Determination of normal splenic volume on computed tomography in relation to age, gender and body habitus

The purpose of our study was to examine variations in normal splenic size in relation to age, gender and body habitus in vivo, and to determine normative data for splenic volume on CT. The width (W), length (L), thickness (Th), cross-sectional areas and volume (Vol) of the spleen were obtained from abdominal CT examinations of 140 patients who underwent CT for indications unrelated to splenic disease. Splenic volume did not vary significantly (–0.04 < r < 0.05, p > 0.10) with the patient's age, gender, height, weight, body mass index or the diameter of the first lumbar vertebra, the latter considered as representative of body habitus on CT. The mean value of the measured splenic volume (S Vol) was 214.6 cm³ with a range from 107.2 to 314.5 cm³. S Vol correlated well with all the linear and the maximal cross-sectional area measurements and could be calculated using the formula: S Vol = 30 + 0.58 (W × L × Th.). Employing the same formula splenic volume was reliably assessed in 47 patients with clinically evident splenomegaly. Quantitative assessment of splenic volume might be of value in assessing mild variations in splenic size, because splenomegaly is the most common manifestation of splenic involvement in many disorders. Received 29 January 1996; Revision received 24 June 1996; Accepted 15 July 1996     

Age-dependent reference values of the thyroid gland in pediatric population; from routine computed tomography data

PurposeTo evaluate age-dependent reference values for measurements of the thyroid gland in pediatric patients.MethodIn total 425 chest and neck computed tomography images of pediatric patients without pathology of the thyroid gland were retrospectively reviewed. Measurements of the thyroid gland were obtained in three dimensions (width, depth, length). The total volume was the sum of volumes of each lobe. Measurements were compared among the six groups according to age from 0 to 18 years.ResultsThere were moderate to strong positive linear correlations between age and all values (r = 0.58–0.82, all p < 0.001). The total volume of the thyroid gland showed a strong positive linear correlation with the three linear measurements of each lobe (all r > 0.7, all p < 0.001). Among these measurements, the depth of the right lobe showed the highest Pearson correlation coefficient with the total volume of the thyroid gland (r = 0.859).ConclusionThe depth of right lobe could be a representative measurement of total thyroid gland volume, similar to prior findings in adults.     

Assessment of parathyroid glands in hemodialysis patients by using color Doppler sonography

The aim of this study was to assess the role of color and spectral Doppler ultrasound (CDU) in the evaluation of enlarged parathyroid glands in hemodialysis patients with secondary hyperparathyroidism. Fourteen hemodialysis patients with elevated intact parathyroid hormone (iPTH) levels were evaluated prospectively with CDU. The volume of each observed parathyroid gland and the spectral CDU data (velocities, resistance and pulsatility indices, systolic to diastolic ratio, and flow volume output (FVO)) were noted. The biochemical data (iPTH, calcium, phosphate levels), and CDU results were analyzed with the Spearman correlation test. Two patients were excluded, and 27 enlarged parathyroid glands were observed in 12 patients. The mean total volume of enlarged parathyroid glands per patient was 1.95 cm³ (0.06–5.5 cm³). Arterial supply was demonstrated in 78% (21/27) of enlarged parathyroid glands. Mean total FVO of enlarged glands per patient was 238.5 ml/min (620–0 ml/min) and mean iPTH level was 1,477 pg/ml (643–3,132 pg/ml). The positive correlations of total volume (p = 0.022), iPTH (p = 0.024), and FVO (p = 0.022) were statistically significant. In secondary hyperparathyroidism, total volume of the visualized enlarged parathyroid glands and the total of FVOs per patient are positively correlated with iPTH levels which may help clinical management and follow-up of end-stage renal disease patients.     

