Pulmonary embolism (PE) is a potentially life-threatening condition, mandating urgent diagnosis and treatment [1]. Computed Tomography Pulmonary Angiogram (CTPA) is the preferred diagnostic modality for PE, however nondiagnostic examination remains the most important drawback [2,3]. Spectral detector CT (SDCT) is a new dual energy acquisition technology where a single x-ray tube potential is applied and two layers of detectors separate low and higher energies [4]. This gives the ability to generate virtual monoenergetic images (VMI), synthesizing data as if the patient was scanned using a...

CTPA protocol No written informed consent was required as scans were performed as per routine protocol: All patients underwent SDCT on Phillips iQOn Elite Tube voltages were set to 120kVp Vessel enhancement via injection of 50-75 ml of 350 mg/ml iodinated contrast material Bolus tracking performed at the level of pulmonary trunk with manual triggering All CTPA studies routinely contained a polyenergetic (120 kVP) and VMI (45keV) image set archived to PACS Image and data analysis A retrospective chart review was conducted via PACS for...

A total of 199 patients were examined, 98 females (49%) and 101 males (51%). The mean patient age was 52 years. 37/199 examinations (19%) were nondiagnostic, defined as mean pulmonary trunk attenuation < 250 HU on polyenergetic imaging. 2/37 (5%) were repeated and 1/37 (3%) went on for V/Q scan (Figure 2).[Fig 2] Of note, these nondiagnostic studies demonstrated attenuation on VMI > 250 HU (383, 318 and 517 HU). The mean attenuation of pulmonary trunk at polyenergetic imaging was 358.41 HU (SD 33.04). The...

Multiple factors can lead to nondiagnostic CTPA, for example technical factors such as injection timing and patient factors such as cardiac output. This may lead to additional radiation from repeat CTPA or delayed diagnosis with further V/Q scan. Our preliminary experience with SDCT demonstrates that despite nearly 20% nondiagnostic opacification on polyenergetic CTPA, less than 2% of all examinations had repeat CTPA or subsequent V/Q scan performed. In our experience this is likely due to the demonstrated increased pulmonary vasculature opacification on VMI which is...

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