Hsieh et al. 18 healthy volunteers. The lead workers came from a paint factory that had 30 employees, and we included all eligible lead-exposed work- ers, except one female who was pregnant and seven employees who worked in business and sales and were not present in the factory dur- ing the examination days. The 18 nonexposed healthy controls volunteered when we posted an open announcement in the same area but at different plants in industries that did not use lead; thus, their socioeconomic status was similar to the lead workers. We excluded all participants with a history of alcoholism, drug abuse, and major neurologic disorders, such as severe head injury, stroke, or epilepsy. The protocol for this study was approved by the Institutional Review Board of Kaohsiung Medical University, and we obtained informed consent from each participant. Blood and bone lead measurements. On the same day as the MRI study, we took blood samples, measured bone lead levels, and administered the questionnaires. The blood samples were obtained by venipuncture and analyzed for whole-blood lead levels using a Zeeman-effect graphite furnace atomic absorption spectrometer (5100 PC with AS 60 autosampler; Perkin-Elmer, Waltham, MA, USA) in the same laboratory. For intral- aboratory quality control, standard commer- cial materials (Betherning Institute, Bio-Rad; Hercules, CA, USA) were used, and all coef- ficients of variation were < 3%. We examined the bone lead levels at two anatomic sites, the right middle tibia and the right patella, in vivo using K-shell XRF (KXRF) (Canberra Industries, Inc., Meriden, CT, USA). The middle tibia and patella were representative of primarily cortical and trabecular bones, respectively. Cortical and trabecular bones have different kinetics with respect to bone lead, which probably reflects differing architectures and bone dynamics. This phenomenon has been demonstrated directly by the differences in bone uptake and release of lead over time in follow-up KXRF studies comparing the two bone types (Tsaih et al. 2001). This painless, noninvasive mea- surement was performed for 30 min at each skeletal location. Radiation dosimetry studies of dose to skin, bone red marrow, and the pelvic area have demonstrated that a typical 109Cd KXRF measurement gives extremely low effective dose values of < 1 microsievert (µSv), significantly below the proposed limit of negligibility of 10 µSv (Hu et al. 1998; Somervaille et al. 1988; Todd et al. 1992). On the same day, the participants answered questionnaires that contained items regarding sex, age, health status, occupation, educational level, body mass index (BMI), and lifestyle habits, including smoking, drink- ing, and the chewing of betel nut. MRI and MRS. We examined all patients using a 3.0-T whole-body magnetic reso- nance system (General Electric Company, Milwaukee, WI, USA) with a 40 mT/m maximum gradient capability. A head coil for conventional MRI and proton MRS was used. To evaluate the anatomic structures, before they underwent proton MRS, both the patient and control groups underwent conventional magnetic resonance proto- cols, including fast spin-echo T2-weighted (T2W) axial images [repetition time (TR), 4,000 msec; echo time (TE), 102 msec; field of view (FOV), 240 mm × 240 mm; thickness, 5 mm], fluid-attenuated inversion recovery (FLAIR) T2W axial images (TR, 8,627 msec; TE, 157.5 msec; inversion time, A B C Figure 1. The measurement of MRS in vivo. (A) Basal ganglion. (B) Frontal lobe. (C) Occipital lobe. 942 ovlume 117 | number 6 | June 2009 • Environmental Health Perspectives 2,100 msec; FOV, 240 mm × 240 mm; thick- ness, 5 mm), diffusion-weighted images (TR, 8,000 msec; TE, 71.7 msec; FOV, 240 mm × 240 mm; thickness, 5 mm; b-value, 1,000) with apparent diffusion coefficient (ADC) and enhanced ADC mapping, and FLAIR T1-weighted axial images (TR, 1,800 msec; TE, 9.8 msec; inversion time, 2,100 msec; FOV, 240 mm × 240 mm; thickness, 5 mm). We used a two-dimensional MRS imag- ing sequence with point-resolved spectro- scopy (PRESS) volume preselection. The slice (thickness 15 mm) was transverse ori- ented. We examined three regions: frontal lobe, occipitoparietal lobe, and basal ganglia regions (Figure 1). Position and size of the PRESS box with outer volume suppressed were adjusted to partly exclude subcutaneous fat without excluding brain tissue. Four addi- tional saturation bands were used to reduce string lipid signals from outside the volume of interest (VOI). We accomplished water suppression using three preceding chemical shift selective saturation (CHESS) pulses. Field homogeneity was optimized automati- cally over the selected VOI by observing the water signal. Spectra were acquired with TR 1,500 msec, TE 144 msec, and a matrix size of 16 × 16 over an FOV of 16 cm, resulting in a scan time of 6.4 min for each region. We performed postprocessing of the MRS imaging data sets using the Functool soft- ware package version 2.2.49 (General Electric Company). Spectral data sets were zero filled to 1,024 points, multiplied by a 1.25-Hz Lorentzian function, and Fourier transformed in a time domain and in two spatial domains. Marquardt curve fitting was performed by using a Gaussian line shape to calculate the area under the peak for the metabolites N-acetyl aspartate (NAA), total creatine (tCr), and choline (Cho). We calculated the peak area ratios of Cho:tCr and NAA:tCr. One trained rater, who was blind to the subject group status when the measurements were performed, conducted the choice of the voxels in all areas. Three voxels in each loca- tion, including gray matter, subcortical white matter, and deep white matter of the frontal lobes, the occipital lobes, and the basal gan- glia, were carefully chosen. We used mean values for analysis. Statistical analyses. To summarize data, we used descriptive statistics to calculate the means of the continuous variables age, work- ing duration (in years), BMI, blood lead lev- els, and bone lead levels. We used descriptive rates and proportions for categorical variables such as sex and uses of tobacco, alcohol, and betel nut. t-Tests were used to compare dif- ferences in continuous variables between the two groups, and the chi-square or Fisher exact tests were used to test differences in nominal variables between the two groups. Multiple