Lung CT stabilization with high-frequency non-invasive ventilation (HF-NIV) and breath-hold (BH) in lung nodule assessment by PET/CT.

PURPOSE: To evaluate the effect of lung stabilization using high-frequency non-invasive ventilation (HF-NIV) and breath-hold (BH) techniques on lung nodule detection and texture assessment in PET/CT compared to a free-breathing (FB) standard lung CT acquisition in PET/CT. MATERIALS AND METHODS: Six patients aged 65 ± 7 years, addressed for initial assessment of at least one suspicious lung nodule with 18F-FDG PET/CT, underwent three consecutive lung PET/CT acquisitions with FB, HF-NIV and BH. Lung nodules were assessed on all three CT acquisitions of the PET/CT and characterized for any size, volume and solid/sub-solid nature. RESULTS: BH detected a significantly higher number of nodules (n = 422) compared to HF-NIV (n = 368) and FB (n = 191) (p < 0.001). The mean nodule size (mm) was 2.4 ± 2.1, 2.6 ± 1.9 and 3.2 ± 2.4 in BH, HF-NIV and FB, respectively, for long axis and 1.5 ± 1.3, 1.6 ± 1.2 and 2.1 ± 1.7 in BH, HF-NIV and FB, respectively, for short axis. Long- and short-axis diameters were significantly different between BH and FB (p < 0.001) and between HF-NIV and FB (p < 0.001 and p = 0.008), but not between BH and HF-NIV. A trend for higher volume was shown in FB compared to BH (p = 0.055) and HF-NIV (p = 0.068) without significant difference between BH and HF-NIV (p = 1). We found a significant difference in detectability of sub-solid nodules between the three acquisitions, with BH showing a higher number of sub-solid nodules (n = 128) compared to HF-NIV (n = 72) and FB (n = 44) (p = 0.002). CONCLUSION: We observed a higher detection rate of pulmonary nodules on CT under BH or HF-NIV conditions applied to PET/CT than with FB. BH and HF-NIV demonstrated comparable texture assessment and performed better than FB in assessing size and volume. BH showed a better performance for detecting sub-solid nodules compared to HF-NIV and FB. The addition of BH or HF-NIV to PET/CT can help improve the detection and texture characterization of lung nodules by CT, therefore improving the accuracy of oncological lung disease assessment. The ease of use of BH and its added value should prompt its use in routine practice.

Comparison Between Magnetic Resonance Imaging and Computed Tomography in the Detection and Volumetric Assessment of Lung Nodules: A Prospective Study.

Rationale and Objectives: Computed tomography (CT) lung nodule assessment is routinely performed and appears very promising for lung cancer screening. However, the radiation exposure through time remains a concern. With the overall goal of an optimal management of indeterminate lung nodules, the objective of this prospective study was therefore to evaluate the potential of optimized ultra-short echo time (UTE) MRI for lung nodule detection and volumetric assessment. Materials and Methods: Eight (54.9 ± 13.2 years) patients with at least 1 non-calcified nodule ≥4 mm were included. UTE under high-frequency non-invasive ventilation (UTE-HF-NIV) and in free-breathing at tidal volume (UTE-FB) were investigated along with volumetric interpolated breath-hold examination at full inspiration (VIBE-BH). Three experienced readers assessed the detection rate of nodules ≥4 mm and ≥6 mm, and reported their location, 2D-measurements and solid/subsolid nature. Volumes were measured by two experienced readers. Subsequently, two readers assessed the detection and volume measurements of lung nodules ≥4mm in gold-standard CT images with soft and lung kernel reconstructions. Volumetry was performed with lesion management software (Carestream, Rochester, New York, USA). Results: UTE-HF-NIV provided the highest detection rate for nodules ≥4 mm (n = 66) and ≥6 mm (n = 32) (35 and 50%, respectively). No dependencies were found between nodule detection and their location in the lung with UTE-HF-NIV (p > 0.4), such a dependency was observed for two readers with VIBE-BH (p = 0.002 and 0.03). Dependencies between the nodule's detection and their size were noticed among readers and techniques (p < 0.02). When comparing nodule volume measurements, an excellent concordance was observed between CT and UTE-HF-NIV, with an overestimation of 13.2% by UTE-HF-NIV, <25%-threshold used for nodule's growth, conversely to VIBE-BH that overestimated the nodule volume by 28.8%. Conclusion: UTE-HF-NIV is not ready to replace low-dose CT for lung nodule detection, but could be used for follow-up studies, alternating with CT, based on its volumetric accuracy.

Lung MRI assessment with high-frequency noninvasive ventilation at 3 T.

