Pilot Study for the Prediction of Response to Radiotherapy Using (18)FFluorothymidine PET in Nasopharyngeal Cancer: Comparison with (18)FFDG PET / 핵의학분자영상

PURPOSE: This study was performed to know whether [(18)F]Fluorothymidine (FLT) positron emission tomography (PET) can be used to monitor early response to radiotherapy in comparison with [(18)F]Fluorodeoxyglucose (FDG) PET, and to establish the optimal imaging time for prediction of therapy response. MATERIALS AND METHODS: Two patients with nasopharyngeal cancer underwent serial FLT PET and FDG PET before and during radiotherapy. Three on-treatment FLT and FDG PET scans were performed on 1 week, 2 weeks and 3 weeks (at each time of 10 Gy, 20 Gy and 30 Gy delivered). The peak standardized uptake values (SUV(peak)) of primary tumors were measured on FLT and FDG PET. Then, percent changes of SUV(peak) after therapy were calculated. RESULTS: In two patients, baseline values of SUV(peak) on FDT PET were higher than those on FLT PET (FLT vs FDG; 3.7 vs 5.0, and 5.7 vs 15.0). In patient 1, FLT SUV(peak) showed 78%, 78% and 84% of decrease on 1 week, 2 and 3 weeks after treatment, whereas FDG SUV(peak) showed 18%, 52% and 66% of decrease, respectively. In patient 2, FLT SUV(peak) showed 75%, 75% and 68% of decrease, whereas FDG SUV(peak) showed 51%, 49% and 58% of decrease, respectively. Both patients reached to complete remission after radiotherapy. CONCLUSION: After radiotherapy, the decrease of FLT tumor uptake preceded the decrease of FDG tumor uptake in patients with nasopharyngeal cancer, and 1 week after therapy may be appropriate time for the assessment of early response. FLT PET might be more useful than FDG PET for monitoring early response to radiotherapy.

Multimodality and Application Software / 핵의학분자영상

Medical imaging modalities to image either anatomical structure or functional processes have developed along somewhat independent paths. Functional images with single photon emission computed tomography (SPECT) and positron emission tomography (PET) are playing an increasingly important role in the diagnosis and staging of malignant disease, image-guided therapy planning, and treatment monitoring. SPECT and PET complement the more conventional anatomic imaging modalities of computed tomography (CT) and magnetic resonance (MR) imaging. When the functional imaging modality was combined with the anatomic imaging modality, the multimodality can help both identify and localize functional abnormalities. Combining PET with a high-resolution anatomical imaging modality such as CT can resolve the localization issue as long as the images from the two modalities are accurately coregistered. Software-based registration techniques have difficulty accounting for differences in patient positioning and involuntary movement of internal organs, often necessitating labor-intensive nonlinear mapping that may not converge to a satisfactory result. These challenges have recently been addressed by the introduction of the combined PET/CT scanner and SPECT/CT scanner, a hardware-oriented approach to image fusion. Combined PET/CT and SPECT/CT devices are playing an increasingly important role in the diagnosis and staging of human disease. The paper will review the development of multimodality instrumentations for clinical use from conception to present-day technology and the application software.

The Serial Change of Cerebral Hemodynamics by Vascular Territory after Extracranial-Intracranial Bypass Surgery in Patients with Atherosclerosis of Cerebral Arteries / 핵의학분자영상

PURPOSE: To assess the effect of extracranial-intracranial (EC-IC) bypass surgery on hemodynamic improvement, we evaluated serial regional cerebral hemodynamic change of the middle cerebral artery (MCA) in symptomatic patients with atherosclerotic occlusion of the internal carotid artery (ICA) or MCA using (99m)Tc-ECD acetazolamide stress brain perfusion SPECT (Acetazolamide SPECT). MATERIAL AND METHODS: The patients who had suffered a recent stroke with atherosclerotic ICA or MCA occlusion underwent EC-IC bypass surgery and Acetazolamide SPECT at 1 week before and three to six months after surgery. For image analysis, attenuation corrected images were spatially normalized to SPECT templates with SPM2. Anatomical automated labeling was applied to calculate mean counts of each Volume-Of-Interest (VOI). Seven VOIs of bilateral frontal, parietal, temporal regions of the MCA territory and the ipsilateral cerebellum were defined. Using mean counts of 7 VOIs, cerebral perfusion index and perfusion reserve index were calculated. RESULTS: Seventeen patients (M:F=12:5, mean age: 53+/-2yr) were finally included in the analysis. The cerebral blood flow of the parietal region increased at 1 week (p=0.003) and decreased to the preoperative level at 3-6 months (p=0.003). The cerebrovascular reserve of the frontal and parietal regions increased significantly at 1 week after surgery (p<0.01) and improved further at 3-6 months. CONCLUSION: Cerebrovascular reserve of the MCA territory was significantly improved at early postoperative period after EC-IC bypass and kept improved state during long-term follow-up, although cerebral blood flow did not significantly improved. Therefore, cerebrovascular reserve may be a good indicator of postoperative hemodynamic improvement resulted from bypass effect.

