MR 203 Week 6

Larynx and Neck Imaging: Indications and Setup

  • Indications for laryngeal imaging:
    • Carcinoma or suspected malignancy in the larynx region
    • Vocal cord nodules or polyps or other cord disorders
    • Trauma to the laryngeal region
    • Reconstruction planning of the larynx/vocal cords
    • Post-radiation therapy changes to the larynx area and vocal cords
  • Equipment and coils:
    • Anterior neck coil is preferred
    • Some setups have coil options for TMJs or other regions, but for the neck use the anterior neck coil
  • Patient positioning and immobilization:
    • Patient is supine
    • Place a wedge under the feet and knees to flex the legs (comfortable positioning)
    • Longitudinal light placed midline, then a horizontal line through the thyroid cartilage (just below the Adam's apple) or just below the hyoid bone
    • Centering: head in neutral, IPL (pupillary line) parallel to the imaging plane; prevent head tilt
  • Landmarks and centering principles:
    • Centering point around the mid-neck region, roughly around vertebral levels C3–C5
    • The exam targets tiny structures in this area; expect to use thin slice gaps for high detail
  • Planes, localization, and coverage:
    • Field of view planned to cover from the mouth/hard palate down to the sternoclavicular (SC) joints, i.e., the anterior neck region
    • Coverage can extend from the hard palate to the SC joints; the field can be tailored to shrink unnecessarily into the brain if not required
    • Localizers typically axial or coronal; sagittal localizer used to set up sagittal images
  • Slice orientation and relationships:
    • Axial slices: set to be parallel to the larynx for tumor evaluation; acquired from a coronal or axial localizer, then sagittal reconstructions
    • Sagittal fast spin echo sequence (for testing): typically used for sagittal coverage; mention of a T1/T2 variant may appear in slides but may not be tested
    • Coronal fast spin echo T1: similar to C-spine planning, box moved downward to include anterior neck; ensure field includes all relevant anatomy from hard palate to SC joints
    • The coronal prescription is often like a C-spine or head study, with adjustments to include the anterior neck anatomy
  • Axial and coronal planning details:
    • Axial slices are very thin; anatomy is small; best to set up with axial or coronal localizers first, then acquire the axial stack parallel to the larynx
    • Coronal slices should be obtained from posterior to anterior, moving inferiorly; consider keeping field of view forward from the spine
    • Try to include the hard palate and the SC joint in the coverage; may require reducing the superior field of view to avoid unnecessary brain imaging
  • Specific sequences commonly used:
    • Axial fast spin echo sequences (T1, T2): thin slices; parallel to the larynx
    • Coronal fast spin echo sequences (T1): broad overview of thyroid/cartilage and laryngeal structures
    • Sagittal fast spin echo sequence (noted as possible T1/T2 in slides; may not be on the test)
  • Additional notes:
    • The coronal and sagittal stack planning should resemble the C-spine workflow; images acquired as axials, coronal, and sometimes sagittals depending on protocol
    • The goal is to obtain crisp detail of tiny laryngeal structures with thin slices and minimal aliasing
    • Operator might adjust slice thickness, gaps, and orientation to maximize coverage of the thyroid cartilage, hyoid bone, Adam's apple, and surrounding soft tissue

Functional Imaging and Specialized Neck Sequences

  • Phonation (vocal cord function) imaging:
    • During phonation (speaking/motion of vocal cords), use a fast and coherent spoiled gradient echo sequence to assess function
    • Functional imaging can be used to evaluate how the cords move, and may be part of exam discussion on vocal function
  • Fat suppression and post-processing:
    • In some protocols, fat-suppressed post-contrast sequences are employed to improve lesion conspicuity in the neck

