celiac artery was noted on the lateral projection, the tube was angled 50° toward the feet to "open up" the celiac axis. Not infrequently the celiac artery will ascend rather than descend. In such cases, angling the tube toward the head will demonstrate the celiac axis to better advantage. Angled views may also prove to be useful in evaluating involvement
Technical Notes
225
TECHNICAL NOTES
Vol. 118
of the celiac and proximal splenic and hepatic arteries by neoplasms and arteriosclerosis. 1 From the Departments of Radiology (S. S.) and Surgery (H. H.), Montefiore Hospital and Medical Center and Albert Einstein College of Medicine, Bronx, N. Y. 10467 (Reprint requests to Montefiore Hospital). Accepted for publication in July 1975. sjh
Interfacing a Programmable Desk Calculator to a Hard-Wired Data System 1 Douglas Shearer, Ph.D., and Marvin Rollins, M.D. The primary disadvantage of hard-wired data systems for use in nuclear medicine is the fact that that the data contained in the memory bank are not accessible to the user and often must be processed mathematically before they can be employed in interpretation, particularly in dynamic studies. The authors describe a relatively inexpensive programmable device which can be used in conjunction with the data system and overcomes these limitations to a great extent. INDEX TERMS:
Computers. Nuclear Medicine
Radiology 118:225-226, January 1976
Fig. 1. Hewlett-Packard 9830A calculator and Ohio Nuclear Series 150 data system.
llilIlI
A
o 00
From the viewpoint of the user, there is no appreciable difference between hard-wired and software-based data systems when it comes to acquisition and storage of data generated by a gamma camera; however, there is a marked difference in each system's ability to retrieve and process stored data. Hard-wired systems cannot manipulate stored data except through the fixed algorithms installed at the factory by the manufacturer, i.e., smoothing, uniformity, correction, image subtraction, histogram generation, etc. The inflexibility of this approach severely limits the usefulness of the hardwired system standing alone. For many nuclear medicine studies, it is necessary to perform several operations on the data before they are in a suitable form for interpretation, e.g., fitting exponentials or gamma functions to time-activity curves in cardiac output studies, background and crosstalk corrections of ventricular curves in ejection fraction studies, etc. The flexibility of the software system can be approached without losing the desirable characteristics of the hard-wired system, i.e., ease and speed of operation and reduced cost, by transferring the stored data to storage in an inexpensive digital device which is capable of processing data through the software approach. In our department,an Ohio Nuclear Series 100 gamma camera has been interfaced to an Ohio Nuclear Series 150 hard-wired data system fitted with a dual-channel chart recorder whose output has been modified to feed directly into a Hewlett-Packard 9830A programmable desk calculator using an interface developed by Ohio Nuclear (Fig. 1). The calculator in this institution initially contained only 2K words of internal memory storage but has since been upgraded to 6K with a word length of 16 bits. The calculator is also provided with
o
0
1250
0
o
1 TIME ISEC5.1 o
o
o
a.SEIIIVED TIIIUE
o
B
o
8
8 10
15
20
3D
35
TIME ISEC5.1
Fig. 2. A. Count rate from standard source. B. Effect of dead-time correction on count rate.
tape cassette storage (giving an additional 40K of available memory), so that the internal memory does not limit the quantity of data which can be acquired. The BASIC programming language employed is rather slow in execution time but is suitable for use by personnel with little computer experience. The 9830A is fitted with a Hewlett-Packard 9866A thermal line printer capable of producing 80 characters per line, 250 lines per minute for hard-copy output of histograms or results of computations.
