Ehab M. Kamel

Head and neck imaging with PET and PET/CT: artefacts from dental metallic implants

Abstract. Germanium-68 based attenuation correction (PETGe68) is performed in positron emission tomography (PET) imaging for quantitative measurements. With the recent introduction of combined in-line PET/CT scanners, CT data can be used for attenuation correction. Since dental implants can cause artefacts in CT images, CT-based attenuation correction (PETCT) may induce artefacts in PET images. The purpose of this study was to evaluate the influence of dental metallic artwork on the quality of PET images by comparing non-corrected images and images attenuation corrected by PETGe68 and PETCT. Imaging was performed on a novel in-line PET/CT system using a 40-mAs scan for PETCT in 41 consecutive patients with high suspicion of malignant or inflammatory disease. In 17 patients, additional PETGe68 images were acquired in the same imaging session. Visual analysis of fluorine-18 fluorodeoxyglucose (FDG) distribution in several regions of the head and neck was scored on a 4-point scale in comparison with normal grey matter of the brain in the corresponding PET images. In addition, artefacts adjacent to dental metallic artwork were evaluated. A significant difference in image quality scoring was found only for the lips and the tip of the nose, which appeared darker on non-corrected than on corrected PET images. In 33 patients, artefacts were seen on CT, and in 28 of these patients, artefacts were also seen on PET imaging. In eight patients without implants, artefacts were seen neither on CT nor on PET images. Direct comparison of PETGe68 and PETCT images showed a different appearance of artefacts in 3 of 17 patients. Malignant lesions were equally well visible using both transmission correction methods. Dental implants, non-removable bridgework etc. can cause artefacts in attenuation-corrected images using either a conventional 68Ge transmission source or the CT scan obtained with a combined PET/CT camera. We recommend that the non-attenuation-corrected PET images also be evaluated in patients undergoing PET of the head and neck.

[18F]-fluorodeoxyglucose positron emission tomography in patients with suspected recurrence of breast cancer

AimTo evaluate the role of [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) in patients presenting with a suspicion of breast cancer relapse after primary treatment.Materials and methodsSixty consecutive female patients with clinical (n=35) or radiological (n=25) suspicion of breast cancer recurrence were evaluated by FDG-PET. Positive PET findings were further evaluated by histological examination or clinical and radiological follow-up. In 25 patients, the serum tumor marker (CA 15-3) status was compared to the PET results.ResultsDisease relapse was proven in 40 patients. Additionally, in three patients a second cancer was diagnosed with (n=1), and without (n=2) concomitant disease relapse. PET missed local recurrence in three patients, and was false positive in another four. In patient-based analysis, the overall sensitivity, specificity, and accuracy were 89%, 84%, and 87%, and 100%, 97%, and 98% for locoregional recurrence and distant metastases, respectively. FDG-PET was more sensitive than the serum tumor marker CA 15-3 in detecting relapsed breast cancer.ConclusionFDG-PET is a valuable tool in the follow-up of patients with breast cancer.

Computed tomographic angiography in acute pulmonary embolism: do we need multiplanar reconstructions to evaluate the right ventricular dysfunction?

Purpose: To compare the indices of right ventricular dysfunction (RVD) obtained from axial transverse images with those derived from the reconstructed 4-chamber and short-axis views in patients with acute pulmonary embolism (PE). Materials and Methods: Eighty-eight patients with acute PE were retrospectively enrolled. For each patient, axial transverse images and reconstructed 4-chamber and short-axis views were reviewed. Measurements of the ratios of right ventricle to left ventricle (RV/LV) diameters and RV/LV areas were then obtained from all series. Values derived from each method were compared and correlated to arterial obstruction index. Results: In the studied cohort, RV/LV diameters and RV/LV areas obtained from axial transverse images and the reconstructed 4-chamber views were not statistically different. In contrast, a statistically significant difference was observed between the values of RV/LV areas derived from both axial transverse and 4-chamber views and those obtained from short-axis views (P < 0.0001). There was a weak to moderate correlation between both RV/LV diameters and RV/LV areas and the computed tomographic obstruction index. However, when the study cohort was divided into 3 subgroups with an arterial obstruction index of less than 15% (n = 26), 15% to 30% (n = 21), and greater than 30% (n = 41), those who had values greater than 30% revealed the highest correlation with the indices of RVD. Conclusions: In patients with acute PE, the indices of RVD derived from axial transverse images and the reconstructed 4-chamber views yield comparative values. Given the simplicity of the former analysis, it should be taken into consideration for risk stratification in acute PE.

The value of FDG-PET in patients with painful total knee arthroplasty

PurposeThe purpose of this study was to evaluate 18F-fluorodeoxyglucose (FDG) uptake in patients with painful total knee arthroplasty and to relate FDG uptake to the location of soft tissue pain.MethodsTwenty-eight patients with painful total knee arthroplasty had a clinical examination, standard radiographs, CT measurement of rotation of the femoral component and FDG-PET (18 PET/CT, 10 PET). The diagnosis of infection was based on microbiological examinations of surgical specimens (n=12) or clinical follow-up for at least 6 months (n=16), 99mTc-labelled monoclonal antibody scintigraphy and joint aspiration.ResultsTwenty-seven of 28 patients presented with diffuse synovial FDG uptake. Additional focal extrasynovial FDG uptake was observed in 19 knees. Twenty-four of the 28 patients had a diagnosis of internal femoral malrotation. The remaining four patients showed no rotation (0°) and 3°, 4° and 7° of external rotation, respectively. Three patients presented with the additional diagnosis of an infected total knee replacement. Pain was described as diffuse (n=10) or focal (n=18). In two knees a relationship between pain location and FDG uptake was observed. Of ten patients with a severe internal femoral component rotation (>6°), seven had focal uptake, four in the femoral periosteum and three in the tibial periosteum. The difference between knees with severe malrotation and the remaining knees was not significant (p=1.000, Fishers Exact Test).ConclusionDiffuse synovial and focal extrasynovial FDG-PET uptake is commonly found in patients with malrotation of the femoral component and is not related to pain location. The information provided by FDG-PET does not contribute to the diagnosis and management of individual patients with persistent pain after total knee replacement.