• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2004.11a
• /
• pp.91-95
• /
• 2004

Several MRI studies have reported reductions in temporal lobe volumes in Alzheimer's disease (AD). Measures have been usually obtained with regions-of-interest (ROI) drawn manually on selected medial and lateral portions of the temporal lobes, with variable choices of anatomical borders across different studies. We used the automated voxel-based morphometry (VBM) approach to investigate gray matter abnormalities over the entire extension of the temporal lobe in 10AD patients (MM5E 22)and 22 healthy controls. Foci of significantly reduced gray matter volume in AD patients were detected in both medial and lateral temporal regions, most significantly in the right and left posterior parahippocarmpal gyri. At a more flexible statistical threshold (P<0.01, uncorrected for multiple comparisons), circumscribed foci of significant gray matter reduction were also detected in the right amygdala/enthorinal cortex, the anterior and posterior borders of the superior temporal gyrus bilaterally, and the anterior portion of the left middle temporal gyrus. These VBM results confirm previous findings of temporal lobe atrophic changes in AD, and suggest that these abnormalities may be confined to specific sites within that lobe, rather than showing a widespread distribution.

• Tuberculosis and Respiratory Diseases
• /
• v.63 no.6
• /
• pp.521-525
• /
• 2007

Positron emission tomography/computed tomography (PET/CT) is valuable for the diagnosis of malignancies. However, PET/CT is unable to discriminate exactly between inflammation and a neoplasm. We report a case of a 50-year-old man with pulmonary paragonimiasis that was suspicious for lung cancer, as detected by PET/CT. The use of PET/CT revealed multilobulated consolidation on the right lung and patchy consolidation on the left lung, with increased fluorodeoxyglucose (FDG) uptake. In addition, the left paraaortic lymph node (LN) and peripancreatic LN showed enlargement with increased FDG uptake. Lung cancer with multiple lymph node metastases was suspected from the increased standardized uptake values (SUV>4.5) determined by PET/CT. We performed wedge resection via video-assisted thoracic surgery (VATS) and found Paragonimus westermani eggs in the involved tissues.

• BLOOD RESEARCH
• /
• v.53 no.4
• /
• pp.281-287
• /
• 2018

Background Bone marrow involvement (BMI) affects the lymphoma stage, survival, and treatment. Bone marrow biopsy (BMB) and fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) are useful techniques to detect BMI. Both have advantages and disadvantages. We aimed to identify factors that could be used to predict BMI with positive and negative results on PET/CT compare them with BMB in newly diagnosed patients with lymphoma. Methods We included 22 non-Hodgkin and 16 Hodgkin lymphoma patients in this single center study. All patients had PET/CT examination and BMB before treatment. BMI in BMB was reported as negative or positive. Bone marrow was classified into 3 types by FDG uptake on PT/CT; diffuse involvement, focal involvement, and normal bone marrow. Results PET/CT and BMB results were concordant (7 positive, 15 negative) in 22 patients (57%). We evaluated concordant and discordant patient characteristics and risk-stratified patients for BMI. Our findings suggest that patients with diffuse FDG uptake on PET/CT, especially patients with advanced age and low platelet and white blood cell counts, are likely to have BMI and could potentially forego BMB. Patients with negative PET/CT findings and no significant laboratory abnormalities are very unlikely to have BMI. Conclusion Our results suggest that BMI should not be decided solely based PET/CT or BMB findings. It is reasonable to use both diagnostic assays along with clinical and laboratory findings. PET/CT result, clinical and laboratory findings could be useful for predicting BMI in patient for whom BMB is contraindicated.

• Journal of the Korean Society of Radiology
• /
• v.13 no.3
• /
• pp.473-479
• /
• 2019

PET-CT improves performance and reduces the time by combining PET and CT of spatial resolution, and uses CT scan for attenuation correction. This study analyzed PET image evaluation. The condition of the tube voltage and current of CT will be changed using. Uniformity phantom and resolution phantom were injected with 37 MBq $^{18}F$ (fluorine ; 511 keV, half life - 109.7 min), respectively. PET-CT (Biograph, siemens, US) was used to perform emission scan (30 min) and penetration scan. And then the collected image data were reconstructed in OSEM-3D. The same ROI was set on the image data with a analyzer (Vinci 2.54, Germany) and profile was used to analyze and compare spatial resolution and image quality through FWHM and SI. Analyzing profile with pre-defined ROI in each phantom, PET image was not influenced by the change of tube voltage or exposure dose. However, CT image was influenced by tube voltage, but not by exposure dose. When tube voltage was fixed and exposure dose changed, exposure dose changed too, increasing dose value. When exposure dose was fixed at 150 mA and tube voltage was varied, the result was 10.56, 24.6 and 35.61 mGy in each variables (in resolution phantom). In this study, attenuation image showed no significant difference when exposure dose was changed. However, when exposure dose increased, the amount of dose that patient absorbed increased too, which indicates that CT exposure dose should be decreased to minimum to lower the exposure dose that patient absorbs. Therefore future study needs to discuss the conditions that could minimize exposure dose that gets absorbed by patient during PET-CT scan.

