Postmortem whole-body CT angiography: evaluation of two contrast media solutions

OBJECTIVE: The objective of our study was to establish a standardized procedure for postmortem whole-body CT-based angiography with lipophilic and hydrophilic contrast media solutions and to compare the results of these two methods. MATERIALS AND METHODS: Minimally invasive postmortem CT angiography was performed on 10 human cadavers via access to the femoral blood vessels. Separate perfusion of the arterial and venous systems was established with a modified heart-lung machine using a mixture of an oily contrast medium and paraffin (five cases) and a mixture of a water-soluble contrast medium with polyethylene glycol (PEG) 200 in the other five cases. Imaging was executed with an MDCT scanner. RESULTS: The minimally invasive femoral approach to the vascular system provided a good depiction of lesions of the complete vascular system down to the level of the small supplying vessels. Because of the enhancement of well-vascularized tissues, angiography with the PEG-mixed contrast medium allowed the detection of tissue lesions and the depiction of vascular abnormalities such as pulmonary embolisms or ruptures of the vessel wall. CONCLUSION: The angiographic method with a water-soluble contrast medium and PEG as a contrast-agent dissolver showed a clearly superior quality due to the lack of extravasation through the gastrointestinal vascular bed and the enhancement of soft tissues (cerebral cortex, myocardium, and parenchymal abdominal organs). The diagnostic possibilities of these findings in cases of antemortem ischemia of these tissues are not yet fully understood.

Venous thromboembolism and occult malignancy: simultaneous detection during pulmonary CT angiography with CT venography

OBJECTIVE: We explored the potential for patients with proven venous thromboembolism or pulmonary embolism (PE) to have occult malignancies detected during the same CT examination. To verify this, we compared the presence of occult malignancies identified on pulmonary artery CT angiography (CTA) and CT venography (CTV) when venous thromboembolism (VTE) was present. SUBJECTS AND METHODS: Pulmonary artery CTA combined with CTV was performed on a 16-MDCT scanner on 186 adult patients suspected of having pulmonary embolism without any known malignancies. CTV was performed from the diaphragm to the knee 180 seconds after CTA. Two radiologists evaluated the presence of VTE, that is PE or deep venous thrombosis (DVT), and tumor lesions on both examinations in consensus. The malignant nature of the possibly identified tumors was confirmed by pathologic examination. RESULTS: VTE was found in 49 patients (26%). Malignant tumors were detected in 24 patients (13%). Eleven patients with malignant tumors had VTE (46% of patients with malignant tumors; 22% with VTE and 6% of all patients). There was correlation with presence of malignancies between both and DVT and DVT associated with PE but not between presence of malignancies and PE only. Patients with DVT and those with DVT associated with PE had a risk ratio of 3.2 and 3.3, respectively, for having a malignant tumor discovered simultaneously. CONCLUSION: A high number of malignant tumors can be incidentally discovered on pulmonary artery CTA, even more so with additional CTV. Radiologists should scrutinize scans to pick up unknown malignancies, especially in patients with identified VTE.

Sixty-four-detector CT angiography of infrarenal aortic neck length and angulation: prospective analysis of interobserver variability

PURPOSE: To quantify the interobserver variability of abdominal aortic aneurysm (AAA) neck length and angulation measurements. MATERIALS AND METHODS: A total of 25 consecutive patients scheduled for endovascular AAA repair underwent follow-up 64-row computed tomographic (CT) angiography in 0.625-mm collimation. AAA neck length and angulation were determined by four blinded, independent readers. AAA neck length was defined as the longitudinal distance between the first transverse CT slice directly distal to the lowermost renal artery and the first transverse CT slice that showed at least a 15% larger outer aortic wall diameter versus the diameter measured directly below the lowermost renal artery. Infrarenal AAA neck angulation was defined as the true angle between the longitudinal axis of the proximal AAA neck and the longitudinal axis of the AAA lumen as analyzed on three-dimensional CT reconstructions. RESULTS: Mean deviation in aortic neck length determination was 32.3% and that in aortic neck angulation was 32.1%. Interobserver variability of aortic neck length and angulation measurements was considerable: in any reader combination, at least one measurement difference was outside the predefined limits of agreement. CONCLUSIONS: Assessment of the longitudinal extension and angulation of the infrarenal aortic neck is associated with substantial observer variability, even if measurement is carried out according to a standardized protocol. Further studies are mandatory to assess dedicated technical approaches to minimize variance in the determination of the longitudinal extension and angulation of the infrarenal aortic neck.

