Three-dimensional topographical variation of femoral cartilage T2 in healthy volunteer knees.

OBJECTIVE: Quantitative knee cartilage T2 assessment on limited two-dimensional midsagittal or midcoronal planes may be insufficient to assess variations in normal cartilage composition. The purpose of this work was to reveal characteristic 3D distribution of T2 values in femoral cartilage in healthy volunteer knees. MATERIALS AND METHODS: Sixteen volunteers were enrolled in this study. One knee joint in each volunteer was imaged using a 3D fast image employing steady-state acquisition cycled phases (FIESTA-C) sequence for modeling distal femoral morphology, as well as a sagittal T2 mapping of cartilage. 3D distribution of cartilage T2 values was generated for the femoral condyles. At each medial and lateral condyle, four regions of interest (ROI) were manually defined based on the cartilage covered by the 3D surface model of the medial and lateral menisci. RESULTS: The 3D maps showed a relatively inhomogeneous distribution of cartilage T2 on the medial and lateral condyles. Cartilage T2 values in the internal half of the weight-bearing zone were significantly higher than those in all other zones on both lateral and medial condyles. CONCLUSIONS: Analysis of 3D distribution of femoral cartilage T2 may be valuable in determining the site-specific normal range of cartilage T2 in the healthy knee joint.

Reduced-dose chest CT with 3D automatic exposure control vs. standard chest CT: quantitative assessment of emphysematous changes in smokers' lung parenchyma.

OBJECTIVES: To determine the capability of reduced-dose chest CT with three-dimensional (3D) automatic exposure control (AEC) on quantitative assessment of emphysematous change in smoker' lung parenchyma, compared to standard chest CT. METHODS: Twenty consecutive smoker patients (mean age 62.8 years) underwent CT examinations using a standard protocol (150 mAs) and a protocol with 3D-AEC. In this study, the targeted standard deviations number was set to 160. For quantitative assessment of emphysematous change in lung parenchyma in each subject using the standard protocol, a percentage of voxels less than -950 HU in the lung (%LAA(-950)) was calculated. The 3D-AEC protocol's %LAA was computed from of voxel percentages under selected threshold CT value. The differences of radiation doses between these two protocols were evaluated, and %LAAs(-950) was compared with the 3D-AEC protocol %LAAs. RESULTS: Mean dose length products were 780.2 ± 145.5 mGy cm (standard protocol), and 192.0 ± 95.9 (3D-AEC protocol). There was significant difference between them (paired Student's t test, p<0.00001). Meanwhile, only setting -960 HU yielded no significant difference (paired Student's t test, p=0.32) between %LAAs(-950) and 3D-AEC protocol %LAAs. In adopting the feasible threshold CT values of the 3D-AEC protocol, the 3D-AEC protocol %LAAs were significantly correlated with %LAAs(-950) (r = 0.98, p<0.001) and limits of agreement from Bland-Altman analysis was 0.52 ± 4.3%. CONCLUSIONS: Changing threshold CT values demonstrated that reduced-dose chest CT with 3D-AEC can substitute for the standard protocol in assessments of emphysematous change in smoker' lung parenchyma.

Quantitative bronchial luminal volumetric assessment of pulmonary function loss by thin-section MDCT in pulmonary emphysema patients.

OBJECTIVES: To determine the capability of quantitative bronchial luminal volume to assess pulmonary function loss and disease severity in pulmonary emphysema patients. METHODS: Thirty-seven smokers (mean age, 68.1 years) underwent CT examinations and pulmonary function tests. For the quantitative assessment, luminal voxels of trachea and bronchi were computationally counted and the ratio of the following luminal voxels to all luminal voxels was obtained: (1) the lobe bronchi and the peripheral bronchi (Ratio(lobe)), and (2) the main bronchi and the peripheral bronchi (Ratio(main)). To determine the capability of these assessments to predict pulmonary function loss, these ratios were correlated with pulmonary function tests. To determine the capability for predicting disease severity, these ratios were compared between clinical groups. RESULTS: These ratios were no significant correlated with vital capacity and forced vital capacity (FVC) (p > 0.05), however significantly correlated with forced expiratory volume in 1s (FEV1) (Ratio(lobe): r = 0.61, p < 0.0001, Ratio(main): r = 0.58, p < 0.0005) and FEV1/FVC (Ratio(lobe): r = 0.36, p < 0.05, Ratio(main): r = 0.33, p < 0.05). The Ratio(lobe) of smokers without COPD was significantly different from those of moderate COPD and severe or very severe COPD (p < 0.05), while that of mild COPD was significantly different from that of severe or very severe COPD (p < 0.01). The Ratio(main) of severe or very severe COPD patients was significantly different from those of other groups (p < 0.05). CONCLUSIONS: Quantitative bronchial luminal volumes were reflected the airflow limitation parameters and was corresponded to clinical groups in emphysema patients.

