Detection of Small Pulmonary Nodules with Ultrashort Echo Time Sequences in Oncology Patients by Using a PET/MR System

Abstract

).q RSNA, 2015 Purpose:To investigate the utility of a free-breathing ultrashort echo time (UTE) sequence for the evaluation of small pulmonary nodules in oncology patients by using a hybrid positron emission tomography (PET)/magnetic resonance (MR) imaging system and to compare the nodule detection rate between UTE and a conventional three-dimensional gradient-recalled-echo (GRE) technique. Materials and Methods:In this HIPAA-compliant, institutional review board-approved prospective study, 82 pulmonary nodules were identified in eight patients with extrathoracic malignancies. Patients underwent free-breathing UTE and dual-echo three-dimensional GRE imaging of the lungs in a hybrid PET/MR imaging unit immediately after clinical PET/computed tomography (CT). CT was considered the reference standard for nodule detection. Two reviewers identified nodules and obtained measurements on MR images. The McNemar test was used to evaluate differences in nodule detection rate between MR techniques, and interrater agreement was assessed by using Bland-Altman plots. Results:Mean nodule diameter 6 standard deviation was 6.2 mm 6 2.7 (range, 3-17 mm). The detection rate was higher for UTE imaging than for dual-echo GRE imaging for nodules of at least 4 mm (82% vs 34%, respectively; P , .001), with the largest difference in detection noted in the 4-8-mm nodule group (79% vs 21%, P , .001). UTE imaging displayed a higher detection rate than dual-echo GRE imaging for nodules without fluorodeoxyglucose avidity (68% vs 22%, respectively; P , .001). Interrater reliability of nodule detection with MR imaging was high (k = 0.90 for UTE imaging and k = 0.92 for dual-echo GRE imaging). Conclusion:A free-breathing UTE sequence has high sensitivity for the detection of small pulmonary nodules (4-8 mm) and outperformed a three-dimensional dual-echo GRE technique for the detection of small, non-fluorodeoxyglucose-avid nodules.q RSNA, 2015

MRI for solitary pulmonary nodule and mass assessment: Current state of the art

“…In addition, recent results of national lung cancer screening trials as well as previously reported results of CT-based lung cancer screenings have led to a growing need for management of pulmonary nodules in routine clinical practice. [15][16][17][18][19][20][21][22] Two major MR sequences have come into use in this setting: the turbo spin-echo (SE)-based technique and the gradient-echo (GRE) technique, with varying results for reduction of cardiac-and respiratory-motion artifacts. [9][10][11][12] For these reasons, pulmonary nodule detection and characterization on MRI has become an important diagnostic tool for pulmonary diseases and has been tested extensively during the last few years.…”

FDG Whole-Body PET/MRI in Oncology: a Systematic Review

“…To overcome the size effect, a free-breathing ultrashort echo time (UTE) sequence has been evaluated in patients having small metastatic lung nodules. UTE sequence showed a higher detection rate for lung nodules with small size, non-FDG avid, not-subpleural location (p < 0.001) [66]. On the other hand, one study reported that post-contrast VIBE sequence images of MRI could not improve detection rate of pulmonary nodules more than non-contrast VIBE images (jackknife alternative freeresponse receiver-operating-characteristics value of 0.848 vs. 0.837, respectively) [67].…”

Role of Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Imaging in Diagnosis and Staging of Lung Cancer

“…Diğer taraftan FDG tutulumu göstermeyen ve MR görüntülemede saptanamayıp sadece BT görüntülerinde izlenen nodüllerin çok büyük bir kısmının (%96.4) takipte kaybolduğu ya da stabil seyrettiği, dolayısıyla benign karakterde olduğu gösterilmiştir (67). Küçük akciğer nodüllerinin MR ile görüntülenmesini sağlamak amacıyla UTE (ultrashort echo time) gibi özel sekanslar geliştirilmiştir (68). Ayrıca hibrid PET/MR sistemlerinde, toraksın PET ve MR görüntülemeleri eş zamanlı olarak yürütüldüğünden, PET görüntüsünde solunum hareketleri için düzeltme işlemi MR görüntülemeden yararlanarak yapılabilir.…”