226
TECHNICAL NOTES
Operation
Data are acquired from the camera via the data system and stored on 9-track magnetic tape. A maximum of two areas of interest are set up as required for output to the chart recorder. A general program has been written to input as many sets of dual areas as desired to the computer. For long studies in which the available internal storage is not sufficient to hold the data, acquisition can be halted while the contents of the internal memory are transferred onto a cassette before continuing the data acquisition. When the data are loaded, they can be processed in precisely the same way as they would be in a small computer and the hard-copy output taken off the printer. Applications Dead- Time Correction: In the absence of a hard-wired dead-time correction, it is almost impossible to acquire reliable quantitative data from a high-count-rate dynamic study, e.g., cardiac flow. This limitation can be overcome using the method suggested by Freedman et al. (1). A well-shielded radioactive source (usually 99mTc) is attached to the collimator outside the area of interest. Prior to injection, the count rate from the source alone is recorded. The study is then run and recorded. Areas of interest are set up over the source and the region or regions to be examined and the data from these areas are fed into the calculator. A program has been written to correct the counts from the region of interest by using the known counting rate from the standard source as a control. Figure 2 shows the source counting rate during the study as well as the cardiac counting rate both before and after correction. Cardiac Output: Using the corrected counting rate from the heart, the cardiac output, cardiac index, etc., can be obtained directly. A hard-copy output of all relevant data is obtained at the end of the study. Transit- Time Measurements: Transit-time measurements are useful diagnostic tools in blood-flow studies of all types. Using areas of Interest where desired, the peak-to-peak times can readily be printed out. More complicated measuremerits may also be performed if required.
A .Collimator for Reduced Radiation Dose with Improved Visualization of Soft Tissues 1 Michael L. Freedman. Ph.D.• and Stephen R. Matteson. D.D.S. The authors describe a collimator for use in diagnostic radiology. Clinical radiographs show enhanced soft-tissue detail through the use of interchangeable straight and curved wedge filters, and in situ dosimetry using a head phantom shows that the provision for asymmetric beam limitation results in reduction of absorbed dose. INDEX TERM:
Radiography, apparatus and equipment
Radiology 118:226-228, January 1976
January 1976
Renograms: Using the same technique, renograms can be obtained and the curves for each kidney compared. Background subtraction techniques can be used and renogram parameters of interest calculated and printed out. 99mTc Thyroid Uptakes: Twenty-minute 99 mTc uptake may be assessed with the gamma camera (2); however, several manipulations are required, e.g., subtraction of blood background using an area Over the mediastinum. These can be performed by the calculator and the per cent uptake computed and compared with 1:he normal range. Again, a hard-copy output is sent out directly in the report.
CONCLUSIONS Hard-wired data systems are very useful in departments with limited programming support. Basic image-manipulation processes such as uniformity correction and smoothing can be accomplished immediately at the touch of a button. However, the limitations of this type of data system become apparent when more flexible data-processing is required. Using the method described here, these limitations can be greatly overcome. The inexpensive programmable calculator described can be used not only for the nuclear medicine procedures discussed above but also elsewhere in the department, e.g., as a stand-alone treatment planning system (3) or a terminal for a large computer in a radiotherapy time-sharing system, as well as patient records, billing, etc. In fact, the applications of the small nondedicated programmable calculator are limited only by the imagination of the user.
REFERENCES 1. Freedman GS, Kinsella T, Dwyer A: A correction method for high-count-rate quantitative radionuclide angiography. Radiology 104:713-715, Sep 1972 2. Higgins HP, Ball D, Eastham S: 20-min 99mTc thyroid uptake: a simplified method using the gamma camera. J Nucl Med 14:907911, Dec 1973 3. Saylor WL: A new calculator for radiotherapy treatment planning. Radiology 115:738, Jun 1975 1 From Lutheran Medical Center, 2609 Franklin Blvd., Cleveland, Ohio 44113. Accepted for publication in June 1975. sjh
Collimation of a diagnostic x-ray beam commonly proceeds symmetrically around the central ray (CR), resulting in relative uniformity of both (a) radiation dispersion and (b) distortion in the size and shape of the image. In roentgenographic cephalometry there is a fixed relationship between the patient positioning device (cephalostat) and the x-ray tube target such that the CR passes through the ear rods (1). Thus normal and oblique films of the maxilla or mandible employing a cephalostat result in exposure to anatomical sites remote from those of primary interest (2, 3). Also, imaging of facial soft-tissue features, which is desirable in cephalometric studies, indicates the use of a wedge filter which does not reduce osseous tissue detail. We wish to describe a highly adaptable device which has provisions for variable collimation and filtration. Studies with a head phantom demonstrate reduced radiation exposure, and clinical use shows increased film information.
