市原 隆

Purpose: Previous studies using dynamic perfusion CT and volume perfusion CT (VPCT) software consistently underestimated the stress myocardial blood flow (MBF) in normal myocardium to be 1.1-1.4 ml/min/g, whilst the O 15-water PET studies demonstrated the normal stress MBF of 3-5 ml/min/g. We hypothesized that the MBF determined by VPCT (MBF-VPCT) is actually presenting the blood-to-myocardium transfer constant, K1. In this study, we determined K1 using Patlak plot (K1-Patlak) and compared the results with MBF-VPCT. Material and methods: 17 patients (66 +/- 9 years, 7 males) with suspected coronary artery disease (CAD) underwent stress dynamic perfusion CT, followed by rest coronary CT angiography (CTA). Arterial input and myocardial output curves were analyzed with Patlak plot to quantify myocardial K1. Significant CAD was defined as > 50% stenosis on CTA. A simulation study was also performed to investigate the influence of limited temporal sampling in dynamic CT acquisition on K1 using the undersampling data generated from MRI. Results: There were 3 patients with normal CTA, 7 patients with non-significant CAD, and 7 patients with significant CAD. K1-patlak was 0.98 +/- 0.35 (range 0.22-1.67) ml/min/g, whereas MBF-VPCT was 0.83 +/- 0.23 (range 0.34-1.40) ml/min/g. There was a linear relationship between them: (MBF-VPCT) +/- 0.58 x (K1-patlak) + 0.27 (r(2) = 0.65, p < 0.001). The simulation study done on MRI data demonstrated that Patlak plot substantially underestimated true K1 by 41% when true K1 was 2.0 ml/min/g with the temporal sampling of 2RR for arterial input and 4RR for myocardial output functions. Conclusions: The results of our study are generating hypothesis that MBF-VPCT is likely to be calculating K1-patlak equivalent, not MBF. In addition, these values may be substantially underestimated because of limited temporal sampling rate. (C) 2016 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

Nephron-sparing surgery has been proven to positively impact the postoperative quality of life for the treatment of small renal tumors, possibly leading to functional improvements. Laparoscopic partial nephrectomy is still one of the most demanding procedures in urological surgery. Laparoscopic partial nephrectomy sometimes results in extended warm ischemic time and severe complications, such as open conversion, postoperative hemorrhage and urine leakage. Robot-assisted partial nephrectomy exploits the advantages offered by the da Vinci Surgical System to laparoscopic partial nephrectomy, equipped with 3-D vision and a better degree in the freedom of surgical instruments. The introduction of the da Vinci Surgical System made nephron-sparing surgery, specifically robot-assisted partial nephrectomy, safe with promising results, leading to the shortening of warm ischemic time and a reduction in perioperative complications. Even for complex and challenging tumors, robotic assistance is expected to provide the benefit of minimally-invasive surgery with safe and satisfactory renal function. Warm ischemic time is the modifiable factor during robot-assisted partial nephrectomy to affect postoperative kidney function. We analyzed the predictive factors for extended warm ischemic time from our robot-assisted partial nephrectomy series. The surface area of the tumor attached to the kidney parenchyma was shown to significantly affect the extended warm ischemic time during robot-assisted partial nephrectomy. In cases with tumor-attached surface area more than 15 cm(2), we should consider switching robot-assisted partial nephrectomy to open partial nephrectomy under cold ischemia if it is imperative. In Japan, a nationwide prospective study has been carried out to show the superiority of robot-assisted partial nephrectomy to laparoscopic partial nephrectomy in improving warm ischemic time and complications. By facilitating robotic technology, robot-assisted partial nephrectomy will be more frequently carried out as a safe, effective and minimally-invasive nephron-sparing surgery procedure.

The purpose of this study was to develop a method to determine time discrepancies between input and myocardial time signal intensity (TSI) curves for accurate estimation of myocardial perfusion with first-pass contrast-enhanced MRI. Estimation of myocardial perfusion with contrast-enhanced MRI using kinetic models requires faithful recording of contrast content in the blood and myocardium. Typically, the arterial input function (AIF) is obtained by setting a region of interest in the left ventricular cavity. However, there is a small delay between the AIF and the myocardial curves, and such time discrepancies can lead to errors in flow estimation using Patlak plot analysis. In this study, the time discrepancies between the arterial TSI curve and the myocardial tissue TSI curve were estimated based on the compartment model. In the early phase after the arrival of the contrast agent in the myocardium, the relationship between rate constant K-1 and the concentrations of Gd-DTPA contrast agent in the myocardium and arterial blood (LV blood) can be described by the equation K-1 = {dC(myo)(t(peak))/dt}/C-a(t(peak)), where C-myo(t) and C-a(t) are the relative concentrations of Gd-DTPA contrast agent in the myocardium and in the LV blood, respectively, and t(peak) is the time corresponding to the peak of Ca(t). In the ideal case, the time corresponding to the maximum upslope of C-myo(t), t(max), is equal to t(peak). In practice, however, there is a small difference in the arrival times of the contrast agent into the LV and into the myocardium. This difference was estimated to correspond to the difference between t(peak) and t(max). The magnitudes of such time discrepancies and the effectiveness of the correction for these time discrepancies were measured in 18 subjects who underwent myocardial perfusion MRI under rest and stress conditions. The effects of the time discrepancies could be corrected effectively in the myocardial perfusion estimates. (C) 2015 Elsevier Inc. All rights reserved.

