Ultra Low Dose CT Pulmonary Angiography with Iterative Reconstruction.
OBJECTIVE
Evaluation of a new iterative reconstruction algorithm (IMR) for detection/rule-out of pulmonary embolism (PE) in ultra-low dose computed tomography pulmonary angiography (CTPA).


METHODS
Lower dose CT data sets were simulated based on CTPA examinations of 16 patients with pulmonary embolism (PE) with dose levels (DL) of 50%, 25%, 12.5%, 6.3% or 3.1% of the original tube current setting. Original CT data sets and simulated low-dose data sets were reconstructed with three reconstruction algorithms: the standard reconstruction algorithm "filtered back projection" (FBP), the first generation iterative reconstruction algorithm iDose and the next generation iterative reconstruction algorithm "Iterative Model Reconstruction" (IMR). In total, 288 CTPA data sets (16 patients, 6 tube current levels, 3 different algorithms) were evaluated by two blinded radiologists regarding image quality, diagnostic confidence, detectability of PE and contrast-to-noise ratio (CNR).


RESULTS
iDose and IMR showed better detectability of PE than FBP. With IMR, sensitivity for detection of PE was 100% down to a dose level of 12.5%. iDose and IMR showed superiority to FBP regarding all characteristics of subjective (diagnostic confidence in detection of PE, image quality, image noise, artefacts) and objective image quality. The minimum DL providing acceptable diagnostic performance was 12.5% (= 0.45 mSv) for IMR, 25% (= 0.89 mSv) for iDose and 100% (= 3.57 mSv) for FBP. CNR was significantly (p < 0.001) improved by IMR compared to FBP and iDose at all dose levels.


CONCLUSIONS
By using IMR for detection of PE, dose reduction for CTPA of up to 75% is possible while maintaining full diagnostic confidence. This would result in a mean effective dose of approximately 0.9 mSv for CTPA.
Department of diagnostic and interventional Radiology, Technische Universität München, Munich, Germany.
Andreas
http://orcid.org/0000-0003-4394-862X
A
Sauter
Philips GmbH, Innovative Technologies, Research Laboratories, Hamburg, Germany.
Thomas
T
Koehler
Department of diagnostic and interventional Radiology, Technische Universität München, Munich, Germany.
Alexander A
AA
Fingerle
Philips GmbH, Innovative Technologies, Research Laboratories, Hamburg, Germany.
Bernhard
B
Brendel
Department of diagnostic and interventional Radiology, Universitätsklinikum Tübingen, Tübingen, Germany.
Vivien
V
Richter
Department of diagnostic and interventional Radiology, Technische Universität München, Munich, Germany.
Michael
M
Rasper
Department of diagnostic and interventional Radiology, Technische Universität München, Munich, Germany.
Ernst J
EJ
Rummeny
Department of diagnostic and interventional Radiology, Technische Universität München, Munich, Germany.|Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, Garching, Germany.
Peter B
PB
Noël
Department of diagnostic and interventional Radiology, Technische Universität München, Munich, Germany.
Daniela
D
Münzel
D000465:Algorithms; D000072226:Computed Tomography Angiography; D003287:Contrast Media / Q000737:chemistry; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D011655:Pulmonary Embolism / Q000175:diagnosis / Q000000981:diagnostic imaging; D011857:Radiographic Image Interpretation, Computer-Assisted
D003287:Contrast Media