Chronic thyroiditis in patients with advanced breast carcinoma: metabolic and morphologic changes on PET-CT

Purpose  To investigate clinical implications of FDG uptake in the thyroid glands in patients with advanced breast carcinoma by comparing metabolic and morphologic patterns on positron emission tomography (PET)/computed tomography (CT). Methods  The institutional review board waived the requirement for informed consent. A retrospective analysis was performed in 146 women (mean age 54 years) with advanced breast carcinoma who received systemic treatment. All patients underwent PET-CT before and after treatment. All PET-CT studies were reviewed in consensus by two reviewers. Morphologic changes including volume and mean parenchymal density of the thyroid glands were evaluated. Maximum standardized uptake value (SUVmax) and total lesion glycolysis (TLG) were determined to evaluate metabolic changes. These parameters were compared between patients with chronic thyroiditis who received thyroid hormone replacement therapy and those who did not. Results  Of the 146 patients, 29 (20%) showed bilaterally diffuse uptake in the thyroid glands on the baseline PET-CT scan. The SUVmax showed a linear relationship with volume (r = 0.428, p = 0.021) and the mean parenchymal density (r = −0.385, p = 0.039) of the thyroid glands. In 21 of the 29 patients (72%) with hypothyroidism who received thyroid hormone replacement therapy, the volume, mean parenchymal density, SUVmax, and TLG of the thyroid glands showed no significant changes. In contrast, 8 of the 29 patients (28%) who did not receive thyroid hormone replacement therapy showed marked decreases in SUVmax and TLG. Conclusion  Diffuse thyroid uptake on PET-CT represents active inflammation caused by chronic thyroiditis in patients with advanced breast carcinoma. Diffuse thyroid uptake may also address the concern about subclinical hypothyroidism which develops into overt disease during follow-up.     

MDCT Linear and Volumetric Analysis of Adrenal Glands: Normative Data and Multiparametric Assessment

Objectives

To study linear and volumetric adrenal measurements, their reproducibility, and correlations between total adrenal volume (TAV) and adrenal micronodularity, age, gender, body mass index (BMI), visceral (VAAT) and subcutaneous adipose tissue volume (SAAT), presence of diabetes, chronic alcoholic abuse and chronic inflammatory disease (CID).

Methods

We included 154 patients (M/F, 65/89; mean age, 57 years) undergoing abdominal multidetector row computed tomography (MDCT). Two radiologists prospectively independently performed adrenal linear and volumetric measurements with semi-automatic software. Inter-observer reliability was studied using inter-observer correlation coefficient (ICC). Relationships between TAV and associated factors were studied using bivariate and multivariable analysis.

Results

Mean TAV was 8.4?±?2.7 cm³ (3.3–18.7 cm³). ICC was excellent for TAV (0.97; 95 % CI: 0.96–0.98) and moderate to good for linear measurements. TAV was significantly greater in men (p?<?0.0001), alcoholics (p?=?0.04), diabetics (p?=?0.0003) and those with micronodular glands (p?=?0.001). TAV was lower in CID patients (p?=?0.0001). TAV correlated positively with VAAT (r?=?0.53, p?<?0.0001), BMI (r?=?0.42, p?<?0.0001), SAAT (r?=?0.29, p?=?0.0003) and age (r?=?0.23, p?=?0.005). Multivariable analysis revealed gender, micronodularity, diabetes, age and BMI as independent factors influencing TAV.

Conclusions

Adrenal gland MDCT-based volumetric measurements are more reproducible than linear measurements. Gender, micronodularity, age, BMI and diabetes independently influence TAV.

Key Points

? Volumetric measurements are more reproducible than linear measurements for adrenal glands. ? Inter-observer reproducibility of adrenal gland volume is excellent using semiautomatic software. ? Gender, age, BMI, and diabetes independently influence total adrenal gland volume. ? Adrenal micronodularity is associated with increased total adrenal gland volume.

     

Preoperative parathyroid gland localization with technetium-99m sestamibi in secondary hyperparathyroidism