Functionally relevant coronary artery disease: comparison of 64-section CT angiography with myocardial perfusion SPECT

PURPOSE: To prospectively determine the accuracy of 64-section computed tomographic (CT) angiography for the depiction of coronary artery disease (CAD) that induces perfusion defects at myocardial perfusion imaging with single photon emission computed tomography (SPECT), by using myocardial perfusion imaging as the reference standard. MATERIALS AND METHODS: All patients gave written informed consent after the study details, including radiation exposure, were explained. The study protocol was approved by the local institutional review board. In patients referred for elective conventional coronary angiography, an additional 64-section CT angiography study and a myocardial perfusion imaging study (1-day adenosine stress-rest protocol) with technetium 99m-tetrofosmin SPECT were performed before conventional angiography. Coronary artery diameter narrowing of 50% or greater at CT angiography was defined as stenosis and was compared with the myocardial perfusion imaging findings. Quantitative coronary angiography served as a reference standard for CT angiography. RESULTS: A total of 1093 coronary segments in 310 coronary arteries in 78 patients (mean age, 65 years +/- 9 [standard deviation]; 35 women) were analyzed. CT angiography revealed stenoses in 137 segments (13%) corresponding to 91 arteries (29%) in 46 patients (59%). SPECT revealed 14 reversible, 13 fixed, and six partially reversible defects in 31 patients (40%). Sensitivity, specificity, and negative and positive predictive values, respectively, of CT angiography in the detection of reversible myocardial perfusion imaging defects were 95%, 53%, 94%, and 58% on a per-patient basis and 95%, 75%, 96%, and 72% on a per-artery basis. Agreement between CT and conventional angiography was very good (96% and kappa = 0.92 for patient-based analysis, 93% and kappa = 0.84 for vessel-based analysis). CONCLUSION: Sixty-four-section CT angiography can help rule out hemodynamically relevant CAD in patients with intermediate to high pretest likelihood, although an abnormal CT angiography study is a poor predictor of ischemia.

[ECG-gated chest CT angiography: value for atypical chest pain evaluation]

PURPOSE: The aim of this study was to evaluate ECG-gated whole chest CTA as a routine triage tool for patients with acute chest pain. MATERIAL AND METHODS: Whole chest CTA with retrospective ECG-gating was performed in 30 patients with acute atypical chest pain. The ten main segments of the coronary arteries, the pulmonary arteries, the aorta, and the myocardium (function, morphology) were independently analyzed by a resident and two senior radiologists. The inter-observer agreement between resident and senior radiologists was calculated. A final diagnosis was determined by consensus. RESULTS: Thirty patients were included. The coronary artery segments, myocardium and pulmonary arteries were considered analyzable in 84%, 90% and 97% of cases respectively. A final diagnosis for the cause of pain was retained in 19 patients: significant coronary artery stenosis (5), pulmonary embolus (5), aortic dissection (1), hypokinetic cardiomyopathy (2), lung parenchymal abnormalities (5), and hiatus hernia (1). Inter-observer agreement ranged from 0.76 to 1 between senior radiologists and from 0.76 to 1 between resident and senior radiologists. The average time of image interpretation ranged from 14 to 15 minutes. CONCLUSION: ECG-gated whole chest CT angiography appears as a promising tool for the evaluation of acute chest pain. Combined evaluation of appearance and function of the myocardium can reveal additional interesting information.

Detection of pulmonary emboli with CT angiography at reduced radiation exposure and contrast material volume: comparison of 80 kVp and 120 kVp protocols in a matched cohort

The detection rate of pulmonary emboli (PE) with computed tomography angiography (CTA) using either a standard or a low-dose protocol, combining reduced radiation exposure and iodine delivery rate, was retrospectively analyzed in a matched cohort of 120 patients.

