Bruno Hochhegger MD, Presenter: Nothing to Disclose

Giordano Rafael Tronco Alves, Abstract Co-Author: Nothing to Disclose

Edson Marchiori MD, PhD, Abstract Co-Author: Nothing to Disclose

Klaus Loureiro Irion MD,PhD, Abstract Co-Author: Nothing to Disclose

Daniela Quinto Dos Reis MD, Abstract Co-Author: Nothing to Disclose

Luciana Volpon Soares Souza MD, Abstract Co-Author: Nothing to Disclose

We aimed to demonstrate the usefulness of chemical-shift Magnetic Resonance Imaging (MRI) in the diagnosis of intranodular fat in pulmonary hamartomas and compare the results with Computed Tomography (CT) findings.  

Seven patients, who presented negative densities but inconclusive thoracic CT for nodule characterization, underwent chemical-shift MRI. Images were reviewed by a 6-year-experienced thoracic radiologist. All nodules had pathological diagnoses of hamartoma. Another observer performed all quantitative MRI measurements, and was unaware of the CT attenuation measurements. Region of Interest (ROIs) were placed on nodule using the largest ellipse while avoiding the edges, where chemical-shift artifacts are present. Identical ROIs were drawn on in- and opposed-phase MRI images. The percentage of signal intensity decrease was calculated using the nodule signal intensity index (nodule lipid index): [(SIIP − SIOP) / SIIP] × 100, where SIIP and SIOP are the signal intensities measured on in- and opposed-phase images, respectively. An index value of more than 17% was considered consistent with a lipid-rich lesion.

All seven cases (five men and two women; age range, 48–65 years) were diagnosed pathologically as hamartomas. No case had characteristic calcifications, and all lesions showed internal fat on histopathological analysis. In CT assessment (Fig. 1), no case showed calcium attenuation and the average density was -21.4 Hounsfield units (SD = 9.6 HU). All cases showed intermediate signal (lower than fat and higher than spinal muscle) in T1-weighted MRI sequences and showed high-intensity signals in T2-weighted sequences. In the chemical-shift MRI setting (Fig. 2), the average nodule signal intensity index was 45.8% (SD = 21.9). The correlation between average nodule signal intensity and CT HUs was -0.94. No nodule showed restriction in diffusion-weighted sequences.

Chemical-shift MRI could be an important tool to detect fat in pulmonary hamartomas with inconclusive CT findings. Our data also confirmed that pulmonary hamartomas had high signal intensity in T2-weighted sequences and showed no restriction in diffusion-weighted sequences. 

Chemical-shift MRI could be an important tool to detect fat in pulmonary hamartomas with inconclusive CT findings

Hochhegger, B, Alves, G, Marchiori, E, Irion, K, Reis, D, Souza, L, Chemical Shift Magnetic Resonance Imaging in Pulmonary Hamartomas: Initial Experience of a Modified Technique in the Assessment of Nodule Fat.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12024396.html