A prospective study of risedronate on regional bone metabolism and blood flow at the lumbar spine measured by 18F-fluoride positron emission tomography.

The effect of risedronate on bone metabolism at the lumbar spine was assessed in 18 women who had a 18F-fluoride PET scan at baseline and after 6 months of therapy. The net plasma clearance of fluoride to bone mineral reflecting osteoblastic activity decreased significantly after therapy. INTRODUCTION: Quantitative radionuclide studies of bone reflect bone blood flow and regional osteoblastic activity, and the latter should change after treatment with a bisphosphonate, although this has not been previously demonstrated. The aim of this study was to examine regional 18F-fluoride kinetics in the lumbar spine measured by 18F-fluoride positron emission tomography (PET) before and after treatment with risedronate. MATERIALS AND METHODS: Eighteen women, with a mean age of 67.0 years and a T-score of less than -2 at the spine or hip, had a dynamic PET scan of the lumbar spine after the injection of 90 MBq 18F-fluoride ion at baseline and 6 months after commencing risedronate therapy. The arterial plasma input function was derived using aorta arterial activity from the PET image. Time-activity curves were measured by placing regions of interest over the lumbar vertebrae. A three-compartmental model was used to calculate bone blood flow (K(1)) and the net plasma clearance of tracer to bone mineral (K(i)). Rate constants k(2), k(3), and k(4), which describe transport between plasma, the extracellular fluid (ECF) compartment, and the bone mineral compartment, respectively, were also measured. RESULTS: Mean vertebral K(i) decreased significantly by 18.4% from baseline (3.32 x 10(-2) ml/min/ml) to 6 months post-treatment (2.71 x 10(-2) ml/min/ml; p = 0.04). This decrease was similar in magnitude to the decrease observed for bone-specific alkaline phosphatase, a marker of bone formation. There was no significant difference in K(1) from baseline (1.49 x 10(-1) ml/min/ml) to 6 months after treatment (1.38 x 10(-1) ml/min/ml; p > 0.05). There was a significant increase in k(2), reflecting the reverse transport of fluoride from the extravascular tissue compartment to plasma, after 6 months of treatment (2.90 x 10(-1)/min versus 4.43 x 10(-1)/min; p = 0.01). No significant changes were seen for k(3) or k(4). There was a significant decrease from baseline in the fraction of tracer in the extravascular tissue space that underwent specific binding to the bone matrix (k(3)/[k(2) + k(3)]), decreasing by 18.1% (p = 0.02). CONCLUSION: K(i), the net plasma clearance to bone mineral reflecting regional osteoblastic activity, displayed a significant decrease after 6 months of antiresorptive therapy. This is the first study to show a direct metabolic effect of antiresorptive therapy on skeletal kinetics at the clinically important site of the lumbar spine. The use of 18F-fluoride PET may provide a useful noninvasive tool to assess novel treatments currently being developed for osteoporosis.     

Differences in skeletal kinetics between vertebral and humeral bone measured by 18F-fluoride positron emission tomography in postmenopausal women.

We have sought to investigate regional differences in skeletal kinetics between lumbar vertebrae and the humerus of postmenopausal women with 18F-fluoride positron emission tomography (PET). Twenty-six women, mean age 62 years, had dynamic PET scans of the lumbar spine and lower humerus after the injection of 180 MBq 18F-fluoride ion. Plasma arterial input functions (IFs) were calculated from a mean IF measured arterially from 10 women and scaled according to late individual venous activity. Vertebral and humeral time activity curves were measured by placing regions of interest (ROI) over lumbar vertebrae and the humeral shaft. Using a three-compartmental model and nonlinear regression analysis the macroconstant Ki, representing plasma clearance of fluoride to bone mineral, and the individual rate constants K1 (related to regional skeletal blood flow) and k2 to k4 describing transport between plasma, an extracellular fluid compartment and a bone mineral compartment, were measured. Mean vertebral Ki (3.47x10(-2) ml x min(-1) x ml(-1)) and K1 (1.08x10(-1) ml x min(-1) x ml(-1)) were found to be significantly greater than humeral Ki (1.64x10(-2) ml min(-1) ml(-1); P<0.0001) and K1 (3.90x10(-2) ml x min(-1) x ml(-1); P<0.0001) but no significant differences were found in k2, k3, and k4. These findings confirm differences in regional skeletal kinetics between lumbar vertebrae and the lower humerus. These observations may help increase our understanding of the regional differences in pathophysiology and response to treatment that have been observed in sites consisting predominantly of either trabecular or cortical bone. 18F-fluoride PET may prove to be a valuable technique in the noninvasive measurement of regional skeletal metabolism.     

