Body planes are imaginary flat surfaces used to divide the body into sections for anatomical study and medical imaging. Understanding these planes is fundamental to interpreting CT scans, MRI images, and ultrasound views.
The Three Primary Body Planes
Sagittal Plane
The sagittal plane divides the body into left and right portions.
Midsagittal (Median) Plane: This plane passes exactly through the midline, dividing the body into equal left and right halves. It passes through the sagittal suture of the skull, the vertebral column, and the midline structures of the body.
Parasagittal Plane: Any sagittal plane that is parallel to the midsagittal plane but offset to one side. These planes divide the body into unequal left and right portions.
Sagittal sections are particularly useful for visualizing the relationship between anterior and posterior structures and are commonly used in imaging the brain, spine, and joints.
Coronal (Frontal) Plane
The coronal plane divides the body into anterior (front) and posterior (back) portions. It is named after the coronal suture of the skull, which it parallels.
Coronal sections are valuable for visualizing structures from front to back, such as the relationship between the ventricles of the brain or the chambers of the heart.
Transverse (Horizontal/Axial) Plane
The transverse plane divides the body into superior (upper) and inferior (lower) portions. It is perpendicular to both the sagittal and coronal planes.
Transverse sections are the most common orientation in CT imaging and provide cross-sectional views of the body. They are essential for visualizing the internal arrangement of organs within body cavities.
Oblique Plane
The oblique plane describes any section that is cut at an angle between the primary planes. Oblique sections are sometimes used to visualize structures that are not well seen in standard planes, such as the long axis of the heart or the alignment of certain joints.
Anatomical Sections in Medical Imaging
CT Imaging
Computed tomography (CT) primarily uses transverse (axial) sections, but modern scanners can reconstruct images in any plane. CT provides excellent bone detail and is used for trauma evaluation, cancer staging, and vascular imaging.
MRI Imaging
Magnetic resonance imaging (MRI) routinely acquires images in all three primary planes. MRI provides superior soft tissue contrast and is the modality of choice for brain, spine, and joint imaging.
Ultrasound
Ultrasound can image in any plane, limited only by the orientation of the transducer. It is real-time and used for obstetrics, cardiac imaging, and abdominal evaluation.
Direction of View
When viewing anatomical sections, it is important to understand the direction from which the section is viewed:
- Sagittal and coronal sections are typically viewed as if the observer is standing in front of the subject
- Transverse sections are viewed from below (as if looking up from the feet), which means the right side of the image corresponds to the left side of the patient
This latter convention, known as radiological convention, is important for interpreting medical images correctly.
Clinical Relevance
Body planes are critical for:
- Planning surgical incisions (surgeons often incise along natural planes)
- Interpreting medical imaging studies
- Describing the location of pathological findings
- Performing and understanding ultrasound examinations
- Radiation therapy planning
A radiologist describing a liver mass might note it is “located in the right lobe, best visualized on coronal images at the level of the portal vein.”