are stored on one of two data locations matrices in the computer memory, the contents of the other matrix are recorded on a 7-track, high-speed magnetic tape unit. Recording from alternate matrices allows data to be recorded with no dead time between successive frames. Frame times may be as short as 0.2 sec. 5. The computer unit sends and receives commands and prints information through a teletype, paper tape perforator, and perforated paper tape reader unit. The teletype printer also produces hard copy output of quantitative results. 6. The display oscilloscope is used to present partially or fully analyzed camera data during or after the time of data gathering. It is also used for displaying graphs and other computer-derived information. A Polaroid camera is used for making photographs of camera image data or graphs displayed on the oscilloscope in either the storage or nonstorage mode. The system also contains a program loader which transfers computer programs or image data between cassette tapes and the computer’s magnetic core memory. This cassette loading unit transfers 4096 twelve-bit words in less than 60 sec. 1.
* Scintillation Data System A-3, Computer Corporation t Pho Gamma III Nuclear Chicago Corporation.
of America, Houston, Texas.
FIG. 1. Computerized scintillation data system.
CBM facing page 252
Fi(,. 3. Anterior view o f the liver. (a) gamma camera oscilloscope display. (b) data system oscilloscope display with background subtraction. (c) data system display contrast set for best visualization of right lobe. (d) contrast set for best visualization of left lobe.
FIG. 4. Data system oscilloscope display of liver and pancreas images. (a) image of rsSe in pancreas and overlying liver. (b) image of 9amTc in liver. (c) computer-derived image of pancreas obtained by subtracting 4b data from 4a data (the spleen also appears on the right in Fig. 4b).
-i J
~1
r~ ~
.,-
~
~
-.--'
t
E'~-E
,
.~ =o~ E=.~ . '~-
O0
0
0
0
0
.~
'
......................
,", ,-. ,-
~0
0
~ ~'.~ .= >~ .~-
= , ~ -~ ._~
==,g~ ~ - ='=-~ --
-
"
-
0
.> .o 'S
, ,...~
.
)
Z..E'= ~ r.
w v
A computerizedscintillationdata systemfor the gammacamera OPERATION
253
OF THE SYSTEM
To prepare the computer for use with the gamma camera, two short programs are entered via the switch registers and the paper tape reader to enable the computer to read from the cassette program loader. This procedure required about 5 min and need be done only once. (To facilitate the use of the computer for other purposes, part of the gamma camera program may be written on the multitrack, high speed magnetic tape, from which it may be rapidly retrieved when required.) The computer is then stopped, the program-starting address is loaded via the switch registers, and the system is ready for use. Gamma camera settings for the pulse-analyzer windows, counts (or time) for data collection, etc., are made in the same manner as if the computer were not interfaced with the camera. To illustrate the simplicity of operation of the data system in data collection, complete instructions for collecting and recording patient data are given here. The magnetic tape is positioned by recalling the last recorded data frame (frame n) i.e. by typing Sn. The typed letter E erases contents of the computer memory, and the typed letter N prepares the system for the next data collection. The number of data frames to be collected and the collection duration for each are set on the control module thumbwheels. When the start button is pressed, the system will then collect the specified number of frames for the specified duration. A typed N on the teletype and a start command on the system control unit are the only manipulations required of the operator between successive studies. Image display
When data are not being collected, data frame n is recalled into computer memory by typing Sn. To display this data frame on the oscilloscope, DD is typed on the teletype. The data recorded as scintillations observed in each of 32 x 32 elements will then be displayed with the oscilloscope display contrast ranging from the element of lowest count content to that of highest count. To display only those elements containing counts between a lower limit 1 and an upper limit u, DI , u is typed on the teletype. This produces a display on the oscilloscope in which the full contrast ranges between the chosen limits. Subsequent displays (typed D) are presented with these contrast limits until new limits are entered via the teletype. Successive frames of image data may be observed in a single computer-controlled pass. To view such a “movie”, the first frame to be viewed is recalled, and the number of frames to be viewed and the display duration are set on the control module thumbwheels. Upon depressing the start button, the magnetic tape will advance through the requested number of frames, each of which will be displayed on the display oscilloscope. Display time per frame may be as short as 0.5 sec. By setting the oscilloscope to the storage mode, successive images can be integrated with preceding ones on the oscilloscope screen. Add-subtract routine
With this program, a composite image may be obtained by taking the sums of or differences between data frames which have been recorded on the magnetic tape. A particular image frame may be added or subtracted any number of times. With this routine it is also possible to display an inverse image by subtracting from an erased (or zero) frame a given frame or a number of frames. This routine is called by typing a J on the teletype. This initiates a dialog between the computer and the operator. The operator responds to repeated “Frame No., Add or Subtract?” questions from the computer to form the desired composite image. After such an
254
MONROE F. JAHNS, ALFRED L. GARZA and THOMAS P. HAYNIE
image has been formed, a printout may be requested. The teletype then prints out a 32 x 32 array of counts in the composite image. Any such image may also be written onto the main magnetic tape.