Statistical parametric mapping for effects of verapamil on olfactory connections of rat brain in vivo using manganese-enhanced MR imaging.

PURPOSE: We investigated the effect of verapamil on the transport of manganese in the olfactory connections of rat brains in vivo using statistical parametric mapping and manganese-enhanced magnetic resonance (MR) imaging. METHODS: We divided 12 7-week-old male Sprague-Dawley rats into 2 groups of six and injected 10 µL of saline into the right nasal cavities of the first group and 10 µL of verapamil (2.5 mg/mL) into the other group. Twenty minutes after the initial injection, we injected 10 µL of MnCl(2) (1 mol/L) into the right nasal cavities of both groups. We obtained serial T(1)-weighted MR images before administering the verapamil or saline and at 0.5, one, 24, 48, and 72 hours and 7 days after administering the MnCl(2), spatially normalized the MR images on the rat brain atlas, and analyzed the data using voxel-based statistical comparison. RESULTS: Statistical parametric maps demonstrated the transport of manganese. Manganese ions created significant enhancement (t-score = 36.6) 24 hours after MnCl(2) administration in the group administered saline but not at the same time point in the group receiving verapamil. The extent of significantly enhanced regions peaked at 72 hours in both groups and both sides of the brain. The peak of extent in the right side brain in the group injected with saline was 70.2 mm(3) and in the group with verapamil, 92.4 mm(3). The extents in the left side were 64.0 mm(3) for the group with saline and 53.2 mm(3) for the group with verapamil. CONCLUSION: We applied statistical parametric mapping using manganese-enhanced MR imaging to demonstrate in vivo the transport of manganese in the olfactory connections of rat brains with and without verapamil and found that verapamil did affect this transport.

Measurement of manganese content in various organs in rats with or without glucose stimulation.

Our purpose in this study was to assess the manganese (Mn) content in various organs in rats with or without glucose stimulation in vivo and in vitro by using magnetic resonance imaging (MRI) and polarized Zeeman atomic absorption spectrophotometry (PZAAS), respectively. MRI studies were performed in 12 rats using a 1.5-T MRI system. The rats were injected intravenously with saline (6 ml/kg) (saline-stimulated group, n = 6) or glucose (2.34 g/kg) (glucose-stimulated group, n = 6). Ten minutes after saline or glucose administration, MnCl2 (0.02 mmol/kg) was injected intravenously, followed by 6 MRI studies at 8-min intervals. After the last MRI study, rats were killed, and the Mn concentrations in various organs were measured using PZAAS. There was a discrepancy between in vivo and in vitro measurements, which appeared to be due to the partial volume effect and/or the contribution of extracellular Mn. The Mn concentration in the pancreas, normalized to that in the liver in the glucose-stimulated group, increased significantly compared to that in the saline-stimulated group, suggesting that the influx of Mn into ß cells in the pancreas increased in response to glucose stimulation. This study suggested that the measurement of the change in the Mn concentration due to glucose stimulation using PZAAS was effective for evaluating ß-cell function in the pancreas.

Inflammatory imaging with ultrasmall superparamagnetic iron oxide.