Thoracoabdominal-aortoiliac multidetector-row CT angiography at 80 and 100 kVp: assessment of image quality and radiation dose

OBJECTIVE: To compare image quality and radiation dose of thoracoabdominal computed tomography (CT) angiography at 80 and 100 kVp and to assess the feasibility of reducing contrast medium volume from 60 to 45 mL at 80 kVp. MATERIALS AND METHODS: This retrospective study had institutional review board approval; informed consent was waived. Seventy-five patients who had undergone thoracoabdominal 64-section multidetector-row CT angiography were divided into 3 groups of 25 patients each. Patients of groups A (tube voltage, 100 kVp) and B (tube voltage, 80 kVp) received 60 mL of contrast medium at 4 mL/s. Patients of group C (tube voltage, 80 kVp) received 45 mL of contrast medium at 3 mL/s. Mean aortoiliac attenuation, image noise, and contrast-to-noise ratio were assessed. The measurement of radiation dose was based on the volume CT dose index. Three independent readers assessed the diagnostic image quality. RESULTS: Mean aortoiliac attenuation for group B (621.1 +/- 90.5 HU) was significantly greater than for groups A and C (485.2 +/- 110.5 HU and 483.1 +/- 119.8 HU; respectively) (P < 0.001). Mean image noise was significantly higher for groups B and C than for group A (P < 0.05). The contrast-to-noise ratio did not significantly differ between the groups (group A, 35.0 +/- 13.8; group B, 31.7 +/- 10.1; group C, 27.3 +/- 11.5; P = 0.08). Mean volume CT dose index in groups B and C (5.2 +/- 0.4 mGy and 4.9 +/- 0.3 mGy, respectively) were reduced by 23.5% and 27.9%, respectively, compared with group A (6.8 +/- 0.8 mGy) (P < 0.001). The average overall diagnostic image quality for the 3 groups was graded as good or better. The score for group A was significantly higher than that for group C (P < 0.01), no difference was seen between group A and B (P = 0.92). CONCLUSIONS: Reduction of tube voltage from 100 to 80 kVp for thoracoabdominal CT angiography significantly reduces radiation dose without compromising image quality. Reduction of contrast medium volume to 45 mL at 80 kVp resulted in lower but still diagnostically acceptable image quality.

Is body weight the most appropriate criterion to select patients eligible for low-dose pulmonary CT angiography? Analysis of objective and subjective image quality at 80 kVp in 100 patients

The objective of this retrospective study was to assess image quality with pulmonary CT angiography (CTA) using 80 kVp and to find anthropomorphic parameters other than body weight (BW) to serve as selection criteria for low-dose CTA. Attenuation in the pulmonary arteries, anteroposterior and lateral diameters, cross-sectional area and soft-tissue thickness of the chest were measured in 100 consecutive patients weighing less than 100 kg with 80 kVp pulmonary CTA. Body surface area (BSA) and contrast-to-noise ratios (CNR) were calculated. Three radiologists analyzed arterial enhancement, noise, and image quality. Image parameters between patients grouped by BW (group 1: 0-50 kg; groups 2-6: 51-100 kg, decadally increasing) were compared. CNR was higher in patients weighing less than 60 kg than in the BW groups 71-99 kg (P between 0.025 and <0.001). Subjective ranking of enhancement (P = 0.165-0.605), noise (P = 0.063), and image quality (P = 0.079) did not differ significantly across all patient groups. CNR correlated moderately strongly with weight (R = -0.585), BSA (R = -0.582), cross-sectional area (R = -0.544), and anteroposterior diameter of the chest (R = -0.457; P < 0.001 all parameters). We conclude that 80 kVp pulmonary CTA permits diagnostic image quality in patients weighing up to 100 kg. Body weight is a suitable criterion to select patients for low-dose pulmonary CTA.

Endoleak detection with CT angiography in an abdominal aortic aneurysm phantom: effect of tube energy, simulated patient size, and physical properties of endoleaks

To analyze the detection of endoleaks with low-tube-voltage computed tomographic (CT) angiography.

