2.6 Patient Screening Workflows

Patient Screening Workflows

The Multiphase MR Safety Screening Process

The patient screening workflow is the primary defense against catastrophic accidents in the Magnetic Resonance (MR) environment. Because the static magnetic field ($B_0$) is always active (24 hours a day, 7 days a week), screening must be treated as an active, rigorous clinical protocol, rather than a passive administrative task.

The American College of Radiology (ACR) recommends a multiphase screening process consisting of at least three distinct steps before any patient, companion, or staff member enters the MR magnet room (Zone IV):

1. The Written Screening Questionnaire: Completed by the patient, guardian, or proxy.
2. The Verbal Interactive Interview: Conducted by a qualified Level 2 MR personnel (most commonly the MRI technologist).
3. The Physical Preparation and Verification: Removal of personal belongings, changing into facility-provided gowns, and optional screening with ferromagnetic detectors (FMDs).

[Written Screening Form] -> [Verbal Interactive Interview] -> [Physical Prep & FMD Check] -> [Zone IV Entry]

The Written Screening Questionnaire

The written form is the foundation of screening. It must be completed shortly before the examination to ensure it reflects the patient's current clinical state. The questionnaire is structured to systematically identify any contraindications, metallic hazards, or biological risks.

Essential Components of the Screening Form

• Implant and Device History: Specific questions regarding pacemakers, implantable cardioverter-defibrillators (ICDs), neurostimulators, cochlear implants, drug infusion pumps, aneurysm clips, intravascular stents, and heart valves.
• Foreign Body Screening: Questions asking if the patient has ever been injured by metallic fragments, shrapnel, or bullets. Crucially, occupational history (e.g., sheet metal workers, welders, machinists) must be detailed to assess the risk of ocular metallic foreign bodies.
• Prior Surgical History: A chronological list of all surgical procedures, including minor outpatient surgeries. Even if the patient believes a surgery was "non-metallic," the technologist must review it to ensure no markers, clips, or devices were left behind.
• Physical/Biological Risks: Verification of pregnancy status (especially in the first trimester), breastfeeding status (relevant if gadolinium is planned), and kidney disease history (requiring renal function assessment / eGFR for contrast safety).
• External Metallic Hazards: Questions identifying transdermal medication patches (which may contain aluminum or other metallic backings that cause burns), tattoos, permanent makeup, or piercings.

The Verbal Interactive Interview

A written form alone is insufficient. Patients often misinterpret medical terminology or fail to recall relevant surgeries. Therefore, a verbal, face-to-face interview conducted by Level 2 MR personnel is mandatory.

Interview Techniques and Communication Rules

• Use Lay Terminology: Instead of asking, "Do you have an implantable cardioverter-defibrillator?" the technologist should ask, "Do you have a device under your skin to help control your heart rhythm, or have you ever had a pacemaker?"
• Review Every Yes and No: The technologist must review each question on the form with the patient, confirming that they understood the question. For example, if a patient checked "No" to surgeries, the technologist should verbally ask, "Have you ever had any surgeries at all in your life, even minor ones?"
• Verify Orbital Metal Risk: If the patient indicates a history of metallic foreign bodies in the eye (or a history of welding/grinding without eye protection), the technologist must halt the workflow. The patient must undergo screening orbital X-rays (typically a baseline set of Waters and lateral views) to verify the absence of ferromagnetic fragments before entering Zone IV. The films must be formally read and cleared by a radiologist.

Screening Companions and Non-MR Personnel

A common source of MRI accidents involves non-patients, such as family members, caregivers, anesthesia staff, or nurses.

• The Absolute Rule: Any individual entering Zone IV must undergo the exact same screening workflow as the patient.
• Companions: If a parent is staying in the room to comfort a pediatric patient, they must fill out a written form and undergo the verbal interview. They must remove all metal, change into scrubs or a gown if necessary, and leave behind cell phones, keys, and wallets.
• Medical Personnel: Nurses, respiratory therapists, and anesthesiologists must be screened. Anesthesiologists must ensure their stethoscopes, pens, and laryngoscopes are MR Safe or Conditional before crossing the threshold of Zone III into Zone IV.

Documentation Checks and Implant Verification

When an implant is identified, the technologist must execute a rigorous verification protocol:

1. Identify the Device: Obtain the manufacturer, model name, model number, and date of implantation. This is often found on the patient's device ID card or in surgical reports.
2. Search the Safety Database: Reference official resources such as the manufacturer's safety manual, the FDA safety database, or reference websites (e.g., MRISafety.com) to check the device's labeling:
   • MR Safe: The device poses no hazards in any MR environment (e.g., plastic or glass).
   • MR Conditional: The device is safe only under specific, verified conditions (e.g., static field strength of 1.5T or 3.0T, maximum spatial field gradient, maximum SAR limits, and specific gradient slew rates). The technologist must program the scanner to match these parameters.
   • MR Unsafe: The device is highly hazardous and must not enter Zone IV.
3. Obtain Radiologist Approval: Any conditional device settings must be reviewed and approved by the supervising radiologist or MR Medical Director, and documented in the patient's chart.
4. "Active" vs. "Passive" Safety Check: Passive screening relies on the patient's memory. Active screening involves checking clinical notes, scanning for scars, and utilizing ferromagnetic detection systems at the entrance of Zone IV to catch any forgotten metallic objects.