Quantification of skeletal kinetic indices in Paget's disease using dynamic 18F-fluoride positron emission tomography.

The purpose of this study was to quantify indices of regional bone metabolism in Paget's disease and to compare these indices with normal bone using dynamic 18F-fluoride positron emission tomography (PET). Seven patients with vertebral Paget's disease had 1 h dynamic 18F-fluoride PET scans performed. The scans included a diseased vertebra and an adjacent normal vertebra. Arterial plasma input functions were also measured. A three-compartment, four-parameter model was used with nonlinear regression analysis to estimate bone kinetic variables. Compared with normal bone, pagetic bone demonstrated higher values of plasma clearance to bone mineral (Ki; 1.03 x 10(-1) vs. 0.36 x 10(-1) ml/min per milliliter; p = 0.018) and clearance to total bone tissue (K1; 2.38 x 10(-1) vs. 1.25 x 10(-1) ml/min per milliliter; p = 0.018), reflecting increased mineralization and blood flow, respectively. Release of 18F-fluoride from bone mineral (k4) was lower in pagetic bone (p = 0.022), suggesting tighter binding of 18F-fluoride to bone mineral. The notional volume of the extravascular bone compartment (K1/k2) was greater in pagetic bone (p = 0.018). Although the unidirectional extraction efficiency from the extravascular space to bone mineral (Ki/K1) was greater in pagetic bone (p = 0.018), a lower pagetic value of k2 (p = 0.028), describing the rate of transfer from the bone extravascular compartment to plasma, suggests that the 18F-fluoride that enters the relatively fibrotic marrow space of pagetic bone may be less accessible for return to plasma. These findings confirm some of the known pathophysiology of Paget's disease, introduce some new observations, and show how dynamic 18F-fluoride PET may be of value in the measurement of regional metabolic parameters in focal bone disorders.     

The relationship between regional bone turnover measured using 18F-fluoride positron emission tomography and changes in BMD is equivalent to that seen for biochemical markers of bone turnover.

Bone turnover is an important determinant of fracture risk. (18)F-fluoride positron emission tomography ((18)F-PET) allows the direct assessment of bone turnover at the clinically important skeletal sites such as the lumbar spine. The aim of this study was to determine if the relationship between regional bone turnover measured using (18)F-PET and changes in bone mineral density (BMD) is equivalent to that seen for global skeletal measurements of biochemical markers of bone turnover. Forty-three women who had previously had an (18)F-PET scan at the lumbar spine, assessment of biochemical markers of bone turnover, and a dual-energy X-ray absorptiometry scan of BMD at the lumbar spine and hip (baseline assessments) were split into 1 of 2 groups: (1) 22 women who commenced treatment for osteoporosis within 2mo of having the baseline assessments (Treatment group); (2) 21 women who had not taken any treatments for osteoporosis since having the baseline assessments (Untreated group). Sixteen of the women in the Treatment group started risedronate therapy as part of a prospective study they were participating in, whereas the decision to treat the remaining 6 women was made by the subject's treating physician. Subjects had between 2 and 5 BMD scans over a median follow-up time of 4.1yr to estimate the annual percentage change in BMD since baseline. The relationship between the tertiles of (18)F-PET skeletal kinetic parameter K(i), reflecting regional bone turnover, and annual changes in lumbar spine and hip BMD were compared to that seen for bone formation (bone-specific alkaline phosphatase, BSALP) and bone resorption (urinary deoxypyridinoline) markers. Treated women in the highest tertile of both regional ((18)F-PET) and global (biochemical markers) bone turnover showed the greatest annual percentage increases in lumbar spine BMD. The annual increase in lumbar spine BMD was 1.8%, 2.2%, and 3.2% for women in the lowest, middle, and highest tertile of BSALP, respectively, which was similar to that obtained for the regional measurement of K(i) of 1.7%, 2.2%, and 2.7% respectively. Untreated women in the highest tertile of regional and global bone turnover had larger decreases in lumbar spine BMD compared to those women in the lowest tertile, with a 1.4- to 4.8-fold difference in the annual decrease in BMD between the two. Less consistent patterns were observed when assessing the relationship between regional and global bone turnover with changes in hip BMD. This study has demonstrated that the relationship between regional bone turnover measured directly at the lumbar spine with changes in BMD is similar to that seen for global skeletal bone turnover using biochemical markers.     

