Hisato Maeda | Search PubMed

PubMed2004

[Simultaneous spatial resolution correction in SPECT reconstruction using OS-EM algorithm].

Single photon emission computed tomography (SPECT) is widely used for Nuclear Medicine. The low spatial resolution is mainly due to the limited collimator resolution. We have developed ordered subsets-expectation maximization (OS-EM) algorithm incorporating three dimensional spatial resolution correction (3D-SRC;horizontal and vertical direction) for distance-dependent blurring. In this paper we evaluate the fundamental properties of OS-EM algorithm including distance-dependent resolution correction using some phantoms (cubic phantom, cardiac and brain phantoms) and 12 patients performed 99mTc-tetrofosmin myocardial SPECT. In cubic phantom, the resolution in transaxial, coronal and sagital images are significantly improved by 3D-SRC. In short axial images of cardiac phantom, 3D-SRC shows more excellent images than no correction. In brain phantom, the blurring at the edge of the brain structure is improved by using OS-EM algorithm with 3D-SRC. In patients, the resolution in transaxial and short axial images is significant improved. These results suggest that this method improves the resolution in SPECT images and 3D-SRC is especially available in SPECT images of other axes in addition to transaxis. This method has advantage that both reconstruction and resolution correction are simultaneously performed. In the near future, we think that OS-EM algorithm incorporating attenuation, scatter and resolution correction will be used for quantitative SPECT images.

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PubMed2002

Differences in fatty acid metabolic disorder between ischemic myocardium and doxorubicin-induced myocardial damage: assessment using BMIPP dynamic SPECT with analysis by the Rutland method.

UNLABELLED: Dynamic myocardial SPECT data acquired with 15-(123)I-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) were analyzed by the Rutland method. The relative time-activity curves generated from dynamic SPECT in normal control subjects were compared with similar curves from patients with established ischemic heart disease (IHD) and doxorubicin-induced myocardial damage (DxMD). Comparison of such time-activity curves may provide some indirect information concerning qualitative differences in BMIPP metabolism. METHODS: Thirteen patients with various malignancies who received doxorubicin, 16 patients with IHD, and 15 normal control subjects were examined. Immediately after the bolus injection of BMIPP, dynamic data acquisition with a 3-head SPECT system was started and continued for 15 min. Using the time-activity curves of the myocardium as the output function (Mo(t)) and the time-activity curves of the left ventricular cavity as the input function (B(t)), the Rutland equation was calculated: Mo(t)/B(t) = F + K integral B(t)dt/B(t), where F is the blood - background subtraction factor and K is the uptake constant. The duration of the linear portion in this equation and the K values were evaluated. RESULTS: Mo(t)/B(t) was plotted against integral B(t)dt/B(t). Mo(t)/B(t) showed a good linear correlation with integral B(t)dt/B(t) from 30 s to 230 +/- 57 s in normal control subjects. The duration of this linearity was prolonged to 317 +/- 79 s in DxMD (P = 0.0014) and shortened to 182 +/- 58 s in IHD (P = 0.039). The mean K value was 0.0740 +/- 0.0184 in normal control subjects, significantly higher than the K values of 0.0599 +/- 0.0148 in DxMD patients (P = 0.026) and 0.0497 +/- 0.0189 (P = 0.0020) in IHD patients. CONCLUSION: Analysis of BMIPP dynamic SPECT data by the Rutland method is useful for detecting qualitative differences in BMIPP metabolism in various types of myocardial damage. It is speculated that the fatty acid metabolic disorder is characterized by a delay in metabolism in DxMD and by increased backdiffusion in IHD.

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