The radiological implications of statistical variations in energy deposition by ionizing radiation were investigated in the conduct of the following experiments: (1) study of the production of secondary particles generated by the passage of the primary radiation through bone and muscle; (2) the study of the ratio of nonreparable to reparable damage in DNA as a function of different energy deposition patterns generated by X rays versus heavy fast charged particles; (3) the use of electronic radiography systems for direct fluoroscopic tomography and for the synthesis of multiple planes and; (4) the determination of the characteristics of systems response to split fields having different contrast levels, and of minimum detectable contrast levels between the halves under realistic clinical situations

Baily, N. A.

English

NASA Technical Reports Server

FINAL REPORT
October 1, 1972 - October 31, 1973
University of California, San Diego
National Aeronautics and Space Administration
Research Grant No. NGL 05-009-103
Principal Investigator: Norman A. Baily
Professor of Radiology
DISTRIBUTION:
5 copies - National Aeronautics and Space Administration
Office of Scientific and Technical Information
1 copy - Dr. Walton Jones, Deputy Director, Life Sciences
Headquarters, NASA
600 Independence Avenue, S.W.
Washington, D.C. 20546
1 copy - Dr. Sherman P. Vinograd, Life Sciences
Headquarters, NASA
600 Independence Avenue, S.W.
Washington, D.C. 20546
1 copy - Dr. Harold Sandler
NASA Ames Research Center
Moffett Field, California
S(NASA-CR-139664) [RESEARCH PROGRESS IN N74-31569
RADIATION DETECTORS, PATTERN RECOGNITION
PROGRAMS, AND RADIATION DAMAGE
"DETERMINATION IN DNA] Final (California Unclas
T niv.) 17 p HC $4.00 CSCL 06R G3./04 47855
https://ntrs.nasa.gov/search.jsp?R=19740023456 2020-03-23T03:53:19+00:00Z
INTRODUCTION
A chapter was prepared for publication in the next edition of Advances in Radiation
Biology entitled, UThe Radiological Implications of Statistical Variations in Energy Deposition
by Ionizing Radiations."
The completed multiwire proportional counter has undergone preliminary testing in
the laboratory using a 212Po alpha source. All aspects of its performance seem to be
satisfactory.
Studies of the minimum detectability which can be achieved by the digitized x-ray
fluoroscopy system have been completed. The studies were conducted using thick water
phantoms (10 cm, 15 cm, and 20 cm). These limits were determined for aluminum, air,
and three concentrations of Renografin-60 (10%, 25%, and 50%).
Pattern recognition programs have been developed for measurement of gall -stone
volumes, bronchi diameters, and vessel diameters. These can be used either with film or
by direct processing of the video signal derived from a fluoroscopic screen.
A large flat-screen (14" x 17") fluoroscopic image intensification (x-ray) system
has been built and undergone preliminary testing. Performance and sensitivity is better
than conventional systems.
One experimental run was made utilizing the UCLA medical cyclotron for determining
DNA damage from proton irradiations. The beam was calibrated using an extrapolation
chamber so that direct comparison of these results with those obtained using x-rays can be
made on the basis of macroscopic exposures. These experiments are designed to test a
radiobiological model incorporating stochastic fluctuations of energy deposition for passage
of heavy charged particles through biologically significant sites.
2RESEARCH SUMMARY
I. Microdosimetry
The chapter, "The Radiological Implications of Statistical Variations in Energy
Deposition by Ionizing Radiations", to be published in the new edition of ADVANCES IN
RADIATION BIOLOGY -i Appendix I' b should appear in June 1974.
This chapter was written to emphasize the concepts and results developed under the
sponsorship of this grant in contrast to the more traditional dosimetric concepts.
One rather large area requires detailed experimental study to complete the physical
picture. This is a detailed study of the production of and contributions due to secondary
particle production generated by the passage of the primary radiation through the site of
interest. To carry out these experiments a multiwire proportional counter capable of
simulating volumes corresponding to biological sites has been constructed and tested in
the laboratory. Initially, studies using radioactive sources will be continued in the laboratory.
Following these, we intend to carry out studies using the UCLA cyclotron which will
provide; 27 MeV 3He, 22 MeV protons, 22 MeV a particles, and 11 MeV deuterons.
If sufficient funding is available higher energy particle beams at SREL and at Berkeley
will be used.
The experimental results using 45 MeV protons comparing frequency distributions of
energy deposition for bone and muscle were included as Appendix A in our semi-annual
report.
2. Radiation Biology
Our cooperative experimental program involving Dr. K. Wheeler of UCSF has been
initiated. Proton irradiations at the UCLA cyclotron have been carried out. These are
designed to study the ratio of non-reparable to reparable damage in DNA as a function
of different energy deposition patterns generated by x rays vs., heavy fast charged particles.