The purpose of this study was to develop a method for automatic and stable determination of the optimal time range for fitting with a Patlak plot model in order to measure myocardial perfusion using coronary X-ray angiography images. A conventional two-compartment model is used to measure perfusion, and the slope of the Patlak plot is calculated to obtain a perfusion image. The model holds for only a few seconds while the contrast agent flows from artery to myocardium. Therefore, a specific time range should be determined for fitting with the model. To determine this time range, automation is needed for routine examinations. The optimal time range was determined to minimize the standard error between data points and their least-squares regression straight line in the Patlak plot. A total of 28 datasets were tested in seven porcine models. The new method successfully detected the time range when contrast agent flowed from artery to myocardium. The mean cross correlation in the linear regression analysis (R-2) was 0.996 +/- A 0.004. The mean length of the optimal time range was 3.61 +/- A 1.29 frames (2.18 +/- A 1.40 s). This newly developed method can automatically determine the optimal time range for fitting with the model.

Objectives: The purpose of this study was to develop a quantitative method for myocardial blood flow (MBF)measurement using contrast-enhanced multidetector computed tomography (MDCT) images with bolus tracking andhelical scanning.Materials and Methods: Nine canine models of left anterior descending artery stenosis were prepared and underwent MDCT perfusion imaging during adenosine infusion to study a wide range of flow parameters. Neutron-activated microspheres were injected to document MBF during adenosine infusion. Six animals underwent dynamic MDCT perfusion imaging, and K1 and k2 (which represent the first-order transfer constants from left ventricular blood to myocardium and from myocardium to the vascular system, respectively) were measured using a two-compartment model. The results were compared against microsphere MBF measurements, and the extraction fraction (E) of contrast agent and the mean value of k1/k2 were calculated. Six animals then underwent helical CT perfusion imaging, and neutron-activated microspheres were injected to document MBF during adenosine infusion. For each animal, based on E, K1/k2, time-registered helical CT myocardial data, and arterial input function data, tables of myocardial CT values versus MBF were simulated for various MBF values to create look-up tables from the myocardial CT value to MBF. The CT-derived MBF values were compared against the microsphere MBF measurements.Results: A strong linear correlation was observed between the MDCT-derived MBF and the microsphere MBF (y =1.065x – 0.616, R2 = 0.838).Conclusions: Regional MBF can be measured accurately using a combination of bolus tracking and time-registeredhelical CT data from contrast-enhanced MDCT scanning during adenosine stress.

The purpose of this study was to develop a novel theory and method for generating regional myocardial perfusion images using fluoroscopy in the coronary angiography lab. We modified the Kety model to introduce the Patlak plot method for two-dimensional fluoroperfusion (FP) imaging. For evaluation, seven porcine models of myocardial ischemia with stenosis in the left coronary artery were prepared. Rest and stress FP imaging were performed using cardiovascular X-ray imaging equipment during the injection of iopamidol via the left main coronary artery. Images were acquired and retrospectively ECG gated at 80 % of the R-R interval. FP myocardial blood flow (MBF) was obtained using the Patlak plot method applied to time-intensity curve data of the proximal artery and myocardium. The results were compared to microsphere MBF measurements. Time-intensity curves were also used to generate color-coded FP maps. There was a moderate linear correlation between the calculated FP MBF and the microsphere MBF (y = 0.9758x + 0.5368, R-2 = 0.61). The color-coded FP maps were moderately correlated with the regional distribution of flow. This novel method of first-pass contrast-enhanced two-dimensional fluoroscopic imaging can quantify MBF and provide color coded FP maps representing regional myocardial perfusion.

