Parotid incidentaloma identified by positron emission/computed tomography: when to consider diagnoses other than warthin tumor

Introduction Parotid gland incidentalomas (PGIs) are unexpected hypermetabolic foci in the parotid region that can be found when scanning with whole-body positron emission/computed tomography (PET/CT). These deposits are most commonly due to benign lesions such as Warthin tumor.

Objective The aim of this study was to determine the prevalence of PGIs identified in PET/CT scans and to assess the role of smoking in their etiology.

Methods We retrospectively reviewed all PET/CT scans performed at our center in search of PGIs and identified smoking status and standardized uptake value (SUVmax) in each case. We also analyzed the database of parotidectomies performed in our department in the previous 10 years and focused on the pathologic diagnosis and the presence or absence of smoking in each case.

Results Sixteen cases of PGIs were found in 4,250 PET/CT scans, accounting for 0.4%. The average SUVmax was 6.5 (range 2.8 to 16). Cytology was performed in five patients; it was benign in four cases and inconclusive in one case. Thirteen patients had a history of smoking. Of the parotidectomies performed in our center with a diagnosis of Warthin tumor, we identified a history of smoking in 93.8% of those patients.

Conclusions The prevalence of PGIs on PET/CT was similar to that reported by other authors. Warthin tumor is frequently diagnosed among PGIs on PET/CT, and it has a strong relationship with smoking. We suggest that a diagnosis other than Warthin tumor should be considered for PGIs in nonsmokers.

Aortic 18F-FDG PET/CT uptake pattern at 60 min (early) and 180 min (delayed) acquisition in a control population: a visual and semiquantitative comparative analysis

18F-Fluoro-2-deoxy-D-glucose (F-FDG) PET/CT acquisition is generally performed 60 min after injection. The normal biodistribution pattern of F-FDG includes activity in the aortic territory due to blood pool activity, which could interfere in the diagnosis of aortic diseases by overlapping the wall uptake. The aim of the study was to evaluate the change over time of F-FDG uptake by the aortic wall and the activity in the lumen in a control population and to establish normal reference values. This prospective study included 15 control patients (mean age: 58.2 years). PET/CT was acquired 60 min (early scan) and 180 min (delayed scan) after an F-FDG injection at a dose of 7 MBq/kg. A visual and semiquantitative analysis of the F-FDG aortic wall uptake was carried out, and lumen activity and the aortic wall to lumen ratio [target-to-background ratio (TBR)] were determined. In the visual analysis all patients showed F-FDG activity at the aortic territory at 60 and 180 min. The pattern of uptake at 60 min was diffuse in all 15 patients (100%), without delineation of the aortic wall uptake; however, at 180 min the uptake pattern of the aortic wall changed to lineal in 14 patients (93.3%). The aortic wall maximum standardized uptake value decreased from 2.07±0.34 to 1.7±0.46 during the delayed acquisition (P=0.0279) and the lumen maximum standardized uptake value decreased highly significantly (1.99±0.35 vs. 1.36±0.32, P=0.0001). Therefore, TBR also increased highly significantly from 1.04±0.06 to 1.25±0.16 (P<0.0001). The high decrease in blood pool activity from 60 to 180 min provides a better delineation of the aortic wall uptake, which corresponds to the normal pattern at that time. The TBR increased significantly at 180 min, and 1.25±0.16 is suggested as the threshold for diagnostic purposes, especially for the diagnosis of vasculitis.

[Findings of the (18)F-FDG PET-CT in a cardiac angiosarcoma complicated by a cardiac rupture]

Primary malignant tumors of the heart are a rare condition. The most common type is the cardiac angiosarcoma. The symptoms of this disease are very nonspecific and can be very difficult to diagnose by conventional imaging techniques. We report the case of a male patient with cardiac angiosarcoma who also had a rare complication, this being cardiac rupture, which required the use of (18)F-FDG PET-CT to demonstrate the mass malignancy and to reach a definitive diagnosis.

[Thymic uptake of 18FFDG following radioiodine ablation therapy]

We report the case of a 47 year-old woman with a history of non-Hodgkin's lymphoma. During the course of her disease, we performed various (18F)FDG PET/CT that identified several significant incidental findings. First, we incidentally identified a hypermetabolic nodule in the left thyroid lobe, whose final diagnosis was differentiated thyroid carcinoma. Second, metabolic activity was visualized in the thymus secondary to ablative treatment with radioiodine. This uptake disappeared in subsequent studies. Several papers have reported thymic rebound following chemotherapy but we have found only one case report of (18F)FDG uptake after radioiodine treatment. On the other hand, this case is of interest because it supports the benefit of studying the hypermetabolic thyroid nodules incidentally detected on the PET/CT performed for other reasons.

[Incidence of focal myocardial (18)F-FDG uptake and correlation with coronary calcifications by PET/CT]

OBJECTIVE

To evaluate the incidence of (18)F-FDG focal uptake in the myocardium as well as its correlation with coronary vessel calcifications.

