ABSTRACT
In order to evaluate the effect of post-reconstruction Gaussian filtering on image quality and myocardial blood flow [MBF] measurement by dynamic N-13 ammonia positron emission tomography [PET], we compared various reconstruction and filtering methods with image characteristics. Dynamic PET images of three patients with coronary artery disease [male-female ratio of 2:1; age: 57, 53, and 76 years] were reconstructed, using filtered back projection [FBP] and ordered subset expectation maximization [OSEM] methods. OSEM reconstruction consisted of OSEM_2I, OSEM_4I, and OSEM_6I with 2, 4, and 6 iterations, respectively. The images, reconstructed and filtered by Gaussian filters of 5, 10, and 15 mm, were obtained, as well as non-filtered images. Visual analysis of image quality [IQ] was performed using a 3-grade scoring system by 2 independent readers, blinded to the reconstruction and filtering methods of stress images. Then, signal-to-noise ratio [SNR] was calculated by noise and contrast recovery [CR]. Stress and rest MBF and coronary flow reserve [CFR] were obtained for each method. IQ scores, stress and rest MBF, and CFR were compared between the methods, using Chi-square and Kruskal-Wallis tests. In the visual analysis, IQ was significantly higher by 10 mm Gaussian filtering, compared to other sizes of filter [P<0.001 for both reader]. However, no significant difference of IQ was found between FBP and various numbers of iteration in OSEM [P=0.923 and 0.855 for readers 1 and 2 respectively]. SNR was significantly higher in 10 mm Gaussian filter. There was a significant difference in stress and rest MBF between several vascular territories. However CFR was not significantly different according to various filtering methods. Post-reconstruction Gaussian filtering with a filter size of 10 mm significantly enhances the IQ of N-13 ammonia PET-CT, without changing the results of CFR calculation
Subject(s)
Humans , Male , Female , Myocardium , Blood Flow Velocity , Image Enhancement , Normal Distribution , Ammonia , Positron-Emission TomographyABSTRACT
OBJECTIVE: To evaluate the efficacy of temozolomide (TMZ) chemotherapy for recurrent anaplastic oligodendroglioma (AO) and anaplastic oligoastrocytoma (AOA). METHODS: A multi-center retrospective trial enrolled seventy-two patients with histologically proven AO/AOA who underwent TMZ chemotherapy for their recurrent tumors from 2006 to 2010. TMZ was administered orally (150 to 200 mg/m2/day) for 5 days per 28 days until unacceptable toxicity occurred or tumor progression was observed. RESULTS: TMZ chemotherapy cycles administered was median 5.3 (range, 1-41). The objective response rate was 24% including 8 cases (11%) of complete response and another 23 patients (32%) were remained as stable disease. Severe side effects (> or =grade 3) occurred only in 9 patients (13%). Progression-free survival (PFS) of all patients was a median 8.0 months (95% confidence interval, 6.0-10.0). The time to recurrence of a year or after was a favorable prognostic factor for PFS (p<0.05). Overall survival (OS) was apparently differed by the patient's histology, as AOA patients survived a median OS of 18.0 months while AO patients did not reach median OS at median follow-up of 11.5 months (range 2.7-65 months). Good performance status of Eastern Cooperative Oncology Group 0 and 1 showed prolonged OS (p<0.01). CONCLUSION: For recurrent AO/AOA after surgery followed by radiation therapy, TMZ could be recommended as a salvage therapy at the estimated efficacy equal to procarbazine, lomustine, and vincristine (PCV) chemotherapy at first relapse. For patients previously treated with PCV, TMZ is a favorable therapeutic option as 2nd line salvage chemotherapy with an acceptable toxicity rate.