PURPOSE: To investigate three MR pulse sequences under high-frequency noninvasive ventilation (HF-NIV) at 3 T and determine which one is better-suited to visualize the lung parenchyma. METHODS: A 3D ultra-short echo time stack-of spirals Volumetric Interpolated Breath-hold Examination (UTE Spiral VIBE), without and with prospective gating, and a 3D double-echo UTE sequence with spiral phyllotaxis trajectory (3D radial UTE) were performed at 3 T in ten healthy volunteers under HF-NIV. Three experienced radiologists evaluated visibility and sharpness of normal anatomical structures, artifacts assessment, and signal and contrast ratio computation. The median of the three readers'scores was used for comparison, p < .05 was considered statistically significant. Incidental findings were recorded and reported. RESULTS: The 3D radial UTE resulted in less artifacts than the non-gated and gated UTE Spiral VIBE in inferior (score 3D radial UTE = 3, slight artifact without blurring vs. score UTE Spiral VIBE non-gated and gated = 2, moderate artifact with blurring of anatomical structure, p = .018 and p = .047, respectively) and superior lung regions (score 3D radial UTE = 3, vs. score UTE Spiral VIBE non-gated = 2.5, p = .48 and score UTE Spiral VIBE gated = 1, severe artifact with no normal structure recognizable, p = .014), and higher signal and contrast ratios (p = .002, p = .093). UTE Spiral VIBE sequences provided higher peripheral vasculature visibility than the 3D radial UTE (94.4% vs 80.6%, respectively, p < .001). The HF-NIV was well tolerated by healthy volunteers who reported on average minor discomfort. In three volunteers, 12 of 18 nodules confirmed with low-dose CT were identified with MRI (average size 2.6 ±â€¯1.2 mm). CONCLUSION: The 3D radial UTE provided higher image quality than the UTE Spiral VIBE. Nevertheless, a better nodule assessment was noticed with the UTE Spiral VIBE that might be due to better peripheral vasculature visibility, and requires confirmation in a larger cohort.

Percussion assisted radiation therapy in Hodgkin lymphoma allows a marked reduction in heart dose.

BACKGROUND AND PURPOSE: Early-stage Hodgkin lymphoma (HL) is a highly curable disease but the treatment can induce late complications many years later. Irradiation of the healthy heart is inevitable during radiation treatment of mediastinal sites. We developed a novel method to induce a prolonged apnea-like state that can help decrease the dose to organs at risk during radiation therapy. We present the results of the first 8 HL patients treated routinely with percussion assisted radiation therapy (PART) in our clinic. MATERIAL AND METHODS: We used a newly developed high-frequency non-invasive ventilation system to suppress respiratory motion for prolonged periods and push the heart away from the treated volume. RESULTS: All 8 patients were able to rapidly learn the technique and had an advantage to be treated by PART. We lowered the mean heart dose by an average of 3 Gy with similar target coverage compared to a classical free breathing treatment plan. They were all treated for 15 radiotherapy sessions by PART without any notable side effects. CONCLUSIONS: Percussion assisted radiation therapy can be used routinely to reduce the dose to the heart in Hodgkin lymphoma.

Ultrashort echo time imaging of the lungs under high-frequency noninvasive ventilation: A new approach to lung imaging.

BACKGROUND: Although ultrashort echo time (UTE) sequences allow excellent assessment of lung parenchyma, image quality remains lower than that of computed tomography (CT). PURPOSE: To investigate a high-frequency noninvasive ventilation (HF-NIV) technique allowing a stabilized inspiration and to compare image quality with current dedicated MR sequences. STUDY TYPE: Prospective. POPULATION: Ten healthy volunteers. FIELD STRENGTH/SEQUENCE: 3D radial UTE sequence at 1.5T. ASSESSMENT: UTE-HF-NIV sequence was compared with UTE-free-breathing (UTE-FB), reconstructed at end expiration (UTE-Exp) and average (UTE-Avg), and breath-hold VIBE sequences. The distance from lung apex to the dome of the right hemidiaphragm was measured. Visual assessment of the visibility and sharpness of normal anatomical structures was carried out. Dedicated software also quantitatively evaluated vessel-lung and right lung-liver interface sharpness. Apparent signal ratio (Sr) and contrast ratios (Cr) were quantitatively evaluated. STATISTICAL TESTS: Wilcoxon signed rank test for visual scores, paired t-test for continuous variables, significance at P < 0.05. RESULTS: The distance between apex and the right hemidiaphragmatic dome was significantly larger (P < 0.001) with UTE-HF-NIV compared with UTE-FB and VIBE acquisitions. Vessel and airway visibility had identical median visual scores with all UTE methods. Median visual scores for sharpness of vessels and airways were significantly higher (P < 0.001) with HF-NIV (vessels = 3; airways = 2) than in UTE-FB (vessels = 2; airways = 1) and VIBE (vessels = 1; airways = 1). Software-based vessel sharpness evaluation resulted in larger values in 8/10 volunteers with UTE-HF-NIV (67.3 ± 9.8) compared with UTE-Avg (62.3 ± 12.6) but the average difference was not significant (P = 0.28). The sharpness of the lung-liver interface was significantly higher (P < 0.001) with HF-NIV (17.3 ± 5.3) compared with UTE-Avg (14.1 ± 3.9). Significantly higher values (P < 0.01) of Sr and Cr were observed with UTE-HF-NIV compared with UTE-FB and VIBE. DATA CONCLUSION: HF-NIV allowing acquisition at full inspiration significantly improves image quality for lung imaging. This could offer the option to alternate some follow-up CT studies by using this technique. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1789-1797.