• Radiation Oncology Journal
• /
• v.33 no.3
• /
• pp.179-187
• /
• 2015

Purpose: The purpose of this study was to investigate the predictable value of pretreatment $^{18}F$-fluorodeoxyglucose positron emission tomography-computed tomography ($^{18}F$-FDG PET-CT) in radiotherapy (RT) for patients with hepatocellular carcinoma (HCC) or portal vein tumor thrombosis (PVTT). Materials and Methods: We conducted a retrospective analysis of 36 stage I-IV HCC patients treated with RT. $^{18}F$-FDG PET-CT was performed before RT. Treatment target was determined HCC or PVTT lesions by treatment aim. They were irradiated at a median prescription dose of 50 Gy. The response was evaluated within 3 months after completion of RT using the Response Evaluation Criteria in Solid Tumors (RECIST). Response rate, overall survival (OS), and the pattern of failure (POF) were analyzed. Results: The response rate was 61.1%. The statistically significant prognostic factor affecting response in RT field was maximal standardized uptake value (maxSUV) only. The high SUV group (maxSUV ${\geq}5.1$) showed the better radiologic response than the low SUV group (maxSUV < 5.1). The median OS were 996.0 days in definitive group and 144.0 days in palliative group. Factors affecting OS were the %reduction of alpha-fetoprotein (AFP) level in the definitive group and Child-Pugh class in the palliative group. To predict the POF, maxSUV based on the cutoff value of 5.1 was the only significant factor in distant metastasis group. Conclusion: The results of this study suggest that the maxSUV of $^{18}F$-FDG PET-CT may be a prognostic factor for treatment outcome and the POF after RT. A %reduction of AFP level and Child-Pugh class could be used to predict OS in HCC.

• Journal of the Korean Society of Radiology
• /
• v.16 no.6
• /
• pp.697-702
• /
• 2022

For imaging in positron emission tomography(PET), it is necessary to measure the position of the scintillation pixel interacting with the gamma rays incident on the detector. To this end, in the conventional system, a flood image of the scintillation pixel is obtained, the imaged area of each scintillation pixel is separated, and the position of the scintillation pixel is specified and acquired as a digital signal. In this study, a deep learning method was applied based on the signal formed by the photosensor of the detector, and a method was developed to directly acquire a digital signal without going through various procedures. DETECT2000 simulation was performed to verify this and evaluate the accuracy of position measurement. A detector was constructed using a 6 × 6 scintillation pixel array and a 4 × 4 photosensor, and a gamma ray event was generated at the center of the scintillation pixel and summed into four channels of signals through the Anger equation. After training the deep learning model using the acquired signal, the positions of gamma-ray events that occurred in different depth directions of the scintillation pixel were measured. The results showed accurate results at every scintillation pixel and position. When the method developed in this study is applied to the PET detector, it will be possible to measure the position of the scintillation pixel with a digital signal more conveniently.

• Journal of the Korean Society of Radiology
• /
• v.16 no.6
• /
• pp.703-708
• /
• 2022

A detector module measuring the depth of interaction(DOI) was designed to improve the spatial resolution of positron emission tomography(PET). The scintillation pixel array consists of two layers, and a light guide is inserted between the layers to make the light generated through the gamma-ray event different for each layer. There are four light guides, and one light guide is designed to be coupled to a 2 × 2 array of scintillation pixels. The light generated from the top layer is moved to the photosensor with a wider distribution through the light guide, and the light generated from the bottom layer is incident on the photosensor with a narrower distribution than the top layer. When a flood image is reconstructed based on the signals obtained from the photosensor by different distributions, scintillation pixels are imaged at different positions for each layer. To verify this, a DETECT2000 simulation tool that simulates the behavior of light in a scintillator was used. By designing a scintillation pixel array, a detector consisting of a light guide and a photosensor, a gamma ray event was generated in all scintillation pixels to obtain a flood imgae. As a result, it was confirmed that the top and bottom layers were imaged at different positions and completely separated. When this detector is applied to PET, it is considered that image quality can be improved through imporved spatial resolution.