Technetium-99m sestamibi scintigraphy has become a valuable tool in locating parathyroid glands in patients with primary hyperparathyroidism. The aim of this study was to evaluate its usefulness in secondary hyperparathyroidism. Twenty patients were injected intravenously with 740 MBq of ^99mTc-sestamibi and images were obtained at 15 min and 2 h post injection. All patients underwent parathyroid ultrasonography (US) as well as bilateral surgical neck exploration and 64 parathyroid glands were removed. US revealed at least one enlarged gland in 15/20 patients (75%), while ^99mTc-sestamibi scintigraphy showed focal areas of increased uptake in at least one gland in 17/20 patients (85%). When imaging results for all glands were evaluated according to surgical results, sensitivity was 54% for parathyroid scintigraphy and 41% for US, and specificity was 89% for both imaging techniques. There was a discrepancy between the two imaging modalities in 28 glands (35%). The mean surgical weight of US-positive glands (1492±1436 mg) was significantly higher than that of US-negative glands (775±703 mg) (P<0.05). However, there were no significant differences in weight between sestamibi-positive and sestamibi-negative glands. When only sestamibi-positive glands were considered, a positive correlation between uptake and weight was found (r=0.4, P<0.05). In conclusion, parathyroid US and ^99mTc-sestamibi scintigraphy are complementary imaging techniques in the preoperative localization of abnormal parathyroid glands in patients with secondary hyperparathyroidism. The limited sensitivity of the techniques means that patients will still require bilateral neck exploration; therefore routine preoperative parathyroid scanning in renal patients is not justified. Received 1 June and in revised form 6 August 1997     

Disease activity and 18F-FDG uptake in organising pneumonia: semi-quantitative evaluation using computed tomography and positron emission tomography

Purpose: The present study was conducted to evaluate whether ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in combination with computed tomography (CT) reflects disease activity in patients with organising pneumonia.Methods: Eighty-eight subjects who were normal (n=66) or who had proven organising pneumonia (n=22) underwent FDG-PET and CT imaging. The subjects included 55 men and 33 women, ranging in age from 24 to 63 years (mean 47 years). PET and CT data sets were digitally fused using a conformational PET/CT fusion algorithm. All scans were evaluated independently by two chest radiologists who were unaware of other clinical data. The visual score, maximal and mean standardised uptake value (SUV), and maximal and mean lesion-to-normal tissue ratio (LNR) were calculated. The imaging results were compared with the laboratory and pulmonary function test results. The inflammatory cells in the lesions were quantified immunohistochemically.Results: The visual score, maximal and mean SUV, and maximal and mean LNR of the patients with organising pneumonia were significantly higher than those of the normal subjects. The patients with air-space consolidation had a significantly higher SUV than those without air-space consolidation (mean±SD 3.08±0.39 vs 2.35±0.56; p<0.05). The number of CD45⁺ cells was positively correlated with the maximal SUV (r=0.632, p<0.01) and the maximal LNR (r=0.453, p<0.05). The number of CD8⁺ T lymphocytes also showed positive correlations with the maximal SUV (r=0.540, p<0.01) and the maximal LNR (r=0.547, p<0.01).Conclusion: Patients with organising pneumonia have an enhanced FDG accumulation which reflects the degree of disease activity.     

Quantification of emphysema: a composite physiologic index derived from CT estimation of disease extent

The combination of functional indices best reflecting the extent of emphysema is not known. High-resolution computed tomography (HRCT) studies of 106 patients with emphysema [men=71; median age=61 (range=26–86 years)] were reviewed and the extent of emphysema was quantified: (a) visually (emphysema_vis) and (b) by automated estimation (emphysema_auto). Functional-morphologic relationships were compared for the two scoring systems, and a composite physiologic index (CPI) (providing the best fit of functional indices against emphysema extent) was derived. Emphysema_vis and emphysema_auto were strongly correlated (r=0.90; p<0.0005), but the extent of emphysema_vis was consistently greater (p<0.00005). Emphysema_vis correlated most strongly with indices of gas transfer [percent predicted single-breath carbon monoxide diffusing capacity (Dl_co) and alveolar volume (K_co); r=−0.70, both p<0.0005]. The combination of physiologic indices most representative of emphysema extent on CT (using visual or automated methods) consisted of K_co and forced expiratory volume in 1 s (FEV₁) levels. The equation explanatory power was higher for visual scoring [emphysema_vis=96.8-(0.67×% predicted K_co)-(0.41×% predicted FEV₁); equation r ²=0.57] than automated estimation (equation r ²=0.48). Weighted combinations of K_co and FEV₁ levels provide a CPI best reflecting morphologic emphysema extent. CPI has the potential to refine the stratification of patients in epidemiological and therapeutic studies.     

