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Analog and digital storage of radioisotope indicator concentration data on FM analog magnetic tape
COMPUTtRS
AND
BIOMEDICAL
Analog
GEORGE
RESEARCH
2, 160-163
(19681
and Digital Storage of Radioisotope Indicator Concentration Data on FM Analog Magnetic Tape’”
S.
MALINDZAK,
Department of Physiology, of Wake Forest University,
JR. AND KENNETH The Bon’man Winston-Salem,
II. SWONWR
Gray School oj Medicine North Carolina 27103
Received March 13. 1968 A scheme is presented which will permit simultaneous storage of the analog signal representing radioisotope indicator concentration data and its digital (BCD) equivalent on FM analog tape. The basic process involve< the modification of a previous design which provides for multiplexing two data channels onto a single tape channel. Record and playback multiplexor networks have been designed to provide this facility.
In a previous report1 a basic scheme was presented for the storage of radioisotope indicator concentration data in digital (BCD) form on FM analog magnetic tape. It is frequently desirable and indeed useful to store both the analog signal corresponding to indicator concentration and its digital (BCD) equivalent on analog magnetic tape such that they have the same time base on playback. The added flexibility in data manipulation and data processing (especially where hybrid analog-digital systems are employed) and the added convenience of having both analog and digital forms of the original experimental data on a single tape provide sufficient reasons to include the additional analog information in the basic scheme. The facility for combining analog information as well as digital radioisotope indicator concentration information on FM analog magnetic tape was provided by multiplexing the start-stop pulses (injector) and the timing pulses (print pulses) in the basic scheme’ and recording the multiplexed signal on analog tape channel 1 (Fig. 1) . The analog equivalent of the indicator concentration is taken from recorder output of the Model 425 Baird Atomic Digital Ratemeter (which results from digital-to-analog conversion of the buffer contents) and recorded directly (FM) on the tape channel 2. The digital pulses resulting from the basic conversion process (proportional to the total number of counts in the :i:This work was supported in part by research grants from the National Institutes 01 Health of the USPHS (HE 8663, FR 0147, HE 00487). the Forsyth County Heart Am.. and the North Carolina Heart Assn. 160
ANALOG
CH.I Start
-Stap;Timing
Pulrrr,
Yultiplrxrd
CH.2
AND DIGITAL
DATA ON FM
t Q...
TAPE
n
1
I
161
L...
...I\...
CH. 3 Data [I]
cu. 7
...
Voice
FIG. 1. Timing diagram and channel designation for storage of analog radioisotope indicator concentration data on FM ana!og magnetic tape.
and digital
buffer register) are recorded in parallel at the same time as the analog signal onto FM analog tape channels 3, 4, 5, and 6 (corresponding to the l-2-4-8 BCD codes). As in the earlier scheme, voice is recorded on to channel 7. The pulse logic of the multiplexer record and playback networks is shown in Fig. 2. Pulses corresponding to start-stop signals from the indicator injector device and positive timing pulses from the print pulse circuits of the digital ratemeter are summed through an operational amplifier as shown at the top of Fig. 2. Since the print pulses are biphasic rectification is required prior to summation in order to include only the positive pulses for recording purposes. The complex pulse pattern consisting of the summation of the start-stop pulses and the positive timing pulses is recorded FM on analog tape at the time the experimental data (i.e., analog signal, digital BCD pulses and voice) are collected. During playback the multiplexed start-stop timing pulses are fed into the level separation network
FIG.
2. Circuit logic for the multiplexing
of the start-stop pulses and timing pulses.
shown in the bottom part of Fig. 2. Two level detectors are employed to separate the positive going timing pulses from the negative going start-stop pulse which in turn supply signal levels to the external sense lines of the computer (LINC) . The computer program has been written to start the sampling process based on the first negative pulse from the playback network (bottom of Fig. 2) appearing on the external sense line. This event is followed by a five-second delay to avoid pump and switching artifacts from the recording and conversion process (hence the superimposed timing pulses are ignored). Sampling continues until the appearance of a second negative pulse on the start-stop channel. At this time the sampling process is halted and the superimposed pulses are again ignored. As before, the computer marks time based on the appearance of the positive timing pulses after the start signal appears. In the laboratory we process experimental data in digital and analog form depending on the specific requirements of the processing effort. For example, we frequently feed the analog signal to an analog processing device (for filtering, etc.) or feed it to a strip chart recorder to obtain a hard copy of the event on a different time base for the purpose of slide preparation. At the same time we require convenient access to other experimentally relevant information such as flow, mean transit time, and volume. The work in the laboratory involves the USC of various dyes as indicators as well as radioisotopes in the study of cardiac output and vascular volumes. Densitometers are not usually equipped to provide BCD digital output as well as an analog signal proportional to the dye concentration. Data sampling rates are
ANALOG
AND DIGITAL
DATA ON FM TAPE
163
usually slow enough that a conventional digital voltmeter can be used to supply the digital conversion required in order to use the scheme presented here. We have designed an interface to perform the appropriate digital data conversion compatible for analog tape recording for indicator concentration functions from dye studies. The details of this interface will be the subject of another report to appear in the near future. I.
G. S., JR., AND K. D. SWONGER: Digital storage of radioisotope indicator concentration data on FM analog magnetic tape. Computers Biomed. Res. 1 ( 1968).
