11
Digital Computers in
Nuclear Medicine
139Digital computers were introduced in nuclear medicine practice in the mid-
1960s, but did not become an integral part in both imaging and nonimag-
ing applications until the mid-1970s. In imaging modalities, the computers
are used to quantitate the distribution of radiopharmaceuticals in an object
both spatially and temporally. Both data acquisition and image processing
in scintigraphy are accomplished by digital computers. In nonimaging appli-
cations, patient scheduling, archiving, inventory of supplies, management of
budget, record keeping, and health physics are just a few examples of what
is accomplished with the help of digital computers. Computational capabil-
ities have advanced tremendously over the years and are still evolving, and
the utility of a computer is limited only by the limitations of hardware and
software.
Basics of a Computer
The basic elements of a computer are a central processing unit(CPU),main
memory,external storageand input/output(I/O) devices, which are con-
nected to one another by pathways called buses. The main memory stores
all program instructions and acquired data, while the CPU executes all
instructions given in a program. External storage includes floppy disks, CD-
ROMs, DVD-ROMs, and hard drives. I/O devices include peripherals such
as keyboards, mouse, video monitors, and printers, whose functions are to
communicate with the computer for input of the acquired data and output
of the processed data. A typical setup of a computer is illustrated in Figure
11.1.
The voltage signals, i.e., electrical pulses from a scintillation camera, are
obtained in analog form and are digitized by the digital computers for
further processing and storage. Digital computers operate with binary
numbers using only two digits, 0 and 1, as opposed to 10 digits 0 to 9 in the
decimal system. The basic unit of the binary system is a bit(binary digit)
that is either 0 or 1. The binary numbers are expressed by placing 0’s and