Case Author(s): James Matthews, M.D., Tom R. Miller, M.D., Ph.D. , 12 August 1994 . Rating: #D3, #Q5
Diagnosis: Quantum mottle (too few particles)
Brief history:
Chest pain, question pulmonary embolism.
Images:
Perfusion scintigraphy.
View main image(vq) in a separate image viewer
Full history/Diagnosis is available below
Diagnosis: Quantum mottle (too few particles)
Full history:
This ia a 68 year-old man with chest pain undergoing evaluation for pulmonary embolism.
Findings:
The chest radiograph was normal and the ventilation images are normal except for mild, diffuse xenon retention in the right lung. Segemental perfusion defects are present in both segments of the right middle lobe. Most strikingly, however, is the very inhomogeneous, patchy appearance of the images.
Discussion:
Pulmonary embolism was felt to be likely, but the images are degraded by severe, diffuse inhomogeneity.
Followup:
Questioning of the technologist revealed that approximately 75% of the Tc-MAA dose was infiltrated in the arm. Based on an estimated administered dose of 250,000 particles, only 50,000-75,000 particles were in the lungs. A second dose of MAA was given and the perfusion images were repeated.
View followup image(vq).
The repeat perfusion images demonstrate uniform perfusion except for the middle lobe defects. The study wss interpreted as high likelihood ratio for pulmonary embolism and the patient was placed on anticoagulants.
Major teaching point(s):
1. The inhomogeneous appearance of the perfusion images strongly suggested quantum mottle artifact. A diffuse airway disease, such as asthma, causing inhomogeneous perfusion was felt to be much less likely because of the essentially normal xenon study and absence of a history of asthma. Pulmonary hypertension frequently gives a similar inhomogeneous perfusion appearance and should also be considered.
2. The quantum mottle phenomenon arises when a small number of particles are administered, leading to an inhomogeneous distribution of particles in the lungs. Collection of too few counts in a study with an appropriate number of particles would give a similar appearance. The threshold for appearance of quantum mottle is 75,000-100,000 particles.
Differential Diagnosis List
1. Quantum mottle artifact.
2. Pulmonary hypertension.
3. Asthma, much less likely.
ACR Codes and Keywords:
References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Other(Artifact))
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Case number: vq002
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