18
F-fluorodeoxyglucose (
18
F-FDG) positron emission tomography/computed tomography (CT) is an important tool widely used in the oncology to stage and restage various malignancies. Intense focal FDG uptake in the lung parenchyma associated with the absence of anatomical lesion detected on CT can be explained by a lung microembolism, known as hot-clot artifact. We report, to the best of our knowledge, the first case describing a single hot-clot artifact located in the same lung as a histologically proven non-small cell lung cancer.
Background Conventional imaging is useful to assess interbody fusion by showing complete trabecular bony bridging, but has a low positive predictive value for pseudarthrosis. Because alterations of bone metabolism may precede structural anatomical changes on computed tomography (CT), we aimed to investigate the ability of fluorine 18 sodium fluoride positron emission tomography/computed tomography (18F-NaF PET/CT) to identify pseudarthrosis after spinal fusion using surgical revision as the reference standard.
Methods We retrospectively reviewed 18F-NaF PET/CT scans performed between February 2019 and September 2020 in patients experiencing pain after spinal fusion. We included the 18 patients who underwent revision surgery for suspicion of pseudarthrosis. Five consecutive patients who were clearly fused on CT served as the control group.
Results In the revision surgery group (n=18), visual assessment by 18F-NaF PET/CT revealed that all 22 cages with an increased 18F-NaF uptake around intercorporal fusion material had mobility at revision surgery, whereas none of the fused patients (n=5) showed uptake around cage/intervertebral disk space. Among the 18 patients with presumed aseptic pseudarthrosis, intraoperative cultures revealed surgical site infection (SSI) caused by Cutibacterium acnes (C. acnes) in seven patients (38.9%). There was a statistically significant difference in standardized uptake values and uptake ratios between the revision surgery and control groups (p=5.3× 10−6 and p=0.0002, respectively).
Conclusions 18F-NaF PET/CT imaging appeared as a useful tool to identify pseudarthrosis following spinal fusion. The unexpectedly high prevalence (38.9%) of SSI caused by C. acnes found in presumed aseptic patients supports the utility of intraoperative cultures in revision cases for pseudarthrosis, even without preoperative clinical suspicion of SSI.
Case presentationA 66-year-old man with a history of aortic aneurysm, treated 5 years before by endovascular aneurysm repair (EVAR), underwent a follow-up CT angiography showing an increased aneurysm size to 64 mm, a proximal endoleak, and an inflammatory thickening of the aneurysm wall. The patient did not have fever or abdominal pain. Laboratory tests showed a normal blood count, a slightly elevated C-reactive protein and a normal procalcitonin.
A 75-year-old man presented with Staphylococcus aureus bacteremia, fever, and right posterior knee pain. Venous Doppler ultrasound of the lower extremity showed an isolated right calf muscle vein thrombosis, without any sign of deep vein thrombosis. 18F-FDG PET/CT revealed an intense focal uptake on the right popliteal artery, suggesting a mycotic aneurysm (MA). Lower limb CT angiography confirmed an MA of the right popliteal artery. The patient underwent surgical procedure with excision of the MA, whose cultures grew methicillin-sensitive S. aureus. Our case highlights the importance of including lower limbs in 18F-FDG PET/CT acquisition in case of suspicion of septic emboli.
An 84-year-old man was referred for the evaluation of a suspected gastrointestinal neoplasia. 18F-FDG PET/CT scan was performed showing, in addition to the physiological myocardial FDG uptake in the left ventricular wall, an unusual diffuse FDG uptake of the bilateral atrial walls. During his visit to the nuclear medicine unit, the patient became unwell, and an ECG was performed, suggestive of an atrioventricular nodal re-entrant tachycardia. Our case highlights the importance of including supraventricular arrhythmia such as atrioventricular nodal re-entrant tachycardia in the differential diagnosis of atrial FDG uptake.
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