A review of the imaging and clinical management of solitary pulmonary nodules

Evaluation and management of pulmonary nodules: state-of-the-art and future perspectives

INTRODUCTION

The imaging evaluation of pulmonary nodules, often incidentally detected on imaging examinations performed for other clinical reasons, is a frequently encountered clinical circumstance. With advances in imaging modalities, both the detection and characterization of pulmonary nodules continue to evolve and improve.

AREAS COVERED

This article will review the imaging modalities used to detect and diagnose benign and malignant pulmonary nodules, with a focus on computed tomography (CT), which continues to be the mainstay for evaluation. The authors discuss recent advances in the lung nodule management, and an algorithm for the management of indeterminate pulmonary nodules.

EXPERT OPINION

There are set of criteria that define a benign nodule, the most important of which are the lack of temporal change for 2 years or more, and certain benign imaging criteria, including specific patterns of calcification or the presence of fat. Although some indeterminate pulmonary nodules are immediately actionable, generally those approaching 1 cm or larger in diameter, at which size the diagnostic accuracy of tools such as positron emission tomography (PET)/CT, single photon emission CT (SPECT) and biopsy techniques are sufficient to warrant their use. The majority of indeterminate pulmonary nodules are under 1 cm, for which serial CT examinations through at least 2 years for solid nodules and 3 years for ground-glass nodules, are used to demonstrate either benign biologic behavior or otherwise. The management of incidental pulmonary nodules involves a multidisciplinary approach in which radiology plays a pivotal role. Newer imaging and postprocessing techniques have made this a more accurate technique eliminating ambiguity and unnecessary follow-up.

Evaluating the possible role of 68Ga-citrate PET/CT in the characterization of indeterminate lung lesions

We sought to determine whether PET/CT imaging with (68)Ga-citrate could be of value in distinguishing benign from malignant lung pathology in a setting with a high prevalence of granulomatous diseases.

METHODS

Thirty-six consecutive patients with indeterminate lung lesions prospectively underwent dual time point (60 and 120 min) (68)Ga-citrate PET/CT study prior to lung biopsy. Qualitative and semi-quantitative measures of tracer uptake in the lung lesions (SUVmax) were compared to the histopathology in order to establish an imaging pattern to distinguish benign from malignant lesions.

RESULTS

Fourteen patients (38.9 %) were diagnosed with a malignant lesion, 12 (33.3 %) with tuberculosis (TB), and 10 participants (27.8 %) with other benign lung lesions. At 60-min post-injection, patients who were diagnosed with a malignant lesion (n = 14) demonstrated a mean SUVmax of 3.36 ± 1.14, with a median value of 3.04 (min = 1.56, max = 4.65).Those with TB (n = 12) demonstrated a SUVmax of 3.99 ± 2.28, and a median value of 3.71 (pct25 = 2.19, pct75 = 4.95). In patients with other benign lesions (n = 10), the following values were observed: a SUVmax of 2.70 ± 1.31, a median value of 2.50 (pct25 = 1.76, pct75 = 3.59). The mean values of these three types of pathology were not statistically significant (p = 0.1919), and therefore the SUVmax could not be used to accurately distinguish between these lesions using both early and delayed imaging.

CONCLUSION

This study, as the first (68)Ga-citrate PET/CT in humans for the in vivo imaging of lung pathology, demonstrated its potential for the detection of both malignancy and TB. However, (68)Ga-citrate seemed incapable of providing a clear distinction between malignant and benign lung lesions in a setting with a high prevalence of granulomatous diseases such as TB.