Radiographic equipment incorporates two radiation sources, generating high-energy and low-energy beams. Recording equipment measures amount of radiation that has penetrated limb. Data are fed into computer that determines mass of the examined bone

Cameron, J. R.

Judy, P. F.

English

NASA Technical Reports Server

August 1975 /b 	 B75-10168 
NASA TECH BRIEF 
Lyndon B. Johnson Space Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 2215. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Determination of Bone Mineral Mass In Vivo 
The problem: 
Radiography can be used to determine bone 
mineral mass in vivo, but conventional methods 
include assumptions that can cause errors of up to 8 
percent. It is generally assumed that only two types of 
tissue are present: bone tissue and soft tissue. In fact, 
there are usually different types of soft tissue present 
with different attenuation coefficients. 
The solution: 
By using radiation sources with two different energy 
levels, bone mineral mass can be determined more 
accurately. 
How it's done: 
The equipment incorporates two radiation sources 
generating high-energy and low-energy beams, re-
spectively. The patient inserts his limb in the beam 
paths. Recording equipment placed on the opposite 
side of the limb measures the amount of radiation that 
has penetrated. The data are fed into a computer 
which then determines the mass of the examined 
bone.
As shown in the illustration, the radiation sources 
are placed behind a shield. Different isotope sources 
can be used to produce the necessary high-energy and 
low-energy radiation beams. For example, 
americium-241 can be used for the high-energy 
output, and iodine-125 can be used for the low-energy 
output. Alternatively gadolinium-153 can be used as 
single source of the two energy levels. The beams are 
transmitted through an aperture in the shield. 
The limb to be examined is placed on a mount (not 
shown) directly in the path of the radiation beams. 
The recording equipment, on the opposite side of the 
limb, includes a scintillation counter, a photomulti-
plier tube, and an amplifier, connected to data-
processing equipment. The scintillation counter 
includes phosphor material . which is thallium-
activated sodium iodide. Heavy radiation shielding 
and a narrow aperture prevent stray radiation from 
entering the counter. 
The limb is irradiated at the two energy levels for a 
fixed period of time. Radiation photons penetrating 
the limb strike the phosphor material, creating 
Shield
Limb	
Photomultiplier 
Shield	 Tube 
adiation 
Radiation 
9 R	 U	 Scintillation Source Counter 
Apertures
Equipment for Determining Bone Mineral Mass
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights. 
Discriminator l-1	 Timer! Scaler 
Amplifier
Timer! Discriminator F''I	 Scaler
Computer
https://ntrs.nasa.gov/search.jsp?R=19750000168 2020-03-19T20:25:29+00:00Z
discrete flashes. The flashes are sensed by the 
photomultiplier which converts them to electrical 
signals. The signal amplitudes are directly propor-
tional to the flash intensities. These signals are 
amplified and fed into discriminators, timer/scalers, 
and a computer. 
The computer is programed to determine the bone 
mineral mass from the following relationship: 
I =10 exp (PBM M BM - I.LSTMST) 
where I is the attenuated beam intensity measured by 
the counter, 1 0
 is the initial beam intensity, PBM and 
!ST are the respective attenuation coefficients of the 
bone and the soft tissue, and MBM and MST are the 
bone mineral mass and soft tissue mass, respectively. 
Using the data obtained from low-energy and 
high-energy beams, MBM and MST are determined 
from two separate logarithmic equations.
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Johnson Space Center 
Code AT3 
Houston, Texas 77058 
Reference: TSP75- 10168 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial 
development should be addressed to: 
Patent Counsel 
Johnson Space Center 
Code AM 
Houston, Texas 77058 
Source: J. R. Cameron and P. F. Judy of

University of Wisconsin 
(MSC-14276)
'1 B75-10168
Categories: 05 (Life Sciences) 
03 (Physical Sciences) 
02 (Electronics Systems)


Determination of bone mineral mass in vivo

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