Preliminary results indicate considerable differences exist and these are what would be
predicted from the energy deposition distribution functions.
3. Radiobiological Models
The work done on such models is presented in parts 5 and 6 of Appendix 1.
4. Electronic Radiography
The use of the electronic radiography system for direct fluoroscopic tomography
and for the synthesis of multiple planes has been described in Appendix B of the semi-annual
report. The use of this system for cutting body sections through organs in motion should be
of particular value to the NASA for cardiovascular studies.
A complete study of the digitized system for detection and quantitation of small
changes in tissue masses has been undertaken. The early work was described in Appendix C
of the semi-annual report.
Another set of experiments was designed to determine the characteristics of the
system's response to split fields having different contrast levels and to determine the
minimum detectable contrast levels between the halves under realistic clinical situations.
The experimental set-up is shown in Fig. 1. The target-to-tabletop distance was 40 inches.
The dimensions of the water phantom were 50 cm x 50 cm x 50 cm. In all experiments the
field size was 10 cm x 10 cm at the tabletop. The absorbers or air cavities were placed so
as to cover half of the x -ray field and centered at the midpoint of the water scatterer.
The water depth ranged between 10 cm and 20 cm, thereby introducing scattering comparable
to that which would be present in a clinical situation. The contrasts calculated are all
referred to the unperturbed half of the field. Experiments were conducted using aluminum
(as an approximation for bone), Renografin-60, and air.
4The results are shown in Figs. 2 through 5. The values of the ordinate were computed
by selecting two adjacent areas occupying a tabletop area of 1.5 cm2 (320 picture elements)
each having its horizontal center line at the center of the x-ray field and interior edges 1 cm
from the absorber or cavity edge.
Fig. 2 shows the response curves obtained for aluminum absorbers. A was obtained
using 120 kVp and a water depth of 20 cm. B represents the data for 100 kVp and 15 cm
of water. C was obtained Ising 90 kVp and 10 cm of water.
Fig. 3 shows the results for various concentrations of Renografin-60. A is for a
10 percent solution, B for 25 percent, and C for 50 percent. The thickness of the water
phantom was 20 cm and the tube potential 120 kVp. The Renografin-60 solutions were
contained in plexiglass containers having a thickness of 0.25". These were supported on a
platform of 0.25" polystyrene. Equal thicknesses of these materials were placed in the other
half of the field and the water level reduced accordingly.
Figs. 4 and 5 show the results obtained with air cavities. The geometry was identical
to that used to obtain the Renografin-60 data. Fig. 4 shows the complete response while
Fig. 5 shows the data obtained for thin cavities on an expanded scale. The data in Fig. 4
was obtained using 120 kVp and 20 cm water. Curve A, in Fig. 5 is the same data plotted
on an expanded scale, while B is that obtained using a potential of 100 kVp and 20 cm water.
Using the slope of the initial straight portions of these curves (or straight lines), one
can obtain a value for the minimum degree of contrast that can be reliably differentiated in
each case. We choose to use a value of two standard deviations to determine these. The
results are shown in Table I. In all cases less than 1 mm of material can be detected even in
the presence of a large scattering volume. In previous work we have found that the addition
of a 12:1 moving grid was found to improve the contrast of the image substantially.
5However, in clinical use this would, of course, increase the patient dose. We have not
measured this effect quantitatively.
In all cases the response, when treated as contrast, shows a linear response with
absorber thickness up to considerable thicknesses. This is not a case of small absorber
thickness giving a truly exponential response and being approximated by a linear function.
The data does not plot linearly when treated semi-logarithmically. If we ignore scattering
and other perturbing factors such as curvature of the input screen and inverse square effects,
the conatrast or relative video signal levels are given by:
/ 2 t - 1 tC 1 - e e (1)
where; A2 = attenuation coefficient of water
I1 = attenuation coefficient of absorber
t = absorber thickness.
For small t, this reduces to:
C = l t ( 1 + A2 t) - Cp2 t (2)
At larger thicknesses the response does not remain linear but decreases in the case of
absorbers which are more dense or have a greater linear absorption coefficient than water
and increases more rapidly with cavity size in the case of air. In the manner in which our
data was computed Equation (1) becomes for air cavities,
C = 1 - 2 t eI (11)
6and for small cavities,
C = P2 t (1 - Alt) - Pit (21)
where; 1 = attenuation coefficient of air
t = cavity thickness
The minimum detectable contrast seems to be mainly limited by scatter and electronic
noise. Both of these are amenable to improvements in the experimental set-up. However,
decreasing scatter by the addition of a grid with a higher ratio would involve an increase
in patient dose. Signal-to-noise ratios can be increased by any number of electronic
improvements in circuitry, system configuration, and digitization equipment.