• Journal of the Korean Society of Radiology
• /
• v.18 no.2
• /
• pp.65-71
• /
• 2024

To achieve high resolution and sensitivity of positron emission tomography (PET) for small animals, the detector is constructed using very thin and long scintillation pixels. Due to the structure of these scintillation pixels, spatial resolution deterioration occurs outside the system's field of view. To solve this problem, we designed a detector that could improve spatial resolution by measuring the interaction depth and improve sensitivity by using a quasi-block scintillator. A quasi-block scintillator size of 12.6 mm x 12.6 mm x 3 mm was arranged in four layers, and optical sensors were placed on all sides to collect light generated by the interaction between gamma rays and the scintillator. DETECT2000 simulation was performed to evaluate the performance of the designed detector. Flood images were acquired by generating gamma-ray events at 1 mm intervals from 1.3 mm to 11.3 mm within the scintillator of each layer. The spatial resolution and peak-to-peak distance for each location were measured in an 11 x 11 array of flood images. The average measured spatial resolution was 0.25 mm, and the average distance between peaks was 1.0 mm. Through this, it was confirmed that all locations were separated from each other. In addition, because the light signals of all layers were measured separately from each other, the layer of the scintillator that interacted with the gamma rays could be completely separated. When the designed detector is used as a detector in a PET system for small animals, it is considered that excellent spatial resolution and sensitivity can be achieved and image quality can be improved.

• Journal of Korean Neurosurgical Society
• /
• v.63 no.3
• /
• pp.397-405
• /
• 2020

Objective : We retrospectively evaluated the efficacy of Gamma Knife radiosurgery (GKS) for recurrent nasopharyngeal carcinoma (NPC) in patients who previously underwent radiotherapy, and analyzed the treatment outcomes over 14 years. Methods : Ten patients with recurrent NPC who had previously received radiotherapy underwent stereotactic radiosurgery using a Gamma Knife^® (Elekta Inc, Atlanta, GA, USA) between 2005 and 2018. The median target volume was 8.2 ㎤ (range, 1.7-17.8), and the median radiation dose to the target was 18 Gy (range, 12-30). The median follow-up period was 18 months (range, 6-76 months). Overall and local failure-free survival rates were determined using the Kaplan-Meier method. Results : The NPCs recurred at the primary cancer site in seven patients (70%), as distant brain metastasis in two (20%), and as an extension into brain in one (10%). The recurrent tumors in seven of the 10 patients (70%) were found on the routine follow-up imaging studies. Two patients presented with headache and one with facial pain. Local failure after GKS occurred in five patients (50%) : two of whom died eight and 6 months after GKS, respectively. No adverse radiation effects were noted after GKS. The 1- and 3-year overall survival rates after GKS were 90% and 77%, respectively. The local failure-free survival rates at 6 months, 1 year, and 3 years after GKS were 80%, 48%, and 32%, respectively. The median interval from GKS to local failure was 8 months (range, 6-12). Univariate analysis revealed that using co-registration with positron emission tomography-computed tomography (PET-CT) and magnetic resonance imaging (MRI) was associated with a lower local failure rate of recurrent NPC (p=0.027). Conclusion : GKS is an acceptable salvage treatment option for patients with recurrent NPC who previously received radiation therapy. PET-CT and MRI co-registration for dose planning can help achieve local control of recurrent NPC.

• Journal of Trauma and Injury
• /
• v.20 no.1
• /
• pp.52-56
• /
• 2007

Marjolin's ulcer is a rare and often-aggressive cutaneous malignancy that arises in previously traumatized or chronically inflamed skin, particularly after burns. We experienced two cases after burns. Case I involved a forty eight year-old man who had suffered from a flame burn at the parietal scalp area, where had been initially described three years earlier as a full-thickness wound including the pericranium. The man consulted us for a persistent ulcerative and infected wound on the burned lesion during the last 24 months, which turned out on the contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) to be the squamous cell carcinoma with involving the skull and the dura mater. Although the posterior auricular lymph node was enlarged on the ipsilateral side, recent positron emission tomography (PET) CT did not show any metastatic lesion. It was impossible for us to resect the intracranial involvement of the tumor radically, and the postoperative PET CT still showed a focal fluorodeoxyglucose (FDG) uptake around the wall of the superior sagittal sinus. We think that an aggressive combined approach is essential for treatment in early stages for a high success rate, before the intracranial structures are involved because there is no consensus on the treatment for advanced disease, and the results are generally poor. Case 1 also did not involve a radical resection because of the intracranial invasion to the wall of superior sagittal sinus and the possibility of damage to the major cortical veins. He received adjuvant radiotherapy and must be followed periodically. Case 2 involved an eighty six year-old women who suffered from a painful scalp ulcer lesion after flame burns three years earlier. Unlike case 1, neither tumor infiltration into the dura nor lymph node enlargement was observed on the contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET) CT. We did a radical resection of the tumor, including the involved bone, and a cranioplasty with bone cement.