負荷心筋パーフュージョンMRI画像を用いた定量解析の際、最も処理時間を必要とする左室心筋領域設定のための自動化アルゴリズムの開発を行い、得られた左室心筋の輪郭を手動にて設定した輪郭と比較し、両者の左室心筋輪郭より算出した心筋血流値を比較した。虚血性心疾患を疑い、薬剤負荷心筋パーフュージョンMRI検査を施行した17例を対象とした。5例において本法を適応することができなかった。視覚的評価では自動設定された左室心筋領域は左室および右室内腔や肺なとの心筋以外の組織を含むことなく、左室心筋領域内に設定されていた。設定した左室心筋領域の面積は手動よりも有意に大きくなった。開発した左室心筋領域の自動設定アルゴリズムは心筋パーフュージョンMRIの定量解析に要する時間を大幅に短縮し、再現性の高い定量解析を日常臨床に導入できる可能性が示唆された。

For the absolute quantification of myocardial blood flow (MBF), Patlak plot-derived K1 need to be converted to MBF by using the relation between the extraction fraction of gadolinium contrast agent and MBF. This study was conducted to determine the relation between extraction fraction of GdDTPA and MBF in human heart at rest and during stress. Thirty-four patients (19 men, mean age of 66.5 +/- 11.0 years) with normal coronary arteries and no myocardial infarction were retrospectively evaluated. First-pass myocardial perfusion MRI during adenosine triphosphate stress and at rest was performed using a dual bolus approach to correct for saturation of the blood signal. Myocardial K1 was quantified by Patlak plot method. Mean MBF was determined from coronary sinus flow measured by phase contrast cine MRI and left ventricle mass measured by cine MRI. The extraction fraction of Gd-DTPA was calculated as the K1 divided by the mean MBF. The extraction fraction of Gd-DTPA was 0.46 +/- 0.22 at rest and 0.32 +/- 0.13 during stress (P < 0.001). The relationship between extraction fraction (E) and MBF in human myocardium can be approximated as E = 1 - exp(-(0.14 x MBF + 0.56)/ MBF). The current results indicate that MBF can be accurately quantified by Patlak plot method of first-pass myocardial perfusion MRI by performing a correction of extraction fraction. Magn Reson Med 66: 1391-1399, 2011. (C) 2011 Wiley Periodicals, Inc.

The purpose of this study was to develop a quantitative method formyocardial blood flow (MBF) measurement that can be used to derive accurate myocardial perfusion measurements from dynamic multidetector computed tomography (MDCT) images by using a compartment model for calculating the first-order transfer constant (K(1)) with correction for the capillary transit extraction fraction (E). Six canine models of left anterior descending (LAD) artery stenosis were prepared and underwent first-pass contrast-enhanced MDCT perfusion imaging during adenosine infusion (0.14-0.21 mg/kg/min). K(1), which is the first-order transfer constant from left ventricular (LV) blood to myocardium, was measured using the Patlak plot method applied to time-attenuation curve data of the LV blood pool and myocardium. The results were compared against microsphere MBF measurements, and the extraction fraction of contrast agent was calculated. K(1) is related to the regional MBF as K(1) = EF, E = (1 = exp(-PS/F)), where is the permeability-surface area product and is myocardial flow. Based on the above relationship, a look-up table from K(1) to MBF can be generated and Patlak plot-derived K(1) values can be converted to the calculated MBF. The calculated MBF and microsphere MBF showed a strong linear association. The extraction fraction in dogs as a function of flow (F) was E = (1 - exp(-(0.2532F + 0,7871)/F)). Regional MBF can be measured accurately using the Patlak plot method based on a compartment model and look-up table with extraction fraction correction from K(1) to MBF.

Purpose: The objective of this study is to determine regional left ventricle (LV) function and temporal heterogeneity of LV wall contraction by analyzing regional time-volume curve (TVC) after Fourier fitting and to assess altered systolic and diastolic functions and temporal indices of myocardial contraction in infarcted segments in comparison with noninfarcted myocardium in patients with myocardial infarction (MI). Methods: Steady-state cine magnetic resonance (MR) and late gadolinium-enhanced (LGE) MR images were acquired using a 1.5-T MR system in 60 patients with MI. Regional LV Function was determined by analyzing regional TVC in 16 segments. The fitted regional TVC was generated by Fourier Curve fitting with five harmonics. Regional LV ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), time to end-systole and time to peak filling (TPF) were determined from TVC and the first derivative curve. Results: On LGE MR imaging (MRI), MI was observed in 307 of 960 segments (32.0%). Regional EF and PER averaged in LGE segments were 49.3 +/- 14.5%. and 2.83 +/- 0.65 end-diastolic Volume (EDV)/s, significantly lower than those in normal segments (66.7 +/- 11.9% and 3.63 +/- 0.60 EDV/s, P<.001 and P<.01, respectively). In addition, regional PFR, an index of diastolic function. was significantly reduced in LGE segments (1.94 +/- 0.54 vs. 2.86 +/- 0.68 EDv/s, P<.01). Time to end-systole and TPF were significantly greater in LGE segments (380.2 +/- 57.6 and 169.3 +/- 45.4 ins) than in normal segments (300.9 +/- 55.1 and 132.3 +/- 43.0 ms, P<.01 and P<.01, respectively). Conclusions: Analysis of regional TVC on cine MRI after Fourier fitting allows quantitative assessment of-regional systolic and diastolic LV functions and temporal heterogeneity of LV wall contraction fit patients with MI. (C) 2009 Elsevier Inc. All rights reserved.