The purpose of this study was to investigate the usefulness and feasibility of magnetic resonance imaging (MRI) with ultrasmall superparamagnetic iron oxide (USPIO) (USPIO-enhanced MRI) for imaging inflammatory tissues. First, we investigated the relationship between the apparent transverse relaxation rate (R2*) and the concentration of USPIO by phantom studies and measured the apparent transverse relaxivity (r2*) of USPIO. Second, we performed animal experiments using a total of 30 mice. The mice were divided into five groups [A (n=6), B (n=6), C (n=6), sham control (n=6), and control (n=6)]. The mice in Groups A, B, C and control were subcutaneously injected with 0.1 ml of turpentine oil on Day 0, while those in the sham control group were subcutaneously injected with 0.1 ml of saline. The mice in Groups A, B, C and sham control were intraperitoneally injected with 200 µmol Fe per kilogram body weight of USPIO (28 nm in diameter) immediately after the first MRI study on Days 3, 5, 7 and 7, respectively, and those in the control group were not injected with USPIO. The second and third MRI studies were performed at 24 and 48 h after USPIO administration, respectively. The maps of R2* were generated from the apparent transverse relaxation time (T2*)-weighted images with six different echo times. The phantom studies showed that there was a linear relationship between R2* and the concentration of USPIO (r=0.99) and the r2* value of USPIO was 105.7 mM(-1) s(-1). There was a significant increase of R2* in inflammatory tissues in Group C at 24 h after USPIO administration compared with the precontrast R2* value. Our results suggest that USPIO-enhanced MRI combined with R2* measurement is useful for detecting inflammatory tissues.

Loaded cartilage T2 mapping in patients with hip dysplasia.

PURPOSE: To evaluate the change in cartilage T2 values with loading in patients with hip dysplasia. MATERIALS AND METHODS: Fifteen patients with hip dysplasia and nine asymptomatic healthy volunteers were evaluated between April 2008 and February 2009. All subjects provided written informed consent before participation in this prospective, institutional review board-approved study. Midcoronal T2 mapping of hips was performed under unloaded and loaded conditions (with 50% body weight) at 3.0-T magnetic resonance (MR) imaging. Loading was achieved with a mechanical loading system. T2 values under unloaded conditions and the change in T2 values at the weight-bearing area of the acetabular and femoral cartilage with loading were compared between normal and dysplastic hips. The change in T2 with loading was correlated with the patient's age and body mass index as well as with the center-edge angle determined on conventional radiographs. RESULTS: The decrease in cartilage T2 at the outer superficial zones of the acetabular cartilage with loading was significantly greater in patients with hip dysplasia than in healthy volunteers: The mean T2 change with loading was -7.6% +/- 10.6 (+/-standard deviation) for dysplastic hips and 1.2% +/- 10.9 for normal hips (P = .04). Among patients with hip dysplasia, there was a positive correlation between the center-edge angle on anteroposterior radiographs and T2 changes with loading at the outer deep zones of the acetabular cartilage. CONCLUSION: Cartilage T2 mapping with loading during MR imaging enabled the detection of site-specific changes in cartilage T2 in dysplastic hips.

Quantitative and qualitative assessments of lung destruction and pulmonary functional loss from reduced-dose thin-section CT in pulmonary emphysema patients.

RATIONALE AND OBJECTIVES: Academic and clinical interest in reducing radiation from computed tomography (CT) examinations has increased, and the purpose of this study was to determine the capabilities of reduced-dose multidetector-row CT (MDCT) in assessing lung destruction and pulmonary functional loss in pulmonary emphysema patients. MATERIALS AND METHODS: Twenty-five consecutive smokers (15 men and 10 women; mean age 67.9 years; age range 49-86 years) underwent MDCT examinations using two different effective tube currents (standard-dose protocol [150 mAs] and reduced-dose protocol [50 mAs]). For quantitative and qualitative assessments of lung destruction in each subject, percentage of low attenuation emphysematous destruction areas (%LAAs) were computationally calculated, and visual emphysema scores (ESs) were determined for both protocols. To determine the capabilities for quantitative and qualitative assessments of lung destruction by using reduced-dose protocol, %LAAs and ESs of both protocols were compared statistically. To compare the capabilities for quantitative and qualitative assessments of pulmonary functional loss, %LAAs and ESs of both protocols were correlated with forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC). RESULTS: %LAAs and ESs had significant correlations between both protocols (%LAAs: r = 0.95, P < .001; ESs: r = 0.97, P < .001). The limits of agreement of %LAAs were -1.8 + or - 9.2%. The agreement of ESs between both protocols was substantial (kappa = 0.70). %LAAs and ESs of both protocols had significant correlations with FEV1/FVC (%LAAs of 150 mAs: r = -0.49, P < .05; %LAAs of 50 mAs: r = -0.44, P < .05; ESs of 150 mAs: r = -0.67, P < .001; ESs of 50 mAs: r = -0.66, P < .001). CONCLUSION: Reduced-dose MDCT had a potential of substitution for standard-dose MDCT on the both assessments in pulmonary emphysema patients.