MALINDZAK,
AND
BIOMEDICAL
Analog
GEORGE
RESEARCH
2, 160-163
(19681
and Digital Storage of Radioisotope Indicator Concentration Data on FM Analog Magnetic Tape’”
S.
MALINDZAK,
Department of Physiology, of Wake Forest University,
JR. AND KENNETH The Bon’man Winston-Salem,
II. SWONWR
Gray School oj Medicine North Carolina 27103
Received March 13. 1968 A scheme is presented which will permit simultaneous storage of the analog signal representing radioisotope indicator concentration data and its digital (BCD) equivalent on FM analog tape. The basic process involve< the modification of a previous design which provides for multiplexing two data channels onto a single tape channel. Record and playback multiplexor networks have been designed to provide this facility.
In a previous report1 a basic scheme was presented for the storage of radioisotope indicator concentration data in digital (BCD) form on FM analog magnetic tape. It is frequently desirable and indeed useful to store both the analog signal corresponding to indicator concentration and its digital (BCD) equivalent on analog magnetic tape such that they have the same time base on playback. The added flexibility in data manipulation and data processing (especially where hybrid analog-digital systems are employed) and the added convenience of having both analog and digital forms of the original experimental data on a single tape provide sufficient reasons to include the additional analog information in the basic scheme. The facility for combining analog information as well as digital radioisotope indicator concentration information on FM analog magnetic tape was provided by multiplexing the start-stop pulses (injector) and the timing pulses (print pulses) in the basic scheme’ and recording the multiplexed signal on analog tape channel 1 (Fig. 1) . The analog equivalent of the indicator concentration is taken from recorder output of the Model 425 Baird Atomic Digital Ratemeter (which results from digital-to-analog conversion of the buffer contents) and recorded directly (FM) on the tape channel 2. The digital pulses resulting from the basic conversion process (proportional to the total number of counts in the :i:This work was supported in part by research grants from the National Institutes 01 Health of the USPHS (HE 8663, FR 0147, HE 00487). the Forsyth County Heart Am.. and the North Carolina Heart Assn. 160
ANALOG
CH.I Start
-Stap;Timing
Pulrrr,
Yultiplrxrd
CH.2
AND DIGITAL
DATA ON FM
t Q...
TAPE
n
1
I
161
L...
...I\...
CH. 3 Data [I]
cu. 7
...
Voice
FIG. 1. Timing diagram and channel designation for storage of analog radioisotope indicator concentration data on FM ana!og magnetic tape.
and digital
buffer register) are recorded in parallel at the same time as the analog signal onto FM analog tape channels 3, 4, 5, and 6 (corresponding to the l-2-4-8 BCD codes). As in the earlier scheme, voice is recorded on to channel 7. The pulse logic of the multiplexer record and playback networks is shown in Fig. 2. Pulses corresponding to start-stop signals from the indicator injector device and positive timing pulses from the print pulse circuits of the digital ratemeter are summed through an operational amplifier as shown at the top of Fig. 2. Since the print pulses are biphasic rectification is required prior to summation in order to include only the positive pulses for recording purposes. The complex pulse pattern consisting of the summation of the start-stop pulses and the positive timing pulses is recorded FM on analog tape at the time the experimental data (i.e., analog signal, digital BCD pulses and voice) are collected. During playback the multiplexed start-stop timing pulses are fed into the level separation network
FIG.
2. Circuit logic for the multiplexing
of the start-stop pulses and timing pulses.
shown in the bottom part of Fig. 2. Two level detectors are employed to separate the positive going timing pulses from the negative going start-stop pulse which in turn supply signal levels to the external sense lines of the computer (LINC) . The computer program has been written to start the sampling process based on the first negative pulse from the playback network (bottom of Fig. 2) appearing on the external sense line. This event is followed by a five-second delay to avoid pump and switching artifacts from the recording and conversion process (hence the superimposed timing pulses are ignored). Sampling continues until the appearance of a second negative pulse on the start-stop channel. At this time the sampling process is halted and the superimposed pulses are again ignored. As before, the computer marks time based on the appearance of the positive timing pulses after the start signal appears. In the laboratory we process experimental data in digital and analog form depending on the specific requirements of the processing effort. For example, we frequently feed the analog signal to an analog processing device (for filtering, etc.) or feed it to a strip chart recorder to obtain a hard copy of the event on a different time base for the purpose of slide preparation. At the same time we require convenient access to other experimentally relevant information such as flow, mean transit time, and volume. The work in the laboratory involves the USC of various dyes as indicators as well as radioisotopes in the study of cardiac output and vascular volumes. Densitometers are not usually equipped to provide BCD digital output as well as an analog signal proportional to the dye concentration. Data sampling rates are
ANALOG
AND DIGITAL
DATA ON FM TAPE
163
usually slow enough that a conventional digital voltmeter can be used to supply the digital conversion required in order to use the scheme presented here. We have designed an interface to perform the appropriate digital data conversion compatible for analog tape recording for indicator concentration functions from dye studies. The details of this interface will be the subject of another report to appear in the near future. I.
G. S., JR., AND K. D. SWONGER: Digital storage of radioisotope indicator concentration data on FM analog magnetic tape. Computers Biomed. Res. 1 ( 1968).
MALINDZAK,