Preliminary Study on Performance Evaluation of a Stacking-structure Compton Camera by Using Compton Imaging Simulator / 의학물리

A Compton camera, which is based on the geometrical interpretation of Compton scattering, is a very promising gamma-ray imaging device considering its several advantages over the conventional gamma-ray imaging devices: high imaging sensitivity, 3-D imaging capability from a fixed position, multi-tracing functionality, and almost no limitation in photon energy. In the present study, a Monte Carlo-based, user-friendly Compton imaging simulator was developed in the form of a graphical user interface (GUI) based on Geant4 and MATLAB (TM). The simulator was tested against the experimental result of the double-scattering Compton camera, which is under development at Hanyang University in Korea. The imaging resolution of the simulated Compton image well agreed with that of the measured image. The imaging sensitivity of the measured data was 2~3 times higher than that of the simulated data, which is due to the fact that the measured data contains the random coincidence events. The performance of a stacking-structure type Compton camera was evaluated by using the simulator. The result shows that the Compton camera shows its highest performance when it uses 4 layers of scatterer detectors.

A Comparative Study of Subset Construction Methods in OSEM Algorithms using Simulated Projection Data of Compton Camera / 핵의학분자영상

PURPOSE: In this study we propose a block-iterative method for reconstructing Compton scattered data. This study shows that the well-known expectation maximization (EM) approach along with its accelerated version based on the ordered subsets principle can be applied to the problem of image reconstruction for Compton camera. This study also compares several methods of constructing subsets for optimal performance of our algorithms. MATERIALS AND METHODS: Three reconstruction algorithms were implemented; simple backprojection (SBP), EM, and ordered subset EM (OSEM). For OSEM, the projection data were grouped into subsets in a predefined order. Three different schemes for choosing nonoverlapping subsets were considered; scatter angle-based subsets, detector position-based subsets, and both scatter angle- and detector position-based subsets. EM and OSEM with 16 subsets were performed with 64 and 4 iterations, respectively. The performance of each algorithm was evaluated in terms of computation time and normalized mean-squared error. RESULTS: Both EM and OSEM clearly outperformed SBP in all aspects of accuracy. The OSEM with 16 subsets and 4 iterations, which is equivalent to the standard EM with 64 iterations, was approximately 14 times faster in computation time than the standard EM. In OSEM, all of the three schemes for choosing subsets yielded similar results in computation time as well as normalized mean-squared error. CONCLUSION: Our results show that the OSEM algorithm, which have proven useful in emission tomography, can also be applied to the problem of image reconstruction for Compton camera. With properly chosen subset construction methods and moderate numbers of subsets, our OSEM algorithm significantly improves the computational efficiency while keeping the original quality of the standard EM reconstruction. The OSEM algorithm with scatter angle- and detector position-based subsets is most available.

ProMACE-CytaBOM Combination Chemotherapy in Stage II/III/IV Intermediate- and High-Grade Non-Hodgkin's Lymphoma / 대한혈액학회지

BACKGROUND: CHOP regimen is four-drug, first-generation combination chemotherapy that has been the standard treatment for patients with aggressive non-Hodgkin's lymphoma for the last 20 years. The second- and third-generation regimens have been developed in an attempt to improve the treatment outcome, but recent randomized studies failed to demonstrate an advantage of these regimens compare to the first-generation CHOP regimen. So, we performed clinical study of 8-drug combination chemotherapy, ProMACE-CytaBOM regimen for patients with non-Hodgkin's lymphoma to evaluate the response rate, overall survival, and toxicity. METHODS: Between November 1992 and Feb. 1997, previously untreated stage II/III/IV intermediate- and high-grade non-Hodgkin's lymphoma patients were treated with a ProMACE- CytaBOM regimen including cyclophosphamide 650 mg/m2 IV on day 1, adriamycin 25 mg/m2 IV on day 1, etoposide 120 mg/m2 IV on day 1, cytosine arabinoside 300 mg/m2 IV on day 8, bleomycin 5 mg/m2 IV on day 8, vincristine 1.4 mg/m2 IV on day 8, methotrexate 120 mg/m2 IV on day 8, and prednisone 60 mg/m2 PO on day 1 to day 14 with 3 weeks interval. RESULTS: Twenty eight patients (87.5%) were evaluable. Patient characteristics include: Median age 57.5 years (17-75) and 15 patients were 60 years or old; clinical stage II in 12 patients (37.5%), stage III in 7 patients (21.9%), and stage IV in 13 patients (40.6%). Objective response were 22 CR, 4 PR, 2 PD with 92.8% response rate. The complete response rate was associated with the International Prognostic Index (low risk 100%; low intermediate risk 70%; high and high intermediate risk 50%, P<0.05), but age did not influence the response rate. The median survival time was 23.6 months, and 1-year, 3-year, 5-year total survival and relapse-free survival rate were 75.0% 52.0% 34.7%, 84.4% 84.4% 54.3%, respectively. International Prognostic Index was correlated well with survival time (1-year 3-year 5-year survival : Low risk 91.7% 91.7% 91.7% vs low intermediate risk 80.0% 41.1% 27.4% vs high and high intermediate 33.3% 16.6% 0%, P< 0.005), however age was negatively associated with survival time (1-year 3-year 5-year survival : Below the 60 years 81.3% 75.0% 37.5% vs age greater than 60 years 66.7% 34.3% 22.9%, P<0.05). Grade 3/4 toxicities were anemia in 28.6%, neutropenia in 64.3%, thrombocytopenia in 14.3%, vomiting in 35.7%, oral mucositis in 14.3%, alopecia in 25.0%, increased AST in 3.6% and generation CHOP regimen, with higher treatment-related death due to infection. Therefore, ProMACE-CytaBOM combination chemotherapy is not routinely recommended to treat the patients with non-Hodgkin's lymphoma. CONCLUSION: These data indicate that IDA+BHAC induction chemotherapy seems to be comparable to other combinations for induction chemotherapy in AML. More longer follow-up period is needed for assessing the impact of BHAC-containing regimen on the outcome of autologous and allogeneic hematopoietic stem cell transplantation.

A Case of Congenital Corneal Staphyloma

A case of congenital corneal staphyloma was presented. This 4 year-old boy was premature born and received oxygen in theLincubator during one month after birth. He showed mental retardation, articulation disturbance and gait disturbance. The right eye was free from any anomaly. The left eye was undergone enucleation for cosmetic improvement because of corneal opacity at birth. A detailed histologic examination of the congenital corneal staphyloma was given; epidermidialization of the corneal epithelium, scarring and vascularization of the stroma, with an absence of Bowman's membrane were shown. Descemet-endotheliallayer was completely defective in keratoiridic and corneal-abnormal pigment layer adhesions, but found in the seperated portion between cornea and iris. Iris root was not found in normal position. An abnormal pigment epithelial layer from ciliary epithelium was covered the surface of trabecular meshwork(anterior chamber angle) and an abnormal pigmentation of the trabecular meshwork poorly developed, which was running on iris pigment epithelium and covering inner surface of the cornea. The ciliary body, especially the process was atrophic. The lens was thin membranous and cataractous. Abnormal fibrinous band in the retinal capillary bed was argyrophilic strand. It was suggested that these findings of anterior corneal staphyloma was resulted from primary developmental anomaly of mesodermal and/or neuroectodermal tissue.