Quantitatively assessed CT imaging measures of pulmonary interstitial pneumonia: effects of reconstruction algorithms on histogram parameters.

This study aimed the influences of reconstruction algorithm for quantitative assessments in interstitial pneumonia patients. A total of 25 collagen vascular disease patients (nine male patients and 16 female patients; mean age, 57.2 years; age range 32-77 years) underwent thin-section MDCT examinations, and MDCT data were reconstructed with three kinds of reconstruction algorithm (two high-frequencies [A and B] and one standard [C]). In reconstruction algorithm B, the effect of low- and middle-frequency space was suppressed compared with reconstruction algorithm A. As quantitative CT parameters, kurtosis, skewness, and mean lung density (MLD) were acquired from a frequency histogram of the whole lung parenchyma in each reconstruction algorithm. To determine the difference of quantitative CT parameters affected by reconstruction algorithms, these parameters were compared statistically. To determine the relationships with the disease severity, these parameters were correlated with PFTs. In the results, all the histogram parameters values had significant differences each other (p<0.0001) and those of reconstruction algorithm C were the highest. All MLDs had fair or moderate correlation with all parameters of PFT (-0.64

Investigation on the optimal position for the quantification of hepatic perfusion by use of dynamic contrast-enhanced computed tomography in rats.

Our purpose in this study was to investigate the optimal position for the quantification of hepatic perfusion by using a dual-input, single-compartment model and dynamic contrast-enhanced computed tomography (DCE-CT) in rats. The DCE-CT studies were performed with the animals in the supine and prone position, with an interval of 1 day, on six male Sprague-Dawley rats. The distance between the inferior vena cava (IVC) and portal vein was calculated. The arterial hepatic blood flow (AHBF) and portal hepatic blood flow (PHBF) were also estimated by use of time-density curves (TDCs) in the aorta, portal vein, and liver. The distance between the IVC and portal vein in the supine position (3.68 +/- 0.22 mm) was significantly greater than that in the prone position (2.56 +/- 0.19 mm). The estimated AHBF (102.1 +/- 8.9 ml/100 ml/min) and PHBF values (114.8 +/- 19.7 ml/100 ml/min) in the prone position were significantly overestimated and underestimated, respectively, as compared to those in the supine position (76.1 +/- 4.2 ml/100 ml/min for AHBF and 235.1 +/- 17.3 ml/100 ml/min for PHBF). We concluded that the supine position was more appropriate than the prone position for the quantification of hepatic perfusion by use of a dual-input, single-compartment model and DCE-CT in rats, because the TDC in the portal vein is affected less by the TDC in the IVC in the supine position than in the prone position.

Error analysis of the quantification of hepatic perfusion using a dual-input single-compartment model.

We performed an error analysis of the quantification of liver perfusion from dynamic contrast-enhanced computed tomography (DCE-CT) data using a dual-input single-compartment model for various disease severities, based on computer simulations. In the simulations, the time-density curves (TDCs) in the liver were generated from an actually measured arterial input function using a theoretical equation describing the kinetic behavior of the contrast agent (CA) in the liver. The rate constants for the transfer of CA from the hepatic artery to the liver (K(1a)), from the portal vein to the liver (K(1p)), and from the liver to the plasma (k(2)) were estimated from simulated TDCs with various plasma volumes (V(0)s). To investigate the effect of the shapes of input functions, the original arterial and portal-venous input functions were stretched in the time direction by factors of 2, 3 and 4 (stretching factors). The above parameters were estimated with the linear least-squares (LLSQ) and nonlinear least-squares (NLSQ) methods, and the root mean square errors (RMSEs) between the true and estimated values were calculated. Sensitivity and identifiability analyses were also performed. The RMSE of V(0) was the smallest, followed by those of K(1a), k(2) and K(1p) in an increasing order. The RMSEs of K(1a), K(1p) and k(2) increased with increasing V(0), while that of V(0) tended to decrease. The stretching factor also affected parameter estimation in both methods. The LLSQ method estimated the above parameters faster and with smaller variations than the NLSQ method. Sensitivity analysis showed that the magnitude of the sensitivity function of V(0) was the greatest, followed by those of K(1a), K(1p) and k(2) in a decreasing order, while the variance of V(0) obtained from the covariance matrices was the smallest, followed by those of K(1a), K(1p) and k(2) in an increasing order. The magnitude of the sensitivity function and the variance increased and decreased, respectively, with increasing disease severity and decreased and increased, respectively, with increasing stretching factor except for V(0). Identifiability analysis showed that the identifiability between K(1)(p) and k(2) was lower than that between K(1)(a) and k(2) or between K(1a) and K(1p). In conclusion, this study will be useful for understanding the accuracy and reliability of the quantitative measurement of liver perfusion using a dual-input single-compartment model and DCE-CT data.

