Incidence and Significance of Hypermetabolic PET-CT Findings in Unilateral TVF Motion Impairment

OBJECTIVE

To determine the incidence and significance of asymmetric hypermetabolic laryngeal findings on positron emission tomography-computed tomography (PET-CT) in patients with unilateral true vocal fold (TVF) motion abnormalities.

STUDY DESIGN

Retrospective cohort.

SETTING

Single-center tertiary care institution.

SUBJECTS AND METHODS

The medical records of patients with unilateral TVF motion abnormalities were reviewed. The incidence of normal and asymmetric hypermetabolic laryngeal findings was calculated in patients who underwent PET-CT and laryngeal examination, operative laryngoscopy with biopsy, or injection medialization laryngoplasty.

RESULTS

A total of 135 patients with unilateral TVF motion abnormalities underwent PET-CT. After exclusion of patients who completed new or surveillance imaging for a laryngeal neoplasm (n = 27), asymmetric hypermetabolic findings in the larynx were noted in 21 (19%) cases: 13 (12%) on the contralateral side of the impaired TVF, 8 (7%) on the ipsilateral side. Two (25%) patients with ipsilateral hypermetabolism had concerning subsequent fiberoptic laryngeal examinations prompting operative biopsy. There was no evidence of inflammatory or neoplastic disease in all patients with contralateral hypermetabolic findings. Fifteen patients completed PET-CT scans after injection medialization procedures; 6 (40%) displayed avidity ipsilateral to the side of the injection. The median time from injection to scan was 27 days, as opposed to 193 days in the unremarkable scans (P = .011).

CONCLUSION

Contralateral hypermetabolism in patients with unilateral TVF motion abnormalities may represent a false-positive finding. Ipsilateral hypermetabolic uptake without recent fold instrumentation warrants prompt diagnostic evaluation.

Staging of Non-Small-Cell Lung Cancer

Staging of lung cancer serves 2 purposes; it attempts to classify patients into groups where particular treatments are appropriate and defines those groups based on expected prognosis. The eighth edition of the International Association for the Study of Lung Cancer staging system deals with the issues raised by screening with fine cut computed tomography. Each phase of staging is a legitimate dataset on its own. Molecular profiling of lung cancer has led to the development of an increasing number of novel agents to treat systemic disease. Prognosis is increasingly determined by genetic susceptibility of the specific cancer.

Left Vocal Cord Paralysis Detected by PET/CT in a Case of Lung Cancer

We report a patient with lung cancer. The first PET/CT imaging revealed hypermetabolic mass in the left aortopulmonary region and hypermetabolic nodule in the anterior segment of the upper lobe of the left lung. After completing chemotherapy and radiotherapy against the primary mass in the left lung, the patient underwent a second PET/CT examination for evaluation of treatment response. This test demonstrated, compared with the first PET/CT, an increase in the size and metabolic activity of the primary mass in the left lung in addition to multiple, pathologic-sized, hypermetabolic metastatic lymph nodes as well as multiple metastatic sclerotic areas in bones. These findings were interpreted as progressive disease. In addition, an asymmetrical FDG uptake was noticed at the level of right vocal cord. During follow-up, a laryngoscopy was performed, which demonstrated left vocal cord paralysis with no apparent mass. Thus, we attributed the paralytic appearance of the left vocal cord to infiltration of the left recurrent laryngeal nerve by the primary mass located in the apical region of the left lung. In conclusion, the knowledge of this pitfall is important to avoid false-positive PET results.

Vocal cord paralysis: anatomy, imaging and pathology

Vocal cord paralysis (VCP) can be caused by any process that interferes with the normal function of the vagal nerves or recurrent laryngeal nerves. It may be a first sign of extensive and severe pathology. Radiologists must therefore be able to recognise the imaging findings of VCP and know the course of the vagal and recurrent laryngeal nerves. This review focuses on the anatomy and imaging evaluation of these nerves and thereby the possible sites for pathology causing VCP. The imaging characteristics and imaging mimics of VCP are discussed and cases from daily practice illustrating causes of VCP are presented.

• Vocal cord paralysis may be the first presentation of severe pathology.

• Radiologists must be aware of imaging characteristics and mimics of vocal cord paralysis.

• Lesions along the vagal nerves and recurrent laryngeal nerves can cause vocal cord paralysis.

Relation Between Metabolic Activity of the Broca Region and F-18 FDG Uptake in Vocal Cords

Objective: We aimed to investigate if increased F-18 Fluoro Deoxyglucose (F-18 FDG) uptake observed in vocal cords (VC) of the patients on Positron Emission Tomography/Computarize Tomography (PET/CT) scans is connected to speaking of the patients or not. If so, we expected to detect an increased metabolic activity in Broca's area. In this study, we have retrospectively searched for a correlation between the activity in the Broca's area and vocal cords of patients who had undergone FDG PET for different indications.