The objectives of this study were to develop a method for quantifying myocardial K, and blood flow (MBF) with minimal operator interaction by using a Patlak plot method and to compare the MBF obtained by perfusion MRI with that from coronary sinus blood flow in the resting state. A method that can correct for the nonlinearity of the blood time-signal intensity curve on perfusion MR images was developed. Myocardial perfusion MR images were acquired with a saturation-recovery balanced turbo field-echo sequence in 10 patients. Coronary sinus blood flow was determined by phase-contrast cine MRI, and the average MBF was calculated as coronary sinus blood flow divided by left ventricular (LV) mass obtained by cine MRI. Patlak plot analysis was performed using the saturation-corrected blood time-signal intensity curve as an input function and the regional myocardial time-signal intensity curve as an output function. The mean MBF obtained by perfusion MRI was 86 +/- 25 ml/min/100 g, showing good agreement with MBF calculated from coronary sinus blood flow (89 +/- 30 ml/min/100 g, r = 0.74). The mean coefficient of variation for measuring regional MBF in 16 LV myocardial segments was 0.11. The current method using Patlak plot permits quantification of MBF with operator interaction limited to tracing the LV wall contours, registration, and time delays. Magn Reson Med 62:373-383, 2009. (C) 2009 Wiley-Liss, Inc.

OBJECTIVES The purpose of this study is to validate the accuracy of multidetector computed tomography (MDCT) to measure differences in regional myocardial perfusion during adenosine stress in a canine model of left anterior descending (LAD) artery stenosis, during first-pass, contrast-enhanced helical MDCT. BACKGROUND Myocardial perfusion imaging by MDCT may have significant implications in the diagnosis and treatment of coronary artery disease. METHODS Eight dogs were prepared with a LAD stenosis, and contrast-enhanced MDCT imaging was performed 5 min into adenosine infusion (0.14 to 0.21 mg/kg/min). Images were analyzed using a semiautomated approach to define the regional signal density (SD) ratio (myocardial SD/left ventricular blood pool SD) in stenosed and remote territories, and then compared with microsphere myocardial blood flow (MBF) measurements. RESULTS Mean MBF in stenosed versus remote territories was 1.37 +/- 0.46 ml/g/min and 1.29 +/- 0.48 ml/g/min at baseline (p = NS) and 2.54 +/- 0.93 ml/g/min and 8.94 +/- 5.74 ml/g/min during adenosine infusion, respectively (p < 0.05). Myocardial SD was 92.3 +/- 39.5 HU in stenosed versus 180.4 +/- 41.9 HU in remote territories (p < 0.001). There was a significant linear association of the SD ratio with MBF in the stenosed territory (R = 0.98, p = 0.001) and between regional myocardial SD ratio and MBF < 8 ml/g/min, slope = 0.035, SE = 0.007, p < 0.0001. Overall, there was a significant non-linear relationship over the range of flows studied (LR chi-square [2 degrees of freedom] = 31.8, p < 0.0001). CONCLUSIONS Adenosine-augmented MDCT myocardial perfusion imaging provides semiquantitative measurements of myocardial perfusion during first-pass MDCT imaging in a canine model of LAD stenosis.

For transmission computed tomography (TCT) systems using a centered transmission source with a fan-beam collimator, the transmission projection data are truncated. To achieve sufficiently large imaging field of view (FOV), we have designed the combination of an asymmetric fan-beam (AsF) collimator and a small uncollimated sheet-source for TCT, and implemented AsF sampling on a two-head SPECT system. The purpose of this study is to evaluate the feasibility of our TCT method for quantitative emission computed tomography (ECT) in clinical application. Sequential Tc-99m transmission and Tl-201 emission data acquisition were performed in a cardiac phantom (30 cm in width) with a myocardial chamber and a patient study. Tc-99m of 185 MBq was used as the transmission source. Both the ECT and TCT images were reconstructed with the filtered back-projection method after scatter correction with the triple energy window (TEW) method. The attenuation corrected transaxial images were iteratively reconstructed with the Chang algorithm utilizing the attenuation coefficient map computed from the TCT data. In this AsF sampling geometry, an imaging FOV of 50 cm was yielded. The attenuated regions appeared normal on the scatter and attenuation corrected (SAC) images in the phantom and patient study. The good quantitative accuracy on the SAC images was also confirmed by the measurement of the Tl-201 radioactivity in the myocardial chamber in the phantom study. The AsF collimation geometry that we have proposed in this study makes it easy to realize TCT data acquisition on the two-head SPECT system and to perform quantification on Tl-201 myocardial SPECT.