Prediction of Prognosis to Concurrent Chemo-Radiotherapy by Standardized Uptake Value of 2-18F Fluoro-2-Deoxy-D-Glucose for Nasopharyngeal Carcinomas / 대한방사선종양학회지

PURPOSE: To prospectively evaluate the use of positron emission tomography with the glucose analog fluorodeoxyglucose (FDG-PET) to predict disease-free survival (DFS) after concurrent chemo-radiotherapy (CCRT) in patients with non-disseminated nasopharyngeal carcinoma (NPC). MATERIASL AND METHODS: We studied 41 patients with non-disseminated NPC scheduled to undergo platinum- based CCRT were eligible for this study. Patients were studied by FDG-PET prior to the CCRT. FDG uptake of tumors were measured with the maximal standardized uptake value (SUV). RESULTS: Complete response rate was 100%. In ten patients who presented with any component of treatment failure, the median SUVmax was 8.55 (range: 2.49~14.81) in any component of failure and the median SUVmax was 6.48 (range: 2.31~26.07) in the remaining patients without any such failure. Patients having tumors with high FDG uptake had a significantly lower 3-year DFS (51% v 91%, P=0.0070) compared with patients having low uptake tumors. CONCLUSION: FDG uptake, as measured by the SUV, has potential value in predicting DFS in NPC treated by CCRT. High FDG uptake may be a useful parameter for identifying patients requiring more aggressive treatment approaches.

Change of FDG Uptake According to Radiation Dose on Squamous Cell Carcinoma of the Head and Neck / 대한방사선종양학회지

PURPOSE: To evaluate whether positron emission tomography (PET) with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) can be used to predict of early response to definitive aim radiotherapy (RT) in squamous cell carcinoma of the head and neck using response rate and locoregional control as study endpoints. MATERIALS AND MEHTODS: Twenty-two patients with head and neck cancer underwent a FDG-PET study before RT, after a first dose of 46 Gy, and after a second dose of more than 70 Gy. Standard uptake value (SUV) was calculated for primary tumor (n=22) and neck lymph node (n=10). Attenuation corrected PET scans acquired 60 min after tracer injection were used for evaluation of FDG uptake in tumors. A quantitative FDG uptake index was expressed as SUVlean (corrected for lean body mass). The follow-up time was at least 5 months (range 5-15 months). RESULTS: A total of 22 primary tumors and 10 metastatic lymph nodes were analyzed in FDG-PET. In the first PET study the mean SUV in the primary tumors and nodes were 6.4 (SD, 2.6) and 4.6 (SD, 2.3), respectively. In the second PET, study performed after 46 Gy RT the mean SUV in primary tumor and node decreased to 2.9 (SD, 1.9, p<0.001) and 1.7 (SD, 1.3) respectively. In the third PET study performed at the full dose (more than 70 Gy), RT the mean SUV in the primary tumors and nodes decreased to 2.3 (SD, 1.5, p<0.001) and 1.5 (SD, 1.1) respectively. CONCLUSION: FDG uptake in tumors showed a significant decrease after the 46 Gy and more than 70 Gy of RT for squamous cell carcinoma of the head and neck. Reduction of metabolic activity after 46 Gy of radiotherapy is closely correlated with radiation response.

Feasibility of Reflecting Improvement of Tumor Hypoxia by Mild Hyperthermia in Experimental Mouse Tumors with 18F-Fluoromisonidazole / 대한방사선종양학회지

PURPOSE: The aims of this study were to evaluate the change of [18F]fluoromisonidazole ([18F]FMISO) uptake in C3H mouse squamous cell carcinoma-VII (SCC-VII) treated with mild hyperthermia (42oC) and nicotinamide and to assess the biodistribution of the markers in normal tissues under similar conditions. METHODS AND MATERIALS: [18F]FMISO was producedby our hospital. Female C3H mice with a C3H SCC-VII tumor grown on their extremities were used. Tumors were size matched. Non-anaesthetized, tumor-bearing mice underwent control or mild hyperthermia at 42oC for 60 min with nicotinamide (50 mg/kg i.p. injected) and were examined by gamma counter, autoradiography and animal PET scan 3 hours after tracer i.v. injected with breathing room air. The biodistribution of these agents were obtained at 3 h after [18F]FMISO injection. Blood, tumor, muscle, heart, lung, liver, kidney, brain, bone, spleen, and intestine were removed, counted for radioactivity and weighed. The tumor and liver were frozen and cut with a cryomicrotome into 10-micrometer sections. The spatial distribution of radioactivity from the tissue sections was determined with digital autoradiography. RESULTS: The mild hyperthermia with nicotinamide treatment had only slight effects on the biodistribution of either marker in normal tissues. We observed that the whole tumor radioactivity uptake ratios were higher in the control mice than in the mild hyperthermia with nicotinamide treated mice for [18F]FMISO (1.56+/-1.03 vs. 0.67+/-0.30; p=0.063). In addition, autoradiography and animal PET scan demonstrated that the area and intensity of [18F]FMISO uptake was significantly decreased. CONCLUSION: Mild hyperthermia and nicotinamide significantly improved tumor hypoxia using [18F]FMISO and this uptake reflected tumor hypoxic status.