MATERIAL AND METHODS

A total of 130 patients who underwent an oncological PET/CT study were reviewed retrospectively. Sixty-five had undergone a myocardial perfusion study because of clinical suspicion of coronary artery disease (group 1). There were no significant differences in age and gender regarding another group of the same series (n=65; group 2). Focal myocardial (18)F-FDG uptake and the presence of coronary vessel calcifications were identified by 2 independent observers.

RESULTS

Group 1: in 18 out of 65 patients (28%) focal myocardial (18)F-FDG uptake was identified (5 had 2 foci; total: 23 foci). In 43 out of 65 studies (66%), calcification was identified in the coronary vessels. Group 2: in 6 out of 65 patients (9%) focal myocardial (18)F-FDG uptake was identified (1 had 2 foci; total: 7 foci). In 17 out of 65 studies (26%), calcification was identified in the coronary vessels. Comparative analysis: focal myocardial (18)F-FDG uptake and coronary vessel calcifications were more frequent in the group 1 patients (p<0.01). There was no correlation between the presence of coronary vessel calcifications and focal myocardial (18)F-FDG uptake in individual patients in both groups (group 1: p=0.7; group 2: p=0.163).

CONCLUSIONS

PET/CT allows simultaneous assessment of focal myocardial (18)F-FDG uptake and myocardial vessel calcifications. Patients with clinical suspicion of coronary artery disease have a higher incidence of focal myocardial (18)F-FDG uptake and coronary calcifications. However, (18)F-FDG focal uptake is often observed in sites remote from those with calcification.

[Utility of PET-CT on radiotherapy planning of head and neck cancer. Our initial experience]

OBJECTIVE

To describe the methods used for the incorporation of FDG-PET-CT on radiotherapy planning of patients with head and neck cancer and also to evaluate the impact of FDG-PET-CT on staging and tumor volume definition.

MATERIAL AND METHODS

A prospective study in which 20 patients with head and neck tumor submitted for radiotherapy treatment were included. All underwent a whole body PET- CT (GE DSTE 16) for staging and restaging, also acquiring an additional 3h delayed PET image with diagnostic CT parameters for planning. A CT scan with diagnostic protocol, tabletop available for radiotherapy treatment and the same personalized head-shoulder mask were used in the latter. Lymph node involvement and/or distant involvement were evaluated, considering the changes in staging. We also evaluated the differences in volumes obtained between the different techniques. The threshold value used for delineating PET gross tumor volume (GTV) was empirically established and ranged from 20-40% of the maximum SUV.

RESULTS

Radiotherapy planning was performed with PET-CT in 20 patients between October 2007 to September 2008. A total of 29 lesions (18 primary lesions because 2 patients were excluded as no tumor was observed on the PET CT images, and 11 nodes). The most frequent location was oropharynx (5 patients). Mean maxSUV of the 29 lesions was 14.4 (range 5.0 and 26.4). No statistically significant differences were found between the GTV PET and GTV CT (mean 21.9cm³ and 19.3cm³, respectively). PET-CT modified the staging in 20% of the patients, with a diagnostic and therapeutic impact of 50 and 25%, respectively.

CONCLUSION

The incorporation of PET-CT in routine radiotherapy planning is a promising technique that requires close collaboration between the nuclear medicine and radiotherapy oncology departments. PET-CT achieves better staging in patients and has a significant diagnostic and therapeutic impact. The use of the hybrid technique avoids problems arising from co-registry as well as a second examination for planning with the consequent advantage for the patient. Nonetheless, more prospective and randomized studies with pathology specimens are needed to evaluate the real impact in the tumor volume definition.

18F-FDG PET/CT for early prediction of response to neoadjuvant chemotherapy in breast cancer

PURPOSE

The aim of this study was to prospectively evaluate 18F-FDG PET/CT in predicting response to neoadjuvant chemotherapy in large primary breast cancer.

METHODS

Fifty consecutive patients underwent PET/CT at baseline and after the second cycle. Baseline MRI was performed to establish tumour size. All findings were confirmed by histopathological analysis. Changes in maximum standardized uptake value (SUV(max)) between baseline study and after two cycles of neoadjuvant chemotherapy (epirubicin + cyclophosphamide + taxanes) were compared using response evaluation criteria in solid tumours (RECIST) criteria and the Miller and Payne (M&P) scale.

RESULTS

The mean tumour size was 4.3 +/- 1.4 cm. Forty patients were considered responders and ten as non-responders. SUV(max) changes in patients with good prognosis (M&P grades 4-5) were higher than in patients with bad prognosis (M&P grades 1-3) (p = 0.025). SUV(max) changes between responders and non-responders following RECIST criteria were also statistically significant (p = 0.0028). A cut-off DeltaSUV value of 40% differentiates both groups, with a sensitivity of 77% and a specificity of 80%.

CONCLUSION

18F-FDG PET/CT can predict response to neoadjuvant chemotherapy at an early stage.