To evaluate the clinical utility of a new method with dynamic single photon emission computed tomography (SPECT) and scatter and attenuation compensation to estimate both total and regional liver Function quantitatively. Five controls, 20 patients with chronic liver disease, and 2 patients with Budd-Chiari syndrome were studied. Dynamic liver SPECT data were acquired during 20 minutes after injection of Technetium (Tc)-99m diethylenetriaminepentaacetic acid (DTPA) galactosyl human serum albumin (GSA) with scatter and attenuation compensation. The binding rate constant of Tc-99m GSA (K-u) was derived quantitatively from the Patlak plot based on kinetic models for GSA receptor binding. The mean K-u was obtained by dividing the K-u value (total K-u) by the liver volume. Both total and mean K-u were significantly lower in patients with chronic liver disease than in controls (302 +/- 112 vs. 523 +/- 78 mi/min, p < 0.001, 0.26 <plus/minus> 0.11 vs. 0.43 +/- 0.03 ml/min/cm(3); p < 0.001). In the patient group, both total and mean K-u were significantly correlated with the results of conventional liver function tests and the histological severity of chronic liver disease. In 2 patients with Budd-Chiari syndrome, the mean K-u was lower in the right lobe, where the hepatic veins were occluded, than in the left lobe, where draining veins were patent. In conclusion, this method is a reliable diagnostic technique for estimating total and regional liver function.

Background, To evaluate the possibility of predicting the development of doxorubicin-induced cardiomyopathy, we performed quantitative assessment of the early kinetics of iodine-123 beta-methyl-iodophenyl-pentadecanoic acid (I-123 BMIPP) by means of dynamic myocardial SPECT. Methods, Thirty-six patients with various malignancies were examined, I-123 BMIPP dynamic myocardial SPECT was performed before chemotherapy, after chemotherapy, or both. Immediately after the injection of I-123 BMIPP (111 MBq), 30-second dynamic SPECT data were acquired successively for 15 minutes. The left ventricular (LV) myocardium was divided into 8 segments in short-axial and vertical slices, By using the time-activity curve (TAC) of each myocardial segment [Mo(t)] as an output function and the TAC of the LV cavity [B(t)] as an input function, the Rutland equation, Mo(t)/B(t)= F + K integralB(t)dt/B(t), was used as a means of assessing all segments. Results, Mo(t)/B(t) showed a good linear correlation with integralB(t)dt/B(t) from 30 seconds to 4 minutes in all 456 segments. The mean K value of 8 LV segments was significantly lower after chemotherapy than before chemotherapy (0.071 +/- 0.019 [n = 21] vs 0.095 +/- 0.025 [n = 36], P <.001). In 21 patients in whom dynamic SPECT was performed both before and after chemotherapy, the mean K values of left ventricle showed a significant decrease, from 0.101 +/- 0.024 to 0.071 + 0.019 (P <.0001). The fractional change in the value of K after chemotherapy showed a significant linear correlation with the administered dose of doxorubicin (r = 0.648, P <.002). Conclusion. I-123 BMIPP dynamic myocardial SPECT may be clinically useful, because it permits the early detection of doxorubicin-induced cardiomyopathy.

The aim of this study was to evaluate the effects of scatter correction (SC) and attenuation correction (AC) on the quantification of dopamine transporters using I-123-beta-CIT brain SPET images. Quantitative analysis was carried out using static SPET images obtained 23 h after injection. We calculated V-3" [(striatal-occipital)/occipital ratio] values from images without correction, with AC, and with SC and AC. Two types of regions of interest (ROI) were plated on the striatum: a small square ROI and a larger ROI containing most of the striatum. After validating the correction method in a phantom experiment, a human study was carried out involving eight normal volunteers and 15 patients. The larger ROI yielded smaller V-3" values. The effect of attenuation correction was modest, whereas that of scatter correction was marked. It was shown that beta-CIT SPET quantification was affected by the size of the ROI, photon scattering and attenuation, and that scatter and attenuation correction improved the accuracy of the quantification. Methodological standardization in image processing and the type of ROI should be considered when a multi-centre trial is planned. ((C) 1999 Lippincott Williams & Wilkins).