Measurement of skeletal flow with positron emission tomography and 18F-fluoride in femoral head osteonecrosis

Positron emission tomography (PET) with ¹⁸F-fluoride was utilized to determine the regional blood flow to the femoral head in early osteonecrosis. Five patients with a history of unilateral hip trauma and a normal contralateral side were selected. Skeletal flow and fluoride uptake in the abnormal and normal hips were compared directly, and the relation between bone blood flow and final outcome, i.e., surgical replacement or conservative treatment, was evaluated. In this pilot study, a flow ratio of at least 2 between the abnormal and normal femoral head was necessary to predict a successful outcome with a conservative regimen. A minimum flow of 0.04 ml/min/ ml was measured in one patient whose affected femoral head healed conservatively. Our preliminary study indicates that this type of highly technical investigation appears feasible in clinical practice and permits prediction of the outcome depending upon regional skeletal flow measurements in vivo. Received: 22 January 1998     

Assessing regional hypoxia in human renal tumours using 18F-fluoromisonidazole positron emission tomography

OBJECTIVE: To assess renal tumours for hypoxic regions using 18F-fluoromisonidazole (18F-FMISO) positron emission tomography (PET), a recognized noninvasive method for detecting hypoxia in tumours, as renal cell carcinoma (RCC) can be potentially cured with nephrectomy but recurrence develops in most patients, who then respond poorly to treatments such as chemotherapy, and hypoxia is known to confer resistance to radiotherapy and chemotherapy in many solid tumours. PATIENTS AND METHODS: In all, 17 patients had 18F-FMISO PET scans before nephrectomy for presumed RCC. Specimens were examined histologically, and immunohistochemistry was used to compare the microvessel density (MVD) as an indicator of angiogenesis in the tumour and normal parenchyma, in 15 patients. Tumour oxygenation was measured invasively in three patients using a polarographic oxygen sensor probe. RESULTS: Of the 15 patients with histological results, 11 had RCC and four had other tumours. Although there was a trend there was no statistically significant (P = 0.14) difference in the maximum standardized uptake value (SUV(max)) when comparing the region of the kidney involved with RCC; the mean (95% confidence interval) SUV(max) in the tumours was 1.3 (0.15), whilst that in the normal contralateral kidney was 1.1 (0.22). The MVD was greater in RCC, at 13.7 (3.1) mean vessels per high-power field than in normal tissue, at 6.9 (1.9). Hypoxia as measured polarographically was detected in three RCCs (median pO2 9.6 mmHg) compared to normal parenchyma at 37.6 mmHg. CONCLUSIONS: Although 18F-FMISO scans showed significant uptake in other solid tumours, there was only mild 18F-FMISO uptake in the present RCCs. The invasive measurements indicated that there was hypoxia in RCC, but the median pO2 did not fall below 9.5 mmHg. Further direct studies of renal tumour oxygenation combined with therapies directed towards hypoxia may allow a better understanding of the relationship between 18F-FMISO results and the biological significance of hypoxia in RCC.     

Differential effects of teriparatide on regional bone formation using 18F‐fluoride positron emission tomography