Attenuation correction in cardiac PET/CT with three different CT protocols: a comparison with conventional PET

Purpose CT-based attenuation correction may influence cardiac PET owing to its higher susceptibility to misalignment compared with conventional ⁶⁸Ge transmission scans. The aims of this study were to evaluate whether CT attenuation correction leads to changes in tracer distribution compared with conventional cardiac PET and to determine a suitable CT protocol. Methods A total of 27 patients underwent PET/CT and subsequently a PET scan. Twenty patients received a low-dose CT (LDCT group; 120 kV, 26 mA, 8-s scan time), seven patients a slow CT (SCT group; 120 kV, 99 mA, 46-s scan time) and ten patients an ultra-low-dose CT (ULDCT group; 80 kV, 13 mA, 5-s scan time) as the transmission scan in PET/CT. Polar maps were divided into 17 segments and regression analysis was computed in every scan pair (CT attenuation corrected–⁶⁸Ge attenuation corrected). Correlation coefficient (r), the slope (s) and the offset (os) of the regression line were determined. Visual assessment of misalignment between the transmission and emission data was performed. The effective dose of the different transmission scans was calculated. Results Overall, there was a moderate correlation between the mean values measured in all segments on PET/CT and on PET when using LDCT (r=0.78, p<0.0001), SCT (r=0.79, p<0.0001) and ULDCT (r=0.82, p<0.0001). No differences were observed when comparing the scores assigned in the visual misalignment assessment in the three groups (p=0.12). The differences between the results from the regression analysis observed in the respective groups were not statistically significant (Kruskal-Wallis p=0.11 for r, p=0.67 for s and p=0.27 for os). The effective dose was lowest for the ULDCT. Conclusion Our study shows that CT-based attenuation correction is feasible for cardiac PET imaging. The results indicate that ultra-low-dose CT is the preferable choice for transmission scanning.     

Ultrasonography versus computed tomography in evaluation of the femoral trochlear groove morphology: a pilot study on healthy, young volunteers

The aim of the study was to verify the efficacy of ultrasonography (US) in evaluating the morphology of normal trochlea, especially the sulcus angle and the trochlear depth, in comparison with computed tomography (CT) (gold standard). The knees of 11 asymptomatic volunteers were subjected to US and CT evaluation of the same section planes and the results were compared. For statistical evaluation Spearman's correlation coefficient analysis was used. A statistically significant correlation was found between the two diagnostic procedures (sulcus angle: r = 0.820; trochlear depth: r = 0.802; Spearman's correlation coefficient) and the intra-observer variability for the US measurements (sulcus angle: r = 0.966; trochlear depth: r = 0.914; Spearman's correlation coefficient). The mean value of sulcus angle and trochlear depth was 132 ° and 5.6 mm, respectively, similar to those reported in the literature. We conclude that evaluation by US of both sulcus angle and trochlear depth is as reproducible and sensitive as that performed with CT. Received 22 January 1996; Revision received 11 April 1997; Accepted 22 May 1997     

胸部CT扫描中颈部伸展体位应用价值的探讨

目的 探讨在胸部CT扫描中患者颈部伸展使甲状腺腺体上移以减少甲状腺辐射暴露的可能性。方法 对2017年3至6月北京朝阳医院进行胸部CT检查1 994例患者的图像资料进行比较分析,按颈部体位不同分为伸展组和常规组,每组997例,伸展组患者头颈部后仰成颌顶位。常规组采用常规头颅扫描头架,头部正常体位。以第一肋骨头为基准计数标志,观察两组患者甲状腺腺体暴露于扫描范围内的腺体长度及腺体全部移出扫描范围的例数。比较两组患者原发射线区域内甲状腺腺体扫描长度的差别。结果 伸展组患者甲状腺腺体暴露于扫描范围内的长度（4.69±5.68） mm,显著短于常规组（17.16±6.68） mm患者,差异有统计学意义（U=91 073.5,P<0.05）,并且伸展组患者甲状腺腺体完全脱离扫描范围内的例数519例,多于常规组32例,差异有统计学意义（U=594.8,P<0.05）。52.1%患者的甲状腺腺体完全脱离扫描范围内原发射线的辐射暴露。结论 胸部CT扫描时患者颈部伸展可以使甲状腺腺体位于扫描野内的长度缩短,有效提高甲状腺的辐射防护。     