The linearity of the system's response to changes in contrast over a rather large
range of clinically interesting values will tend to make quantitative determinations simple,
accurate, and allow extrapolation of experimental data for other calculations. The values
given in this paper would certainly be different using another system or with a change in
components. However, we feel the values given, the form of the system's response, and
minimum detectable contrasts are typical of what can be expected from this type of system.
7CONCLUSIONS
1. The response of digitized fluoroscopic imaging systems is linear with contrast
over a rather wide range of absorber and cavity thicknesses.
2. Contrast changes associated with the addition of aluminum, iodine containing
contrast agents and air of thicknesses 1 mm or less can be detected with a 95% confidence
level.
3. The standard deviation associated with such determinations using clinically
available x-ray generators and video disc recording is less than 1 percent.
A large flat screen x-ray image intensifier has been constructed and some preliminary
results obtained. Sensitivity achieved makes dose reduction a factor often greater than
previously reported for our system using a conventional x-ray image intensifier. A paper
describing these results and a comparison of the images obtained with that of the conventional
device will appear shortly in the bulletin of the SPIE.
8PAPERS PRESENTED AT MEETINGS
1. Detection Capability of Differential Radiographic Absorption Through the Use of
Fluoroscopic Images, Crepeau, R.L., Baily, N.A., 12th Ann. San Diego Biomed.Symp.
2. Frequency Distributions of Energy Deposition by 44 MeV Protons at Bone-Soft Tissue
Interfaces, Baily, N.A., Steigerwalt, J.E., and Hilbert, J.W., 1973 Annual
Meeting of the AAPM.
3. Electro-Fluoroplanigraphy, Baily, N.A., Lasser, E.C., and Crepeau, R.L., 1973
Annual Meeting of the AAPM.
4. The Calculation of Proportional Counter Energy Deposition Spectra from Experimental
Data, Steigerwalt, J.E., and Baily, N.A., 1973 Annual Meeting of the AAPM.
5. Differential Radiographic Absorption Measured From Digitalized Fluoroscopic Images,
Crepeau, R.L., and Baily, N.A., 1973 Annual Meeting of the AAPM.
6. Electronic Tomography, Baily, N.A., Crepeau, R.L., and Lasser, E.C., Symp. on
Electronic Imaging Techniques in Diagnostic Radiology, Univ. of Pittsburgh, 1973.
PAPERS PUBLISHED
1. Applications of A Digitalized Radiographic-Fluorographic Processing System to
Physiologic Data Extraction, Crepeau, R.L., Baily, N.A., and Silverman, N.R.,
Proc. of the San Diego Biomed. Symp., 11:317-322 (1972).
2. The Calculation of Proportional Counter Energy Deposition Spectra From Experimental
Data, Steigerwalt, J.E., Baily, N.A., Rad. Res. 51:480 (1972).
93. A Video-Roentgenography System For Special Procedures and The Acquisition of Quanti-
tative Data, Baily, N.A., Lasser, E.C., and Crepeau, R.L., Proc. of the 3rd Int. Conf.
on Medical Physics, Gothenburg, Sweden, 1972, 2.7 (1972).
4. Electro-Fluoroplanigraphy, Baily, N.A., Lasser, E.C., and Crepeau, R.L., Radiology
107: 669-671 (1973).
5. The Calculation of Proportional Counter Energy Deposition Spectra From Experimental
Data, Steigerwalt, J.E., Baily, N.A., Rad. Res. 53: 1-14 (1973).
6. Detection Capability of Differential Radiographic Absorption Through the Use of
Fluoroscopic Images, Crepeau, R.L., Baily, N.A., Proc. of the 12th San Diego Biomed.
Symp., 277-283 (1973).
7. Frequency Distributions of Energy Deposition by 44 MeV Protons at Bone-Soft Tissue
Interfaces, Baily, N.A., Steigerwalt, J.E., and Hilbert, J.W., AAPM Quarterly
Bull. 7: 101 (1973).
8. Electro-Fluoroplanigraphy, Baily, N.A., Lasser, E.C., and Crepeau, R.L., AAPM
Quarterly Bull. 7:91 (1973).
9. The Calculation of Proportional Counter Energy Deposition Spectra from Experimental
Data, Steigerwalt, J.E., Baily, N.A., AAPM Quarterly Bull. 7: 101 (1973).
10. Differential Radiographic Absorption Measured From Digitalized Fluoroscopic Images,
Crepeau, R.L., Baily, N.A., AAPM Quarterly Bull. 7: 91 (1973).
11. The Calculation of Proportional Counter Energy Deposition Spectra From Experimental
Data. II. Very Small Energy Losses and High Energy Delta Rays, Baily, N.A.,
Steigerwalt, J.E., Rod. Res. 56: 213-221 (1973).
