Some of the disadvantages of magnetic resonance for imaging of the chest include a prolonged data acquisition time, partial volume averaging, and limited ability to visualize calcium. Also, pleural effusions may not be as easily visualized with MR because visualization depends upon the type of pulse sequence chosen. By prolonging the TR of the pulse sequence, one may increase the ability to demonstrate pleural effusions. The total imaging time for an MR study of the chest is approximately an hour in contrast to 30 minutes for a CT examination. As a consequence of these disadvantages, MR usually is used as a complementary procedure to CT. It is either a technique employed when CT is equivocal, and it is often used as the first line modality for patients who have allergies to iodinated contrast media. Additionally, MR has been used to differentiate tumor recurrence from fibrosis in selected patients. canadian family pharmacy
Since MR allows multiplanar imaging, it is important to understand when the coronal and sagittal plane of imaging is beneficial for evaluation of patients with chest diseases to provide diagnostic information not obtainable on transverse MR or CT images. It has been found that the coronal plane of imaging is superior to the transaxial plane for evaluation of the aortopulmonary window (Fig 2) and for masses within the lung apex or base . The transaxial plane is superior in evaluating the pretracheal space, subcarinal space, and hili. At the level of the pulmonary hili, lateral hilar masses are better delineated on coronal images than are anterior or posterior hilar masses. The coronal plane, using a short TR sequence allows evaluation of most node-bearing mediastinal compartments and provides adequate mass to fat contrast. The sagittal plane allows delineation of lesions within the lung apices and bases and provides another view of the mediastinal vasculature which allows detection of the effect surrounding masses have on these vessels. Sagittal images are useful for evaluation of the thoracic aorta and for evaluating the relationship of subcarinal masses to the trachea, left atrium, and pulmonary artery.
Figure 2. Value of coronal MR images for the aortocopulmonary window. A (left). Transverse CT image obtained after a second bolus of contrast medium to help determine the relationship of the bronchogenic carcinoma (white arrows) to the main (P) and left (LP) pulmonary artery and to the aorticopulmonary window. The CT was indeterminate for evaluation of the AP window (A = aorta). B (right). Coronal gated MR image demonstrates the tumor (white arrows) extending into the AP window (curved arrow). Note the superb delineation of the tumor in relation to the main pulmonary artery (P). LA = left atrium, LV = left ventricle, C = carina.
Tags: blood vessels, carcinoma, pulmonary, thorax