In 27 adults with suspected respiratory infection, an ultra-low-dose PCCT chest protocol achieved a mean effective dose of 0.11 ± 0.04 mSv, essentially matching the German reference dose for a two-view chest radiograph. Despite this very low exposure, PCCT provided substantially more diagnostic information than radiography.
PCCT changed the main diagnosis in 11/27 patients (41%) and changed therapy in 10/27 (37%). It detected previously occult infiltrates in 5 patients, confidently excluded an infiltrate in 10, and provided clinically relevant additional findings in 4.
The approach appears most useful when radiography is equivocal or clinical suspicion remains high, particularly in immunosuppressed patients. It is not a complete substitute for standard contrast-enhanced CT: 2/27 patients required an additional CT for suspected pulmonary embolism or pleural empyema.
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Figure 1. Comparison of CXR and ULD-CT in 6 patients of our study cohort demonstrating the clinical significance and the limitations of ULD-CT. a, b Consolidation in the right lower lobe, occult in the CXR hidden behind the right diaphragm. c, d Bilateral opacities, occult in the CXR due to the low density. e, f Bilateral opacities in the CXR; the ULD-CT shows the pattern of an organizing pneumonia as additional information. g, h Bilateral opacities in the CXR; the ULD-CT shows the pattern of sarcoidosis as additional information. i, j Bilateral opacities in the CXR; the ULD-CT shows pleural masses. k, l Basal opacities in CXR and consolidation and pleural effusion in ULD-CT; for the diagnosis of a pleural empyema, the ULD-CT was not sufficient and a standard CT with contrast was needed.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Scan area | Chest |
Acquisition mode | Ultra-low-dose PCCT |
Contrast | Unenhanced |
Breathing | Full inspiration |
Tube voltage [kV] | 100 |
Spectral shaping | Tin filtration |
IQ level | 3 |
Scan mode | Flash |
Pitch | 2 |
Table speed [mm/s] | 461 |
Scan time | <1 s for whole chest |
Matrix | 512 × 512 |
Reconstruction slice thickness [mm] | 1.0 |
Reconstruction increment [mm] | 0.7 |
Kernel | BR40 |
Iterative reconstruction | Strength 2 |
CTDIvol [mGy] | 0.19 ± 0.05 |
DLP [mGy·cm] | 6.3 ± 2.1 |
Effective dose [mSv] | 0.11 ± 0.04 |
Key Results
Parameter | Main finding |
|---|
Study population | 27 patients; median age 68 years; 59% immunosuppressed |
Mean effective PCCT dose | 0.11 ± 0.04 mSv |
Occult infiltrate detected | 5/27 (19%) |
Infiltrate confidently excluded | 10/27 (37%) |
Main diagnosis changed | 11/27 (41%) |
Therapy changed | 10/27 (37%) |
Source:
Dettmer S, Werncke T, Nikolova Mitkovska V, Brod T, Joean O, Vogel-Claussen J, Wacker F, Welte T, Rademacher J. Photon Counting Computed Tomography with the Radiation Dose of a Chest X-Ray: Feasibility and Diagnostic Yield. Respiration. 2024;103(2):88–94. doi:10.1159/000536065.
