A Cardiac Magnetic Resonance (CMR) imaging exam creates detailed pictures of the heart’s structure and function. The actual time spent inside the MRI machine for the scan typically ranges from 45 to 90 minutes, depending on the complexity of the required images. However, the total time you should plan to spend at the facility for the entire appointment is significantly longer, generally between 1.5 and 2.5 hours, as the process involves several steps beyond the image acquisition itself. The ultimate duration is influenced by the specific clinical questions the physician is trying to answer and how well the patient can cooperate during the procedure.
Total Appointment Length Versus Scan Time
The total appointment length is the logistical timeframe, encompassing everything from check-in to final equipment removal. This total time accounts for activities that must occur before the scan can begin and ensures patient safety throughout the process.
The scan time is the portion of the visit where the imaging sequences are actively being acquired while the patient is inside the MRI machine. This period is highly variable because the technologist must monitor the image quality in real-time. If there is patient movement or an issue with the timing of the images, sequences may need to be repeated, which extends the time spent within the scanner.
Step-by-Step Breakdown of the Procedure
Preparation Phase
The appointment begins with a preparation phase, which involves safety screening. If the study requires contrast material, a small intravenous (IV) line is placed in the arm for later injection. This initial setup usually takes 15 to 30 minutes before the patient enters the scanning room.
Setup Phase
Once in the room, the setup phase commences, where the patient is positioned comfortably on the scanner table. Electrocardiogram (ECG) leads are attached to the chest to monitor the heart’s electrical activity, allowing the scanner to synchronize image acquisition with the cardiac cycle. The patient is then moved into the bore of the machine, and a coil is placed over the chest.
Scanning Phase
The scanning phase consists of multiple short acquisitions, each sequence capturing a different view or characteristic of the heart tissue. Many of these sequences require the patient to hold their breath for a short duration, typically 10 to 20 seconds, to prevent motion from respiration from blurring the images. The quality of the final images relies heavily on the patient’s ability to follow these breathing instructions precisely.
If contrast (Gadolinium) is used, it is typically injected midway through the scan, requiring a brief pause in the imaging sequences. Additional sequences are then performed 10 to 20 minutes after the injection to assess myocardial viability and scar tissue, effectively extending the machine time. After all necessary images are acquired, the post-scan time is brief, only requiring the removal of the ECG leads and the IV line before the patient is free to leave.
Specialized Imaging Protocols That Increase Duration
Specialized studies push the scan time toward the upper end of the expected range, sometimes exceeding 90 minutes. One such protocol is Pharmacologic Stress Testing (Stress CMR), which evaluates blood flow to the heart muscle under simulated stress. This requires the administration of a medication, such as Dobutamine or Adenosine, while the patient is in the scanner to temporarily increase the heart rate or dilate the blood vessels.
The stress portion of the exam adds substantial time because it involves careful monitoring by a physician and nurse, alongside the specific imaging sequences performed before, during, and after the medication is administered. Advanced mapping studies also increase the duration by adding specialized sequences not included in a routine study. These include T1 and T2 mapping to quantify the amount of water or fat in the heart muscle, or sequences to measure iron overload, which are crucial for diagnosing specific diseases.
Patient factors can unintentionally lengthen the procedure. Involuntary movements, like coughing or difficulty holding one’s breath for the required 10 to 20 seconds, necessitate the re-scanning of sequences to ensure diagnostic image quality.