Magnetic Resonance Imaging (MRI) uses strong magnetic fields and radio waves to create detailed pictures of the body’s internal structures. A thoracic spine MRI focuses on the mid-back region, extending from the base of the neck to the bottom of the rib cage. This imaging technique provides detailed views of the bones, soft tissues, and surrounding organs, useful for evaluating mid-back issues. Understanding the images and report provides insight into potential problems, but a physician must always provide the final medical interpretation.
The Thoracic Spine Structure
The thoracic spine is the longest section of the vertebral column, consisting of twelve individual vertebrae labeled T1 through T12. These bones are stacked, forming the central axis of the back and anchoring the rib cage. Unlike the cervical and lumbar regions, the thoracic spine primarily provides stability and support.
Between each pair of vertebral bodies is an intervertebral disc, which acts as a cushion and shock absorber. The vertebral canal runs vertically through the center of the stacked vertebrae, creating a protective tunnel that houses the spinal cord.
The spinal cord is a dense bundle of nerve tissue that transmits signals between the brain and the rest of the body. Nerves branch off the spinal cord at each level, exiting the column through small openings on the sides called foramina. In the thoracic region, these nerves supply sensation and movement to parts of the chest, abdomen, arms, and hands.
Understanding MRI Terminology and Views
Interpreting an MRI requires understanding the different image types, determined by how the machine processes the signal from hydrogen protons. The two primary sequences are T1-weighted (T1W) and T2-weighted (T2W) images, which highlight different tissue properties.
T1-weighted images are useful for visualizing anatomical detail because they show fat as bright and fluid, such as cerebrospinal fluid (CSF), as dark. Bone marrow appears intermediate to bright, while the dense outer bone cortex appears dark.
T2-weighted images are excellent for identifying pathology because they highlight water and fluid, which appear very bright. This sequence is effective for detecting inflammation, edema, or cysts, as these conditions involve increased water content. On T2 images, the spinal cord and soft tissues are clearly visible against the bright surrounding CSF.
The images are presented in different viewing planes, or “slices.” The sagittal view provides a side-to-side profile, helpful for assessing vertebral alignment and the relationship between discs and the spinal cord. The axial view presents cross-sectional slices, allowing detailed evaluation of the spinal canal’s width and any compression on exiting nerve roots.
Sometimes, a contrast agent is injected intravenously before the scan. This material enhances the visibility of certain tissues or abnormalities, such as tumors or infections, by causing them to appear brighter on T1-weighted images. Contrast helps differentiate between conditions that might otherwise look similar on a non-contrast scan.
Identifying Common Findings
A normal thoracic spine MRI shows consistently aligned vertebral bodies with smooth contours and well-hydrated intervertebral discs, which appear bright on T2-weighted images. Deviations signal a potential problem, such as a disc herniation or bulge, where disc material extends beyond its boundary. A herniation appears dark on T2 images (less water content), potentially pushing into the spinal canal and compressing the spinal cord or a nerve root.
Spinal stenosis is a common finding, representing a narrowing of the spaces within the spine that puts pressure on the nerves or spinal cord. On axial slices, this narrowing is visually apparent as a reduction in the space surrounding the spinal cord or the exiting foramina. This narrowing can be caused by bulging discs, thickening ligaments, or bone spurs.
Vertebral compression fractures, often associated with osteoporosis or trauma, are also detectable. A recent fracture may show a misshapen vertebral body with a low signal on T1 images and a high signal on T2 images, indicating edema or bleeding within the bone marrow.
Inflammation or edema in the soft tissues or bone is recognized by an abnormal brightness on T2-weighted sequences. This bright T2 signal reflects increased water content, a sign of active infection, trauma, or a tumor. The radiologist describes the size and location of these findings, noting if they are causing any contact or “mass effect” on adjacent nervous structures.
How to Interpret the Radiologist’s Report
The radiologist’s report is the summary of the MRI findings, structured in a standardized medical format. Reports begin with the Clinical Indication, stating why the study was performed, followed by the Technique section, detailing the sequences and use of contrast material. The Findings section is the longest part, providing a systematic review of the visible anatomy.
In the Findings section, you will encounter jargon like “degenerative changes,” a broad term for age-related wear and tear, such as osteoarthritis. A phrase like “intact alignment” means the vertebrae are properly stacked without abnormal curvature or slippage. If the radiologist notes a “signal abnormality,” it suggests a deviation from healthy tissue.
The Impression or Conclusion is the most important section, condensing the detailed findings into a summary of the most significant observations. This section usually lists the most likely diagnoses or conditions correlating with the patient’s symptoms. Patients should review this report with their treating physician, who integrates the imaging results with the physical examination and medical history to formulate a final diagnosis and treatment plan.