Introduction
Recent PET/CT systems have improved sensitivity and spatial resolution by smaller PET detectors and improved reconstruction software. In addition, continuous-bed-motion mode is now available in some PET systems for whole-body PET imaging. In this review, we describe the advantages of dynamic whole-body FDG-PET in oncology studies.
Methods
PET–CT imaging was obtained at 60 min after FDG administration. Dynamic whole-body imaging with continuous bed motion in 3 min each with flow motion was obtained over 400 oncology cases. For routine image analysis, these dynamic phases (usually four phases) were summed as early FDG imaging. The image quality of each serial dynamic imaging was visually evaluated. In addition, changes in FDG uptake were analyzed in consecutive dynamic imaging and also in early delayed (90 min after FDG administration) time point imaging (dual-time-point imaging; DTPI). Image interpretation was performed by consensus of two nuclear medicine physicians.
Result
All consecutive dynamic whole-body PET images of 3 min duration had acceptable image quality. Many of the areas with physiologically high FDG uptake had altered uptake on serial images. On the other hand, most of the benign and malignant lesions did not show visual changes on serial images. In the study of 60 patients with suspected colorectal cancer, unchanged uptake was noted in almost all regions with pathologically proved FDG uptake, indicating high sensitivity with high negative predictive value on both serial dynamic imaging and on DTPI. We proposed another application of serial dynamic imaging for minimizing motion artifacts for patients who may be likely to move during PET studies.
Discussion
Dynamic whole-body imaging has several advantages over the static imaging. Serial assessment of changes in FDG uptake over a short period of time is useful for distinguishing pathological from physiological uptake, especially in the abdominal regions. These dynamic PET studies may minimize the need for DPTI. In addition, continuous dynamic imaging has the potential to reduce motion artifacts in patients who are likely to move during PET imaging. Furthermore, kinetic analysis of the FDG distribution in tumor areas has a potential for precise tissue characterization.
Conclusion
Dynamic whole-body FDG-PET imaging permits assessment of serial FDG uptake change which is particularly useful for differentiation of pathological uptake from physiological uptake with high diagnostic accuracy. This imaging can be applied for minimizing motion artifacts. Wide clinical applications of such serial, dynamic whole-body PET imaging is expected in oncological studies in the near future.
A novel aerosol observation and sampling system using a combination of a balloon and a UAV is developed in order to retrieve observation apparatuses and aerosol samples easily at low cost. Observation apparatuses are installed on a motor-glider UAV named Phoenix, and the apparatuses conduct observation and sampling during ascent of the Phoenix suspended by a free balloon. The Phoenix is automatically separated from the balloon at a target altitude, returns to the ground station by gliding automatically, and it is retrieved with the use of a parachute. Four sets of this system were prepared and brought to Syowa Station which is one of the Japanese Antarctic Stations by the first-and the fourth-named authors as summer team members of the 54th Japanese Antarctic Research Expedition (JARE54) in December 2012. Five observation flights were conducted in January 2013 using Phoenix-03. Aerosol observation and sampling in the five flights were successfully performed up to 10,000 m in altitude. Details of the Phoenix and flight results are described in this paper.
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