Teriparatide increases skeletal mass, bone turnover markers, and bone strength, but local effects on bone tissue may vary between skeletal sites. We used positron emission tomography (PET) to study ¹⁸F‐fluoride plasma clearance (K_i) at the spine and standardized uptake values (SUVs) at the spine, pelvis, total hip, and femoral shaft in 18 postmenopausal women with osteoporosis. Subjects underwent a 1‐hour dynamic scan of the lumbar spine and a 10‐minute static scan of the pelvis and femurs at baseline and after 6 months of treatment with 20 µg/day teriparatide. Blood samples were taken to derive the arterial input function and lumbar spine K_i values evaluated using a three‐compartment model. SUVs were calculated for the spine, pelvis, total hip, and femoral shaft. After 6 months treatment with teriparatide, spine K_i values increased by 24% (p = .0003), while other model parameters were unchanged except for the fraction of tracer going to bone mineral (k₃/[k₂ + k₃]), which increased by 23% (p = .0006). In contrast to K_i, spine SUVs increased by only 3% (p = .84). The discrepancy between changes in K_i and SUVs was explained by a 20% decrease in ¹⁸F^? plasma concentration. SUVs increased by 37% at the femoral shaft (p = .0019), 20% at the total hip (p = .032), and 11% at the pelvis (p = .070). Changes in bone turnover markers and BMD were consistent with previous trials. We conclude that the changes in bone formation rate during teriparatide treatment as measured by ¹⁸F^? PET differ at different skeletal sites, with larger increases in cortical bone than at trabecular sites. © 2011 American Society for Bone and Mineral Research.     

The role of insulin in human brain glucose metabolism: an 18fluoro-deoxyglucose positron emission tomography study

The effect of basal insulin on global and regional brain glucose uptake and metabolism in humans was studied using 18-fluorodeoxyglucose and positron emission tomography (FDG-PET). Eight healthy male volunteers aged 49.3 +/- 5.1 years were studied twice in random order. On each occasion, they received an infusion of 0.1 mg. kg(-1). min(-1) somatostatin to suppress endogenous insulin production. In one study 0.3 mU. kg(-1). min(-1) insulin was infused to replace basal circulating insulin levels, and in the other study a saline infusion was used as control. We sought stimulatory effects of basal insulin on brain glucose metabolism particularly in regions with deficiencies in the blood-brain barrier and high density of insulin receptors. Insulin levels were 27.07 +/- 1.3 mU/l with insulin replacement and 3.51 +/- 0.4 mU/l without (P = 0.001). Mean global rate of brain glucose utilization was 0.215 +/- 0.030 mmol. kg(-1). min(-1) without insulin and 0.245 +/- 0.021 mmol. kg(-1). min(-1) with insulin (P = 0.008, an average difference of 15.3 +/- 12.5%). Regional analysis using statistical parametric mapping showed that the effect of basal insulin was significantly less in the cerebellum (Z = 5.53, corrected P = 0.031). We conclude that basal insulin has a role in regulating global brain glucose uptake in humans, mostly marked in cortical areas.     

Differences in regional bone perfusion and turnover between lumbar spine and distal humerus: F-fluoride PET study of treatment-naïve and treated postmenopausal women

The functional imaging technique of ¹⁸F-fluoride positron emission tomography (¹⁸F-PET) allows the non-invasive assessment of regional bone blood perfusion and turnover. Bone perfusion and turnover measured using ¹⁸F-PET correlate closely with those obtained experimentally and so they can be readily applied in clinical research studies. The aim of this study was to compare bone perfusion and turnover between the lumbar spine and humerus in both treatment naïve postmenopausal women (n = 11) and those on stable antiresorptive therapy (n = 12). All women had a BMD T-score of less than − 2 at the spine and/or hip. Each woman had a dynamic PET scan of the lumbar spine and distal humerus after injection of 90 MBq ¹⁸F-fluoride. Using a three-compartmental model bone perfusion (K₁), the net plasma clearance of tracer to bone mineral (K_i) reflecting regional bone turnover and the rate constants k₂–k₄ describing the transport of fluoride between plasma, an extravascular bone compartment and bone mineral compartment were calculated. Mean bone perfusion (K₁) and bone turnover (K_i) were significantly higher at the lumbar spine compared to the humerus for both treatment-naïve and antiresorptive groups. K₁ values were on average 3 times greater while K_i was approximately 50% greater at the lumbar spine. The rate constant k₂, the reverse transport of fluoride from the extravascular compartment to plasma, was significantly lower at the humerus compared to the lumbar spine in both groups. The ratio K_i/K₁ describing the unidirectional extraction efficiency to bone mineral was significantly greater at the humerus compared to the lumbar spine for both study groups. No significant differences between skeletal sites were observed for k₃ or k₄. In conclusion a significant skeletal heterogeneity was observed in terms of bone perfusion and turnover between the lumbar spine and humerus. ¹⁸F-PET may aid in our understanding of the importance of bone perfusion in osteoporosis and differences in regional bone turnover with disease and in response to therapy.     