Validation of a new cardiac image fusion software for three-dimensional integration of myocardial perfusion SPECT and stand-alone 64-slice CT angiography

Purpose Combining the functional information of SPECT myocardial perfusion imaging (SPECT-MPI) and the morphological information of coronary CT angiography (CTA) may allow easier evaluation of the spatial relationship between coronary stenoses and perfusion defects. The aim of the present study was the validation of a novel software solution for three-dimensional (3D) image fusion of SPECT-MPI and CTA. Methods SPECT-MPI with adenosine stress/rest ^99mTc-tetrofosmin was fused with 64-slice CTA in 15 consecutive patients with a single perfusion defect and a single significant coronary artery stenosis (≥50% diameter stenosis). 3D fused SPECT/CT images were analysed by two independent observers with regard to superposition of the stenosed vessel onto the myocardial perfusion defect. Interobserver variability was assessed by recording the X, Y, Z coordinates for the origin of the stenosed coronary artery and the centre of the perfusion defect and measuring the distance between the two landmarks. Results SPECT-MPI revealed a fixed defect in seven patients, a reversible defect in five patients and a mixed defect in three patients and CTA documented a significant stenosis in the respective subtending coronary artery. 3D fused SPECT/CT images showed a match of coronary lesion and perfusion defect in each patient and the fusion process took less than 15 min. Interobserver variability was excellent for landmark detection (r = 1.00 and r = 0.99, p < 0.0001) and very good for the 3D distance between the two landmarks (r = 0.94, p < 0.001). Conclusion 3D SPECT/CT image fusion is feasible, reproducible and allows correct superposition of SPECT segments onto cardiac CT anatomy.     

Preoperative evaluation of hepatic functional reserve following hepatectomy by technetium-99m galactosyl human serum albumin liver scintigraphy and computed tomography

It is extremely important to have a good grasp of the acceptable limit of hepatectomy before operation because postoperative liver failure can take a fatal course; however, baseline data on the limit of hepatectomy have not been clearly defined. We therefore evaluated and compared the predicted remnant liver function obtained by computed tomography(CT) and technetium-99m diethylenetriamine penta-acetic acid-galactosyl human serum albumin (^99mTc-GSA) liver scintigraphy in order to obtain precise data regarding remnant liver function before hepatectomy. We investigated 20 patients undergoing hepatectomy using the clearance rate of indocyanine green (KICG) as a parameter, and compared the predicted postoperative KICG obtained by CT and by transaxial single-photon emission tomographic (SPET) images acquired by ^99mTc GSA liver scintigraphy before hepatectomy. In GSA studies, based on time-activity curves for the heart and liver, we compared HH15 (heart activity at 15 min divided by heart activity at 3 min), LHL15 (liver activcity at 15 min divided by heart plus liver activity at 15 min) and K_L (obtained from the time-activity curve for the liver) in 103 patients. In 58 patients without increased serum bilirubin, K_L was compared with KICG. In four patients, occlusion of the right portal vein was performed with the aim of carrying out secondary hepatectomy, and changes in liver volume were compared between CT and ^99mTc GSA liver scintigraphy. The correlation coefficient between the postoperative KICG predicted by CT and the actual postoperative KICG was rather poor, at r = 0.569 (P<0.05); that between the postoperative KICG predicted by ^99mTc GSA liver scintigraphy and the actual postoperative KICG was good, at r = 0.788 (P<0.01); correlations between K_L and HH15 and between K_L and LHL15 in 103 patients were very good or good, at r = 0.906 (P<0.001) and r = 0.807 (P<0.001), respectively, and that between K_L and KICG in 58 patients was very good, at r = 0.916 (P<0.001). In all four cases of right portal vein occlusion, the remnant liver volume ratio was markedly increased after occlusion in GSA compared with CT, and the postoperative KICG predicted by GSA after occlusion was closer to the actual postoperative KICG than that predicted by CT. It is concluded that ^99mTc GSA liver scintigraphy is useful for predicting remnant liver function before hepatectomy and for evaluating changes in regional liver function after occlusion of the portal vein unilaterally. Received 20 March and in revised form 24 June 1998     

