Grading Lung Uptake on Gallium Scan

Diffuse uptake of Gallium by the lungs may be normal at 24 hours, but abnormal at 48 hours. Gallium uptake at 48 hours can be graded to aid in diagnosis. A grade of 2 or more is considered abnormal. The posterior projection is used, as it is thought to minimize sensitivity to differences in body size, gender, and habitus.

Grade	Amount of Uptake
1	Similar to soft tissue background
2	Greater than soft tissue, but less than bone marrow
3	Greater than bone marrow, but less than liver
4	Greater than liver

I'm unable to find a peer-reviewed reference addressing the specificity and sensitivity of different grades for different pathologic processes.

Diffusely increased lung uptake on ⁶⁷Ga can be seen with:

• Infection: Pneumocystis jiroveci, Mycobacterium, etc.
• Hypersensitivity pneumonitis:
• Sarcoidosis:

References

Line BR at al. Gallium-67 scanning to stage the alveolitis of sarcoidosis: correlation with clinical studies, pulmonary function studies, and bronchoalveolar lavage. Am Rev Respir Dis. 1981 Apr;123(4 Pt 1):440-6. Line BR, Hunninghake GW, Keogh BA, Jones AE, Johnston GS, Crystal RG