Diagnostic values of positron emission tomography versus triple-phase bone scan in hip arthroplasty loosening

Introduction The most frequent complications of total hip arthroplasty are septic and aseptic wear-induced loosening. A reliable differentiation between septic and aseptic loosening with current diagnostic tools is not possible. Therefore, we examined the diagnostic valency of positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) in cases of septic or aseptic hip arthroplasty loosening compared with conventional triple-phase bone scan (TPBS).Materials and methods Fifty patients with 70 total hip replacements (symptomatic n=50, asymptomatic n=20) were examined by means of FDG-PET and TPBS to detect septic and aseptic loosening and differentiate between the two. A differentiated algorithm subdivided into categories I–V was developed for FDG-PET. Additionally, standardized uptake values (SUV) were calculated from the lesion with the highest FDG uptake. Interpretations of the TPBS were done according to the criteria described by Wilson. The final diagnosis was based on operative findings including microbiological and histological examinations (n=50), while the remaining asymptomatic arthroplasties (n=20) were integrated into a clinical follow-up (9 months).Results Sensitivity/specificity of FDG-PET was 91%/92% (accuracy 91%) compared with 78%/70% (accuracy 74%) for TPBS. A high correlation could be proved between FDG-PET investigation and operative histopathological findings (r_Spear0.9). No significant differences were found regarding cemented and uncemented implanted hip arthroplasties (p0.05). Calculation of the SUV turned out to be inappropriate as a sole criterion for image interpretation.Conclusion FDG-PET is a promising, highly accurate examination method to detect polyethylene and metal wear-induced chronic inflammation followed by periprosthetic osteolysis. In addition, FDG-PET has a significantly higher sensitivity and specificity than TPBS for differentiating between aseptic loosening and infection.     

Decrease in vertebral bone density after hip arthroplasty: A quantitative computed tomography study in 18 arthrosis cases

We investigated the bone mineral density (BMD) of the lumbar vertebrae L1-3 with quantitative computed tomography (OCT) in 18 patients who had been operated on with hip arthroplasty because of unilateral arthrosis. In an earlier prospective study, we did not find any bone mineral changes in the femur or tibia after hip arthroplasty in spite of a large increase of the thigh muscle mass as a sign of a remobilization after the operation.

The median BMD had decreased 5.3-8.4 percent in all the measured vertebrae after 6 months postoperatively. Because of the patients' improved walking ability after the operation, this decrease in cancellous vertebral BMD is interpreted as a sign of a posttraumatic osteopenia.     

In vivo skeletal imaging of 18F-fluoride with positron emission tomography reveals damage- and time-dependent responses to fatigue loading in the rat ulna

The skeletal response to damaging fatigue loading is not fully understood. We used (18)F-fluoride PET to describe the time course of the skeletal response following the creation of increasing levels of in vivo, fatigue-induced damage. The right forelimbs of 40 adult rats were loaded in vivo in cyclic compression to four levels of subfracture, fatigue displacement: 30, 45, 65, or 85% of fracture displacement. Rats were injected with a bone-seeking radionuclide ((18)F-fluoride) on days 0 (4 h), 2, 4, 7, 9, 11, 18, 24, and 30, and imaged using a small animal positron emission tomography (PET) scanner. We quantified fluoride uptake in the central 50% of the right (loaded) and left (control) forelimbs. There were significant increases in fluoride uptake in loaded forelimbs compared to control on day 0 for all displacement groups. Normalized uptake (loaded/control) reached peak levels 4 to 9 days after loading. Normalized uptake depended significantly on the level of fatigue displacement. Normalized uptake increased progressively from the 30 to the 45% displacement level (P < 0.001), and from the 45 to the 65% level (P < 0.001) but did not differ between 65 and 85% (P = 0.41). Histologically, we observed a rapid periosteal response with increased vascularity as early as day 1 and abundant woven bone formation between days 3 and 7. Periosteal and woven bone thicknesses were greater in bones subjected to more fatigue displacement. We conclude that a single bout of fatigue loading leads to a transient increase in the uptake of (18)F-fluoride, that the uptake is in proportion to the level of initial damage and is associated with increased vascularity and woven bone formation in the first week after loading.     

