Article Figures & Data
Figures
- FIGURE 1.
(A) Phantom consisting of 2 types of hip prostheses in solution of 18F-FDG and water: a cobalt steel hip prosthesis and a Ti-Al-V hip prosthesis with ceramic head. Furthermore, phantom included 2 solid steel balls (2.5 and 3.8 cm in diameter). Phantom was scanned in mCT PET/CT scanner. Cold artifact caused by metal is present in standard PET reconstruction (B), whereas on iMAR PET reconstruction (C) these artifacts were not visible.
- FIGURE 2.
Patient with uptake in palatine tonsils (arrows in A) and 18F-FDG–avid lymph nodes (arrows in B). Metal artifacts are visible on standard PET/CT reconstruction (A), whereas iMAR PET/CT reconstruction (B) shows less distortion.
- FIGURE 3.
Patient with possible malignant cyst in right ovary, which was not interpretable due to metal artifacts. Effect of metal artifact on CT is also visible on PET. Region between both hip implants show lower activity for standard PET/CT (A and B), which is clearly visible in bladder, whereas iMAR PET/CT (C and D) shows image closer to true distribution of 18F-FDG.
- FIGURE 4.
Bland–Altman plots of ROI measurements, shown for HU measurements on CT (A) and SUVmean measurements for PET reconstructions (B). In the figure, difference between 2 measurements (standard − iMAR) is plotted against mean of these 2 measurements. Effect of algorithm not only is visible on CT image, but also influences PET image.
- FIGURE 5.
PET images of phantom when CT was misaligned by 3 mm (laterally in region of prosthetic femoral heads). (A) Normal, CT attenuation-based reconstruction. (B and C) One and 10 iterations of TOF-MLACF reconstruction.
Tables
Characteristic Value Sex Male 12 Female 9 Age (y) 65.4 ± 8.6 Weight (kg) 80.8 ± 21.4 Radiopharmaceutical 18F-FDG 14 68Ga-PSMA 7 Type of prosthesis Dental implants 6 Hip prostheses 12 Shoulder prostheses 1 Screws in vertebrae 2 Indication PET/CT scan Staging/detection of disease 16 Radiotherapy planning 1 Therapy response monitoring 4 Data are values, unless otherwise indicated.
- TABLE 2
Results of Scoring of PET/CT Images by Nuclear Medicine Physicians (Reader 1/Reader 2)
Questions Dental implant (n = 6) Hip implant, 18F-FDG (n = 5) Hip implant, 68Ga-PSMA (n = 7) Shoulder implant (n = 1) Vertebra screw (n = 2) When normal CT was used, did metal artifacts affect your interpretation of the PET/CT image in a negative way?* 5/6 4/5 6/7 0/1 0/1 When iMAR CT was used, did metal artifacts affect your interpretation of the PET/CT image in a negative way?* 0/0 0/0 0/0 0/0 0/1 Was iMAR helpful?* 5/6 5/5 7/7 1/1 0/1 Was NAC PET helpful?* 2/2 3/3 0/2 0/0 0/0 Did the visual interpretation indicate that PET and CT were well aligned or misaligned? Answered with well aligned. 6/4 5/3 7/7 1/1 2/2 How much confidence do you have in your interpretation of the PET/CT image? (scale, 0%–100%; improvement of [%]) 30/37 22/28 41/30 10/0 1/5 Did the diagnosis/staging of the disease change when the iMAR CT was used?* 1/0 2/1 1/1 0/0 0/0 When normal CT was used, were more diagnostic tools needed because of the metal artifacts?* 0/2 1/1 1/0 0/0 0/0 ↵* Answered with yes.
NAC = non–attenuation-corrected.
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