Free Breathing Multi-parametric quantitative Assessment of Mesothelioma with MRI
Ravi Teja Seethamraju1, Noreen Dunham2, Donna Oka2, Aida Faria2, and Ritu Randhawa Gill2

1MR R&D, Siemens Healthcare, Boston, MA, United States, 2Radiology, Brigham and Women's Hospital, Boston, MA, United States

Synopsis

We demonstrate that free breathing multi-parametric quantitative assessment of mesothelioma with MRI is feasible. DCE imaging of the thorax with 3D Radial stack of stairs gradient echo (radial VIBE) sequence can be acquired while free breathing and the resulting pharmacokinetic maps are of higher diagnostic value than current standard of 2D or 3D FLASH acquisitions without the need for co-registration. Similarly DWI with readout segmented EPI (RESOLVE) provides similar diagnostic value with a free breathing acquisition. These two biomarkers help improve the evaluation of tumor in mesothelioma patients.

BACKGROUND

MR imaging of the thorax is currently not the primary modality of choice for non-invasive diagnosis due to the inherent issues with susceptibility from the air tissue interfaces and the breathing motion. CT on the other hand which is the current primary modality is however being restricted due to growing concern for radiation exposure. While susceptibility with MRI can be addressed by the development of short echo time sequences, it is difficult to achieve optimal motion compensation when fast time resolution is required for reasonable pharmacokinetic analysis [1]. Likewise diffusion (DWI) which is gaining popularity in the evaluation of prostate and liver diseases suffers from the same issues that curtail dynamic contrast enhanced imaging (DCE) of the lung. With the help of two new sequences, namely radial VIBE [2] for DCE imaging and read out segmented diffusion (RESOLVE) for DWI [3], it is possible to overcome these difficulties. These sequences are very robust to motion and reduce susceptibility over conventional sequences.

METHODS

In an IRB approved study, 12 patients with mesothelioma were scanned on a 3T scanner (Trio a Tim System, Siemens Healthcare, Germany) after administration of 0.1mmol/kg of Magnevist (Bayer Healthcare, USA). Dynamic acquisitions were acquired with a 3D radial VIBE sequence with a TE=1.5ms and TR=3ms. The voxel dimensions were set to be 2mm isotropic and with a time resolution of 3s acquired for 5 minutes. For quantification in terms of Gd concentration a T1 map was created from four sets of a breath held Cartesian VIBE sequence (7s acquisition each) with similar parameters as the radial VIBE and with flip angles of 2, 5, 10 and 15. Pharmacokinetic analysis was performed on a commercial software (Tissue4D, Siemens Healthcare, Germany). DWI imaging was performed with the RESOLVE sequence also set to 2mm isotropic resolution and with b values of 50, 250, 500 and 750, TE=54ms and TR=4400ms.

DISCUSSION

Contrary to conventional thought, the respiratory motion in patients with thoracic diseases is considerably limited when compared to healthy subjects. The motion tolerance as found in the radial VIBE and the RESOLVE sequences was sufficient to compensate the limited motion, provide robust imaging and analysis in the patient cohort with Mesothelioma. The images acquired with the 3D radial VIBE sequence did not require any co-registration between the individual time points. Also the RESOLVE sequence exhibited very little distortions compared to the conventional 2D unsegmented EPI sequence, hence the images could be easily co-registered to the radial VIBE data. This allowed for direct comparison of the parameters from both these two biomarkers.

RESULTS

Fig 1. is a representative example of a patient who had pneumonia along with Mesothelioma. Visually on native pre contrast or post contrast images it is hard to differentiate the areas that are affected, however contrast enhancement curves for the ROIs clearly shows that the enhancement is different in these two regions. Fig 2. shows that the kTrans values are different in these two regions (Pneumonia~ 3 times tumor) and iAUC values show a similar trend. In Fig 3. the contours from Fig 2 when copied on to the B0 and ADC images shows perfect co-registration that allows for direct comparison of the biomarkers. The ADC values for the pneumonia is slightly higher to that of the tumor.

CONCLUSION

We have demonstrated that free breathing multi-parametric quantitative assessment of mesothelioma with MRI is feasible. DCE imaging of the thorax with 3D Radial VIBE sequence can be acquired while free breathing and the resulting pharmacokinetic maps are of higher diagnostic value than current standard 2D or 3D FLASH acquisitions [1] without the need for co-registration, further DWI with RESOLVE provides similar diagnostic value as acquired while free breathing. These two biomarkers help improve the evaluation of tumor in mesothelioma patients.

Acknowledgements

No acknowledgement found.

References

1. Tokuda J., et.al., Impact of Non-rigid Motion Correction Technique on Pixel-wise Pharmacokinetic Analysis of Free-breathing Pulmonary Dynamic Contrast-Enhanced MR Imaging, J Magn Reson Imaging. Apr 2011; 33(4): 968–973.

2. Chandarana H, et al. Free-breathing radial 3D fat-suppressed T1-weighted gradient echo sequence: a viable alternative for contrast-enhanced liver imaging in patients unable to suspend respiration. Invest Radiol 2011;46:648–653

3. Porter DA, Heidemann RM., High resolution diffusion-weighted imaging using readout-segmented echo-planar imaging, parallel imaging and a two-dimensional navigator-based reacquisition., Magn Reson Med. 2009 Aug;62(2):468-75

Figures

Fig 1. ROIs outlining Aorta (red), pulmonary artery (green), tumor (yellow) and pneumonia(cyan). Corresponding contrast enhancement curves. Note that the curves exhibit hardly any ripples due to motion. The tumor and pneumonia are clearly differentiated in the rise times and steady state values.

Fig 2. Ktrans and iAUC maps for the corresponding slice with the ROIs from Fig 1. overlaid. Ktrans for pneumonia ROI is 3 times that of the tumor and the iAUC is about 1.5 times.

Fig 3. B0 and ADC maps from resolve co-registered with the images from Fig. 1 and ROIs copied over. The ADC for the pneumonia is only slightly higher than the tumor.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
1605