JOURNAL CLUB: CT Dose Optimization for Whole-Body PET/CT Examinations

Abstract

OBJECTIVE. The objective of this study was to optimize CT protocols for whole-body PET/CT by reducing radiation dose while minimizing effects on image quality. MATERIALS AND METHODS. Before protocol optimization, a survey of 140 consecutive patients was conducted to establish the baseline dose from a whole-body PET/CT examination. Another sample of 100 patients was surveyed to evaluate the reduction of radiation dose after implementation of the new protocol. Effective dose from the CT component of the examination was estimated using dose-length product (DLP) values from reports generated by the scanner and anatomy-specific conversion factors. Twenty-six patients who underwent studies before and after the optimization were included in an analysis of image quality. All 26 patients had maintained the same weight between the examinations and were scanned in the same position using a similar technique except for the changes made for CT dose optimization. The studies were randomized and blinded for an experienced PET and CT reader who graded the imaging quality of anatomic structures. RESULTS. CT protocol optimization resulted in a 32% reduction of the mean CT radiation dose: The mean effective dose was reduced from 8.1 to 5.5 mSv. The blinded analysis of image quality showed no clinically significant degradation of the lower-dose studies. The only structures visualized statistically better on the higher-dose CT scans were the carotid arteries and the region of the posterior triangle. CONCLUSION. The results of this study showed that optimization of CT acquisition can effectively reduce radiation dose in a whole-body PET/CT examination without significantly sacrificing image quality.

Methods of CT Dose Estimation in Whole-Body 18F-FDG PET/CT

“…ED derived from the CT component of whole-body PET/CT varies widely, from 5 to 25 mSv, among PET facilities (2)(3)(4)(5)(6)(7)(8). Mean whole-body ED in all 80 patients was 4.61 mSv, indicating relatively low dose, in this study.…”

“…The problem of CT acquisition additional to PET is an increase in radiation exposure. The effective dose (ED) derived from the CT component varies widely from 5 to 25 mSv (2)(3)(4)(5)(6)(7)(8) and often exceeds the ED from 18 F-FDG injection. Although a large amount of radiation exposure is required to acquire highquality CT images for diagnostic purposes, lesion localization and attenuation correction can be achieved on CT images of lower quality.…”

“…ED of the CT component of wholebody PET/CT may be calculated as a product of the scanner-derived whole-body DLP value and a conversion factor for the trunk (6,8). This method is convenient but neglects regional differences in calculating CTDIvol and in determining the conversion factor from DLP to ED.…”

In vivo evaluation of PEGylated 64Cu-liposomes with theranostic and radiotherapeutic potential using micro PET/CT

“…In PET/CT scanning procedures, the effective dose is a combination of the dose from the PET and the dose from the CT. Therefore in addition to the radiation dose from the decaying 64 Cu radionuclide, the dose from a whole-body CT scanning should be added to the total effective dose, and is normally estimated to be less than 10 mSv [31,32]. A total effective dose less than 20 mSv per patient (both CT and PET) therefore predicts that a start administration activity of 200 MBq of 64 Culiposomes should be acceptable in a clinical study.…”

Diagnostic Reference Levels of CT Radiation Dose in Whole-Body PET/CT

“…But estimates of PET/CT effective dose are variable and critically depend on an institution's specific CT technique and activity administration protocol (14). In general, the CT component of a PET/CT examination can contribute more than 50% of the total-examination effective dose (10)(11)(12)(13).…”