MRI Sinogram is a specific imaging technique that combines magnetic resonance imaging (MRI) and the administration of a contrast material into the sinus tract or body cavity and is utilised to assess sinus tracts, fistulas, and any kind of unusual passageways within the human body. This technique offers a detailed picture (image) of the course and length of the sinus or fistulous path and of the condition of the tissue around the path.

MRI Sinogram is particularly useful if a conventional fistulogram is inadequate, a CT-based sinogram is inadequate, or if patients do not want to be exposed to radiation. It provides excellent soft tissue contrast and aids in the visualization of inflammatory changes associated with it or the presence of an abscess.

Purpose of MRI Sinogram

1. Evaluation of Sinus Tracts

• Determines the course for a contraction/expansion and its goals.
• Assists in distinguishing simple sinus pathways from complex sinus pathways.

2. Fistula Assessment

• Establishes internal spaces, multiple branches, and relationships with adjacent buildings.
• Helps to map out physiologic tracts before surgery.

3. Detection of Infection and Inflammation

• Makes a diagnosis of cellulitis, inflammatory changes around the tract, and abscess.

4. Post-Surgical Follow-Up

• Takes up the grading of sinus or fistula healing or surgery recurrence.

5. Tumor Evaluation

• Discovers the underlying neoplastic causes that may lead to chronic draining sinuses.

Common Clinical Indications

• Chronic perianal fistulas.
• Wounds that do not heal after surgery with sinus formation.
• Constant discharging sinuses in the chest wall, abdomen, or extremities.
• Sinus tracts evaluation in osteomyelitis.
• A complicated pilonidal sinus infection.
• Infected implants / orthopedic hardware sinus tracts.

Procedure for MRI Sinogram

Before the Scan

• A detailed medical history is obtained to identify the site, duration, and past treatments of the sinus or fistula.
• Any contraindications to MRI, such as incompatible implants, are assessed.
• The patient is given information regarding the procedure (including injection of contrast into the tract).
• Use of sterile precautions in the administration of contrast media.

During the Scan

• The external opening of the sinus is cleaned and sterilized.
• A small tube (cannula or catheter) is inserted through the sinus opening.
• Some diluted MRI-compatible contrast injection (usually gadolinium-based) is slowly injected into the tract and fills the lumen.
• Images are taken right after contrast to eliminate leakage or absorption of the contrast from the tract from which the image is being constructed.
• The area being scanned is probed in several planes to map an entire tract of land.
• Typical MRI scans consist of the T1-weighted, T2-weighted, and fat-suppressed before and after administration of a contrast agent.

After the Scan

• Then the catheter is taken out, and the hole is washed.
• With sedation, the patient will not be able to resume normal activities.
• The radiologist inspects the path, side branches, hollows within the tract, and any pathology that may be present.

MRI Sequences Used in Sinogram Studies

T1-Weighted Pre-Contrast

• Assesses anatomical details and baseline tract appearance.

T2-Weighted Images

• Highlight fluid-filled tracts and surrounding edema.

Fat-Suppressed T2/STIR Sequences

• Improve detection of inflammation and abscesses in surrounding tissues.

Post-Contrast T1-Weighted Fat-Suppressed Images

• Clearly delineate tract enhancement, side branches, and connections to organs or cavities.

3D Sequences

• Allow multiplanar reconstruction for precise surgical mapping.

Advantages of MRI Sinogram

• Magnetic resonance has much better soft tissue contrast than computed tomography's sinogram.
• Works without using X-rays or other forms of radiation and can be used in repeated studies.
• Improved visualisation of inflammatory changes and abscesses.
• In some cases, the complexity of the images makes it necessary to map them with multiplanar imaging to be sure.
• Identifies the subtle secondary tracts which may not be visualised by conventional sinography.

Limitations

• Larger, more expensive, and not as available as CT.
• Needs careful injection with dye to prevent extravasation
• Not suitable for patients with some metal implants or those with extreme claustrophobia.
• Longer scan time than with the CT sinogram.

Common Findings Detected

Simple Sinus Tract

• Single straight tract without branching

Complex Sinus Tract

• Multiple branches or interconnected tracts

Internal Openings

• Connections to hollow organs, joints, or other anatomical structures

Associated Abscess

• Localized fluid collection with rim enhancement

Inflammatory Changes

• Edema, soft tissue thickening, and hyperintensity around the tract

Underlying Bone Involvement

• Osteomyelitis features such as marrow edema and cortical destruction

Tumorous Cause

• Mass lesions involving or surrounding the sinus tract

When is an MRI Sinogram Preferred?

• For recurrent or complex fistulas, surgical planning may be necessary.
• Do not use radiation if there is a risk, and particularly in younger patients.
• If you need a detailed assessment of soft tissues as well as a tract map.
• If the CT examination is not helpful.

Patient Preparation Tips

• Clothing should be loose and comfortable, and free of any metal accessories.
• Let the radiology staff know if the patient is allergic to any drugs, has used contrast before, or has implants or surgery in the area to be scanned.
• Take into account hygiene precautions before the procedure in order to minimize the risk of infection.
• Do not move during imaging for clear images.

Applications in Different Body Regions

Perianal Region

• Assesses intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric fistulas
• Identifies secondary extensions that influence surgical planning

Chest Wall

• Evaluates sinus tracts due to post-thoracotomy infection or empyema

Abdominal Wall

• Detects postoperative fistulas connecting to bowel loops

Extremities

• Maps sinus tracts related to chronic osteomyelitis

Spine

• Detects cutaneous sinuses in spinal infections or post-surgical complications

Conclusion

MRIs are also highly effective, radiation-free imaging modalities for the evaluation of sinus tracts/fistulas with excellent soft tissue detail, under a new generation of MRI Sinogram available. It has exquisite mapping of the origin, course, and termination of the tract and can identify side branches, internal openings, and complications like inflammatory changes or abscesses.

This detailed information is crucial for the proper surgical planning, preventing recurrence, and appropriate medical or surgical management. In cases of complex, recurrent, or unclear radiographs, the MRI Sinogram is especially helpful.