Dose-dependent regional cerebral blood flow changes during remifentanil infusion in humans: a positron emission tomography study

BACKGROUND: The current study investigated dose-dependent effects of the mu-selective agonist remifentanil on regional cerebral blood flow (rCBF) in volunteers using positron emission tomography (PET). METHODS: Ten right-handed male volunteers were included in a 15O-water PET study. Seven underwent three conditions: control (saline), low remifentanil (0.05 microg x kg(-1) x min(-1)), and moderate remifentanil (0.15 microg x kg(-1) x min(-1)). The remaining three participated in the low and moderate conditions. A semirandomized study protocol was used with control and remifentanil conditions 3 or more months apart. The order of low and moderate conditions was randomized. Cardiovascular and respiratory parameters were monitored. Categoric comparisons between the control, low, and moderate conditions and a pixelwise correlation analysis across the three conditions were performed (P < 0.05, corrected for multiple comparisons) using statistical parametric mapping. RESULTS: Cardiorespiratory parameters were maintained constant over time. At the low remifentanil dose, significant increases in relative rCBF were noted in the lateral prefrontal cortices, inferior parietal cortices, and supplementary motor area. Relative rCBF decreases were observed in the basal mediofrontal cortex, cerebellum, superior temporal lobe, and midbrain gray matter. Moderate doses further increased rCBF in mediofrontal and anterior cingulate cortices, occipital lobe transition, and caudal periventricular grey. Significant decreases were detected in the inferior parietal lobes. These dose-dependent effects of remifentanil on rCBF were confirmed by a correlation analysis. CONCLUSION: Remifentanil induced dose-dependent changes in relative rCBF in areas involved in pain processing. At moderate doses, rCBF responses were additionally detected in structures known to participate in modulation of vigilance and alertness. Insight into the mechanisms of opioid analgesia within the pain-processing neural network may lead to a better understanding of antinociception and opioid treatment.     

18-fluorodeoxyglucose positron emission tomography in cystic carcinoma of the breast

Cystic infiltrating ductal carcinoma of the breast is uncommon and frequently misdiagnosed because of the predominant cystic presentation clinically. Three premenopausal patients presented with huge cystic breast lesions measuring 10, 19, and 20 cm for 12-, 6-, 10-months duration, respectively. In the first patient, mammography showed a high-density, well-circumscribed huge breast mass, whereas in the other two patients mammography was not possible because of the huge breast size. In all three patients, breast ultrasound showed large cystic lesions suggestive of tumor with central necrosis or bleeding from which a variable amount (270, 1300, 600 ml) of bloody fluid was aspirated, respectively. In the first two patients, cytologic examination of the aspirate showed evidence of malignant cells, whereas the third patient was diagnosed by histologic examination of the cyst wall biopsy. In all three patients, a whole-body positron emission tomography (PET) scan showed intense focal 18-fluorodeoxyglucose (FDG) breast uptake corresponding to the solid component and a ringlike uptake corresponding to the cystic component most likely representing tumor necrosis, hemorrhage, or both. Furthermore, whole-body PET scan was valuable in predicting the response to chemotherapy, characterizing the pelviabdominal mass and detecting the presence of hepatic and spinal metastases in the three patients, respectively. 18-FDG PET scan can help characterize a cystic breast mass by identifying the extent of the cystic and the solid component. It is also useful in staging cystic infiltrating ductal carcinoma by detecting lymph node involvement as well as distant metastases.     

Precision of 18F-fluoride PET skeletal kinetic studies in the assessment of bone metabolism

Summary

We assessed the precision of lumbar spine ¹⁸F-PET measurements based on 58 scans performed on 20 postmenopausal women. The percentage coefficient of variation (%CV) (95% confidence interval) was 9.2% (7.5–11.8) for standardised uptake values, 11.7% (9.5–14.9) for plasma clearance measurements using the Patlak method and 14.5% (11.7–18.5) for plasma clearance measurements using the Hawkins three-compartment model.

Introduction

¹⁸F-Fluoride positron emission tomography (¹⁸F-PET) is a non-invasive technique that allows the assessment of regional bone turnover in patients with metabolic bone disease. Knowledge of the precision errors of ¹⁸F-PET measurements is important for planning the number of subjects required for research studies.

