COMPUTER-ANALYSIS OF MAMMOGRAPHY PHANTOM IMAGES (CAMPI) - AN APPLICATION TO THE MEASUREMENT OF MICROCALCIFICATION IMAGE QUALITY OF DIRECTLYACQUIRED DIGITAL IMAGES
Dp. Chakraborty, COMPUTER-ANALYSIS OF MAMMOGRAPHY PHANTOM IMAGES (CAMPI) - AN APPLICATION TO THE MEASUREMENT OF MICROCALCIFICATION IMAGE QUALITY OF DIRECTLYACQUIRED DIGITAL IMAGES, Medical physics, 24(8), 1997, pp. 1269-1277
The purpose of this investigation was to apply the recently developed
CAMPI (computer analysis of mammography phantom images) method to a Fi
scher Mammotest Stereotactic Digital Biopsy machine. Another aim was t
o further elucidate the nature of the empirically introduced CAMPI mea
sures. Images of an American College of Radiology (ACR) accreditation
phantom centered on the largest two speck groups were obtained on this
machine under a variety of x-ray conditions. An additional measure, a
lternative SNR (ASNR) is introduced which is complementary to the SNR
measure. Analyses of the Mammotest images revealed that the mAs and kV
p dependencies of the CAMPI measures could be understood from basic im
aging physics principles. It is shown that: (1) the measures reflect t
he expected linearity of the digital detector and Poisson photon stati
stics; (2) under automatic exposure control (AEC) conditions the signa
l (SIG) measure is proportional to subject contrast; and (3) under AEC
conditions the noise (NOI) measure is proportional to the square root
of the average absorbed photon energy. Correspondence with basic imag
ing physics principles shows that the measures are significantly free
of artifacts. Precision of the CAMPI measures exceeds that of human ob
servers by orders of magnitude. CAMPI measures are expected to be mere
relevant to clinical mammography than Fourier metrics as the measurem
ents are done on objects of arbitrary shape and size that were designe
d by the manufacturer to resemble Various detection tasks in mammograp
hy. It is concluded that CAMPI can perform objective and highly precis
e evaluations of phantom image quality in mammography. It could be use
d as a sophisticated quality control tool, as a replacement for the cu
rrent ACR/MQSA phantom evaluation program, and to evaluate the rapidly
evolving digital mammography technology. (C) 1997 American Associatio
n of Physicists in Medicine.