Investigation of the Signal Characteristics of a Small Gamma Camera System Using NaI(Tl)-Position Sensitive Photomultiplier Tube / 대한핵의학회잡지

PURPOSE: We characterized the signals obtained from the components of a small gamma camera using NaI(Tl)-position sensitive photomultiplier tube (PSPMT) and optimized the parameters employed in the modules of the system. MATERIALS AND METHODS: The small gamma camera system consists of a NaI(Tl) crystal (60x60x6 mm3) coupled with a Hamamatsu R3941 PSPMT, a resister chain circuit, preamplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a resistive charge division circuit which multiplexes the 34 cross wire anode channels into 4 signals (X+, X-, Y+, Y-). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic. The gamma camera control and image display was performed by a program implemented using a graphic software. RESULTS: The characteristics of signal and the parameters employed in each module of the system were presented. The intrinsic sensitivity of the system was approximately 8x103 counts/sec/microcurie. The intrinsic energy resolution of the system was 18% FWHM at 140 keV. The spatial resolution obtained using a line-slit mask and 99mTc point source were, respectively, 2.2 and 2.3 mm FWHM in X and Y directions. Breast phantom containing 2~7 mm diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view. CONCLUSION: We proposed a simple method for development of a small gamma camera and presented the characteristics of the signals from the system and the optimized parameters used in the modules of the small gamma camera.

Quantification of Myocardial Blood flow using Dynamic N-13 Ammonia PET and factor Analysis / 대한핵의학회잡지

PURPOSE: We evaluated the feasibility of extracting pure left ventricular blood pool and myocardial time-activity curves (TACs) and of generating factor images from human dynamic N-13 ammonia PET using factor analysis. The myocardial blood flow (MBF) estimates obtained with factor analysis were compared with those obtained with the user drawn region-of-interest (ROI) method. MATERIALS AND METHODS: Stress and rest N-13 ammonia cardiac PET imaging was acquired for 23 min in 5 patients with coronary artery disease using GE Advance tomograph. Factor analysis generated physiological TACs and factor images using the normalized TACs from each dixel. Four steps were involved in this algorithm: (a) data preprocessing; (b) principal component analysis; (c) oblique rotation with positivity constraints; (d) factor image computation. Area under curves and MBF estimated using the two compartment N-13 ammonia model were used to validate the accuracy of the factor analysis generated physiological TACs. The MBF estimated by factor analysis was compared to the values estimated by using the ROI method. RESULTS: MBF values obtained by factor analysis were linearly correlated with MBF obtained by the ROI method (slope=0.84, r=0.91). Left ventricular blood pool TACs obtained by the two methods agreed well (Area under curve ratio: 1.02 (0~1 min), 0.98 (0~2 min), 0.86 (1~2 min)). CONCLUSION:: The RESULTS of this study demonstrates that MBF can be measured accurately and noninvasively with dynamic N-13 ammonia PET imaging and factor analysis. This method is simple and accurate, and can measure MBF without blood sampling, ROI definition or spillover correction. KW: N-13 ammonia, PET, Myocardial blood flow, Factor analysis

Recent Developments in Nuclear Medicine Instrumentation / 대한핵의학회잡지

The goals of developments in nuclear medicine instrumentation are to offer a higher-quality image and to aid diagnosis, prognosis assessment or treatment planning and monitoring. It is necessary for physicists and engineers to improve or design new instrumentation and technique, and to implement, validate, and apply these new approaches in the practice of nuclear medicine. The researches in physical properties of detectors and crystal materials and advance in image analysis technology have improved quantitative and diagnostic accuracy of nuclear medicine images. This review article presents recent developments in nuclear medicine instrumentation, including scatter and attenuation correction, new detector technology, tomographic image reconstruction methods, 511 keV imaging, dual modality imaging device, small gamma camera, PET developments, image display and analysis methods.