Quantification of Left Ventricular Parameters Obtained by Automated Software for 64-Slice Multidetector Computed Tomography and Comparison with Magnetic Resonance Imaging

The dataset obtained with 64-slice multidetector CT (MDCT) for coronary artery evaluation can be used to calculate important left ventricular (LV) volumetric parameters. We compared LV parameters derived by new, commercially available, fully automated software for MDCT (Syngo Circulation, Siemens, Germany) to cardiac magnetic resonance (CMR) as a reference standard. Twenty patients underwent CMR after completing a clinically indicated MDCT. Ejection fraction (EF), end-systolic volume (ESV), end-diastolic volume (EDV), stroke volume (SV), and myocardial mass (MM) for MDCT were obtained using automated software and were compared to CMR measurements, with papillary muscles (PMs) included in, or excluded from, the blood pool. The Pearson correlation coefficient (r) and Bland-Altman method were used to determine agreement between methods. When PMs were included in the blood pool, the correlation was excellent for EF (r = 0.92, p < 0.001), ESV (r = 0.86, p < 0.001), and EDV (r = 0.80, p < 0.001). When PMs were excluded from CMR, correlation was still very good for EF (r = 0.89, p < 0.001), ESV (r = 0.82, p < 0.001), and EDV (r = 0.82, p < 0.001). MDCT values for SV and MM showed a good correlation compared to both CMR methods. When PMs were included, the correlation was good for SV (r = 0.70, p < 0.001), and MM (r = 0.70, p < 0.001); when they were excluded, the correlation was less robust but still significant for SV (r = 0.71, p < 0.001) and MM (r = 0.73, p < 0.001). In conclusion, EF, ESV, and EDV obtained by MDCT using simple, automated software correlated very well with CMR; SV and MM showed good correlation. Automated analysis of volumetric parameters by MDCT can be reliably utilized for clinical purposes.     

CT attenuation of paired HRCT scans obtained at full inspiratory/expiratory position: comparison with pulmonary function tests

The purpose of this prospective study was to measure lung attenuation at paired HRCT obtained at full inspiratory/expiratory position, to correlate with pulmonary function tests (PFTs) and to characterize different types of ventilatory impairment. One hundred fifty-five patients with and without pulmonary disease underwent paired HRCT obtained at full inspiratory/expiratory position. Three scan pairs were evaluated by densito- and planimetry using dedicated software. The PFTs were available for correlation in all patients (mean interval 5 days). Mean lung density (MLD) at full inspiration was –813 HU, and MLD at full expiration was –736 HU; both, as well as the expiratory attenuation increase, demonstrated significant correlations with static and dynamic lung volumes: up to r=0.68, p<0.05 for residual volume. The MLD and emphysema indices correlated markedly better for scans obtained at full expiration than at full inspiration, e.g. correlation with the residual volume: r=0.68 compared with r=0.55. Even better correlations were obtained for the lung area (229 cm² at inspiration, 190 cm² at expiration), up to r=0.74 for the lung area in expiration and the intrathoracic gas volume. Inspiratory MLD and the expiratory attenuation increase were able to differentiate obstructive and restrictive ventilatory impairment from normal subjects, the best results were obtained from scans obtained at full expiratory position (p<0.05). In conclusion, scans obtained at full expiratory position reveal more functional information than scans obtained at full inspiratory position. Quantitative analysis of CT obtained at full expiratory position provides good estimations of static and dynamic lung volumes as well as significant differences between normal subjects and patients with ventilatory impairment. Electronic Publication     

Evaluation of right ventricular function with multidetector computed tomography: comparison with magnetic resonance imaging and analysis of inter- and intraobserver variability