Methods

Twenty osteoporotic postmenopausal women had ¹⁸F-PET scans of the lumbar spine at 0, 6 and 12?months after stopping long-term bisphosphonate treatment. No significant changes in the PET measurements were seen over the 12-month period, and the data were deemed suitable for a precision study. Precision errors were evaluated for standardised uptake values (SUVs) and for the fluoride plasma clearance to bone mineral (K _i) determined using the Patlak and Hawkins methods. Precision errors were expressed as the %CV and were calculated for the mean L1–L4 region and for individual vertebrae.

Results

%CV (95% confidence interval) for the L1–L4 region was 9.2% (7.5–11.8) for SUV, 11.7% (9.5–14.9) for K _i measured using the Patlak method and 14.5% (11.7–18.5) for K _i measured using the Hawkins method. There was no significant difference between precision errors obtained for the L1–L4 region and those obtained for a single vertebra.

Conclusions

SUV measurements showed the smallest precision error followed by the Patlak method, while the Hawkins method gave the largest error. Measuring a smaller region of interest did not increase the precision error, suggesting that the factor determining the errors may be scanner calibration.     

Fluorine-18 fluorodeoxyglucose positron emission tomography findings in spondylodiscitis: preliminary results

Nuclear medicine procedures can be helpful in diagnosing spine infections. The purpose of the study was to evaluate the findings of positron emission tomography with fluorine-18 fluorodeoxyglucose (FGD-PET) in the detection of spondylodiscitis. We performed FDG-PET in 16 patients with suspected spondylodiscitis. All the patients were operated and underwent histopathological examination. The FDG-PET findings were graded and evaluated by two independent nuclear medicine physicians. Of the 16 patients, 12 had a histopathologically confirmed spondylodiscitis. In all these 12 patients, FDG-PET was true-positive. In the four patients without spondylodiscitis, FDG-PET showed three true-negative and one false-positive result. In spondylodiscitis, the mean standard uptake value (SUV) of FDG was 7.5 (SD+/-3.8). The PET scans depicted the paravertebral soft tissue involvement in cases of spondylodiscitis. Our first results showed that FDG-PET is a very sensitive imaging procedure in the detection of spondylodiscitis. Compared to other nuclear medicine procedures, PET enables a rapid imaging with acceptable radiation dose and high spatial resolution.     

PET分析丙泊酚对人脑葡萄糖能量代谢的影响

目的　应用正电子发射计算机体层显像(PET)技术,观察丙泊酚对人脑不同区域内葡萄糖能量代谢(CMGlu)的影响,探讨丙泊酚在人脑可能的作用部位。方法　健康志愿者 7 名,每位志愿者分别在清醒、丙泊酚 1 .5μg/ml(镇静)和 3 0μg/ml(意识消失)靶浓度状态下注射18氟脱氧葡萄糖(18F -FDG)显像剂,平衡后进行PET扫描。以清醒状态作为对照,通过靶控输注(TCI)丙泊酚使志愿者达到镇静和意识消失状态。结果　(1)与清醒状态比较,镇静状态下脑电双频指数(BIS)明显降低(P<0. 05),平均动脉压(MAP)、呼吸频率(RR)和心率(HR)等指标无显著性改变;而意识消失状态下,MAP、BIS降低,呼吸抑制,呼气末二氧化碳分压( PET CO2 )升高,均有显著性差异(P<0. 05)。(2)与清醒状态比较,镇静状态下全脑的CMGlu下降(18. 0±4. 0)%。CMGlu的下降在大脑皮质最为明显(P<0. 05)。CMGlu在丘脑、小脑、海马和桥脑等区域也有不同程度的降低,但与清醒状态比较,无显著性差异。意识消失状态下,全脑 CMGlu 与清醒状态比较显著下降了(34. 1±7 .0)%(P<0 .05),在丘脑、大脑皮质、小脑和海马等区域 CMGlu明显低于清醒状态(P<0 .05),其中丘脑降幅最大为(51. 5±5 .0)%。结论　丙泊酚麻醉可明显降低全脑能量代谢,低剂量的丙泊酚首先影响皮层区的能量代谢,