Lower Iodine Load in Routine Contrast-Enhanced CT: An Alternative Imaging Strategy

256 Slice Multi-detector Computed Tomography Thoracic Aorta Computed Tomography Angiography: Improved Luminal Opacification Using a Patient-Specific Contrast Protocol and Caudocranial Scan Acquisition

CLINICAL RELEVANCE STATEMENT

Caudocranial scan direction and contrast injection timing based on measured patient vessel dynamics can significantly improve arterial and aneurysmal opacification and reduce both contrast and radiation dose in the assessment of thoracic aortic aneurysms (TAA) using helical thoracic computed tomography angiography (CTA).

OBJECTIVES

To investigate opacification of the thoracic aorta and TAA using a caudocranial scan direction and a patient-specific contrast protocol.

MATERIALS AND METHODS

Thoracic aortic CTA was performed in 160 consecutive patients with suspected TAA using a 256-slice computed tomography scanner and a dual barrel contrast injector. Patients were subjected in equal numbers to one of two contrast protocols. Patient age and sex were equally distributed across both groups. Protocol A, the department's standard protocol, consisted of a craniocaudal scan direction with 100 mL of contrast, intravenously injected at a flow rate of 4.5 mL/s. Protocol B involved a caudocranial scan direction and a novel contrast formula based on patient cardiovascular dynamics, followed by 100 mL of saline at 4.5 mL/s. Each scan acquisition comprised of 120 kVp, 200 mA with modulation, temporal resolution 0.27 seconds, and pitch 0.889:1. The dose length product was measured between each protocol and data generated were compared using Mann-Whitney U nonparametric statistics. Receiver operating characteristic analysis, visual grading characteristic (VGC), and κ analyses were performed.

RESULTS

Mean opacification in the thoracic aorta and aneurysm measured was 24 % and 55%, respectively. The mean contrast volume was significantly lower in protocol B (73 ± 10 mL) compared with A (100 ± 1 mL) (P<0.001). The contrast-to-noise ratio demonstrated significant differences between the protocols (protocol A, 18.2 ± 12.9; protocol B, 29.7 ± 0.61; P < 0.003). Mean effective dose in protocol B (2.6 ± 0.4 mSv) was reduced by 19% compared with A (3.2 ± 0.8 mSv) (P < 0.004). Aneurysmal detectability demonstrated significant increases by receiver operating characteristic and visual grading characteristic analysis for protocol B compared with A (P < 0.02), and reader agreement increased from poor to excellent.

CONCLUSIONS

Significant increase in the visualization of TAAs following a caudocranial scan direction during helical thoracic CTA can be achieved using low-contrast volume based on patient-specific contrast formula.

Geriatric chest imaging: when and how to image the elderly lung, age-related changes, and common pathologies

Even in a global perspective, societies are getting older. We think that diagnostic lung imaging of older patients requires special knowledge. Imaging strategies have to be adjusted to the needs of frail patients, for example, immobility, impossibility for long breath holds, renal insufficiency, or poor peripheral venous access. Beside conventional radiography, modern multislice computed tomography is the method of choice in lung imaging. It is especially important to separate the process of ageing from the disease itself. Pathologies with a special relevance for the elderly patient are discussed in detail: pneumonia, aspiration pneumonia, congestive heart failure, chronic obstructive pulmonary disease, the problem of overlapping heart failure and chronic obstructive pulmonary disease, pulmonary drug toxicity, incidental pulmonary embolism pulmonary nodules, and thoracic trauma.