Will PE Show Up on MRI for Myeloma?
No, a pulmonary embolism (PE) will not be reliably detected on a standard MRI scan ordered for multiple myeloma evaluation, and MRI is not an appropriate imaging modality for diagnosing PE.
Why MRI is Not Used for PE Detection
MR angiography (MRA) of the pulmonary arteries has significant limitations for PE diagnosis and is not recommended as a standard imaging test. 1
Key Limitations of MRA for PE:
High rate of technically inadequate studies: The PIOPED III trial found that 25% of MRA studies were technically inadequate for PE diagnosis 1
Poor sensitivity: Among technically adequate MRA studies, sensitivity was only 78% with specificity of 99% 1
Limited subsegmental detection: MRA cannot reliably visualize subsegmental pulmonary emboli, which are frequently present 1
Longer study duration: MRA takes significantly longer than CT pulmonary angiography (CTPA), creating problems for potentially unstable patients 1
Limited availability: MRA is used far less commonly than CTPA and may not be available emergently 1
Standard Imaging for PE Diagnosis
CT pulmonary angiography (CTPA) is the first-line diagnostic imaging modality for suspected PE and should be used instead of MRI. 1, 2
Why CTPA is Preferred:
Excellent accuracy: Sensitivity of 83-99% and specificity of 96-100% 2
Rapid acquisition: Short scan time allows emergency diagnosis 2
High negative predictive value: 96% in patients with low or intermediate clinical probability, with only 1.1% recurrence rate at 3 months after negative CTPA 1, 2
Identifies alternative diagnoses: Can detect pneumonia, pulmonary edema, aortic dissection, and other conditions when PE is excluded 1, 2
24/7 availability: Readily available in most medical centers 2
Clinical Context for Myeloma Patients
Multiple myeloma patients, particularly those receiving immunomodulatory agents (thalidomide, lenalidomide, pomalidomide), have significantly increased risk of thromboembolic events including PE. 3, 4, 5
Risk Factors in Myeloma:
Thalidomide-based regimens: Thalidomide monotherapy (OR 3.33) and thalidomide/steroid combinations (OR 4.24) significantly increase PE risk 5
Hyperviscosity: Elevated serum globulin levels in myeloma contribute to thrombosis risk 6
Immobility: Patients with advanced disease or bone pain may have prolonged bed rest, further increasing risk 6
Appropriate Diagnostic Algorithm for PE in Myeloma Patients
If PE is suspected in a myeloma patient, follow this pathway:
Clinical probability assessment: Use Wells score or Geneva score to determine pretest probability 7
D-dimer testing: If low clinical probability and negative D-dimer, PE can be safely excluded without imaging 1, 8
CTPA imaging: If intermediate/high probability or positive D-dimer, proceed directly to CTPA 1, 2
Alternative if contrast contraindicated: Use ventilation-perfusion (V/Q) scan if patient has severe renal failure, iodine allergy, or pregnancy 2, 8, 7
Lower extremity ultrasound: Consider as adjunct in patients with contraindications to CT contrast or clinical signs of deep vein thrombosis 9
Common Pitfall to Avoid
Do not rely on skeletal MRI studies ordered for myeloma staging to detect or exclude PE. Standard myeloma imaging protocols focus on bone marrow and skeletal structures, not pulmonary vasculature, and will miss pulmonary emboli even if present 1. If PE is clinically suspected, order dedicated PE imaging (CTPA) regardless of other scheduled imaging studies.