Emergency Radiology

, Volume 26, Issue 2, pp 145–153 | Cite as

Evaluation of image quality and radiation dose saving comparing knowledge model–based iterative reconstruction on 80-kV CT pulmonary angiography (CTPA) with hybrid iterative reconstruction on 100-kV CT

  • Davide IppolitoEmail author
  • Andrea De Vito
  • Cammillo Talei Franzesi
  • Luca Riva
  • Anna Pecorelli
  • Rocco Corso
  • Andrea Crespi
  • Sandro Sironi
Original Article



To evaluate dose reduction and image quality of 80-kV CT pulmonary angiography (CTPA) reconstructed with knowledge model–based iterative reconstruction (IMR), and compared with 100-kV CTPA with hybrid iterative reconstruction (iDose4).

Materials and methods

One hundred and fifty-one patients were prospectively investigated for pulmonary embolism; a study group of 76 patients underwent low-kV setting (80 kV, automated mAs) CTPA study, while a control group of 75 patients underwent standard CTPA protocol (100 kV; automated mAs); all patients were examined on 256 MDCT scanner (Philips iCTelite). Study group images were reconstructed using IMR while the control group ones with iDose4. CTDIvol, DLP, and ED were evaluated. Region of interests placed in the main pulmonary vessels evaluated vascular enhancement (HU); signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated.


Compared to iDose4-CTPA, low-kV IMR-CTPA presented lower CTDIvol (6.41 ± 0.84 vs 9.68 ± 3.5 mGy) and DLP (248.24 ± 3.2 vs 352.4 ± 3.59 mGy × cm), with ED of 3.48 ± 1.2 vs 4.93 ± 1.8 mSv. Moreover, IMR-CTPA showed higher values of attenuation (670.91 ± 9.09 HU vs 292.61 ± 15.5 HU) and a significantly higher SNR (p < 0.0001) and CNR (p < 0.0001).The subjective image quality of low-kV IMR-CTPA was also higher compared with iDose4-CTPA (p < 0.0001).


Low-dose CTPA (80 kV and automated mAs modulation) reconstructed with IMR represents a feasible protocol for the diagnosis of pulmonary embolism in the emergency setting, achieving high image quality with low noise, and a significant dose reduction within adequate reconstruction times(≤ 120 s).


Radiation Tomography Pulmonary embolism 



Computed tomography


Computed tomography pulmonary angiography


Knowledge model–based iterative reconstruction


Hybrid iterative reconstruction


Multidetector computed tomography


Hounsfield unit


Dose-length product


Computed tomography dose index


Effective dose


Signal-to-noise ratio


Contrast-to-noise ratio


Milliamperage seconds


Region of interest






Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Informed consent

Every patient gave his informed consent, as required by our Institution.


The authors have nothing to disclose.


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Copyright information

© American Society of Emergency Radiology 2018

Authors and Affiliations

  • Davide Ippolito
    • 1
    • 2
    Email author
  • Andrea De Vito
    • 1
    • 3
  • Cammillo Talei Franzesi
    • 1
    • 3
  • Luca Riva
    • 1
    • 3
  • Anna Pecorelli
    • 1
    • 2
  • Rocco Corso
    • 1
  • Andrea Crespi
    • 3
    • 4
  • Sandro Sironi
    • 2
    • 5
  1. 1.Department of Diagnostic Radiology“San Gerardo” HospitalMonzaItaly
  2. 2.School of MedicineUniversity of Milano-BicoccaMonzaItaly
  3. 3.School of MedicineUniversity of Milano-BicoccaMilanItaly
  4. 4.Department of Medical Physics“San Gerardo” HospitalMonzaItaly
  5. 5.Department of Diagnostic RadiologyH Papa Giovanni XIIIBergamoItaly

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