Effect of automatic tube current modulation on radiation dose and image quality for low tube voltage multidetector row CT angiography: phantom study

RATIONALE AND OBJECTIVES: To evaluate the effect of automatic tube current modulation on radiation dose and image quality for low tube voltage computed tomography (CT) angiography. MATERIALS AND METHODS: An anthropomorphic phantom was scanned with a 64-section CT scanner using following tube voltages: 140 kVp (Protocol A), 120 kVp (Protocol B), 100 kVp (Protocol C), and 80 kVp (Protocol D). To achieve similar noise, combined z-axis and xy-axes automatic tube current modulation was applied. Effective dose (ED) for the four tube voltages was assessed. Three plastic vials filled with different concentrations of iodinated solution were placed on the phantom's abdomen to obtain attenuation measurements. The signal-to-noise ratio (SNR) was calculated and a figure of merit (FOM) for each iodinated solution was computed as SNR(2)/ED. RESULTS: The ED was kept similar for the four different tube voltages: (A) 5.4 mSv +/- 0.3, (B) 4.1 mSv +/- 0.6, (C) 3.9 mSv +/- 0.5, and (D) 4.2 mSv +/- 0.3 (P > .05). As the tube voltage decreased from 140 to 80 kVp, image noise was maintained (range, 13.8-14.9 HU) (P > .05). SNR increased as the tube voltage decreased, with an overall gain of 119% for the 80-kVp compared to the 140-kVp protocol (P < .05). The FOM results indicated that with a reduction of the tube voltage from 140 to 120, 100, and 80 kVp, at constant SNR, ED was reduced by a factor of 2.1, 3.3, and 5.1, respectively, (P < .001). CONCLUSIONS: As tube voltage decreases, automatic tube current modulation for CT angiography yields either a significant increase in image quality at constant radiation dose or a significant decrease in radiation dose at a constant image quality.

Optimal sequence timing of CT angiography and perfusion CT in patients with stroke

OBJECTIVE Standard stroke CT protocols start with non-enhanced CT followed by perfusion-CT (PCT) and end with CTA. We aimed to evaluate the influence of the sequence of PCT and CTA on quantitative perfusion parameters, venous contrast enhancement and examination time to save critical time in the therapeutic window in stroke patients. METHODS AND MATERIALS Stroke CT data sets of 85 patients, 47 patients with CTA before PCT (group A) and 38 with CTA after PCT (group B) were retrospectively analyzed by two experienced neuroradiologists. Parameter maps of cerebral blood flow, cerebral blood volume, time to peak and mean transit time and contrast enhancements (arterial and venous) were compared. RESULTS Both readers rated contrast of brain-supplying arteries to be equal in both groups (p=0.55 (intracranial) and p=0.73 (extracranial)) although the extent of venous superimposition of the ICA was rated higher in group B (p=0.04). Quantitative perfusion parameters did not significantly differ between the groups (all p>0.18), while the extent of venous superimposition of the ICA was rated higher in group B (p=0.04). The time to complete the diagnostic CT examination was significantly shorter for group A (p<0.01). CONCLUSION Performing CTA directly after NECT has no significant effect on PCT parameters and avoids venous preloading in CTA, while examination times were significantly shorter.

Pitfalls in post-mortem CT-angiography--intravascular contrast induces post-mortem pericardial effusion

We present a case where multi-phase post-mortem computed tomography angiography (PMCTA) induced a hemorrhagic pericardial effusion during the venous phase of angiography. Post-mortem non-contrast CT (PMCT) suggested the presence of a ruptured aortic dissection. This diagnosis was confirmed by PMCTA after pressure controlled arterial injection of contrast. During the second phase of multi-phase PMCTA the presence of contrast leakage from the inferior cava vein into the pericardial sac was noted. Autopsy confirmed the post-mortem nature of this vascular tear. This case teaches us an important lesson: it underlines the necessity to critically analyze PMCT and PMCTA images in order to distinguish between artifacts, true pathologies and iatrogenic findings. In cases with ambiguous findings such as the case reported here, correlation of imaging findings with autopsy is elementary.

Multi-phase postmortem CT angiography: recognizing technique-related artefacts and pitfalls

BACKGROUND AND PURPOSE Multi-phase postmortem CT angiography (MPMCTA) is increasingly being recognized as a valuable adjunct medicolegal tool to explore the vascular system. Adequate interpretation, however, requires knowledge about the most common technique-related artefacts. The purpose of this study was to identify and index the possible artefacts related to MPMCTA. MATERIAL AND METHODS An experienced radiologist blinded to all clinical and forensic data retrospectively reviewed 49 MPMCTAs. Each angiographic phase, i.e. arterial, venous and dynamic, was analysed separately to identify phase-specific artefacts based on location and aspect. RESULTS Incomplete contrast filling of the cerebral venous system was the most commonly encountered artefact, followed by contrast agent layering in the lumen of the thoracic aorta. Enhancement or so-called oedematization of the digestive system mucosa was also frequently observed. CONCLUSION All MPMCTA artefacts observed and described here are reproducible and easily identifiable. Knowledge about these artefacts is important to avoid misinterpreting them as pathological findings.

