Diagnosis of pulmonary emboli and image quality at CT pulmonary angiography: Influence of imaging direction with multidetector CT

Evaluation of imaging quality of pulmonary 64-MDCT angiography in pregnancy and puerperium

OBJECTIVE

The aim of this study was to quantitatively and qualitatively evaluate pulmonary 64-MDCT angiography image quality in pregnancy and puerperium, compared with female nonpregnant control subjects.

MATERIALS AND METHODS

The study group comprised 124 consecutive pregnant and postpartum women and 124 female nonpregnant control subjects who presented with suspected pulmonary embolism. The individual studies were evaluated for subjective and objective diagnostic quality.

RESULTS

Objective measurements of the arterial enhancement in the pulmonary trunk and left and right pulmonary arteries found that there was no statistically significant difference in attenuation values between the pregnant and puerperium group and the control group for pulmonary artery opacification. The mean attenuation in the pulmonary trunk was 270.54 HU in the pregnant group, 277.53 HU in the puerperium group, and 293.90 HU in the control group.

CONCLUSION

We found no significant difference in diagnostic quality of pulmonary CT angiography using MDCT between the study and control groups. The use of MDCT acquisition, faster injection rates, higher contrast medium concentration, and higher trigger levels may decrease the number of nondiagnostic studies in this population. MDCT may be a worthwhile investigation in the majority of pregnant patients with suspected pulmonary embolism.

Image quality of computed tomographic pulmonary angiography for suspected pulmonary embolus in patients with diffuse interstitial lung disease

PURPOSE

To investigate the effect of diffuse interstitial lung disease (DILD) on the image quality of computed tomographic pulmonary angiography (CTPA).

MATERIALS AND METHODS

The study group comprised 130 patients with DILD who underwent CTPA between April 2005 and April 2009. One hundred and thirty patients without significant parenchymal lung disease were used as a control group. Contrast enhancement of pulmonary arteries in the left upper lobe and right lower lobe was evaluated to the sub-subsegmental level both subjectively and objectively. The global and lobar extents of interstitial lung disease were also estimated in the study group. Subjective assessment was performed by 2 observers, initially independently and subsequently by consensus in cases of discordance.

RESULTS

At the sub-subsegmental level, the number of patients with adequately opacified arteries was significantly lower in the DILD group (29.2% left upper lobe, 36.2% right lower lobe) compared with the control group (78.5% left upper lobe, 89.2% right lower lobe) (P<0.001). Subjective image quality scores of the sub-subsegmental arteries were strongly correlated with mean vascular attenuation values at this level (P<0.001) but not to the global or lobar extent of lung parenchymal disease. There was no clinically significant difference in image quality (either subjectively or objectively) between the DILD and control groups in the subsegmental and more proximal arterial branches.

CONCLUSIONS

In the majority of patients with DILD, CTPA image quality is sufficient only to the subsegmental level. Emboli at the sub-subsegmental level, which may have greater clinical significance in patients with DILD than in those without, are unlikely to be excluded using CTPA.

Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome

Triple-rule-out (TRO) computed tomographic (CT) angiography can provide a cost-effective evaluation of the coronary arteries, aorta, pulmonary arteries, and adjacent intrathoracic structures for the patient with acute chest pain. TRO CT is most appropriate for the patient who is judged to be at low to intermediate risk for acute coronary syndrome (ACS) and whose symptoms may also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. Although a regular cardiac rhythm remains an important factor in coronary CT image quality, newer CT scanners with 64 or more detector rows afford rapid electrocardiographically (ECG) gated imaging to provide high-quality TRO CT studies in patients with a heart rate of up to 80 beats per minute. Injection of iodinated contrast material (< or = 100 mL) is tailored to provide simultaneous high levels of arterial enhancement in the coronary arteries and aorta (> 300 HU) and in the pulmonary arteries (> 200 HU). To limit radiation exposure, the TRO CT examination does not include the entire chest but is constrained to incorporate the aortic arch down through the heart. Scanning parameters, including prospective ECG tube current modulation and prospective ECG gating with the "step-and-shoot" technique, are tailored to reduce radiation exposure (optimally, 5-9 mSv). When performed with appropriate attention to timing and technique, TRO CT provides coronary image quality equal to that of dedicated coronary CT angiography and pulmonary arterial images that are free of motion artifact related to cardiac pulsation. In an appropriately selected emergency department patient population, TRO CT can safely eliminate the need for further diagnostic testing in over 75% of patients.

Computer tomography for venous thromboembolic disease

Venous thromboembolic disease is composed of two disease entities: pulmonary thromboembolism/pulmonary embolism and deep venous thrombosis. Clinical signs and symptoms of venous thromboembolic disease often are nonspecific and, as a result, the diagnosis may be difficult. If left untreated, pulmonary embolism can lead to a potentially fatal outcome. This article focuses on CT angiography as the diagnostic modality for thromboembolic pulmonary embolism and briefly discusses nonthromboembolic pulmonary embolism.