This study was performed to prospectively compare multidetector computed tomography (MDCT) with 16 simultaneous sections and magnetic resonance imaging (MRI) for the assessment of global right ventricular function in 50 patients. MDCT using a semiautomatic analysis tool showed good correlation with MRI for end-diastolic volume (EDV, r = 0.83, p < 0.001), end-systolic volume (ESV, r = 0.86, p < 0.001) and stroke volume (SV, r = 0.74, p < 0.001), but only a moderate correlation for the ejection fraction (EF, r = 0.67, p < 0.001). Bland Altman analysis revealed a slight, but insignificant overestimation of EDV (4.0 ml, p = 0.08) and ESV (2.4 ml, p = 0.07), and underestimation of EF (0.1%, p = 0.92) with MDCT compared with MRI. All limits of agreement between both modalities (EF: ±15.7%, EDV: ±31.0 ml, ESV: ±18.0 ml) were in a moderate but acceptable range. Interobserver variability of MDCT was not significantly different from that of MRI. For MDCT software, the post-processing time was significantly longer (19.6 ± 5.8 min) than for MRI (11.8 ± 2.6 min, p < 0.001). Accurate assessment of right ventricular volumes by 16-detector CT is feasible but still rather time-consuming.     

Standardised uptake values from PET/CT images: comparison with conventional attenuation-corrected PET

Purpose In PET/CT, CT-derived attenuation factors may influence standardised uptake values (SUVs) in tumour lesions and organs when compared with stand-alone PET. Therefore, we compared PET/CT-derived SUVs intra-individually in various organs and tumour lesions with stand-alone PET-derived SUVs. Methods Thirty-five patients with known or suspected cancer were prospectively included. Sixteen patients underwent FDG PET using an ECAT HR+scanner, and subsequently a second scan using a Biograph Sensation 16PET/CT scanner. Nineteen patients were scanned in the reverse order. All images were reconstructed with an iterative algorithm (OSEM). Suspected lesions were grouped as paradiaphragmatic versus distant from the diaphragm. Mean and maximum SUVs were also calculated for brain, lung, liver, spleen and vertebral bone. The attenuation coefficients (μ values) used for correction of emission data (bone, soft tissue, lung) in the two data sets were determined. A body phantom containing six hot spheres and one cold cylinder was measured using the same protocol as in patients. Results Forty-six lesions were identified. There was a significant correlation of maximum and mean SUVs derived from PET and PET/CT for 14 paradiaphragmatic lesions (r=0.97 respectively; p<0.001 respectively) and for 32 lesions located distant from the diaphragm (r=0.87 and r=0.89 respectively; p<0.001 respectively). No significant differences were observed in the SUVs calculated with PET and PET/CT in the lesions or in the organs. In the phantom, radioactivity concentration in spheres calculated from PET and from PET/CT correlated significantly (r=0.99; p<0.001). Conclusion SUVs of cancer lesions and normal organs were comparable between PET and PET/CT, supporting the usefulness of PET/CT-derived SUVs for quantification of tumour metabolism.     

Normal uptake of <Superscript>18</Superscript>F-FDG in the testis: an assessment by PET/CT

Objective The aim of this study was to assess the physiological uptake of ¹⁸F-fluoro-2-deoxyglucose (FDG) by an apparently normal testis with combined positron emission tomography–computed tomography (PET/CT) and its correlation with age, blood glucose level, and testicular volume. Methods The testicular uptake of ¹⁸F-FDG, expressed as the standardized uptake value (SUV), was measured on PET/CT images in 203 men. The correlation between SUV and age, blood glucose level, and testicular volume was assessed. Results The SUV in the total of 406 testes was 2.44 ± 0.45 (range 1.23–3.85). The SUV was 2.81 ± 0.43 (2.28–3.85) for 30–39 years (n = 12), 2.63 ± 0.45 (1.77–3.75) for 40–49 years (n = 64), 2.46 ± 0.35 (1.44–3.15) for 50–59 years (n = 82), 2.51 ± 0.41 (1.50–3.46) for 60–69 years (n = 86), 2.43 ± 0.47 (1.42–3.29) for 70–79 years (n = 86), and 2.18 ± 0.45 (1.23–3.03) for 80–89 years (n = 76). When we calculated the mean SUV of bilateral testes in each patient, there were significant statistical differences between those in the age group of 30–39 years and 80–89 years, 40–49 years and 80–89 years, and 50–60 years and 80–89 years, when using an unpaired test with Bonferroni correction. The laterality index (|L − R|/(L + R) × 2) in 203 men was 0.066 ± 0.067 (0–0.522). There was a mild correlation between the mean SUV and age (r = −0.284, P < 0.001) as well as between the mean SUV and mean volume (r = +0.368, P < 0.001). There was no correlation between the mean SUV and glucose blood level (r = −0.065, P = 0.358). Conclusions Some uptake of FDG is observed in the normal testis and declines slightly with age. Physiological FDG uptake in the testis should not be confused with pathological accumulation.     

