“This higher pitch for PCD CTPA leads to a shorter acquisition time, in turn possibly reducing the susceptibility to pulsation or respiratory artifacts. This reduction in artifacts likely acts in combination with the higher CNR and SNR of PCD CTPA to yield the technique’s observed higher subjective image quality. The more rapid acquisition for PCD CTPA may be particularly advantageous in patients with pulmonary embolism, who commonly present with tachycardia and dyspnea,” wrote lead study author Pauline Pannenbecker, M.D., who is affiliated with the Department of Diagnostic and Interventional Radiology at University Hospital Wurzburg in Germany, and colleagues.
Three Key Takeaways
- Improved image quality with photon counting technology. The study suggests that photon counting technology, specifically high-pitch photon counting detector (PCD) for computed tomography pulmonary angiography (CTPA) exams, provides significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) compared to traditional dual-energy energy-integrating detection (EID) methods. This improvement in image quality can aid in better diagnostic accuracy and interpretation.
- Reduced radiation dosing. Photon counting CTPA was found to have lower radiation dosing compared to EID CTPA. The study reports lower CT dose index volume (CTDIvol), effective dose, and dose length product (DLP) for PCD CTPA. This reduction in radiation exposure is important for patient safety and aligns with the principles of optimizing medical imaging to minimize potential harm.
- Advantages in imaging obese patients. The use of photon counting technology, with an expanded spectral field of view (FOV), is highlighted as advantageous for imaging obese patients. The larger FOV with PCD CT may contribute to improved image quality in larger patients, particularly due to the use of a single voltage for both x-ray tubes, reducing susceptibility to artifacts commonly associated with dual-energy EID CTPA methods.
The study authors also pointed out lower radiation dosing for PCD CTPA in contrast to EID CTPA, noting lower CT dose index volume (CTDIvol) of 3.9 mGy vs. 5.5 mGy, a lower effective dose (2.2 mSv vs. 2.8 mSv, and a reduced dose length product (DLP) of 123.5 mGy*cm vs. 157 mGy*cm.
For the imaging of obese patients, the study authors said an expanded spectral field of view (FOV) with PCD CT (50 cm) offers another advantage over EID CT with a spectral FOV of 35.3 cm.
“Use of PCD CT for CTPA may improve image quality in large patients given the use of the same voltage for both x-ray tubes (120 kVp in this study) in contrast with distinct tube potentials for dual-energy EID CTPA (90 kV and Sn150 kV in this study). The use of a single voltage for PCD CTPA may lessen susceptibility to artifacts from photon starvation … ,” added Pannenbecker and colleagues.
(Editor’s note: For related content, see “Current Concepts with Advances in Photon-Counting Computed Tomography,” “Emerging Concepts with ICM Reduction and Photon Counting for Coronary CT Angiography” and “Study Says Photon-Counting CT Offers Better Lung Assessment than Conventional CT.”)
Beyond the inherent limitations of a single-center study, the authors acknowledged a small sample size and the lack of an independent reference standard for confirming that additional pulmonary emboli detected on iodine maps are true positives. The researchers conceded they did not assess the location and extent of pulmonary emboli. They also noted that anatomic image maps and iodine maps were not assessed in separate sessions.