The aim of the study is to develop an ultra high-resolution pinhole SPECT system and analyze the performance by simulations. The pinhole SPECT was conducted with a Toshiba GCA-7200A gamma camera. The diameter of the pinhole was 1 mm. Data were acquired with a 128 x 128 matrix, and the distance from the center of rotation (COR) to the pinhole was 20 mm [case 1] of 28 mm [case 2]. The data were collected at 4 degree increments over 360 degrees. The Feldkamp method was used for image reconstruction. Before the image reconstruction, we corrected the COIL of the pinhole collimator. The imaging voxel was 0.27 x 0.27 x 0.27 mm(3) [case 1] or 0.4 x 0.4 x 0.4 mm(3) [case 2]. From the experiments with a resolution phantom the spatial resolution (FWHM) was 1.1 mm [case 1] or 1.3 mm [case 2]. The pinhole SPECT was also examined for in vivo imaging for studies of the heart in mice which were injected with Tc-99m-Tetrofosmin intravenously. In the reconstructed image the heart muscle of the mouse was clearly visualized. We also investigated the spatial resolution of the reconstructed image by means of simulations.

The aim of this study was to obtain quantitative iodine-123 brain single-photon emission tomographic (SPET) images with scatter and attenuation correction. We used a triple-headed SPET gamma camera system equipped with fan-beam collimators with a technetium-99m line transmission source placed at one of the focal lines of the fan-beam collimators. Four energy windows were employed for data acquisition: (a) 126-132 keV, (b) 132-143 keV, (c) 143-175 keV and (d) 175-186 keV. A simultaneous transmission-emission computed tomography scan (TCT-ECT) was carried out for a brain phantom containing I-123 solution. The triple energy window scatter correction was applied to the I-123 ECT data measured by means of the windows (b), (c) and (d) acquired by two detectors. Attenuation maps were reconstructed from Tc-99m TCT data measured by means of the windows (a), (b) and (c) acquired by one detector. Chang's iterative attenuation correction method using the attenuation maps was applied to the I-123 ECT images. In the phantom study cross-calibrated SPET values obtained with the simultaneous mode were almost equal to those obtained with the sequential mode, and they were close to the true value, within an error range of 5.5%. In the human study corrected images showed a higher grey-to-white matter count ratio and relatively higher uptake in the cerebellum, basal ganglia and thalamus than uncorrected images. We conclude that this correction method provides improved quantification and quality of SPET images and that the method is clinically practical because it requires only a single scan with a 99mTc external source.

A practical method for scatter and attenuation compensation was employed in thallium-201 myocardial single-photon emission tomography (SPET or ECT) with the triple-energy-window (TEW) technique and an iterative attenuation correction method bg using a measured attenuation map. The map was reconstructed from technetium-99m transmission CT (TCT) data. A dual-headed SPET gamma camera system equipped with parallel-hole collimators was used for ECT/TCT data acquisition and a new type of external source named "sheet line source" was designed for TCT data acquisition. This sheet line source was composed of a narrow lone fluoroplastic tube embedded in a rectangular acrylic board. After injection of Tc-99m solution into the tube by an automatic injector, the board was attached in front of the collimator surface of one of the two detectors. After acquiring emission and transmission data separately ol simultaneously, we eliminated scattered photons in the transmission and emission data with the TEW method, and reconstructed both images. Then, the effect of attenuation in the scatter-corrected ECT images was compensated with Chang's iterative method by using measured attenuation maps. Our method was validated by several phantom studies and clinical cardiac studies. The method offered improved homogeneity in distribution of myocardial activity and accurate measurements of myocardial tracer uptake. We conclude that the above correction method is feasible because a new type of Tc-99m external source may not produce truncation in TCT images and is cost-effective and easy to prepare in clinical situations.

Scintigraphy with I-123-MIBG and (TI)-T-201 was compared in patients with various diseases including diabetes mellitus, with and without sympathetic nervous dysfunction. This study was done to assess lung uptake of these tracers semiquantitatively Methods: Thirty-eight patients with diabetes mellitus, seven patients with dilated cardiomyopathy (DCM), 12 patients with hypertrophic cardiomyopathy (HCM) and eight healthy subjects were studied. Sympathetic nervous dysfunction was observed in 13 of the 38 diabetic patients. Simultaneous imaging with I-123-MIBG and (TI)-T-201 was performed, The ratio of lung to-total injected dose count and washout rate in the lung were calculated from dynamic images acquired in the initial 2 min and static images acquired at 15 min and at 4 hr after injection of the tracers. Results: Lung uptake of I-123-MIBG at 4 hr was significantly increased in the diabetic group as compared with those in the other groups, In diabetic patients with sympathetic nervous dysfunction, the lung uptake ratio of I-123-MIBG at 4 hr was significantly higher than that in the diabetic patients without sympathetic nervous dysfunction, due to decreased clearance of I-123-MIBG from the lung. On the other hand, increased lung uptake of (TI)-T-201 was observed in DCM patients at both 15 min and 4 hr. There was no significant difference between lung uptake of (TI)-T-201 in diabetic patients and that in healthy subjects. Conclusion: Lung uptake of I-123-MIBG was increased and lung washout of I-123-MIBG was decreased in diabetic patients with sympathetic nervous dysfunction, while lung uptake of (TI)-T-201 was not altered, Iodine-123-MIBG scintigraphy of the lung may provide information on sympathetic nervous activity in diabetic patients. It is a promising method for studying the kinetics of norepinephrine in the lung because MIBG is taken up in the lung by the same mechanism as norepinephrine.

