A semiquantitative cortical circumferential normalization method for clinical evaluation of rCBF brain SPECT

The authors studied 33 normal patients who ranged in age from 8 to 71 years to establish a normative data base for young-age, middle-age, and older-age subjects using a computer automated semi-quantitative cortical annular region of interest (ROI) method. The data were grouped to obtain a "young age-range" normative data base of mean age +/- 1 S.D. = 13.1 +/- 4.8 years (seven subjects with an age range of 6 to 20 years); a "middle age-range" normative data base of mean age +/- 1 S.D. = 39 +/- 2.7 years (12 subjects with an age range of 35 to 43 years); and an "older age-range" normative data base of mean age +/- 1 S.D. = 59.7 +/- 5.8 years (14 subjects with an age range of 55 to 71 years). Normative values were obtained for brain level parallel to and positioned at 3.5, 5.5, and 7.5 cm above the canthomeatal (CM) line. The results show that the average global rCBF indices (defined as cortical/cerebellar ratios) for the young age-range group were 0.98, 0.99, 1.07; middle age-range group were 0.84, 0.86, and 0.88; and older age-range group were 0.86, 0.87 and 0.87 for CM + 3.5 cm, CM + 5.5 cm, and CM + 7.5 cm, respectively. In routine clinical studies, on more then 2,000 Tc-99m HMPAO brain SPECT scans, the authors have employed this semi-quantitative cortical circumferential normalization method of analysis to accurately calculate indices representing cortical blood flow values. This method also allows efficient comparison of individual patient values to age-range matched normal control groups to assist in disease diagnosis.