Application Of FD-CT Based CBV Imaging In Neuro Intervention

BackgroundIn the past ten years, flat detector equipped angiographic C-arm cone beam computed tomography (FD-CT) systems can be used directly within the interventional suite. This technique enabled higher image quality and lower X-ray dose, and thus reduced hazarders to both patients and clinicians. Along with the development of FD-CT, contrast resolution up to 1000 Hounsfield unit could be achieved, allowing optimized visualization of the vessel and high contrast object (bone, clip, coils, stent and calcifications). Imaging of low contrast structures, though inferior to CT, could be satisfying for detecting visualizing muscle, brain and hemorrhage, facilitating evaluation of soft tissue.To acquire 3D image, the C-arm rotated for 200 degrees around the region of interest, generating series of 2D projection images, which were then reconstructed using reconstruction algorithms similar as for CT.In the diagnosis and treatment of cerebral vascular diseases, FD-CT allowed acquisition of high quality 3D vessel structure, as well as CT-like cross-sectional images, which can be applied into detection of brain SAH, hemorrhage and hematoma during the treatment, and also enable real time evaluation during aneurysm coiling and stenting procedures. Due to its superior spatial resolution than CT imaging, FD-CT has been proven to provide detailed 3D structures of both intracranial and extracranial stent. Reports have shown that with FD-CT, extravasation of contrast medium could be effectively detected. Nowadays, it has been shown that it is possible to measure the cerebral blood volume (CBV) and then display these values as a CBV map. This novel image technology provides an immediate quantitative measurement of regional CBV variations and means to accurately measure presence and extent of ischemia for AIS patients, which further assists patient selection, diagnosis and treatment of ischemic cerebral vascular diseases.Statistics show that only 3% of all patients with acute ischemic stroke were treated with thrombolytic therapy, and only 10% of the patients were performed within 3 hours after the onset of the disease. This is largely due to that the patients have to receive a series of image examinations, and this image examination process lack of expert consensus, leading to the result that a clear judgment cannot be made within short tome and effective treatment could not be performed to the patient. Therefore, a fast and simple approach of imaging can be very useful to enhance the procedure of diagnosis and treatment of patients. Moreover, imaging examination and treatment rooms are usually located differently, and the patient transfer may cause additional treatment delay. With the concept of "Time is brain", FD-CT based CBV imaging make it possible o achieve one-stop imaging provides. Struffert T has made extraordinary efforts in the development and implementation of the combined technologies of DSA, CT, CTA and CTP in the same interventional suite. The combination of these imaging technologies help to reduce overall procedure time and offer great benefit to patients, etc, patients transferred directly from emergency department can receive complete diagnosis and treatment within one interventional suite.As with all new emerging technologies, FD-CT based CBV imaging technology is still under continuous improvement. At present, its image quality is not as good as conventional helical CT, and therefore, the reliability of FD-CT based CBV images needs to be investigated. Besides, to maximum the benefits of CBV imaging, certain requirements of interventional room have to be met, and the operation has to be in line with the clinicians’routine practice. For example, arterial injection of contrast medium is commonly adopted in the interventional room, which requires us to explore an approach using arterial catheter contrast medium injection to generate reliable CBV images and provide image evidence to support the treatment of ischemic cerebral vascular diseaseThe focus of this work is to discuss the feasibility of using artery access for FD-CT based CBV image generation, and to find out optimal injection site for obtaining standardized as well as reliable of FD-CT CBV images. Next, the accuracy of FD-CT based CBV images is verified against CTP CBV images, in order to prove that whether FD-CT based CBV images provide sufficient guidance and can replace the CTP CBV in the interventional suite. We have further explored the value of using super-selective artery injection to obtain regional CBV to guide the treatment procedures such