Reproducibility of whole-body <Superscript>131</Superscript>I scan and serum thyrotropin and stimulated thyroglobulin values in patients studied twice after injection of recombinant human thyrotropin

Purpose Recombinant human TSH (rhTSH) is used to increase radioiodine uptake during imaging of thyroid cancer, obviating the need to render the patient hypothyroid. We assessed the reproducibility of radioiodine uptake, serum thyrotropin (TSH), and stimulated serum thyroglobulin (Tg) levels after rhTSH administration. Methods A retrospective review was performed of patients at Stanford who underwent whole-body ¹³¹I scanning for surveillance of thyroid cancer twice after thyroidectomy and ¹³¹I ablation, with rhTSH prior to each scan. Forty-eight hour radioiodine uptake, peak serum TSH, and stimulated serum Tg levels for each study were recorded. Paired t tests and correlation analysis were used to assess interexamination repeatability. Results Twenty-three patients underwent two scintiscans with rhTSH, for a total of 46 exams. There was no significant difference between percent uptake at 48 h in the paired exams (p=0.40). Serum TSH level was measured in 45 of 46 exams; TSH exceeded 50 mIU/l in all cases, and there was no significant difference between paired TSH levels (p=0.93). All patients had stimulated serum Tg levels measured, with no significant difference between paired Tg levels (p=0.40); after excluding one patient whose Tg changed from 15.8 ng/ml to undetectable between scans without interval treatment, the p value rose to 0.95. There was a strong correlation among paired uptake values (r=0.85, p<0.0001), peak serum TSH (r=0.69, p=0.0003), and stimulated Tg levels (r=0.81, p<0.0001). No discordant scan interpretations were reported. Conclusion Forty-eight hour radioiodine uptake, peak serum TSH, and stimulated serum Tg levels after administration of rhTSH are repeatable between studies, demonstrating reproducibility of diagnostic results without rendering patients hypothyroid.     

Orientation of trabecular bone in human vertebrae assessed by MRI

The aim of the study was to assess the relative number of bone trabeculae in different orientations by using magnetic inhomogeneity measurements by MR imaging. Twelve defatted human vertebrae (L2–L4) were studied by MR imaging and CT. In the MR measurements the reversible transaxial decay rate, R2', was determined using the GESFIDE sequence. The relative contribution to R2' of bone trabeculae oriented along the x (R2'_x), y (R2'_y) and z (R2'_y) axes was assessed, by rotation of the specimen in the magnetic field. The results were validated by CT measurements of trabecular structure at a resolution of 0.2 × 0.2 × 1 mm, using custom-made software. R2' ranged from 4.9 to 32 s^–1. After separation, theoretical R2'_x ranged from 2.3 to 10.7 s^–1, R2'_y ranged from 2.6 to 14.0 s^–1 and R2'_z ranged from 4.7 to 17.9 s^–1. The number of bone trabeculae per millimeter identified in axial CT images ranged from 0.15 to 0.38 and from 0.039 to 0.22 per millimeter in sagittal images. The difference between axial and sagittal CT images was statistically significant and due to anisotropic voxels. The correlation between R2' and the number of bone trabeculae per millimeter was statistically significant (r = 0.83, p < 0.001 for x orientation; r = 0.63 for y orientation, and r = 0.59 for z orientation, p < 0.05 for both). The relative amount of bone trabeculae in different orientations can be assessed in vitro using R2' measurements. Received: 10 April 1998; Revision received: 3 August 1998; Accepted: 5 August 1998