Technical Notes
225
TECHNICAL NOTES
Vol. 118
of the celiac and proximal splenic and hepatic arteries by neoplasms and arteriosclerosis. 1 From the Departments of Radiology (S. S.) and Surgery (H. H.), Montefiore Hospital and Medical Center and Albert Einstein College of Medicine, Bronx, N. Y. 10467 (Reprint requests to Montefiore Hospital). Accepted for publication in July 1975. sjh
Interfacing a Programmable Desk Calculator to a Hard-Wired Data System 1 Douglas Shearer, Ph.D., and Marvin Rollins, M.D. The primary disadvantage of hard-wired data systems for use in nuclear medicine is the fact that that the data contained in the memory bank are not accessible to the user and often must be processed mathematically before they can be employed in interpretation, particularly in dynamic studies. The authors describe a relatively inexpensive programmable device which can be used in conjunction with the data system and overcomes these limitations to a great extent. INDEX TERMS:
Computers. Nuclear Medicine
Radiology 118:225-226, January 1976
Fig. 1. Hewlett-Packard 9830A calculator and Ohio Nuclear Series 150 data system.
llilIlI
A
o 00
From the viewpoint of the user, there is no appreciable difference between hard-wired and software-based data systems when it comes to acquisition and storage of data generated by a gamma camera; however, there is a marked difference in each system's ability to retrieve and process stored data. Hard-wired systems cannot manipulate stored data except through the fixed algorithms installed at the factory by the manufacturer, i.e., smoothing, uniformity, correction, image subtraction, histogram generation, etc. The inflexibility of this approach severely limits the usefulness of the hardwired system standing alone. For many nuclear medicine studies, it is necessary to perform several operations on the data before they are in a suitable form for interpretation, e.g., fitting exponentials or gamma functions to time-activity curves in cardiac output studies, background and crosstalk corrections of ventricular curves in ejection fraction studies, etc. The flexibility of the software system can be approached without losing the desirable characteristics of the hard-wired system, i.e., ease and speed of operation and reduced cost, by transferring the stored data to storage in an inexpensive digital device which is capable of processing data through the software approach. In our department,an Ohio Nuclear Series 100 gamma camera has been interfaced to an Ohio Nuclear Series 150 hard-wired data system fitted with a dual-channel chart recorder whose output has been modified to feed directly into a Hewlett-Packard 9830A programmable desk calculator using an interface developed by Ohio Nuclear (Fig. 1). The calculator in this institution initially contained only 2K words of internal memory storage but has since been upgraded to 6K with a word length of 16 bits. The calculator is also provided with
o
0
1250
0
o
1 TIME ISEC5.1 o
o
o
a.SEIIIVED TIIIUE
o
B
o
8
8 10
15
20
3D
35
TIME ISEC5.1
Fig. 2. A. Count rate from standard source. B. Effect of dead-time correction on count rate.
tape cassette storage (giving an additional 40K of available memory), so that the internal memory does not limit the quantity of data which can be acquired. The BASIC programming language employed is rather slow in execution time but is suitable for use by personnel with little computer experience. The 9830A is fitted with a Hewlett-Packard 9866A thermal line printer capable of producing 80 characters per line, 250 lines per minute for hard-copy output of histograms or results of computations.
