Lungs and Mediastinum MRI Scan

MRI the Lungs and Mediastinum

 

Chest MRI usually requested by doctors because to study some common indication like:

Mediastinal lymphadenopathy

Central and superior sulcus bronchial tumors

Distinction between neoplasm and consolidated lung

Alternative to CT scan of the mediastinum and chest wall when the patient is hypersensitive to contrast media.

Vascular evaluation of aortic dissection, pulmonary embolus, aortic aneurysm or vascular stenosis.

Lung perfusion studies.

Assessment of diaphragmatic motion.

Equipment needed during the Chest MRI

Some common equipment like:

Body coil or volume torso multi coil array

RC bellows

ECG or peripheral gating leads

Ear plugs or headphones

Patient Positioning – MRI of the Chest

On the examination couch the patient is lying supine and RC bellows if required, and ECG gating leads are attached. Pads are placed under the patient’s knee and beside the patient’s elbow for optimal MR imaging. If the patient is not comfortable supine or if the patient has trouble in confined spaces, prone position may be an alternative position for the patient.

Patient is positioned so that the longitudinal alignment light lies in the midline, and the horizontal alignment light passes through the level of the 4^th thoracic vertebra, or you may align it on the patient’s nipple. To avoid unsatisfactory ECG traces the patient should place to a feet first setting because  this changes in patient’s polarity with the main field.

Gating and Respiratory Compensation Techniques

Suggested Protocol Chest MRI

Coronal Breath Hold Fast Incoherent (Spoiled) GRE / SE T1

It acts as the localizer if the three-plane localization is not available, or it also use as a diagnostic sequence. These are medium slices and are prescribe to the vertical alignment of the lazer light, from the posterior chest muscles to the sternum. The entire lungs from apex to diaphragm or the base of the lung should be included in the image. As the chest anatomy is generally located more anterior the posterior, slice are offset in the anterior direction.

Localizer Chest MRI

 

Axial FSE T1 or GRE T1 – Incoherent Spoiled

It is an transverse T1 view slices of the chest, except slice thickness is adjusted to fit the ROI. It is the prescribe slices from the diaphragm to the apex of the lung or through the ROI.

Axial SE T1

weighted gated image of the

chest or axial imaging.

Axial FSE PD / T2 / SS-FSE T2 or GRE T2

A slice prescription as for Axial T1. It is useful to characterize active tissue such as distinguishing tumors from consolidated lung and evaluate fluid pneumonia or pleural effusion.

Axial SE showing lesion in the left lung

Additional Sequence - Chest MRI

Perfusion Studies

The lung perfusion can be evaluated by either administering contrast or with spin tagged perfusion techniques. In these cases contrast is use or tagged with either contrast or arterial spin tagging applied in the middle of the patient in an attempt to saturate the blood flowing from the heart and into the lungs by way of the pulmonary ateries.

Ventilation Studies

This study is a function with the VQ scan used in nuclear medicine by letting patient breath with hyperpolarized helium gas and holds the breath while scanning.

Coronal Fast Incoherent GRE T1 or SS-FSE T2

This sequence of planning can be used during respiration to assess motion of the diaphragm. In this technique, images are acquired during normal respiration and replayed as a movie or cine loop. 

Use of Contrast Media

Contrast like hypolarized helium gases is use to enhance the image of the lung and hilar masses. This may be helpful to increase the conspicuity of pathology in an area with low inherent contrast and to visualize pleural inflammation. Contrast can also be useful for visualizing chest vessels. Gaseous agents such as hyperpolarized helium gas are under investigation for the evaluation of lung ventilation during inhalation.