Thyroid and Parathyroid Imaging: Indications and Protocols

  • Indications:
    • Goiter assessment, thyroid nodules, and potential thyroid cancer detection
    • Post-radiation therapy changes in the thyroid region
    • Evaluation of possible parathyroid abnormalities or nodules
  • Practical anatomy notes:
    • The thyroid gland sits in the midline neck region anteriorly; surrounding structures include the thyroid cartilage and hyoid bone
    • The Adam's apple (thyroid cartilage) is a key landmark for orientation
  • Equipment and setup:
    • Use the same anterior neck coil as for the larynx imaging
    • Immobilization foam pads and supine positioning remain standard
  • Centering and orientation:
    • Horizontal light line placed just below the thyroid cartilage; approximate centering around C3–C5 levels
    • Coverage from the mouth/hard palate to SC joints; may extend a little above and below to include the thyroid and surrounding tissues
  • Protocol specifics:
    • Typically a combination of axial and coronal planes; sagittal may be used in some centers
    • Very thin slices; multiple nexuses to improve SNR and resolution
    • Axial slices should be parallel to the larynx in this region as well
    • Coronal prescription similar to thyroid imaging in neck protocols; start around the inferior thyroid region and move superiorly
  • Sequences and contrasts:
    • Axial fast spin echo T1 and T2; coronal fast spin echo T1; sagittal variants may appear
    • STIR sequences are useful for thyroid tumor evaluation
    • DWI (diffusion-weighted imaging) helps differentiate benign vs malignant processes, particularly for assessing nodal involvement
    • Fat-saturated post-contrast T1 sequences are commonly used to assess enhancement patterns
    • Post-contrast imaging can be valuable for identifying suspicious nodules or inflammatory/infectious processes
  • Diffusion-weighted imaging considerations:
    • DWI is helpful for distinguishing benign from malignant lesions and evaluating lymph nodes
    • SNR is often poorer in neck DWI due to motion, air/tat tissue interfaces, and small structures
    • Use high-SNR configurations: prefer a high-quality anterior neck coil and potentially multiple receiver channels (multiple nexuses) to improve SNR
  • Technical tips for neck DWI:
    • Expect longer scan times and potential motion; use saturation bands above and below the neck to mitigate motion and vascular pulsation artifacts
    • Consider a smaller FOV and careful coil selection to maximize SNR and reduce artifacts
  • Other practical considerations:
    • The anterior neck anatomy is challenging due to close proximity to air-tissue interfaces, carotid/jugular vessels, swallowing motion, and thyroid tissue signal characteristics
    • For goiter or thyroid cancer evaluation, use appropriate coil, thin slices, and fat suppression to enhance lesion conspicuity
  • Real-world relevance and anecdotes:
    • Public awareness anecdotes (e.g., a high-profile thyroid cancer discovery) illustrate why thyroid imaging is important for early detection and treatment planning

TMJ Imaging: Technique, Setup, and Dynamic Assessments

  • Indications:
    • Temporomandibular joint (TMJ) disorders, including meniscal derangements or internal derangements
    • Evaluation of jaw movement, click/catch, and assessing TMJ anatomy
  • Equipment:
    • Often two small circular coils for bilateral TMJ imaging; typical coil size is about 3'' diameter; you may use two of these if available
    • If dedicated TMJ coils are not available, a head coil may be used; imaging may be performed one joint at a time
  • Patient positioning:
    • Supine position with the patient relaxed
    • Place a mouth-opening device to maintain controlled mouth opening during imaging; common devices include simple clear plastic spacers or improvised devices like a syringe if needed
  • Mouth positions and planes:
    • Acquire images with the mouth closed first (baseline)
    • Then acquire images with the mouth opened to assess articulation and possible impingement or derangement
    • Open-mouth and closed-mouth acquisitions often include sagittal obliques and coronal planes to visualize the condyle relative to the fossa
  • Field-of-view and orientation:
    • Use a small field of view oriented to the TMJ region to maximize spatial resolution while reducing motion artifacts
    • Oblique sagittal planes along the jaw/condyle axis help capture joint dynamics; coronal planes help view the joint laterally
  • Dynamic or motion imaging:
    • Dynamic MRI of the TMJ (open/close mouth) can be performed to evaluate movement patterns and detect functional derangements
    • Some protocols use functional imaging where the patient opens and closes the mouth during acquisition
  • Imaging sequences:
    • Thin axial slices to visualize the joint and surrounding soft tissue
    • Coronal and sagittal plane acquisitions for comprehensive TMJ assessment
    • Orthogonal coronal/axial planes may be used to better align with the condylar neck and the articular eminence
  • Artifacts and mitigation:
    • Expect swallowing, jaw movement, and vascular pulsation to create artifacts
    • Saturation bands and a small FOV help reduce motion and vascular artifacts
    • Instruct patient to minimize swallowing during data acquisition; allow swallowing during non-imaging periods
  • Additional considerations:
    • If contrast is used (arthrography), gadolinium can be injected into the TMJ under T1 post-contrast sequences; this is a more invasive technique and is not routinely performed in all centers
    • Arthrography provides enhanced delineation of the joint capsule and intra-articular structures but can be uncomfortable due to joint injection
  • Practical notes:
    • Demonstrates the value of dynamic imaging for functional assessment of the TMJ
    • If dedicated TMJ coils are unavailable, a head coil remains useful with careful protocol adjustments