226
TECHNICAL NOTES
Operation
Data are acquired from the camera via the data system and stored on 9-track magnetic tape. A maximum of two areas of interest are set up as required for output to the chart recorder. A general program has been written to input as many sets of dual areas as desired to the computer. For long studies in which the available internal storage is not sufficient to hold the data, acquisition can be halted while the contents of the internal memory are transferred onto a cassette before continuing the data acquisition. When the data are loaded, they can be processed in precisely the same way as they would be in a small computer and the hard-copy output taken off the printer. Applications Dead- Time Correction: In the absence of a hard-wired dead-time correction, it is almost impossible to acquire reliable quantitative data from a high-count-rate dynamic study, e.g., cardiac flow. This limitation can be overcome using the method suggested by Freedman et al. (1). A well-shielded radioactive source (usually 99mTc) is attached to the collimator outside the area of interest. Prior to injection, the count rate from the source alone is recorded. The study is then run and recorded. Areas of interest are set up over the source and the region or regions to be examined and the data from these areas are fed into the calculator. A program has been written to correct the counts from the region of interest by using the known counting rate from the standard source as a control. Figure 2 shows the source counting rate during the study as well as the cardiac counting rate both before and after correction. Cardiac Output: Using the corrected counting rate from the heart, the cardiac output, cardiac index, etc., can be obtained directly. A hard-copy output of all relevant data is obtained at the end of the study. Transit- Time Measurements: Transit-time measurements are useful diagnostic tools in blood-flow studies of all types. Using areas of Interest where desired, the peak-to-peak times can readily be printed out. More complicated measuremerits may also be performed if required.
A .Collimator for Reduced Radiation Dose with Improved Visualization of Soft Tissues 1 Michael L. Freedman. Ph.D.• and Stephen R. Matteson. D.D.S. The authors describe a collimator for use in diagnostic radiology. Clinical radiographs show enhanced soft-tissue detail through the use of interchangeable straight and curved wedge filters, and in situ dosimetry using a head phantom shows that the provision for asymmetric beam limitation results in reduction of absorbed dose. INDEX TERM:
Radiography, apparatus and equipment
Radiology 118:226-228, January 1976
January 1976
Renograms: Using the same technique, renograms can be obtained and the curves for each kidney compared. Background subtraction techniques can be used and renogram parameters of interest calculated and printed out. 99mTc Thyroid Uptakes: Twenty-minute 99 mTc uptake may be assessed with the gamma camera (2); however, several manipulations are required, e.g., subtraction of blood background using an area Over the mediastinum. These can be performed by the calculator and the per cent uptake computed and compared with 1:he normal range. Again, a hard-copy output is sent out directly in the report.
CONCLUSIONS Hard-wired data systems are very useful in departments with limited programming support. Basic image-manipulation processes such as uniformity correction and smoothing can be accomplished immediately at the touch of a button. However, the limitations of this type of data system become apparent when more flexible data-processing is required. Using the method described here, these limitations can be greatly overcome. The inexpensive programmable calculator described can be used not only for the nuclear medicine procedures discussed above but also elsewhere in the department, e.g., as a stand-alone treatment planning system (3) or a terminal for a large computer in a radiotherapy time-sharing system, as well as patient records, billing, etc. In fact, the applications of the small nondedicated programmable calculator are limited only by the imagination of the user.
REFERENCES 1. Freedman GS, Kinsella T, Dwyer A: A correction method for high-count-rate quantitative radionuclide angiography. Radiology 104:713-715, Sep 1972 2. Higgins HP, Ball D, Eastham S: 20-min 99mTc thyroid uptake: a simplified method using the gamma camera. J Nucl Med 14:907911, Dec 1973 3. Saylor WL: A new calculator for radiotherapy treatment planning. Radiology 115:738, Jun 1975 1 From Lutheran Medical Center, 2609 Franklin Blvd., Cleveland, Ohio 44113. Accepted for publication in June 1975. sjh
Collimation of a diagnostic x-ray beam commonly proceeds symmetrically around the central ray (CR), resulting in relative uniformity of both (a) radiation dispersion and (b) distortion in the size and shape of the image. In roentgenographic cephalometry there is a fixed relationship between the patient positioning device (cephalostat) and the x-ray tube target such that the CR passes through the ear rods (1). Thus normal and oblique films of the maxilla or mandible employing a cephalostat result in exposure to anatomical sites remote from those of primary interest (2, 3). Also, imaging of facial soft-tissue features, which is desirable in cephalometric studies, indicates the use of a wedge filter which does not reduce osseous tissue detail. We wish to describe a highly adaptable device which has provisions for variable collimation and filtration. Studies with a head phantom demonstrate reduced radiation exposure, and clinical use shows increased film information.