Diagnostic Performance of Coronary Angiography by 64-Row CT

Background: The accuracy of multidetector computed tomographic (CT) angiography involving 64 detectors has not been well established. Methods: We conducted a multicenter study to examine the accuracy of 64-row, 0.5-mm multidetector CT angiography as compared with conventional coronary angiography in patients with suspected coronary artery disease. Nine centers enrolled patients who underwent calcium scoring and multidetector CT angiography before conventional coronary angiography. In 291 patients with calcium scores of 600 or less, segments 1.5 mm or more in diameter were analyzed by means of CT and conventional angiography at independent core laboratories. Stenoses of 50% or more were considered obstructive. The area under the receiver-operating-characteristic curve (AUC) was used to evaluate diagnostic accuracy relative to that of conventional angiography and subsequent revascularization status, whereas disease severity was assessed with the use of the modified Duke Coronary Artery Disease Index. Results: A total of 56% of patients had obstructive coronary artery disease. The patient-based diagnostic accuracy of quantitative CT angiography for detecting or ruling out stenoses of 50% or more according to conventional angiography revealed an AUC of 0.93 (95% confidence interval [CI], 0.90 to 0.96), with a sensitivity of 85% (95% CI, 79 to 90), a specificity of 90% (95% CI, 83 to 94), a positive predictive value of 91% (95% CI, 86 to 95), and a negative predictive value of 83% (95% CI, 75 to 89). CT angiography was similar to conventional angiography in its ability to identify patients who subsequently underwent revascularization: the AUC was 0.84 (95% CI, 0.79 to 0.88) for multidetector CT angiography and 0.82 (95% CI, 0.77 to 0.86) for conventional angiography. A per-vessel analysis of 866 vessels yielded an AUC of 0.91 (95% CI, 0.88 to 0.93). Disease severity ascertained by CT and conventional angiography was well correlated (r=0.81; 95% CI, 0.76 to 0.84). Two patients had important reactions to contrast medium after CT angiography. Conclusions: Multidetector CT angiography accurately identifies the presence and severity of obstructive coronary artery disease and subsequent revascularization in symptomatic patients. The negative and positive predictive values indicate that multidetector CT angiography cannot replace conventional coronary angiography at present. (ClinicalTrials.gov number, NCT00738218.).

Quantitative coronary arterial stenosis assessment by multidetector CT and invasive coronary angiography for identifying patients with myocardial perfusion abnormalities

Semi-quantitative stenosis assessment by coronary CT angiography only modestly predicts stress-induced myocardial perfusion abnormalities. The performance of quantitative CT angiography (QCTA) for identifying patients with myocardial perfusion defects remains unclear. CorE-64 is a multicenter, international study to assess the accuracy of 64-slice QCTA for detecting a parts per thousand yen50% coronary arterial stenoses by quantitative coronary angiography (QCA). Patients referred for cardiac catheterization with suspected or known coronary artery disease were enrolled. Area under the receiver-operating-characteristic curve (AUC) was used to evaluate the diagnostic accuracy of the most severe coronary artery stenosis in a subset of 63 patients assessed by QCTA and QCA for detecting myocardial perfusion abnormalities on exercise or pharmacologic stress SPECT. Diagnostic accuracy of QCTA for identifying patients with myocardial perfusion abnormalities by SPECT revealed an AUC of 0.71, compared to 0.72 by QCA (P = .75). AUC did not improve after excluding studies with fixed myocardial perfusion abnormalities and total coronary arterial occlusions. Optimal stenosis threshold for QCTA was 43% yielding a sensitivity of 0.81 and specificity of 0.50, respectively, compared to 0.75 and 0.69 by QCA at a threshold of 59%. Sensitivity and specificity of QCTA to identify patients with both obstructive lesions and myocardial perfusion defects were 0.94 and 0.77, respectively. Coronary artery stenosis assessment by QCTA or QCA only modestly predicts the presence and the absence of myocardial perfusion abnormalities by SPECT. Confounding variables affecting the relationship between coronary anatomy and myocardial perfusion likely account for some of the observed discrepancies between coronary angiography and SPECT results.