Since primary photons ran provide information concerning the position of radioisotope (RI) accumulation and the energy of the pho to ns, it would seem reasonable to vary the position and width of the energy window depending on the type of RI and the energy resolution of the detector to collect as many of the primary photons as possible. We propose a method for determining energy window width and position for scintigraphic imaging to collect as many of the primary photons as possible, and studied the influence on the Triple Energy Window (TEW) scatter compensation method of setting such energy window levels for Tc-99m(single photopeak) and Tl-201 (multiple photopeaks) using detector with different energy resolution through simulation. The Monte Carlo simulations were verified by comparing the regional energy spectrum at the phantom obtained from the simulation against experimental measurements. The energy window with our proposed method for Tc-99m is 20% and 47.3 % for Tl-201 using gamma camera, and 9.8% for Tc-99m using a semiconductor detector wi th a theorized energy resolution of 7.0 keV.

Quantitative image reconstruction in single photon emission CT requires an accurate attenuation map of a cross section of an object. Several data acquisition geometries have been proposed to obtain the true attenuation map by means of gamma-ray transmission CT (TCT). In the transmission data scattered photons are sometimes measured and they reduce the accuracy of reconstructed TCT images. To investigate the effects of scattered photons in gamma-ray transmission CT, we performed Monte Carlo simulations for several types of data acquisition systems. Examined geometries were (a) an uncollimated flood source and a parallel hole collimator, (b) a collimated hood source and a parallel hole collimator, (c) an uncollimated line source and a symmetric fan beam collimator, and (d) a collimated line source and a symmetric fan beam collimator. The results showed that a fan beam collimator and a line source rejected most of the scattered photons generated inside an object, and that if we collimated emitted photons at the source side, almost all the scattered photons could be rejected at the collimator on the detector side.

We propose a practical method for scatter and attenuation compensation in Tc-99m-ECD brain SPECT using a simultaneous emission CT (ECT) and transmission CT (TCT) acquisition system that includes the following major components: (a) triple-headed SPECT gamma camera equipped with fanbeam collimators; (b) external line sources containing Tc-99m placed at the focal lines of the collimators; and (c) scatter correction by the triple-energy-window (TEW) method. Methods: Projection images were obtained over a 360 degrees rotation scan. After acquisition, scatter correction was performed using the TEW method, which corrected scattered photons pixel by pixel in the projection data. Scatter-corrected ECT images were compensated for attenuation using the TCT images with Chang's iterative method, and were converted to activity concentration (kBq/ml) images by obtaining a cross-calibration scan. After validating this method with phantom studies, it was applied to clinical brain imaging using a combination of 925 MBq Tc-99m-ECD as a radiopharmaceutical and 222 MBq Tc-99m as an external source. ECT and TCT data were acquired separately or simultaneously. Results: SPECT quantification and image quality were improved by performing this correction. The activity concentration images obtained with the simultaneous acquisition were almost identical to those obtained with the separate acquisition. Conclusion: This method was clinically practical and cost-effective for reconstructing quantitative Tc-99m brain SPECT images.

