Nuclear Medicine in Pulmonology

Focus on diagnostics related to:
  - Perfusion and Ventilation Lung Scintigraphy
  - F-18 FDG PET/CT
    - Applications in analyzing solitary pulmonary nodules, mediastinal and/or hilar lymphadenopathy, pleural thickening, and staging of malignant tumors and sarcoidosis.

Radiopharmaceutical Used: Tc-99m macroaggregate of human albumin (MAA)
Administration Method: Intravenous
Mechanism:
- Microembolisation of pulmonary capillaries observed through the distribution of particles that illustrate regional perfusion.

Radiopharmaceutical Used: Tc-99m Technegas (aerosol)
Administration Method: Inhalation
Mechanism:
- Evaluates distribution of gas in the lungs to assess ventilation.

Acute Pulmonary Thromboembolism:
- Findings: Identifying 2 subsegmental or 1 segmental wedge-shaped defects with the base projecting towards the lung periphery and normal ventilation (ventilation/perfusion mismatch).
Segmental Charts: Used in identifying regions of interest with wedge-shaped defects.

Published in: Eur J Nucl Med Mol Imaging (2019)
Sensitivity:
- Lung Scintigraphy: ≥ 96%
- CT Pulmonary Angiography: ≥ 78%
Specificity:
- Lung Scintigraphy: ≥ 97%
- CT Pulmonary Angiography: ≥ 98%
Effective Radiation Dose:
- Lung Scintigraphy: 1.2-2 mSv (additional 1-2 mSv with low-dose CT)
- CT Pulmonary Angiography: 4-20 mSv
Absorbed Breast Radiation Dose:
- Lung Scintigraphy: ≈ 0.8 Gy
- CT Pulmonary Angiography: ≈ 12-44 mGy
Fetal Absorbed Radiation Dose: Considered low in both methods.
Contraindications:
- Lung Scintigraphy: None
- CT Pulmonary Angiography: Iodine allergy, suppressed TSH level, nephropathy.

Radiopharmaceutical Used: F-18 fluorodeoxyglucose (FDG)
- Function: Analogue of glucose, utilized for metabolic imaging.
Uptake Mechanism: Cells with increased glucose metabolism (tumor and inflammatory cells) demonstrate FDG uptake.
Administration Method: Intravenous
Clinical Applications:
  - Analysis of solitary pulmonary nodules, lymphadenopathy, and pleural thickening.
  - Staging of malignant tumors and therapy response tracking.
  - Assessing inflammatory diseases such as sarcoidosis.

Solitary Pulmonary Nodule:
- Diameter larger than 7 mm requires cytological/pathohistological analysis if FDG uptake is observed.
- FDG positive lesion indicates further investigation (especially if uptake is low).
Pleural Thickening:
- In cases like pleural tuberculosis or mesothelioma, cytological/pathohistological analysis is recommended if FDG uptake is observed.
Lymphadenopathy:
- Cytological/pathohistological analysis recommended upon seeing FDG uptake in lymph nodes.

Stages and Therapy Response:
- Utilizes F-18 FDG PET/CT for assessing extent of malignancy and monitoring treatment efficacy.

Example: Sarcoidosis - the extent of involvement can be monitored through FDG PET/CT imaging.
- Involvement indicators might include infected mediastinal lymph nodes and enlarged structures affecting lung functionality.

For suspected Pulmonary Embolism (PE):
- Consider perfusion and ventilation lung scintigraphy if available.
FDG PET/CT:
  - Demonstrates high sensitivity for detection, staging, and therapy response in lung and pleural cancers.
  - Applicable for staging of inflammatory diseases like sarcoidosis or tuberculosis (TB).
  - Note: FDG is not tumor-specific—it also accumulates in lymphoid tissue and inflammatory cells.
  - Uptake pattern, extent, or intensity of FDG does not indicate malignancy.
  - If a lesion is FDG positive, cytological or histological analysis is recommended to ascertain the extent of disease.