Material and Methods: FDG PET/CT scans of 30 patients with (VC [+]) and 30 patients without (VC [-]) bilateral F-18 FDG uptake on their vocal cords were retrospectively evaluated. Brain quantification was carried out on NeuroQ software with 20 iterations using patients' transaxial brain cross sections. On the 20th-23rd-26th-29th cross sections, area/whole brain ratios of the right (R) and left (L) for Broca’s area were calculated. VC (+) and VC (-) patients' R and L Broca's areas were compared using Student's t-test.

Results: There was no significant difference between the Broca's areas of VC (+) and VC (-) patients. L Broca's areas of both VC (+) and VC (-) patients were more active than R Broca's areas (p<0.05). There was a negative correlation between VC (+) patients' SUVmax values in the vocal cords and the activity in their R Broca's region.

Conclusion: In our study, we did not find a significant difference between Broca's areas of VC (+) patients and VC (-) patients, so the activity in their vocal cords does not seem to be related to increased metabolic activity in Broca's areas. We have concluded that the vocal cord activity is not related to speaking of the patients. The activity in the vocal cord might be due to inflammation or, as in the eye muscles, may be associated with high metabolism in laryngeal muscles.

Conflict of interest:None declared.

Reevaluation of FDG-PET/CT in patients with hoarseness caused by vocal cord palsy

OBJECTIVE

Vocal cord palsy (VCP) is a potential cause of hoarseness that results in decreasing mobility of the vocal cord. VCP can arise from a variety of causes; so, systematic screening is warranted for the management of patients with VCP. Asymmetrical fluorodeoxyglucose (FDG) uptake in vocal cords is a well-known feature in patients with VCP, but no detailed analysis has been performed. This study aimed at reevaluating the (18)F-FDG positron emission tomography/computed tomography (PET/CT) for patients with VCP.

METHODS

We retrospectively surveyed the results of FDG-PET/CT for 59 patients with VCP, compared to laryngoscopic findings. Quantitative analysis was performed using maximum standardized uptake value (SUVmax), and regions of interest were drawn over bilateral vocal cords as confirmed from the CT portion of PET/CT. Patients were divided into 3 groups: Group 1 (n = 14), in which VCP was caused by the lesion of the laryngeal area; Group 2 (n = 40), in which VCP was caused by the lesion on the root of the recurrent laryngeal nerve; and Group 3 (n = 5), in which VCP was caused by the lesion from the vagal center to the proximal vagus nerve.

RESULTS

For Group 1, higher FDG uptake in the paralyzed vocal cord was seen in 86 % of patients (mean SUVmax 8.1 ± 5.3 vs. 2.3 ± 0.4, paralyzed vs. non-paralyzed, respectively; P < 0.002). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 79 % for Group 1. Group 2 showed dominant FDG uptake in the non-paralyzed vocal cord (mean SUVmax 2.1 ± 0.9 vs. 1.5 ± 0.4, non-paralyzed vs. paralyzed, respectively; P < 0.001). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 93 % for Group 2. Group 3 showed no statistically significant difference in FDG accumulation between non-paralyzed and paralyzed vocal cords (mean SUVmax 1.8 ± 0.3 vs. 1.7 ± 0.3, non- paralyzed vs. paralyzed, respectively; P = 0.30). The sensitivity of FDG-PET/CT for indicating the lesion causing VCP was 60 % for Group 3.

CONCLUSIONS

FDG accumulation in the vocal cords is dependent on the lesion site causing VCP. In addition, FDG-PET/CT can contribute to identification of the lesion responsible for inducing VCP.

Atlas of confounding factors in head and neck PET/CT imaging

PURPOSE

Interpretation of positron emission tomography/computed tomography (PET/CT) studies in the head and neck region is challenging due to the complex anatomy and nonspecific physiologic and inflammatory FDG uptake. We present an atlas of common confounding factors encountered at our institution.

MATERIALS AND METHODS

We present whole-body fluorodeoxyglucose (FDG) PET/CT studies of 20 patients with various confounding factors in the head and neck. Most patients (15) had a history of head and neck cancer and some (5) of them presented with other primary tumors.

RESULTS

We describe these cases under the following categories: physiologic uptake (6), inflammatory uptake (5), unexpected benign tumors (2), unexpected malignant tumors (4), postradiation changes (2), postsurgical changes (2), and misregistration (1).

CONCLUSIONS

Knowledge of common variants, pitfalls, and treatment effects is essential in accurate reading of PET/CT in the head and neck region.