Jung Woo Yu

Effect of Harderian adenectomy on the statistical analyses of mouse brain imaging using positron emission tomography.

Positron emission tomography (PET) using 2-deoxy-2-[18F] fluoro-D-glucose (FDG) as a radioactive tracer is a useful technique for in vivo brain imaging. However, the anatomical and physiological features of the Harderian gland limit the use of FDG-PET imaging in the mouse brain. The gland shows strong FDG uptake, which in turn results in distorted PET images of the frontal brain region. The purpose of this study was to determine if a simple surgical procedure to remove the Harderian gland prior to PET imaging of mouse brains could reduce or eliminate FDG uptake. Measurement of FDG uptake in unilaterally adenectomized mice showed that the radioactive signal emitted from the intact Harderian gland distorts frontal brain region images. Spatial parametric measurement analysis demonstrated that the presence of the Harderian gland could prevent accurate assessment of brain PET imaging. Bilateral Harderian adenectomy efficiently eliminated unwanted radioactive signal spillover into the frontal brain region beginning on postoperative Day 10. Harderian adenectomy did not cause any post-operative complications during the experimental period. These findings demonstrate the benefits of performing a Harderian adenectomy prior to PET imaging of mouse brains.

Modeling high energy (I-131) pinhole collimator for small animal gamma ray imaging device by Monte Carlo simulation (GATE 6.0)

We investigated optimized collimator designs for I-131 high energy gamma ray imaging on small animal gamma camera. The simulated structures of the pinhole collimator were evaluated by sensitivity, true, scatter and penetration count rates, and spatial resolution. The parameters, which were pinhole diameter, acceptance angle, and aperture thickness, were determined to improve image resolution with geometric conditions. In this study we showed optimized pinhole design for high energy I-131 imaging to meet the tradeoff between sensitivity and resolution

Automated quantitative assessment of myocardial perfusion in rodent PET/SPECT images

The aim of this study was to automatically assessment of the 64Cu-PTSM, 99mTc-MIBI and 201Tl myocardial perfusion image using Multi Gaussian Mixture Model (MGMM). Myocardial infarction (MI) model was prepared through permanently ligated left circumflex artery of rats. PET/SPECT images were acquired using small animal PET/SPECT scanner (InveonTM, Siemens) with physiological monitoring system (BioVet, m2m Imag. Corp.). PET images were obtained at 10 min post injection of 37 MBq/0.2 mL of 64Cu-PTSM via tail vein as list-mode data. SPECT images were acquired at 60 min post IV injection of 110 MBq of Tc99m-MIBI and Tl-201/0.1 mL with 126-154 keV (Tc), 63-77 keV (Tl) energy window and 1.0 mm pinhole collimator. The acquired data was reconstructed by OSEM2D algorithm with 4 iterations. To automatically make the myocardial contour and generate polar map, we used Cedars-Sinai method. Myocardial infarct region of polar map were evaluated by using MGMM method for adaptive threshold calculation and predefined threshold method for absolute threshold calculation. Rat myocardium was stained by hematoxylin and eosin (H&E) for reference value of infarct size after the imaging. The infarct size of PET/SPECT image was defined by infarction area percentage of the total left myocardium. Comparative analysis was performed between MI size of histology and polar map. The size difference in 64Cu-PTSM PET polar map was 6.96 3.53% from the absolute value 40% and 4.40 0.58% from MGMM4. The difference in 99mTc-MIBI SPECT polar map was 8.87 1.16% from the absolute value 40%, and 3.47 1.99% from MGMM4. The difference in 201Tl SPECT polar map was 11.73 1.45% from the absolute value 40%, and 2.97 1.46% from MGMM4. MGMM method showed the possibility of quantitative evaluation for my

Region adaptive PET gating using internal motion estimation

The purpose of this study was to assess the optimal gates number of each region using estimated internal motion. Internal motion has been demonstrated in lung and liver region of small animal by coated molecular sieve. We coated molecular sieve with Pluronic F-127 hydrogel for keeping the activity in the body. All PET studies were performed with a dedicated small animal PET scanner. Respiratory gating was operated the external trigger device synchronized with the list mode acquisition. The trigger signals were simultaneously reflected motion of heart and breathing. The list mode data were converted to sinogram gated 2∼16 bin. In PET image analysis for determining optimal gate number, count and SNR were measured from ROI in the target region. Horizontal and vertical FWHM were measured from line profile in each images. The motion compensation PET image for optimal gate number was confirmed by internal motion. The measured value of lung region showed high count (8.67), high SNR (3.25), and high FWHM (1.83) in 8 bin. In liver region, high count (2.09), high SNR (3.99), and high FWHM (2.23) were revealed in 9 bin. The artificial tumor evaluation study using molecular sieve is a method to assess accurately internal organ motion in the rodent. The gate number for motion correction should be set differently in accordance with the organ because motion level varies as each organ. The estimated internal motion will be a useful method for motion compensation modeling.

Region-specific motion destmation in rodent using PET and MRI image

The acute organ motion estimation in multimodal imaging improves quality of diagnosis and therapy of tumor. It is particularly important in the organ related involuntary movement such as lung and liver. The aim of this study was to compare the region specific motion in rodent using radioactive molecular sieve PET image and MRI image. The molecular sieve was contained 0.37 MBq F-18 and coated with hydrogel. For comparison of internal and external motion, molecular sieve was placed inside lung and liver and attached on the surface of each organ region in SD-rat. PET study was performed using a small animal PET scanner (Inveon) after IV injection of FDG 37 MBq/0.2 mL. List-mode data was synchronized with respiratory gating trigger signal from external monitoring system (Biovet). MRI study was performed using 3-T clinical MRI system (Magnetom Tim Trio) with human wrist coil. Coronal MRI images were acquired using T2-weighted turbo spin echo (TSE) sequence with respiratory triggering. The parameter is as follow settings: TR = 1000 ms, TE = 36 ms, FA = 20. We analyzed moving pattern and variation of movement in lung and liver region following respiratory cycle in both of PET and MRI images. Moving patterns in PET image were different in accordance with where molecular sieve was placed. The variation of lung and liver internal motion was 0.93 and 0.52 in PET image, respectively. Estimated organ motion in MRI image revealed moving pattern based on respiratory cycle. The maximum variation of lung and liver region was 1.75 and 1.36 in MRI image, respectively. We recognized organ motion was different depending on the region and the monitoring signal was overestimated compared to real motion in both of region in PET. This study demonstrated that region-specific motion estimation would realize through aid of MRI images without ext