Compare Technegas Ventilation-Perfusion SPECT and Xenon Ventilation-Perfusion Planar Imaging for Pulmonary Embolism

• Sensitivity of Technegas V/Q SPECT for the diagnosis of PE [ Time Frame: Prospective, 30 days follow-up ] [ Designated as safety issue: No ]
  Compared to the sensitivity of Xenon V/Q Planar imaging. "Truth" based on blinded reader's assessments of V/Q SPECT images compared with subject's final diagnosis resulting from clinical information at 30 days follow-up.
• Specificity of Technegas V/Q SPECT for the diagnosis of PE. [ Time Frame: Prospective, 30 days follow-up ] [ Designated as safety issue: No ]
  Compared to the specificity of Xenon V/Q Planar imaging. "Truth" based on blinded reader's assessments of V/Q SPECT images compared with subject's final diagnosis resulting from clinical information at 30 days follow-up.

• Accuracy of Technegas V/Q SPECT and Xenon V/Q Planar imaging for diagnosis of PE [ Time Frame: prospective, 30 days follow-up. ] [ Designated as safety issue: No ]
  Accuracy of V/Q imaging for diagnosis of PE is determined by the results of blind-read assessment of images compared with truth using a subject's final clinical diagnosis following 30-day follow-up of occurence of PE or death, whichever occurs first.
• Positive predictive value of imaging for diagnosis of PE [ Time Frame: Prospective, 30 days follow-up ] [ Designated as safety issue: No ]
  PPV of V/Q imaging for diagnosis of PE is determined by the results of blind-read assessment of images compared with truth using a subject's final clinical diagnosis following 30-day follow-up of occurence of PE or death, whichever occurs first.
• Negative predictive value of imaging for diagnosis of PE [ Time Frame: Prospective, 30 days follow-up ] [ Designated as safety issue: No ]
  NPV of V/Q imaging for diagnosis of PE is determined by the results of blind-read assessment of images compared with truth using a subject's final clinical diagnosis following 30-day follow-up of occurence of PE or death, whichever occurs first.
• Likelihood ratio for diagnosis of PE [ Time Frame: Prospective, 30 days follow-up ] [ Designated as safety issue: No ]
  Likelihood ratios of V/Q imaging for diagnosis of PE is determined by the results of blind-read assessment of images compared with truth using a subject's final clinical diagnosis following 30-day follow-up of occurence of PE or death, whichever occurs first.
• Safety of Technegas in patients with possible PE [ Time Frame: Prospective, from enrollment through 30 days follow-up ] [ Designated as safety issue: Yes ]
  Safety will be assessed by the incidence of treatment emergence adverse events and changes in clincal laboratory measurements, blood pressure, oxygen saturation, physical examination and pulmonary examination before and after treatment.

Phase 3 within-subject trial of Technegas V/Q SPECT and Tc-99m macro-aggregated albumin (MAA) imaging compared to Xenon-133 V/Q planar and Tc-99m macroaggregate of albumin (MAA) imaging for the diagnosis of Pulmonary Embolism (PE).

This is a Phase 3 within-subject trial of Technegas Ventilation SPECT and Tc-99m MAA perfusion imaging compared to xenon (Xe-133) Ventilation Planar and Tc-99m MAA perfusion imaging for the diagnosis of PE. Diagnosis of PE provided by review of the subjects' documented clinical information after 30 days of follow-up. Primary assessments of efficacy will be based on an independent blind reads of the Technegas V/Q SPECT images by three different readers and the independent blind reads of Xe 133 V/Q planar images by three different readers.

• Drug: Technegas V/Q SPECT
  Technegas Ventilation SPECT imaging and Technetium 99m MAA Perfusion imaging for the diagnosis pf pulmonary embolism.
  Other Name: Technetium-99m (Tc-99m) labeled carbon particles
• Drug: Xenon-133
  Xenon-133 Ventilation Planar imaging and Technetium 99m MAA Perfusion imaging for the diagnosis pf pulmonary embolism.
  Other Name: Xe-133

• Experimental: Technegas
  Technetium-99m (Tc-99m) labeled carbon particles; approximately 1.1 milliCuries of Technegas
  Intervention: Drug: Technegas V/Q SPECT
• Active Comparator: Xenon-133
  Intervention: Drug: Xenon-133

Inclusion Criteria:

Subjects will be enrolled in Cohort 1 if they meet the following requirements:

1. Male or female, at least 18 years of age.
2. Suspected of having PE and be a candidate for Xe-133 V/Q imaging.
3. Willing and able to provide informed consent.
4. Stable and able to undergo Xe-133 planar imaging, Technegas SPECT imaging, and planar/SPECT perfusion imaging and complete follow-up procedures.
5. Willing and agree to complete study procedures, including follow-up safety assessments.
6. Using adequate birth control, if female and fertile.
7. If female, has a negative urine or serum pregnancy test.
8. Agrees to return for a 24-hour and 30 day follow-up safety assessment.

Subjects will be enrolled in Cohort 2 if they meet the above criteria AND subject is likely to have pulmonary embolism based on one or more of the following:

1. Wells Score of 7 or greater. Subjects with a Wells Score less than 7 may be enrolled in Cohort 2 if there is agreement between the investigator and the medical monitor that the subject is at high risk for PE.
2. An abnormal D-dimer test.
3. Positive Doppler ultrasound for DVT.
4. CTA is positive for PE within 24 hours of this imaging study.

Exclusion Criteria:

Subject

1. Has undergone imaging with Iodine-131 (I-131) within 30 days, Thallium-201 (Tl-201) or Indium-111 (In-111) within 10 days, Fluorine 18 (F-18) within 24 hours, or any other radiopharmaceutical not otherwise specified within 72 hours of this imaging study.
2. Has previously undergone an imaging study with a Tc-99m agent, within 48 hours of this imaging study.
3. Is a pregnant or lactating female.
4. Has received Technegas in the past.
5. Was previously enrolled in another investigational study or received an investigational drug within 30 days prior to dosing.
6. Is hemodynamically unstable.
7. Has received therapeutic dose of low molecular weight or unfractionated heparin within 24 hours prior to dosing or Tissue Plasminogen Activator (tPA) within 4 hours prior to dosing or has received treatment for PE between the time of a positive CTA, if performed, and Technegas V/Q SPECT imaging.