SUBOPTIMAL MODULATION OF RADIATION DOSE IN THE COMPUTED TOMOGRAPHY COMPONENT OF WHOLE-BODY POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY

2020 ◽  
Vol 192 (1) ◽  
pp. 69-74
Author(s):  
Yusuke Inoue ◽  
Mizuho Adachi ◽  
Hirokazu Shimizu ◽  
Kazunori Nagahara ◽  
Hiroyasu Itoh ◽  
...  

Abstract Radiation exposure in computed tomography (CT) is automatically modulated by automatic exposure control (AEC) mainly based on scout images. To simulate the whole-body positron emission tomography/CT, CT images of a phantom were obtained using the posteroanterior scout image alone (PA scout) or the posteroanterior and lateral images (PA + Lat scout). Old and new versions of the AEC software were compared. Using the old version of the software and the PA scout, a markedly high dose at the top of the head was observed, which varied depending on the position of the phantom. This issue was resolved in the new version of the software. Radiation dose in the shoulder region was much higher using the PA scout than using the PA + Lat scout, even with the new version of the software. AEC may cause unreasonably high radiation exposure locally, and the appropriateness of the dose modulation pattern should be examined at each facility.

2018 ◽  
Vol 185 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Yusuke Inoue ◽  
Kazunori Nagahara ◽  
Hiroko Kudo ◽  
Hiroyasu Itoh

Abstract We performed phantom experiments to investigate radiation dose in the computed tomography component of oncology positron emission tomography/computed tomography in relation to the scan range. Computed tomography images of an anthropomorphic whole-body phantom were obtained from the head top to the feet, from the head top to the proximal thigh or from the skull base to the proximal thigh. Automatic exposure control using the posteroanterior and lateral scout images offered reasonable tube current modulation corresponding to the body thickness. However, when the posteroanterior scout alone was used, unexpectedly high current was applied in the head and upper chest. When effective dose was calculated on a region-by-region basis, it did not differ greatly irrespective of the scan range. In contrary, when effective dose was estimated simply by multiplying the scanner-derived dose-length product by a single conversion factor, estimates increased definitely with the scan range, indicating severe overestimation in whole-body imaging.


2021 ◽  
Vol 5 (1) ◽  
pp. 1151-1160
Author(s):  
A.S. Lukashevich ◽  

Purpose. The purpose of the article is to evaluate the diagnostic significance of positron emission tomography / computed tomography with 18F -fluorodeoxyglucose (18F -FDG PET/CT) for the diagnosis of prosthetic endocarditis. Methods of research. The study included 82 patients with suspected prosthetic endocarditis in accordance with the criteria proposed by Duke University [1-5]. The patients received hospital treatment at the State Institution RSPC "Cardiology" from January 2016 to March 2021. The study was of a prospective, non-randomized, single-center cohort design. The duration of the monitor period was 12 months from the moment of patients’ inclusion in the study. Whole-body positron emission tomography / computed tomography (PET/CT) examinations were performed in 82 patients. 27 patients were selected for surgical treatment. Conservative treatment group included 16 patients. 27 patients were selected into the observation group, they were suspected to have prosthetic heart valve infection in the primary referral and underwent PET/CT scanning, according to which the diagnosis of prosthetic endocarditis was excluded. The event under the study did not develop in this group during the year of observation. Results and conclusion. The history of infective endocarditis was not statistically significant and did not increase the risk of developing prosthetic endocarditis in the sample presented. The Duke criteria are less reliable in establishing the diagnosis of prosthetic endocarditis. The median number of days from the date of the first prosthesis implantation to the onset of prosthetic endocarditis was about 4 years. This study revealed that the development of the infectious process in the area of the prosthesis was noted in a more distant postoperative period compared to literature data. Histological confirmation of infection was noted in 100% (27 patients) of cases in reoperated patients. The presence of a more formidable complication such as valve ring abscess located mainly in the projection of the aortic valve ring was quite common in both groups. Presepsin and Interleukin-6 have a statistically significant (U = 394,50 p = 0,01 and U = 94,50 p = 0.004) value in the prognosis of prosthetic endocarditis. Considering the data obtained from ROC analysis, it can be said that the cut-off point at which it is possible to diagnose prosthetic endocarditis based on PETCT is 2.85. The presented methods for the interpretation of whole-body FDG-PET/CT images of patients with suspected infectious complications after cardiac surgery, as well as with the presence of prosthetic endocarditis, show high sensitivity and specificity.


Dose-Response ◽  
2020 ◽  
Vol 18 (3) ◽  
pp. 155932582093828
Author(s):  
Weiguo Li ◽  
Lianying Fang ◽  
Jieqing Li

Objective: The aim of this study was to measure occupational exposure doses of technologists who dispense and inject radiopharmaceuticals in 7 positron emission tomography/computed tomography (PET/CT) departments. This was done with the goal to help improving protective designs in PET departments and/or establishing national protection standards. Method: Common LiF thermoluminescence dosimeters (TLDs) were placed on the chest and necklace of the technologists to monitor whole-body and thyroid doses, respectively. Ring TLDs were also worn on both index fingers to measure individual hand doses. All TLDs were assembled and measured once every 3 months for a total of 12 months. Additionally, we measured and compared the dose of TLDs attached to both the inside and the outside of the technologist’s lead coat. Results: Technologists received relatively high exposures, which accounted for 64% to 94% of the collective dose in their respective departments. Their thyroid doses ranged from 1.2 to 1.7 mSv/a; some technologists’ hand doses exceeded 500 mSv/a. Use of a lead coat reduced the average dose by 8%. Conclusion: Technologists working in PET/CT departments were the main population exposed to radiation. This work underscores the need for enhanced protective measures for these workers to better reduce their exposure, particularly for their hands.


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