Indeterminate CT pulmonary angiogram: Why and does it matter?
Ju Hee Yeo1, Lifeng Zhou2, Remy Lim1
1Department of Radiology, North Shore Hospital, Waitemata DHB, Auckland, New Zealand.
Insights
Six percent of CT pulmonary angiograms (CTPA) were indeterminate. The average Hounsfield unit of the pulmonary trunk was a key predictor of indeterminate CTPA, impacting diagnostic accuracy.
Area of Science:
- Radiology
- Medical Imaging
Background:
- Indeterminate CT pulmonary angiograms (CTPA) can lead to diagnostic uncertainty.
- Assessing the rate and causes of indeterminate CTPA is crucial for improving diagnostic yield.
Purpose of the Study:
- To determine the rate of indeterminate CTPA in a general hospital setting.
- To identify factors contributing to indeterminate CTPA and their impact on patient outcomes.
Main Methods:
- Retrospective review of 403 CTPA studies and reports.
- Data collected included patient demographics, scan parameters, and average Hounsfield Unit (HU) of the pulmonary trunk.
- Statistical analyses included univariate and multivariate regression.
Main Results:
- 6% of CTPA studies were indeterminate (suboptimal or non-diagnostic).
- Factors associated with indeterminate studies included patient weight, average pulmonary trunk HU, and effective dose.
- In multivariate analysis, only average pulmonary trunk HU (OR=0.99) predicted indeterminate studies.
- Common causes for indeterminate studies included suboptimal contrast enhancement, motion artifacts, and body habitus.
Conclusions:
- Average Hounsfield Unit of the pulmonary trunk is a significant predictor of indeterminate CTPA.
- Improving contrast enhancement and reducing motion artifacts can decrease indeterminate CTPA rates.
Introduction:
This study assessed the rate of indeterminate CT pulmonary angiogram (CTPA) in a general hospital and evaluated potential contributing factors to an indeterminate CTPA and patients' eventual clinical outcome.
Methods:
Four hundred and three consecutive CTPA and their finalised report from 01/08/2012 to 05/12/2012 at Waitemata DHB were reviewed retrospectively. Patient demographics, scan parameters and average Hounsfield unit (HU) of the main pulmonary trunk (PT) and likely cause of indeterminate study were documented. Studies were categorised into diagnostic, suboptimal or non-diagnostic studies. Univariate and multiple regression analyses were employed.
Results:
Six per cent (n = 24) of the studies were deemed indeterminate which included suboptimal and non-diagnostic studies. Seven pregnant patients were scanned during the study period and four of the seven studies were deemed indeterminate. In univariate analysis, predictors of indeterminate studies included 'weight' (P = 0.022), 'average HU of PT' (P < 0.0001) and 'effective dose' (P = 0.0003). In the multivariate logistic regression model, only 'average HU of PT' was associated with indeterminate studies (OR = 0.99, 95%CI: 0.99, 1.00). Twelve of 24 indeterminate studies had suboptimal pulmonary enhancement with causes including suboptimal timing of contrast bolus, hyperdynamic state due to pregnancy and transient interruption of contrast. Three patients had excessive noise due to body habitus. Eight studies had motion artefacts and one patient had left lower lobe pneumonia which decreased the accuracy. A third of the indeterminate studies were clinically considered as negative by referring clinicians.
Conclusions:
Pulmonary trunk average Hounsfield unit is a predictor of indeterminate CT pulmonary angiogram.
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