Area(s) of interest routine With this program the counts in designated portions of each of a consecutive series of data frames are obtained. To define areas for the computer, the lower left corner of the display is defined as the origin, the variable X ranges from 1 (left edge) to 32 (right edge), and Y ranges from 1 (lower edge) to 32 (upper edge). This routine is called by typing A on the teletype. The teletype asks: number of areas?; X, AX, Y, AY, for each area (these define a rectangle between X and X+AX and between Y and Y -tAY); number of frames to be reviewed; and first frame number. The computer then causes the indicated frames to be reviewed and determines the number of counts recorded within each area of interest for each data frame. At the conclusion of the review, the teletype prints for each area of interest the maximum counts within that area for any of the data frames reviewed. At this time, an analog graph for each area of interest, showing the counts within that area vs. the frame number, is displayed on the oscilloscope. Following oscilloscope display, the computer will cause the total count within each area of interest to be typed out for each frame reviewed. Teletype analog graphs similar to those displayed on the oscilloscope may be obtained at this time. To obtain such typed graphs, a routine is read into the computer memory from the cassette tape program loader. CLINICAL RESULTS Contrast enhancement Figure 3 demonstrates how contrast control can enhance various portions of a display. An anterior view of the liver in a patient injected with 3 mCi of technetium-99m sulfur colloid is shown. In 3a, a photo from the gamma camera oscilloscope is shown. The photo in 3b is from the data system oscilloscope. This display shows all elements whose contents are above background. In 3c, the display contrast has been set for best visualization of the right lobe of the liver, where activity is generally high. In 3d, contrast has been set for best visualization of the left lobe of the liver. Subtraction of images Figure 4 shows an example of the usefulness of the Add-Subtract routine. This image of the pancreas has been obtained by a procedure in which a liver image is subtracted from a liver plus pancreas image.t2v3) ggmTc sulfur colloid injected in a patient localizes in the liver and will yield image data which define the extent of the liver. After such image data are recorded, 75Se-selenomethionine is injected with the patient in the same position. This compound localizes in both the liver and pancreas, and emitted radiation will yield image data which define both of these organs. (The ggmTc is injected and imaged first because the radiation from primary radiation from g8mT~ lies within the energy band of Compton 75Se. Since the primary radiation from ?%e is of higher energy, it can be readily measured in the presence of ggmTc.) Figure 4a shows an image of the radioactivity emitted from ‘%e in a pancreas and an overlying liver. An image of radioactivity from the liver alone is seen in 4b. Figure 4c shows an image of pancreatic radioactivity alone derived by the computer by subtracting the image data of 4b from that of 4a. (The intense activity on the right in 4b is from the spleen.)