MR Volumetry of Lung Nodules: A Pilot Study.

Introduction: Computed tomography (CT) is currently the reference modality for the detection and follow-up of pulmonary nodules. While 2D measurements are commonly used in clinical practice to assess growth, increasingly 3D volume measurements are being recommended. The goal of this pilot study was to evaluate preliminarily the capabilities of 3D MRI using ultra-short echo time for lung nodule volumetry, as it would provide a radiation-free modality for this task. Material and Methods: Artificial nodules were manufactured out of Agar and measured using an ultra-short echo time MRI sequence. CT data were also acquired as a reference. Image segmentation was carried out using an algorithm based on signal intensity thresholding (SIT). For comparison purposes, we also performed manual slice by slice segmentation. Volumes obtained with MRI and CT were compared. Finally, the volumetry of a lung nodule was evaluated in one human subject in comparison with CT. Results: Using the SIT technique, minimal bias was observed between CT and MRI across the entire range of volumes (2%) with limits of agreement below 14%. Comparison of manually segmented MRI and CT resulted in a larger bias (8%) and wider limits of agreement (-23% to 40%). In vivo, nodule volume differed of <16% between modalities with the SIT technique. Conclusion: This pilot study showed very good concordance between CT and UTE-MRI to quantify lung nodule volumes, in both a phantom and human setting. Our results enhance the potential of MRI to quantify pulmonary nodule volume with similar performance to CT.

Chest-MRI under pulsatile flow ventilation: A new promising technique.

OBJECTIVES: Magnetic resonance imaging (MRI) of the chest has long suffered from its sensitivity to respiratory and cardiac motion with an intrinsically low signal to noise ratio and a limited spatial resolution. The purpose of this study was to perform chest MRI under an adapted non invasive pulsatile flow ventilation system (high frequency percussive ventilation, HFPV®) allowing breath hold durations 10 to 15 times longer than other existing systems. METHODS: One volunteer and one patient known for a thymic lesion underwent a chest MRI under ventilation percussion technique (VP-MR). Routinely used sequences were performed with and without the device during three sets of apnoea on inspiration. RESULTS: VP-MR was well tolerated in both cases. The mean duration of the thoracic stabilization was 10.5 min (range 8.5-12) and 5.8 min (range 5-6.2) for Volunteer 1 and Patient 1, respectively. An overall increased image quality was seen under VP-MR with a better delineation of the mediastinal lesion for Patient 1. Nodules discovered in Volunteer 1 were confirmed with low dose CT. CONCLUSION: VP-MR was feasible and increased spatial resolution of chest MRI by allowing acquisition at full inspiration during thoracic stabilization approaching prolonged apnoea. This new technique could be of benefit to numerous thoracic disorders.

[Principles and challenges of mobilisation in intensive care]. / Principes et enjeux de la mobilisation en réanimation.

The harmful consequences of bed rest and inactivity in patients in intensive care have been widely described. The point at which these patients should be mobilised and the methods used however still remain unclear. It is nevertheless important that the mobilisation is implemented early and often, adapted to the condition of the patient and overseen by a cross-disciplinary team.

Apnea-like suppression of respiratory motion: First evaluation in radiotherapy.

BACKGROUND AND PURPOSE: Compensation for respiratory motion is needed while administering radiotherapy (RT) to tumors that are moving with respiration to reduce the amount of irradiated normal tissues and potentially decrease radiation-induced collateral damages. The purpose of this study was to test a new ventilation system designed to induce apnea-like suppression of respiratory motion and allow long enough breath hold durations to deliver complex RT. MATERIAL AND METHODS: The High Frequency Percussive Ventilation system was initially tested in a series of 10 volunteers and found to be well tolerated, allowing a median breath hold duration of 11.6 min (range 3.9-16.5 min). An evaluation of this system was subsequently performed in 4 patients eligible for adjuvant breast 3D conformal RT, for lung stereotactic body RT (SBRT), lung volumetric modulated arc therapy (VMAT), and VMAT for palliative pleural metastases. RESULTS: When compared to free breathing (FB) and maximal inspiration (MI) gating, this Percussion Assisted RT (PART) offered favorable dose distribution profiles in 3 out of the 4 patients tested. PART was applied in these 3 patients with good tolerance, without breaks during the "beam on time period" throughout the overall courses of RT. The mean duration of the apnea-like breath hold that was necessary for delivering all the RT fractions was 7.61 min (SD=2.3). CONCLUSIONS: This first clinical implementation of PART was found to be feasible, tolerable and offers new opportunities in the field of RT for suppressing respiratory motion.