10
12. Frequency Distributions of Energy Deposition by 44 MeV Protons at Bone-Soft Tissue
Interfaces, Baily, N.A., Steigerwalt, J.E., and Hilbert, J.W., Rad. Res. 56:
205-212 (1973).
13. An Electro-Fluoroplanigraphy System For Clinical Use, Baily, N.A., Lasser, E.C.,
and Crepeau, R.L., Invest. Radiol. 8: 276-277 (1973).
PAPERS IN PRESS
1. Electronic Tomography, Baily, N.A., Crepeau, R.L., and Lasser, E.C., Proc. of the
Symp. on Electronic Imaging Techniques In Diagnostic Radiology.
2. The Radiobiological Implications of Statistical Variations In Energy Deposition By
Ionizing Radiations, Baily, N.A., Steigerwalt, J.E., Advances in Radiation Biology
Vol. V.
3. Performance of a Large Screen Fluoroscopic Imaging System, Baily, N.A., Crepeau,
R.L., Proc. of the SPIE.
4. Capabilities of Fluoroscopic Systems to Determine Differential Roentgen Ray Absorption,
Baily, N.A., Crepeau, R.L. Radiology.
PERSONNEL PARTICIPATING IN PROGRAM
1. Norman A. Baily, Professor of Radiology
2. John E. Steigerwalt, Assistant Research Radiation Physicist
3. Ronald L. Crepeau, Assistant Developmental Engineer
4. Earl M. Raeburn, Lab Technician
5. Elliott C. Lasser, Professor of Radiology
FIGURE CAPTIONS
iWater phantom used to determine system response to variations in contrast
levels.
Fig. System response to varying contrast levels produced by aluminum absorbers.
A: 120 kVp, 20 cm water scatterer.
B: 160 kVp, 15 cm water scatterer.
C: 90 kVp, 10 cm water scatterer.
Fig. 3 System response to varying contrast levels produced by several concentrations
of Renografin-60. The water depth was 20 cm and the tube potential 120 kVp.
A: 10 percent concentration;
B: 25 percent, and
C: 50 percent.
Fig. 4 System response to varying contrast levels produced by air cavities when
introduced into 20 cm of water using 120 kVp.
Fig. 5 System response to varying contrast levels produced by air cavities when
introduced into 20 cm of water.
Curve A, is for 120 kVp (same data as used in Fig. 4), and
Curve B, is for 100 kVp.
LUCITE
WATERABSORBER 
INPUT SCREEN
Fig. 1 Water phantom used to determine system response to
variations in contrast levels.
U)
e 80 -
-..
SC=
..)
LUJ
L 60
B
(- A
0
,, 40
J 20-
LU
0 0.5 1.0 1.5cm ALUMINUM
ABSORBER THICKNESS
Fig. 2 System response to varying contrast levels produced by aluminum absorbers.
A: 120 kVp, 20 cm water scatterer. B: 100 kVp, 15 cm water scatterer. C: 90 kVp, 10 cm water scatterer.
S 70
CC
0
S 60-
50
40 
LU
-20 
-
, I0A
w 10 -
0
0 0.1 0.2- 0.3 0.4 0.5 0.6 cm RENOGRAF!I-60
ABSORBER THICKNESS
Fig. 3 System response to varying contrast levels produced by several concentrations of
Renografin-60.. The water depth was 20 cm and the tube potential 120 kVp. A: 10 percent
concentration; B: 25 percent, and C: 50 percent.
80
-. 70
C)
-.>
-J
" 50-
O
3
- 30
.J
2 20
10 -
0
0 I 2 3 c rm AIR
CAVITY THICKNESS
Fig. 4 System response to varying contrast levels produced by
air cavities when introduced into 20 cm of water using 120 kVp.
35
A
o 30-
UL
u 25 -
_.J
.- J
CD
< I
LU 5
0 0.5 1.0 1.5 cm A IR
CAVITY THICKNESS
Fig. 5 System response to varying contrast levels produced by air cavities when introduced
into 20 cm of water. Curve A, is for 120 kVp (same data as used in Fig. 4), and Curve B,
is for 100-kVp.
TABLE I
MINIMUM DETECTABLE CONTRAST LEVELS (Cmi )min
Material Water Depth Tube Potential Standard Deviation Thickness of Material
(cm) (kVp) (percent) (mm) Corresponding to
Cmn at 2 a
min
Al 10 90 0.849 0.6
Al 15 100 0.465 0.5
Al 20 120 0.723 0.6
10%, Renografin-60 20 120 1.10 0.8
25%, Renografin-60 20 120 0.578 0.2
50%, Renografin-60 20 120 0.828 0.1
Air 20 100 0.797 0.4
Air 20 120 0.802 0.9


Research progress in radiation detectors, pattern recognition programs, and radiation damage determination in DNA

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