A new method for quantitative liver study was developed using the tracer technetium-99m diethylene triamine penta-acetic acid-galactosyl human serum albumin (Tc-99m-GSA), an analog ligand of the asialoglycoprotein receptor, which is a hepatocyte surface receptor specific for galactose-terminated glycoproteins. For quantitative dynamic single-photon emission tomographic (SPET) studies, attenuation compensation using transmission computed tomography (TCT) and the triple energy window (TEW) scatter compensation method were evaluated. As the TCT source, we used an uncollimated multi-tube source with the TEW scatter compensation method. To verify the accuracy of cross-calibrated SPET values as compared with measured radioactivities, we performed SPET of a cylindrical water pool phantom which contains seven hot rods filled with different concentrations of Tc-99m activities, simulating the scan conditions in human studies. The results of the phantom studies showed good linearity and accuracy of the SPET values, with R(2)=0.993 and a regression line of y=0.941x+5.48. From the analysis of a kinetic model based on a one-compartment model, focussing on the initial stage of several minutes after Tc-99m-GSA injection and taking the physiological expression presented in a three-compartment analysis into account, we introduced the Rutland equation (Patlak plot) in the Tc-99m-GSA study by which the overall and regional effective hepatic blood flow (EHBF) and hepatic blood pool volume were determined. Preliminary clinical evaluations were performed for four normal male subjects (23-35 years of age) and one patient. Forty sequential 30-s dynamic SPET acquisitions were obtained for a period of 20 min following the intravenous injection of Tc-99m-GSA with venous blood sampling at 10 min. After seat ter compensation, the SPET images were reconstructed with attenuation compensation using an attenuation map obtained from TCT. The average normal value for the total EHBF was 468+/-83 ml/min and that for the hepatic blood pool volume, 777+/-123 ml. Functional images of the distribution of regional values of EHBF (ml/min/voxel) and hepatic blood pool volume (ml/voxel) were also generated corresponding to the original SPET images. The EHBF images showed regional liver function, higher in the right lobe than the left lobe in the normal cases, and the heptic blood pool volume images showed the distribution of intensified high values along major vascular structures. Receptor imaging with Tc-99m-GSA using the Rutland method and dynamic SPET with scatter and attenuation compensation is an effective technique that allows the evaluation of total and regional hepatic functional parameters (EHBF hepatic blood pool) in vivo.

The spatial distribution of scattered photons varies depending on many factors such as object size and source distribution. We propose a triple-energy window (TEW) scatter compensation method for determining position-dependent Compton scatter. We estimated the count of primary photons at each pixel in the acquired image using the 24% main window centered at the photopeak energy and 3 keV scatter rejection windows on both sides of the main window. We conducted a physical evaluation of this method using phantoms and also applied this method to patients in a clinical trial. The TEW method performed Compton scatter compensation with good accuracy.

The physical characteristics of the collimator cause degradation of resolution with increasing distance from the collimator surface. A new convolutional backprojection algorithm has been derived for fan beam SPECT data without rebinding into parallel beam geometry. The projections are filtered and then backprojected into the area within an isosceles triangle whose vertex is the focal point of the fan-beam and whose base is the fan-beam collimator face, and outside of the circle whose center is located midway between the focal point and the center of rotation and whose diameter is the distance between the focal point and the center of rotation. Consequently the backprojected area is close to the collimator surface. This algorithm has been implemented on a GCA-9300A SPECT system showing good results with both phantom and patient studies. The SPECT transaxial resolution was 4.6mm FWHM (reconstructed image matrix size of 256x256) at the center of SPECT FOV using UHR (ultra-high-resolution) fan beam collimators for brain study. Clinically, Tc-99m HMPAO and Tc-99m ECD brain data were reconstructed using this algorithm. The reconstruction results were compared with MRI images of the same slice position and showed significantly improved over results obtained with standard reconstruction algorithms.

High-resolution three-headed single photon emission computed tomography (SPET) equipped with fanbeam collimators was applied to myocardial perfusion imaging in infants aged from 1 to 11 months (n = 5). A tabletop designed specifically for infants was fixed on the SPET couch to reduce the radius of camera rotation to 13.2 cm. Significant improvement in resolution was achieved with the fan-beam collimators compared to parallel-hole high-resolution collimators. With the administration of approximately 37 MBq (26-44 MBq) Tl-201, 5 min acquisition time was possible for SPET imaging, which provided good image quality in all patients. Thus, a smaller administration dose is possible within a practical short acquisition time, High-resolution fan-beam SPET imaging can be a routine diagnostic method for heart disease in newborn babies and infants.

Data acquisition in SPECT assumes that there is no change in radionuclide distribution during data collection. However, this assumption is not valid in radiopharmaceuticals with rapid temporal changes in radioactivity. Artifacts and quantitative errors are studied using phantom studies, mathematical models, and clinical myocardial data. Projection data of each model were sequentially multiplied by weighting coefficients that varied mono-exponentially with time, and the SPECT images were reconstructed. A long data acquisition time in comparison to the clearance of the tracer can be a significant cause of artifact. When the myocardial septum-to-lateral count ratio is used as an index of distortion, a shorter acquisition time than the effective half-life of the tracer is required to reduce the error of the septum-to-lateral count ratio to within 10%. Since 180-degrees rotation acquisition causes artifacts depending on the direction of rotation, 360-degrees acquisition is preferable. Continuous repetitive rotation acquisition is a suitable method for dynamic SPECT to reduce quantitative errors and artifacts.