Generally, FDG-PET/CT image is acquired at the 60th minute after tracer administration. Depending on the clinical case, additional delayed scans may be useful. However, it is difficult to judge whether additional delayed scan is useful or not. The purposes of this study were creation and evaluation of educational programs to help radiological technologists to decide the usefulness of additional delayed scan of FDG-PET/CT. Methods: Educational programs consisted of the instructional materials and the judgment test of clinical cases. The instructional materials provided the valuable findings for differentiation between uptake in the wall of the colon and colon content, distinction between uptake in the lymph node and urinary tract, and evaluation of malignancy. The judgment test of clinical cases consisted of 10 cases selected by a nuclear medicine physician (for 5 of that cases additional delayed scan was decided to be useful). Five experienced technologists and five inexperienced technologists scored the volubility of additional delayed scan pre- and post-training using the instructional materials (the full marks of score is 5). Results: After the educational programs using the instructional materials, the score was improved with the significant difference in both experienced (pre: 3.6±1.4, post: 4.0±1.2) and inexperienced (pre: 2.8±1.5, post: 3.7±1.5) groups (p<0.05). Conclusion: According to the educational programs, technologist might be able to decide whether the additional delayed scan is useful or not. The successful results of this study may improve the interpretation or reduce the total exposure dose of the PET/CT scan.

Purpose: CT perfusion (CTP) is a powerful tool for the assessment of cerebrovascular disease. However, CTP maps are significantly different depending on CTP software and algorithm, even when using identical image data. We developed a phase-ratio image map (PI map), which was a novel perfusion map, without using CTP software. The purpose of this study was to investigate the usefulness of the PI map by comparing it with a positron emission tomography (PET) image. Methods: Twenty patients (16 men, 4 women; mean age: 61.6 years) with unilateral cervical and intracranial steno-occlusive disease underwent CTP. CTP source images were obtained at 1-s intervals of 23 times and 5 intervals using dynamic multiphase imaging. An early-phase image was generated by computing the average of CT images for 5 s in the vicinity of the peak enhancement curve of a normal hemisphere. A delayed-phase image was generated by computing the average of CT images for 5 s immediately after the early phase. The PI map was created by dividing the delayed-phase image by the early-phase image. We investigated the validity of the PI map compared with PET-cerebral blood flow (CBF). Lesion-to-normal ratios between a PET-CBF and the PI map or two conventional CTP-CBFs were observed and compared, and the relative errors were also compared. Result: There was a strong correlation between the PET-CBF and the PI map (R=0.82). Correlations between the PET-CBF and two CTP-CBFs were weak (R=0.30) and middle (R=0.62), respectively. The relative error between the PI map and the PET-CBF was within 10% in most cases. Conclusion: The PI map was more similar to the PET-CBF on perfusion evaluation, and did not depend on CTP software. The robustness and simplicity of the PI mapping method would be advantageous compared with conventional CTP mapping methods.

Objective: The present study aimed to reveal the influence of combination of different collimators and energy windows on the planar sensitivity and the spatial resolution during experimental ²²³Ra imaging, and to determine optimal imaging parameters. Methods: A vial type source containing ²²³Ra solution (4.55 MBq / 5.6 ml) was placed in the air at 100 mm away from the collimator surface. Planar images were acquired with LEHR, LMEGP, ELEGP and MEGP collimators on two dual-head gamma cameras (Symbia intevo (Siemens) and Infinia 3 (GE)). We compared three energy window combinations: 1) single window at 82 keV, 2) double window at 82+154 keV, 3) triple window at 82+154+270 keV. The energy spectrum, the sensitivity and the spatial resolution, such as full-width at half-maximum (FWHM) and full-width at tenth-maximum (FWTM), of each collimator were assessed. Results: Five energy spectra (at around 82, 154, 270, 351 and 405 keV) were essentially observed among four collimators. The sensitivity was high for LEHR collimator, then ELEGP and LMEGP collimator was 3–4 fold, which is greater than MEGP collimator. The 82 keV energy window of four collimators has best spatial resolution. Moreover, the spatial resolution of the 82 keV energy window with LMEGP and ELEGP collimator was almost equal to that of the triple window with MEGP collimator. Conclusions: Optimal imaging parameters were single energy window using LMEGP or ELEGP, and then triple energy window using MEGP collimator.

Background: Invasive-fractional flow reserve (FFR) is the reference standard to evaluate functional ischemia of coronary arteries, and is used to decide if percutaneous transluminal coronary angioplasty is necessary. Recently, computed tomography-derived FFR (CT-FFR) is emerged as an alternative non-invasive method. Objectives: To evaluate the effect of reconstruction methods and image parameters on the accuracy of CT-FFR calculation. Methods: A total of 26 segments in the consecutive 10 coronary CT angiography (CCTA) studies were evaluated. All studies were reconstructed using three different techniques: 1) filtered back projection (FBP), 2) adaptive iterative dose reduction 3D (AIDR 3D), and 3) forward projected model-based iterative reconstruction solution (FIRST). Vessel segmentation was performed automatically by CT-FFR software, with manual adjustment if necessary. Calculated CT-FFR was compared with the invasive FFR data. Results: Compared to FBP, AIDR 3D and FIRST resulted in more successful automatic segmentation. When using FIRST, 7 segments (27%) were completed without manual adjustment. These segments had relatively larger vessel diameter, higher CT number, and lower noise. The difference between the calculated CT-FFR and invasive-FFR was 0.02±0.01. Among the remaining, 10 segments (38%) required manual adjustments of centerline, 7 segments (27%) required manual adjustments of contour, and 2 segments (8%) did not reach to the CT-FFR calculation. Conclusion: AIDR 3D and FIRST were useful for reliable automatic segmentation and analysis of CT-FFR.