Development of a System for Measuring Wall Shear Stress in Blood Vessels using Magnetic Resonance Imaging and Computational Fluid Dynamics.

We developed a system for measuring the wall shear stress (WSS) in blood vessels using magnetic resonance imaging (MRI) and computational fluid dynamics (CFD). The time-dependent velocity at the center of the blood vessel was measured by phase-contrast MRI and was approximated by finite Fourier series, which was used for generating the velocity profile at the inlet for the boundary condition to the CFD method. To validate the CFD method, we compared the WSS obtained by the CFD method with the theoretical value in a straight cylinder with various radii for both steady and pulsatile flows. We also investigated the dependence of the WSS on the inlet velocity profile incorporated into the CFD method. For steady flow, there was a good agreement between the WSS obtained by the CFD method and the theoretical value. For pulsatile flow, there was a relatively good agreement between them when the radius of the cylinder was 2.5 mm and the inlet velocity profile was given by the Womersley solution for fully developed pulsatile flow in a straight circular cylinder. When the radius of the cylinder was 5 mm and/or the inlet velocity profile was assumed to be parabolic, large differences were observed between them, suggesting that the assumption of fully developed flow does not hold true in these cases. In human studies, the vortex due to the secondary blood flow in the carotid arterial sinus was clearly observed. The WSS in the bifurcation was the highest, while that in the carotid arterial sinus was the smallest. In conclusion, the system presented here appears to be useful for measuring the WSS in blood vessels and for analyzing the cause and/or extent of atherosclerosis, and our results suggest that the inlet velocity profile should be carefully considered.

Extraction of arterial input function for measurement of brain perfusion index with 99mTc compounds using fuzzy clustering.

Cerebral blood flow (CBF) can be quantified non-invasively using the brain perfusion index (BPI) determined from radionuclide angiographic data generated with 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO). When measuring the BPI, manual drawing of regions of interest (ROIs) (manual ROI method) for the extraction of the arterial input function (AIF) can lead to serious individual differences. The purpose of this study was to apply the fuzzy c-means (FCM) clustering method to determine AIF, and to investigate its usefulness in comparison with the manual ROI method. Radionuclide angiography was performed using a bolus injection of about 555 MBq of 99mTc-HMPAO, followed by sequential imaging (1 sec/frame x 120 s) using a solid-state gamma camera, and the BPI values were calculated using spectral analysis. To investigate the dependence of BPI on the ROI size, we drew five ROIs with different sizes over the aortic arch, and calculated the BPI using the manual ROI method [BPI(manual)] and the FCM clustering method [BPI(FCM)]. Furthermore, we asked 10 individuals to draw ROIs to investigate the inter-operator variability of the two methods. The mean and standard deviation (SD) of BPI(manual) increased with increasing ROI size, whereas the mean of BPI(FCM) was almost constant regardless of the ROI size; the SD of BPI(FCM) was smaller than that of BPI(manual). The inter-operator variability of the FCM clustering method was smaller than that of the manual ROI method. These results suggest that the FCM clustering method appears to be useful for the measurement of BPI, because it allows a reliable and objective determination of AIF.

Automatic motion correction for quantification of myocardial perfusion with dynamic magnetic resonance imaging.