Acquisition Principles Across Neck Imaging: High-Quality Imaging Practices

  • Common high-yield principles:
    • Thin slices and high-resolution acquisition to visualize small structures in the neck
    • Use of multiple receiver channels (NEX and coil configurations) to boost SNR and detail
    • Rectangular or asymmetrical field-of-view (FOV) to reduce scan time while preserving needed detail
    • Pre- and post-contrast imaging when appropriate, including fat-saturated T1 sequences for lesion conspicuity
  • Artifact reduction strategies:
    • Saturation bands placed above and below the region of interest to mitigate venous pulsation and swallowing motion
    • Gradient moment nulling (to reduce certain T2* and motion-related artifacts)
    • In neck imaging, keep saturation bands as close to the FOV as possible without clipping anatomy
    • For DWI in neck imaging, ensure robust coil performance and patient immobilization to counteract low SNR
  • Motion management and patient instructions:
    • Advise patients not to swallow during image acquisition whenever possible; swallowing can cause motion artifacts
    • Use padding and supports to minimize breathing and posture movement; consider breathing guidance if necessary
  • Field-of-view and localization considerations:
    • The neck field of view should be carefully chosen to avoid unnecessary inclusion of brain structures while including the hard palate and SC joints when needed
    • If the field is extended too far superiorly or inferiorly, it can increase scan time and motion risk

Practical Imaging Scenarios and Tips

  • Field optimization and localizers:
    • Start with axial or coronal localizers, then plan sagittal sets from those; adjust to parallel the C-spine orientation
    • For larynx and neck exams, maintain a consistent IPL alignment and avoid head tilt to ensure reproducible slices
  • Sequence selection summary:
    • Larynx: axial fast spin echo (T1/T2), coronal fast spin echo (T1), sagittal fast spin echo (T1/T2 variants may appear but test reliability varies)
    • Phonation: fast spoiled gradient echo sequences to examine vocal cord motion
    • Thyroid/parathyroid: axial and coronal fast spin echo T1/T2, STIR, DWI, and post-contrast T1 with fat suppression as needed
    • TMJ: thin-slice axial, plus sagittal oblique and coronal acquisitions; dynamic imaging with mouth opening
  • Contrast and post-processing:
    • Gadolinium-based contrast may be used for post-contrast T1 imaging; fat saturation helps highlight enhancement
    • Consider arthrography if joint capsule delineation is needed (arthrogram with gadolinium)
  • Specific clinical pearls:
    • The anterior neck coil yields higher SNR for the neck structures; use a dedicated coil whenever possible
    • When imaging the TMJ, dynamic mouth movement can reveal functional abnormalities not seen on static images
    • The neck region presents numerous small structures; use consistent, thin slices and high-resolution protocols for reliable evaluation

Ethical, Practical, and Real-World Considerations

  • Clinical relevance:
    • Neck MRI is essential for evaluating malignancy risk, nodules, and postoperative changes in the larynx and thyroid region
    • Accurate imaging of the TMJ assists in diagnosing degenerative or derangement conditions and planning potential interventions
  • Patient safety and comfort:
    • Provide clear instructions about swallowing and mouth opening devices to minimize discomfort and motion
    • Be mindful of potential adverse reactions to contrast and ensure appropriate screening prior to gadolinium administration
  • Real-world anecdotes:
    • Public awareness stories (e.g., celebrities with thyroid cancer) underscore the importance of early detection and imaging follow-up when indicated

Quick Reference: Key Anatomical Landmarks and Planes in Neck MRI

  • Landmarks:
    • Adam's apple (thyroid cartilage)
    • Hyoid bone
    • Thyroid gland
    • Hard palate (mouth opening landmarks for coverage)
    • SC joints
  • Vertebral levels often used as rough anchors:
    • C3, C4, C_5
  • Planes and orientations:
    • Axial slices: parallel to the larynx
    • Coronal slices: anterior-posterior orientation, often similar to C-spine coronal planes
    • Sagittal slices: medial-lateral orientation, sometimes used for sagittal fast spin echo
  • Field of view concepts:
    • Narrow FOV for TMJ and neck to improve resolution and reduce motion artifacts
    • Broad FOV for thyroid and entire neck to capture anterior and posterior structures

Summary of Core Takeaways

  • Neck MRI requires precise patient positioning, appropriate coil selection (prefer anterior neck coil), and thin-slice imaging to visualize tiny laryngeal and thyroid structures
  • A combination of axial, coronal, and sagittal planes is used, with attention to pro-grade alignment parallel to the C-spine and larynx
  • Specific sequences support different clinical goals: structural assessment (T1/T2 FSE), functional evaluation (phonation with gradient echo), and tissue characterization (STIR, DWI, fat-sat post-contrast)
  • For TMJ imaging, dynamic (open/close) imaging and dedicated coil setups (two small circular coils) enhance evaluation of the condyle and joint space; arthrography is possible but invasive
  • Artifact mitigation is critical in neck imaging due to swallowing, carotid/jugular vessels, and motion; saturation bands and gradient moment nulling are common strategies
  • Practical considerations, including patient instructions, localizer planning, and maximizing SNR with multiple receiver channels, directly affect image quality and diagnostic yield