Technegas Ventilation Lung Imaging in the United States

RATIONALE

Ventilation lung imaging is performed to evaluate lung function related to bronchopulmonary air distribution into and out of the lungs. Technegas (Cyclomedica USA) is a submicron radioaerosolized particle manufactured in the Technegas Plus System.

CLINICAL INDICATIONS

• Visualization of pulmonary ventilation

• Evaluation of pulmonary embolism when paired with perfusion imaging

CONTRAINDICATIONS

• Pregnancy must be excluded according to local institutional policy. If the patient is breastfeeding, instructions should be provided to pump and discard breast milk for a minimum of 4 h after administration of Technegas aerosol.

• Recent nuclear medicine study (radiopharmaceutical-dependent).

PATIENT PREPARATION/EDUCATION

• The patient may eat and take medications as necessary before the procedure.

• Chest radiography in both the posterior–anterior and lateral projections or chest CT, ideally within 4 h of the scan (acceptable ≤24 h before the scan or since a recent change in clinical status), is required to correlate with the lung scan. An anterior portable chest radiograph is acceptable when a standard chest radiograph is not possible.

• A focused history containing the following elements should be obtained:

  • ○ Signs and symptoms (e.g., shortness of breath, chest pain, fever, cough, syncope, tachycardia, jugular venous distention, or hemoptysis).

  • ○ Relevant history, including known diagnoses (e.g., recent surgery, cancer, chronic obstructive pulmonary disease, immobility, or obesity).

  • ○ Results of D-dimer test if ordered.

  • ○ History of prior deep venous thrombosis or pulmonary embolism.

  • ○ Results/images from prior lung scans.

  • ○ Pertinent findings on chest radiographs.

  • ○ Treatment with anticoagulant or thrombolytic therapy.

  • ○ Results of tests for deep venous thrombosis and other imaging procedures.

• Educating, and practicing the procedure with, the patient before inhalation of the Technegas is critical to procedure success.

  • ○ The practice session should be done under the same conditions as the actual ventilation procedure (e.g., supine position with nose clip).

  • ○ The practice session improves timing, ventilation, and patient compliance (especially with the seal) and offers the opportunity to select the appropriate mouthpiece for that patient.

RADIOPHARMACEUTICAL IDENTITY, DOSE, AND ROUTE OF ADMINISTRATION

• The radiopharmaceutical identity, dose, and route of administration are described in Table 1.

PROTOCOL/ACQUISITION INSTRUCTIONS

• Tables 2 and 3 provide the acquisition parameters for planar imaging and SPECT or SPECT/CT, respectively.

IMAGE PROCESSING

• Planar images should be scaled to visualize areas of uptake or absence of tracer.

• SPECT images should be processed per the manufacturer’s recommendations and the interpreting physician’s preference, including preprocessing, reconstruction (transverse, sagittal, and coronal views), filter selection, and image display.

• Iterative reconstruction is recommended.

• If SPECT/CT is performed, images can be fused for attenuation correction and correlative interpretation.

• For SPECT/CT protocols, refer to the manufacturer’s recommendations for CT acquisition parameters.

• For quantitative ventilation lung scans:

  • ○ Place regions of interest over the right and left lungs in the anterior and posterior projections. Divide each lung into 3 equal rectangular regions of interest on the anterior and posterior views: top, middle, and bottom. The division of the lungs into thirds does not exactly correlate with anatomic divisions of the lung lobes but is reasonably representative.

  • ○ Determine the total activity for each lung in addition to the activity in all 6 regions of interest.

  • ○ Calculate the geometric mean: the square root of the product of the anterior counts multiplied by the posterior counts (√[anterior counts × posterior counts]) for all lung regions. The geometric mean is used because it is more representative than the arithmetic mean ([anterior counts + posterior counts]/2).

  • ○ Calculate the percentage of counts in each region.

DISCLOSURE

No potential conflict of interest relevant to this article was reported.