Korean J Radiol.  2019 Feb;20(2):313-322. 10.3348/kjr.2017.0779.

Computed Tomography Pulmonary Angiography during Pregnancy: Radiation Dose of Commonly Used Protocols and the Effect of Scan Length Optimization

• Hendriks B
• Schnerr RS
• Milanese G
• Jeukens CR
• Niesen S
• Eijsvoogel NG
• Wildberger JE
• Das M

• KMID: 2438262
• DOI: http://doi.org/10.3348/kjr.2017.0779

Abstract

OBJECTIVE
To evaluate the radiation dose for pregnant women and fetuses undergoing commonly used computed tomography of the pulmonary arteries (CTPA) scan protocols and subsequently evaluate the simulated effect of an optimized scan length.
MATERIALS AND METHODS
A total of 120 CTPA datasets were acquired using four distinctive scan protocols, with 30 patients per protocol. These datasets were mapped to Cristy phantoms in order to simulate pregnancy and to assess the effect of an effective radiation dose (in mSv) in the first, second, or third trimester of pregnancy, including a simulation of fetal dose in second and third trimesters. The investigated scan protocols involved a 64-slice helical scan at 120 kVp, a high-pitch dual source acquisition at 100 kVp, a dual-energy acquisition at 80/140 kVp, and an automated-kV-selection, high pitch helical scan at a reference kV of 100 kVref. The effective dose for women and fetuses was simulated before and after scan length adaptation. The original images were interpreted before and after scan length adaptations to evaluate potentially missed diagnoses.
RESULTS
Large inter-scanner and inter-protocol variations were found; application of the latest technology decreased the dose for non-pregnant women by 69% (7.0-2.2 mSv). Individual scan length optimization proved safe and effective, decreasing the fetal dose by 76-83%. Nineteen (16%) cases of pulmonary embolism were diagnosed and, after scan length optimization, none were missed.
CONCLUSION
Careful CTPA scan protocol selection and additional optimization of scan length may result in significant radiation dose reduction for a pregnant patient and her fetus, whilst maintaining diagnostic confidence.

Keyword

Computed tomography; Pulmonary angiography; Radiation dose; Pregnancy; Fetus; Pulmonary embolism

MeSH Terms

Angiography*
Dataset
Diagnosis
Female
Fetus
Humans
Pregnancy Trimester, Third
Pregnancy*
Pregnant Women
Pulmonary Artery
Pulmonary Embolism

Figure

• 

  Fig. 1 Phantom simulation flow chart explaining simulation process.trim. = trimester

• 

  Fig. 2 Software phantom simulations.Phantoms in this Figure are modeled on 37-year-old woman, first presented as non-pregnant female (left) and subsequently simulated in all three pregnancy stages. Red lines indicate original scan length.

• 

  Fig. 3 Scan length adaptation.66-year-old woman who underwent computed tomography of pulmonary arteries was mapped to non-pregnant female Cristy phantom according to body habitus and age. A. Two straight white lines show original scan range, and dose modulation is projected vertically over image. B. Dotted white line (arrow) indicates simulated scan range after 10% caudal range reduction. C. Dotted white lines indicate individual scan range (arrows) optimization; lung apex to top of most caudal diaphragm.

• 

  Fig. 4 Mean original scan length (mm), after 10% caudal range reduction and per-patient optimization, based on 120 original datasets.*There was significant difference between protocol A and B (p = 0.004) in original scan length, which was carried through in 10% range reduction. There was no significant difference between different protocols after individual optimization (p = 0.438).

• 

  Fig. 5 Scan length adaptations for 3rd trimester pregnant women and fetuses (mean effective dose [mSv] per scan protocol).Graphs illustrate impact of optimizing scan length for different scanners and protocols.

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