as IA-thrombolysis, and the recanalization of blood vesselsChapter I Investigations on the improvement of contrast medium injection protocol during FD-CT based CBV acquisitionObjective FD-CT based CBV is an emerging technology and has been under investigations in recent years. This technology provides an immediate quantitative measurement of CBV and means to accurately measure presence and extent of ischemia for AIS patients, which further assists patient selection, diagnosis and treatment of ischemic cerebral vascular diseases. FD-CT based CBV is usually acquired with intra-venous contrast medium injection. Some researched has tested to inject contrast medium into ascending aorta, which provided real-time brain functional information with minimized contrast medium usage. However, unexpected asymmetric perfusion was observed for certain patients without cerebral circulatory disorders. This work tested feasibility of left ventricle contrast medium injection to achieve symmetric perfusion.Methods From January 2013 to June 2014, a total number of 24 patients (13 males, 11 females; mean age was 49.96±10.76 years) without perfusion related cerebral abnormities confirmed by diagnostic DSA were enrolled into this study.14 patients had received intra-ascending aorta contrast medium injection, and 10 patients had received left ventricle contrast medium injection.Conventional DSA examinations, FD-CT based CBV acquisitions and interventional treatments were performed using a single plane rotational FD-CT system (Artis zeego, Siemens Healthcare, Germany). The CBV were acquired before the DSA examination and treatment, and post-processed at a research workstation. As an output, CBV maps which were similar to CTP-CBV were generated. Results With intra-ascending aorta contrast medium injection, a number of asymmetric FD-CT based CBV maps were found. In the regions of bilateral cerebral hemisphere frontal subcortical white matter, basal ganglia, occipital cortex and subcortical white matter, and corona radiate, statistical analysis showed that P<0.05, indicating CBV inconsistency at left and right hemisphere. With left ventricular contrast medium injection, CBV at all these mentioned regions are reliable and symmetric, statistical analysis showed P> 0.05, showing that no significant CBV inconsistency were detected for left and right hemisphere.Conclusions FD-CT based CBV acquisitions using of arterial contrast medium injection (including via ascending aorta and left ventricle) is generally a safe approach. This method has the benefits to reduce contrast medium usage and renal injury and its operation is in line with the clinicians’ routine practice. With intra-ascending aorta contrast medium injection, a number of asymmetric FD-CT based CBV maps were found, requiring further investigations to improve the workflow and to correct the asymmetry. With left ventricle contrast medium injection, the mixing between contrast medium and blood is enhanced before flowing into vertebral and carotid arteries, and thus, reliable symmetric CBV maps could be obtained.Chapter II Value of CCQ DSA in the prediction of FD-CT based CBV symmetryObjective The quality of FD-CT based CBV relies on the homogeneity of contrast medium flowing from carotid artery into the intracranial vessels, as well as adequate time duration. Using ascending aorta injection, due to several reasons including patients’ individual vasculature variations at aortic arch and carotid, and limited length of the ascending aorta, causing non-uniform contrast medium distribution before reaching parenchyma two hemispheres and leading to unreliable CBV maps. To solve this problem, we use color coded quantitative digital subtracted angiography (CCQ-DSA) to predict reliability of FD-CT based CBV by exploring correlation between measurements of CCQ and symmetry of CBV maps.Methods This study had been approved by the hospital ethics committee. All patients signed written informed consent. From January 2013 to June 2014,24 patients (13 males,11 females; mean age was 49.96±10.76 years) enrolled into the study. All patients had received conventional brain CT before the treatment and CTP-CBV either before or after the treatment. DSA examinations, and FD-CT based CBV using aortic injection and left ventricle injections were performed in the interventional suite. Routine aortic arch DSA showing aorta and carotid arteries were converted to color coded images, indicating contrast medium distribution. Area under curve (AUC) was extracted from the curve and compared. rCBV and rAUC was calculated, respectively.Results Among 14 patients of the symmetric CBV