Assessment of the tracer delay effect in whole-brain computed tomography perfusion: results in patients without known neuroanatomic abnormalities.

OBJECTIVE: Whole-brain computed tomography perfusion (CTP) data sets generated by tracer delay-insensitive singular value decomposition plus (SVD+) and standard singular value decomposition (sSVD) deconvolution algorithms were evaluated to quantify relatedness and discrepancies in CTP results. METHODS: Twenty females with symmetrical hemispheric CTP maps indicative of brain tissue without apparent abnormalities were studied. Tissue-specific CTP values were analyzed. RESULTS: Standard SVD values were higher than SVD+ for cerebral blood flow. Other CTP values had minimal differences across brain regions. All simple linear regression models were statistically significant (P < 0.05) except for cerebral blood flow in white matter (P = 0.06). Cerebral blood volume had a good model fit, and mean transit time, a poor fit. CONCLUSIONS: Corresponding fitted CTP values for sSVD and SVD+ based on regression equations for brain-tissue types are presented. Additional research is required to compare SVD+ and sSVD in disease states when significant hemodynamic brain alterations are present.

Assessment of tracer delay effect in whole-brain computed tomography perfusion: results for selected regions of interest in middle cerebral artery acute ischemic strokes.

OBJECTIVE: The objective of this study was to compare the variability of computed tomography perfusion (CTP) results in identical data sets of middle cerebral artery (MCA) acute ischemic stroke (AIS) generated by standard singular value decomposition (sSVD) deconvolution and tracer delay-insensitive singular value decomposition (SVD+) algorithm analyses. METHODS: Whole-brain 320-detector-row CTP data sets from 9 unilateral MCA AIS cases and 9 controls were retrospectively analyzed. Computed tomography perfusion values for the combined core/penumbra, contralateral hemispheres and arterial territories were measured and compared with literature values. Simple linear regression models are provided to predict corresponding SVD+ value and sSVD CTP values. RESULTS: In the core/penumbra, sSVD generated lower cerebral blood flow (CBF) values, higher mean transit time (MTT) values, and a broader range of CBF and MTT values as compared with SVD+. Mean transit time value differences between the core/penumbra and contralateral hemispheres were statistically significant using sSVD, whereas those of SVD+ were not. Goodness of fit between algorithms for the core/penumbra was lower for CBF (0.483) and MTT (0.494), as compared with time to peak (0.891) and cerebral blood volume (0.997). CONCLUSIONS: In this study using identical source data for patients with MCA AIS, use of either sSVD or SVD+ analyses created statistically significant differences in the CTP value results. Tracer delay-sensitive and -insensitive algorithms impact CTP results in AIS and controls, highlighting the need to pursue additional studies that assess the variability, accuracy, and clinical implications of CTP results generated when using heterogeneous deconvolution algorithms.

Appearance and impact of post-operative intracranial clips and coils on whole-brain CT angiography and perfusion.

BACKGROUND: To evaluate the effect of vascular clips and endovascular coils placed for intracranial aneurysms and arteriovenous malformations on whole-brain computed tomography (CT) angiography and perfusion. METHODS: A 320-detector row dynamic volume CT system imaged 11 patients following surgical placement of vascular clips or endovascular coils. The extent of clip and coil subtraction by automated software was evaluated using CT digital subtraction angiography and CT perfusion. Impact on CT perfusion values by retained intracranial devices was compared to age- and gender-matched controls. RESULTS: Clip and coil subtraction on CT angiography was graded as good in 8 and moderate in 3 cases. A residual neck and additional aneurysm were noted in 1 of 11 patients. Post-procedural axial slice level CT perfusion values decreased in reliability with increasing proximity to the metallic devices secondary to beam hardening. However, the intracranial devices did not affect axial slice level CTP values of cerebral blood volume, cerebral blood flow and mean transit time outside of the level of the device. Time to peak values was globally decreased outside of the immediate vascular intervention region. CONCLUSIONS: Advances in CT technology have provided clinically useful subtraction of intracranial clips and coils. While CT perfusion values were altered in device subtraction areas and within beam hardening artifact areas; they can provide valuable postoperative information on whole-brain hemodynamics. In selected cases, the combination of CT angiography and whole-brain CT perfusion can offer an alternative to conventional angiography that is a more invasive option.

Clinical indications and utilization of 320-detector row CT in 2500 outpatients.

Clinical indications and utilization patterns for 3963 CT scans on 2500 consecutive patents on a 320-detector row CT in an outpatient setting were retrospectively analyzed and compared with previously reported CT studies. The impact of the latest generation CT technology, including whole organ perfusion, on indications and utilization patterns during the study period was also assessed. The top five requested CT scan types were abdomen/pelvis, chest, head, sinuses, and coronary CT angiography. Indication and utilization rates were similar to prior studies for abdomen/pelvis, non-cardiac chest, and head CT scans. Abdominal pain and headaches were the most frequent indications for abdomen/pelvis and head CTs, respectively. The 7.3% cardiac CT scan utilization rate was not comparable to rates of up to 72% in self-referral outpatient settings. Whole organ volume CT imaging was utilized in 100% of coronary CT angiography and 22.7% of head CTs. The 320-row CT had fewer negative head and body CT findings as compared to prior reports. The availability of new technology, such as whole organ dynamic scans, appears to have influenced CT indications, utilization and finding rates with a decrease in negative brain and body results. Comparisons with previous outpatient CT studies were similar for multiple categories with the exception of cardiac CT utilization, which is heavily influenced by self-referral. Further study of outpatient imaging indications and utilization rates from multiple centers may benefit from a standardized categorization to improve understanding of the disparate outpatient imaging environment.

Developmental venous anomalies: appearance on whole-brain CT digital subtraction angiography and CT perfusion.

INTRODUCTION: Developmental venous anomalies (DVA) consist of dilated intramedullary veins that converge into a large collecting vein. The appearance of these anomalies was evaluated on whole-brain computed tomography (CT) digital subtraction angiography (DSA) and CT perfusion (CTP) studies. METHODS: CT data sets of ten anonymized patients were retrospectively analyzed. Five patients had evidence of DVA and five age- and sex-matched controls were without known neurovascular abnormalities. CT angiograms, CT arterial-venous views, 4-D CT DSA and CTP maps were acquired on a dynamic volume imaging protocol on a 320-detector row CT scanner. Whole-brain CTP parameters were evaluated for cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP), mean transit time (MTT), and delay. DSA was utilized to visualize DVA anatomy. Radiation dose was recorded from the scanner console. RESULTS: Increased CTP values were present in the DVA relative to the unaffected contralateral hemisphere of 48%, 32%, and 26%; and for the control group with matched hemispheric comparisons of 2%, -10%, and 9% for CBF, CBV, and MTT, respectively. Average effective radiation dose was 4.4 mSv. CONCLUSION: Whole-brain DSA and CTP imaging can demonstrate a characteristic appearance of altered DVA hemodynamic parameters and capture the anomalies in superior cortices of the cerebrum and the cerebellum. Future research may identify the rare subsets of patients at increased risk of adverse outcomes secondary to the altered hemodynamics to facilitate tailored imaging surveillance and application of appropriate preventive therapeutic measures.