Diagnostic accuracy and utility of coronary CT angiography with consideration of unevaluable results: A systematic review and multivariate Bayesian random-effects meta-analysis with intention to diagnose.

OBJECTIVES: To meta-analyze diagnostic accuracy, test yield and utility of coronary computed tomography angiography (CCTA) in coronary artery disease (CAD) by an intention-to-diagnose approach with inclusion of unevaluable results. METHODS: Four databases were searched from 1/2005 to 3/2013 for prospective studies that used 16-320-row or dual-source CTs and provided 3 × 2 patient-level data of CCTA (positive, negative, or unevaluable) versus catheter angiography (positive or negative) for diagnosing ≥50% coronary stenoses. A Bayesian multivariate 3 × 2 random-effects meta-analysis considered unevaluable CCTAs. RESULTS: Thirty studies (3422 patients) were included. Compared to 16-40 row CT, test yield and accuracy of CCTA has significantly increased with ≥64-row CT (P < 0.05). In ≥64-row CT, about 2.5% (95%-CI, 0.9-4.8%) of diseased patients and 7.5% (4.5-11.2%) of non-diseased patients had unevaluable CCTAs. A positive likelihood ratio of 8.9 (6.1-13.5) indicated moderate suitability for identifying CAD. A negative likelihood ratio of 0.022 (0.01-0.04) indicated excellent suitability for excluding CAD. Unevaluable CCTAs had an equivocal likelihood ratio of 0.42 (0.22-0.71). In the utility analysis, CCTA was useful at intermediate pre-test probabilities (16-70%). CONCLUSIONS: CCTA is useful at intermediate CAD pre-test probabilities. Positive CCTAs require verification to confirm CAD, unevaluable CCTAs require alternative diagnostics, and negative CCTAs exclude obstructive CAD with high certainty. KEY POINTS: • This 3 × 2 Bayesian meta-analysis included unevaluable CCTAs with intention-to-diagnose. • CCTA is currently useful at intermediate CAD pre-test probabilities. • Unevaluable CCTAs should not, generally, be treated as if they are positive. • Positive CCTAs require verification by other methods to confirm CAD. • Negative CCTAs exclude CAD with high certainty.

Evaluation of positron emission tomography imaging using [68Ga]-DOTA-D Phe(1)-Tyr(3)-Octreotide in comparison to [111In]-DTPAOC SPECT. First results in patients with neuroendocrine tumors.

PURPOSE: [111In]-DTPAOC (Octreoscan(R)) has been shown to be very useful in the detection of somatostatin receptor (SSTR) positive tumors and their metastases using either conventional scintigraphy or single photon emission computed tomography (SPECT). The main drawback of this method is the limited spatial resolution and a somewhat low receptor affinity of the radiopeptide. Due to the increased spatial resolution and the ability of quantification, an agent for positron emission tomography (PET) imaging of SSTR is desirable. This communication shows our initial experience using [68Ga]-DOTA-D-Phe(1)-Tyr(3)-Octreotide (DOTATOC) in comparison to [111In]-DTPAOC-SPECT in patients with neuroendocrine tumors. PROCEDURES: Four patients, two male and two female (46-55 years old) have been examined by [111In]-DTPAOC scintigraphy and within one month by [68Ga]-DOTATOC-PET. All of them suffered from neuroendocrine tumors and/or their metastases. DOTATOC has been labeled using the positron-emitting generator-nuclide 68Ga (t(1/2) 68 minutes). In two patients with previously known localization of tumor, dynamic PET scans after intravenous bolus-injection of 181+/-17 MBq [68Ga]-DOTATOC until 120 minutes post-injection were acquired. In all patients, the static PET-scans have been acquired after 45 or 60 minutes post-injection (SUV1) and 140 minutes post-injection (SUV2). RESULTS: Similar to [111In]-DTPAOC, [68Ga]-DOTATOC showed the highest uptake in the spleen, followed by the kidneys and the liver. A clear delineation of the pituitary gland could only be achieved by PET. The highest SUVs were found at a plateau between 45 and 90 minutes with a maximum 60 minutes post-injection. Due to the fast tracer accumulation in the tumor and the rapid clearance of the compound, resulting in high tumor to background ratios even 40 minutes after injection, the short half life of 68Ga is reasonable. In two patients more findings have been revealed by [68Ga]-DOTATOC-PET as compared to the [111In]-DTPAOC-SPECT. In comparison to the [111In]-DTPAOC-SPECT [68Ga]-DOTATOC-PET seems to be superior especially concerning small findings with low tracer uptake. Both [111In]-DTPAOC-SPECT and [68Ga]-DOTATOC-PET were less sensitive in the detection of liver metastases of neuroendocrine tumors compared to computerized tomography CT because they showed a lower uptake than the surrounding liver tissue. CONCLUSIONS: According to our initial experiences in a limited number of patients, [68Ga]-DOTATOC is a promising PET tracer for imaging neuroendocrine tumors and their metastases. In comparison to the [111In]-DTPAOC-scan it seems to be superior especially in detecting small tumors or tumors bearing only a low density of SSTRs. It offers excellent imaging properties and very high tumor to background ratios. Further evaluation of [68Ga]-DOTATOC in a larger number of patients is certainly justified.