Respiratory motion makes it difficult to quantify myocardial perfusion with dynamic magnetic resonance imaging (MRI). The purpose of this study was to evaluate an automatic registration method for motion correction for quantification of myocardial perfusion with dynamic MRI. The present method was based on the gradient-based method with robust estimation of displacement parameters. For comparison, we also corrected for motion with manual registration as the benchmark. The myocardial kinetic parameters, K1 (rate constant for transfer of contrast agent from blood to myocardium) and k2 (rate constant for transfer from myocardium to blood), were calculated from dynamic images with a two-compartment model. The images corrected by the present method were similar to those corrected by manual registration. The kinetic parameters obtained after motion correction with the present method were close to those obtained after motion correction with manual registration. These results suggest that the present method is useful for motion correction for quantification of myocardial perfusion with dynamic MRI.

Deconvolution analysis of dynamic contrast-enhanced data based on singular value decomposition optimized by generalized cross validation.

PURPOSE: To present an implementation of generalized cross validation (GCV) for automatically determining the regularization parameter--i.e., the threshold value in deconvolution analysis based on truncated singular value decomposition (TSVD) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data--and to investigate the usefulness of this approach in comparison with TSVD with a fixed threshold value (TSVD-F). METHODS: Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various cerebral blood flows (CBFs), cerebral blood volumes (CBVs), and signal-to-noise ratios (SNRs) for three different types of residue functions (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The TSVD with GCV (TSVD-G) and TSVD-F with a fixed threshold value of 0.2 were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIF, and the estimated values were compared with the assumed values. Additionally, the optimal threshold value was determined from the threshold value in TSVD-F giving the mean CBF value closest to the assumed value and was compared with the threshold value determined with TSVD-G. RESULTS: With TSVD-G, the CBF estimation was substantially improved over a wide range of CBFs for all types of residue functions at the cost of more noise than was seen with TSVD-F. The dependency of the threshold value determined with TSVD-G on the CBF, CBV, and SNR was similar to that of the optimal threshold value, with some discrepancy being observed for the box-shaped residue function, although they did not always agree in terms of absolute value. CONCLUSION: Given an improved SNR, TSVD-G is useful for quantification of CBF with deconvolution analysis of DCE-MRI data.

Autoregressive moving average (ARMA) model applied to quantification of cerebral blood flow using dynamic susceptibility contrast-enhanced magnetic resonance imaging.

PURPOSE: To investigate the feasibility of the autoregressive moving average (ARMA) model for quantification of cerebral blood flow (CBF) with dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) in comparison with deconvolution analysis based on singular value decomposition (DA-SVD). METHODS: Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various CBFs, cerebral blood volumes and signal-to-noise ratios (SNRs) for three different types of residue function (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The ARMA model and DA-SVD were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIFs, and the estimated values were compared with the assumed values. RESULTS: We found that the CBF value estimated by the ARMA model was more sensitive to the SNR and the delay in AIF than that obtained by DA-SVD. Although the ARMA model considerably overestimated CBF at low SNRs, it estimated the CBF more accurately than did DA-SVD at high SNRs for the exponential or triangular residue function. CONCLUSION: We believe this study will contribute to an understanding of the usefulness and limitations of the ARMA model when applied to quantification of CBF with DSC-MRI.

Renal uptake rate measurement of 99m Tc-dimercaptosuccinic acid using spectral analysis.

We developed a new method for measuring the rate of renal uptake of 99mTc-dimercaptosuccinic acid (DMSA) using spectral analysis. The renal uptake rate (per minute) of DMSA (K) was calculated by averaging the tissue impulse response function values obtained by spectral analysis between 10 min and 15 min. The K values obtained by spectral analysis correlated well with the renal uptake rates (%) measured 2h after DMSA administration (r=0.921 with background correction; r=0.924 without background correction). There was a good agreement between the K values obtained by spectral analysis using the kidney time-activity curves with (x) and without (y) background correction (r=0.993, y=1.089x+0.004), suggesting that our method requires no background correction. There was excellent correlation between the K values obtained by spectral analysis using the kidney time-activity curves with (y) and without (x) kidney depth correction (r=0.992, y=1.721x+0.000 with background correction; r=0.990, y=1.720x+0.000 without background correction), suggesting that our method requires no kidney depth correction. These results indicate that spectral analysis is appropriate and useful for the quantification of renal uptake rate of DMSA. We believe that this method will facilitate even more widespread utilization of the quantitative assessment of DMSA uptake by planar scintigraphy, since it needs only 10-15 min for imaging, and background and kidney depth correction and blood sampling are not required.