Ventilation/perfusion scintigraphy

A report skeleton for V/P SPECT in suspected pulmonary embolism, with the pregnancy perfusion-first option. It uses the holistic, binary interpretation criteria of the EANM 2019 guideline: PE present, PE absent or non-diagnostic. It also records extent of embolism and alternative diagnoses.

Based on: EANM guideline for ventilation/perfusion SPECT for diagnosis of pulmonary embolism and beyond (Bajc 2019)

VENTILATION/PERFUSION SPECT

CLINICAL INDICATION:
  [Suspected acute PE / follow-up of treated PE / suspected CTEPH / other]
  Wells or Geneva score: [ ]; D-dimer: [ ]; chest radiograph: [ ]
  Relevant history: [COPD / heart failure / pneumonia / malignancy / prior PE / pregnancy, gestation [ ] weeks]

TECHNIQUE:
  Ventilation: [Technegas / 99mTc-DTPA aerosol / 81mKr], [ ] MBq deposited in the lungs
  Perfusion: 99mTc-MAA [ ] MBq IV, approximately [ ] particles
    [Reduced particle number because of pulmonary hypertension / right-to-left shunt / pneumonectomy / single-lung transplant]
  Protocol: [one-day V/P SPECT / perfusion-only SPECT (pregnancy, first step: [50] MBq MAA; ventilation on day 2 only if perfusion abnormal) / perfusion-only (unstable patient)]
  Low-dose CT: [not performed / performed, DLP [ ] mGy·cm]

COMPARISON:
  [Prior V/P or CTPA dated [ ] / none]

FINDINGS:
  Ventilation: [homogeneous / uneven distribution / central deposition / hotspots / defects at [ ]]
  Perfusion: [normal, conforming to the anatomical lung boundaries / defects at [ ]]
  Mismatched defects (wedge-shaped, pleura-based, conforming to vascular anatomy):
    [none / segments and subsegments: [list]]
  Matched defects: [none / [site]]; stripe sign: [present / absent]
  Reversed mismatch: [none / [site]]
  Non-segmental patterns: [antigravitational dorsal redistribution / other]
  Extent of mismatch: [ ] segments and [ ] subsegments, about [ ]% of total lung parenchyma
  CT (if performed): [ ]

INTERPRETATION CRITERIA (EANM 2019, holistic):
  PE present: V/P mismatch of at least one segment or two subsegments conforming to pulmonary vascular anatomy.
  PE absent: normal perfusion conforming to the anatomical boundaries of the lungs; OR matched or reversed-mismatch defects of any size, shape or number in the absence of mismatch; OR mismatch that does not have a lobar, segmental or subsegmental pattern.
  Non-diagnostic: widespread V/P abnormalities not typical of specific diseases.

IMPRESSION:
  1. [PE PRESENT / NO PE / NON-DIAGNOSTIC]
  2. Extent: [ ] segments / [ ]% of lung [and change from prior study]
  3. Other findings: [pattern consistent with COPD / left heart failure / pneumonia / matched defect, e.g. tumour or atelectasis / none]
  4. [Recommendation, e.g. CTPA for an unperfused lung, follow-up V/P to establish a new baseline]

Before you sign

• Report one conclusion: PE present, PE absent or non-diagnostic. EANM recommends holistic interpretation over the older probabilistic (PIOPED) rules, because holistic reading gives very few non-diagnostic reports.
• A single subsegmental mismatch should be reported, but it does not meet the diagnostic criteria for PE.
• Recognise the alternative diagnoses. COPD gives generally uneven ventilation with less affected perfusion (reversed mismatch). In pneumonia, ventilation defects usually exceed perfusion defects, and preserved perfusion along the pleural border (the stripe sign) is a specific sign of pneumonia. Left heart failure gives antigravitational, non-segmental redistribution of perfusion, which is not PE.
• Absent perfusion to a whole lung with preserved ventilation usually means central tumour or other compression of the pulmonary artery, and only rarely PE. Recommend CTPA.
• In the first 3 months of pregnancy, start with perfusion-only SPECT with 50 MBq MAA. Normal perfusion excludes PE, and ventilation is added the next day only if perfusion is abnormal. After the first trimester, the standard 1-day protocol may be considered.
• Count the mismatched segments and subsegments and express the result as an approximate percentage of the total lung. Embolic burden informs decisions about outpatient management.
• V/P is the imaging test of choice to exclude CTEPH. A pre-discharge or follow-up study gives a new baseline that separates old from new PE.

Sources

1. Bajc M, Schümichen C, Grüning T, et al. EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond. Eur J Nucl Med Mol Imaging. 2019;46:2429–51.
2. Bajc M, Neilly JB, Miniati M, et al. EANM guidelines for ventilation/perfusion scintigraphy. Part 1. Pulmonary imaging with ventilation/perfusion single photon emission tomography. Eur J Nucl Med Mol Imaging. 2009;36:1356–70.