using aortic contrast medium injection,9 patients demonstrated good perfusion symmetry. For the other 5 patients, asymmetric perfusion was detected. Correlation analysis of the rCBV and rAUC showed R=0.967(p<0.001), indicate that the symmetric CBV using aortic contrast medium injection and the CCQ DSA at bilateral common carotid arteries had strong positive correlation. The numbers of patients with bilateral asymmetry in FD-CT CBV image and CCQ DSA image were analyzed by Fisher exact probability method, and there is no significant difference between them (P>0.05). Among 10 patients of the symmetric CBV using left ventricle contrast medium injection,6 patients demonstrated good perfusion symmetry. For the other 4 patients, asymmetric perfusion was detected.Correlation analysis of the rCBV and rAUC showed R=0.522 (P>0.05), indicate that the symmetric CBV using left ventricle contrast medium injection and the CCQ DSA at bilateral common carotid arteries had strong positive correlation. The numbers of patients with symmetric FD-CT CBV image and CCQ DSA image were analyzed by Fisher exact probability method, and there is significant difference between them(P<0.05).Conclusions Without additional contrast medium and X-ray dose, color coded DSA has its advantage to quantify contrast medium concentration in the common carotid arteries. The CBV symmetry using aortic contrast medium injection and the CCQ DSA at bilateral common carotid arteries had strong correlation. Therefore, the combination of CCQ-DSA could help sort out patients who are/are not suitable for undergoing FD-CT based CBV acquisitions. With left ventricle contrast medium injection, a reliable FD-CT based CBV map could be formed regardless of contrast medium concentration at bilateral common carotid arteries.Chapter Ⅲ Validation of FD-CT based CBV and its value in the thrombolysis treatment for AIS patientsObjective In the diagnosis and treatment of cerebral vascular diseases, FD-CT based CBV provides an immediate quantitative measurement of CBV variations and means to accurately measure presence and extent of ischemia for AIS patients, which further assists patient selection, diagnosis and treatment of ischemic cerebral vascular diseases. Real time FD-CT based CBV provides good image evidence for diagnosis and treatment. In our study, we use intra-arterial contrast medium injection to form FD-CT based CBV maps, which were then compared with helical CT CBV, such that we can validate the value of FD-CT based CBV in the AIS patient treated by thrombolysis.Methods From January 2013 to January 2015,19 patients enrolled into the study, 11 of them have underwent routine examination without treatment (4 patients have SAH,3 patients have history of cerebral ischemia,3 patients with dizziness,1 patient with epilepsy). IA thrombolysis was performed for 8 AIS patients. This study had been approved by the hospital ethics committee. All patients signed written informed consent.For the 11 patients without treatment, FD-CT based CBV using left ventricle injections were performed. The resulting CBV maps were compared with CTP CBV to evaluate the agreement. For the 8 AIS patients treated by IA thrombolysis, FD-CT based CBV showing regional CBV variations using super selective arterial contrast medium injection were performed before and after the treatment and were then compared.Results For the 11 patients without treatment, FD-CT based CBV were compared with CTP CBV in the regions of bilateral cerebral hemisphere frontal subcortical white matter, basal ganglia, occipital cortex and subcortical white matter, and corona radiate, no significant differences were found with P>0.05. Correlation analysis of FD-CT based CBV and CTP CBV showed R=0.98 (P<0.01), indicate strong correlation. Bland-Altman test plot showed FD-CT based CBV was slightly lower than CTP CBV, with mean deviation of 0.03±0.17ml/100g. For the 8 AIS patients treated by IA thrombolysis, CBV value in the infarct regions before and after treatment showed that large portion of patients had CBV increase after the treatment, and only 3 patients had no evident perfusion improvement. Statistical analysis showed that FD-CT based CBV maps acquired before and after treatment have significant variations (p<0.01).Conclusions It is feasible to acquire FD-CT based CBV maps using left ventricle contrast medium injection. FD-CT based CBV is highly correlated with CTP CBV and could replace CTP CBV for disease diagnosis and treatment. Using super- selective artery contrast medium injection to form CBV maps further decrease contrast medium usage, and reduce potential injury to the patients.