A computerizedscintillationdata systemfor the gammacamera
255
Area-of-interest sequencing An example of this technique is a renal study obtained with the system. Figure 5a is a posterior view of the midlumbar region of a patient who had been injected with 200 mCi of 1311-hippuran. This image is the sum of 60 successive +-min frames begun immediately after injection of the hippuran. (A computer-generated grid has been projected over the image to assist in defining the areas of interest.) The two regions of interest, the patient’s kidneys, show intense activity in this view. Counts in the areas of interest are then summed for each of the 60 frames. Figure 5b is a photograph of such an oscilloscope display. These curves, commonly called renograms, c4v5)show the concentration of radionuclide within each kidney as a function of time. Figure 5c shows typed graphs for each area of interest for the frames reviewed. Here the teletype has printed the numeral 1 for points on the curve for area of interest number 1, etc. The numerals have been connected by hand-drawn lines to improve clarity. The largest count found in either area of interest on any frame is shown as 100 per cent and all other counts are “normalized” to this value. In Fig. 5d, the counts are normalized separately for each area, i.e. so each curve has one point plotted as 100 per cent.
DISCUSSION In determining the in viva distribution of radionuclides in patients for diagnostic purposes, the radioactivity is usually displayed as an analog image. The interpreting physician may study anterior, posterior, lateral, or other views to evaluate the distribution. The shape, size, and relative concentrations of various portions of the image are studied, and the size of abnormalities and their location relative to anatomical landmarks are noted. Generally, a localized increase (or decrease) in concentration of radioactivity is indicative of a lesion. For example, a decrease of concentration (“cold area”) in the liver is usually caused by decreased reticuloendothelial function at the site of the lesion. In a second category of studies, the desired information is the time rate of change of radioactivity distribution. An example of this type of study is determination of accumulation and elimination of radioactivity in each kidney after radioactive 1311-hippuran has been injected into the patient. As shown in the examples given above, by collecting and presenting the image data in digital as well as analog form, the data obtained can be manipulated and subjected to various displays to obtain additional information or to confirm subjective conclusions. The contrast and brightness in the image may be varied to give optimum viewing characteristics for each region of the display. Quantitative differences may then be obtained between various areas suggested by the analog display. Also, it is useful to compare the relative activity between paired organs such as the kidneys or lungs. By collecting data over a series of successive, short-time intervals, change of radioactivity concentration with time may be plotted, composite Images formed, or one image subtracted from another. Many of the systems designed for data analysis process the data on-line or afterwards in real time. On-line analysis requires that factors controlling the display be preselected. If this selection is not satisfactory, the procedure must be repeated. Systems which allow a “replay” in real time are time-consuming. The system described here overcomes many of these difficulties and lends itself to practical use in our laboratory. We are continuing to expand our experience to assess its over-all usefulness in clinical diagnosis.
256
MONROEF. JAHNS,ALFREDL. GARZA and THOMASP. HAYNIE
SUMMARY
AND CONCLUSIONS
We have described the characteristics and performance of a scintillation data system that makes possible the manipulation and quantification of data obtained with a gamma camera. In prelimary studies the system has demonstrated considerable potential usefulness. Specifically, it has made possible enhancement of images, subtraction scanning, and area of interest sequencing. We are applying these techniques to liver, pancreas, and renal studies with success. Application of this system to other problems in the radioisotope laboratory is being explored. REFERENCES 1. H. 0. ANGER, Gamma-ray and positron scintillation camera, Nucleonics 21(10), 56-59 (1963). 2. P. C. BLANQLJET, C. R. BECK, J. FLEURY and C. J. PALAIS, Pancreas scanning with “Se and losAu using digital-data-processing techniques, J. Nucl. Med. 9, 486-488 (1968). 3. E. KAPLAN, M. BEN PORATH,S. FINK, G. D. CLAYTONand B. JACOBSON,Elimination of liver interference from the selenomethionine pancreas scan, J. Nucl. Med. 7, 807-816 (1966). 4. B. H. STEWARTand T. P. HAYNIE, Critical appraisal of the renogram in renal vascular disease, J.A.M.A. 180,454-459 (1962). 5. G. V. TAPLIN, 0. M. MEREDITH,Jr., H. KADE and C. C. WINTER, The radioisotope renogram, J. Lab. & Clin. Med. 48, 886-901 (1956).