B. Gasparetto

Functional perfusion and blood-brain barrier permeability images in the diagnosis of cerebral tumors by angio CT

We performed rapid sequential CT scanning following iv injection of a bolus of contrast medium and generated three functional images relating to intravascular circulation time (rABCT), vascular volume (Vv) density and blood-brain barrier (BBB) unidirectional constant uptake rate (Ki), respectively. This was accomplished by calculating the first mathematical moment of the monitored time-density curves about the injection time and from the multiple time graph analysis described by Patlack and co-workers. A satisfactory resolution was achieved, allowing separate appreciation of changes in rABCT both in large vessels and in tissue small vessels. Combined evaluation of rABCT and Vv images allowed us to differentiate between tumors.

Functional circulation and blood-brain permeability images by angio CT in the assessment of cerebral ischemia

We performed rapid sequential computerized tomography (CT) scanning following i.v. injection of a bolus of contrast medium, and generated three functional images related, respectively, to intravascular circulation time (rABCT), vascular volume density (Vv) and blood-brain barrier (BBB) unidirectional constant uptake rate (Ki). This was accomplished by calculating the first mathematical moment of the monitored time-density curves about the injection time, and by the multiple time graph analysis described by Patlack and coworkers. A satisfactory resolution was achieved, allowing separate appreciation of changes in rABCT both at large vessels and at tissue small vessels. Combined evaluation of rABCT and Vv images allowed us to draw qualitative conclusions about blood flow and perfusion reserve.

Assessment of regional cerebral blood flow images with non-diffusible contrast media and angio-CT. Comparison with Xe-CT

We derived rCBF (ND-rCBF) images using non-diffusible contrast agent time-density curves obtained by monitoring the first pass with an angio-CT sequence. An appropriate elaboration of the sequence of the images led to the generation of vascular volume (Vv) and regional Arm-Brain circulation time images (rABCT). ND-rCBF was obtained by dividing the Vv image by the rABCT image after having rendered them suitable for such an operation. Regional cerebral vascular volume (rCBF) was assessed by standardizing Vv values with blood contrast concentration and intracranial circulation time (rICT) by subtracting from the rABCT image the inflow mean time, assessed as the lowest rABCT value of the slice. The ND-rCBF images were qualitatively fairly well comparable with synchronous rCBF (D-rCBF) images obtained with the Xe-CT technique. However quantitation of the values by ROI use gave different results, the ND-rCBF image showing considerably higher values. Using indicator images to analyse the rCBF values at different levels of rCBV and rICT, it was shown that there was a significant relation between the two ND-rCBF and D-rCBF values in the 70-80% pixels with higher rABCT and lower rCBF values.

Single photon emission computed tomography with technetium-99m hexamethyl propylenamino oxime in the clinical assessment of cerebral ischemia. A preliminary evaluation.

94 subjects, 64 with cerebral ischemia of varying severity and outcome, and 30 controls were studied with technetium-99m hexamethyl propylenamino oxime single photon emission computed tomography in order to evaluate the suitability of this technique in the assessment of cerebral ischemia. Decreased uptake corresponding to the side of clinical symptomatology and/or to CT lesion was found in 93% of the patients with complete stroke and in 28% of the patients with transient ischemic attack. This procedure can be a useful tool in the routine examination of ischemic patients, although the mechanism underlying brain uptake is far from being completely understood and the possible quantitative evaluation of regional cerebral blood flow is worthy of further assessment.

Assessment of the CO2 response by means of non diffusible contrast media and Angio-CT in patients with cluster headache

We analyzed the possibility of assessing functional vasomotor changes by means of Arm-Brain Circulation Time (rABCT) and Vascular volume images (Vv) obtained with Angio-CT, in basal condition and following CO2 inhalation, in a sample of 48 patients with cluster headache. CO2 inhalation resulted in the appearance of local changes, which were detected in 28 regions. Analysis by indicator images of Vv-dependent rABCT distribution showed two main patterns: abnormal rABCT mostly evident at the smallest Vv pixels and abnormal rABCT dependent on abnormal Vv distribution. The former pattern was linked to abnormality at the circle of Willis; the latter to abnormal local vasomotor responses. Patients with cluster headache showed both patterns, which prompted us to conclude for the presence of low-degree stenosis in carotid arteries and vasomotor instability in peripheral brain vessels.

Functional circulation images by angio-CT in the assessment of small deep cerebral infarctions

We analyzed circulation time (rABCT) and vascular volume density images obtained by angio-computerized tomography (angio-CT) in 63 patients with small deep cerebral infarctions. Abnormalities in the rABCT image were found in 88% of the patients and in the vascular volume image in 48%. Two groups with different clinical pictures were picked out by rABCT changes: one with major-vessel involvement, the other with small-vessel involvement. The perfusional changes found were mainly due to altered vascular canalization rather than to altered vasomotility. The hemodynamic theory could explain the spatial relations between perfusion changes and CT hypodense areas without needing assumptions linking blood flow and metabolism.

Assessment of 99mTc-HM-PAO parameters with SPECT for improved evaluation of blood flow in cerebral lesions

A method for investigating the linearity between blood flow and distribution of 99mTc-HM-PAO uptake in patients undergoing single photon emission computed tomography (SPECT) is presented. This method, based on particular elaboration techniques of sequential multiple acquisitions, provides a local index: cumulative transit time (CTT) related to all factors, other than blood flow, affecting 99mTc-HM-PAO uptake. Because a correct qualitative blood flow estimation is based on the uniformity of the above factors, the occurrence of a change of this index indicates a nonlinear relation between blood flow and 99mTc-HM-PAO uptake distributions. It was shown that although linearity between blood flow and 99mTc-HM-PAO uptake may be questionable, a qualitative assessment of blood flow was correct in 100% of ischemic patients. In nonischemic patients this percentage fell to 60%.

Functional Circulation Time, rCBV and rCBF Images by Angio-CT in the Assessment of Altered Carotid Canalization

A conventional Angio-CT sequence was used to generate functional perfusional images by applying particular models to the contrast first pass curves. We calculated the first mathematical moment of monitored time-DH curves from the injection time and applied to the sequence the multiple time graph analysis described by Patlak. The former provides regional an Arm-Brain circulation time (rABCT) image, the latter two images, one related to vascular volume Vv, the other to the blood brain barrier permeability Ki. The Vv and rABCT images were subsequently uitilized to derive the rCBF image (ND-rCBF). The rABCT, Vv and rCBF images were analyzed in a group of 48 patients with angiographically detected unilateral altered carotid canalization of various degrees and clinical pictures. Direct detection was possible in 37 out of 48 cases and a strong suggestion was derived in the remaining cases. Analysis of rABCT provided the maximal rate of detection and allowed us to derive haemodynamic considerations. Assessment of distribution of rABCT changes and Vv analysis discriminated fairly well between patients with relatively mild and severe clinical pictures.

Valutazione emodinamica delle malformazioni vascolari cerebrali con Angio-TC

Transit time, vascular volume, blood brain barrier permeability and rCBF images, obtained by computerized analysis of Angio-CT, were applied to the study of cerebral vascular malformations. Useful information with respect to the haemodynamic conditions of the lesions as well as the surrounding brain tissue was obtained.

Misure di flusso cerebrale, tempo di transito, volume vascolare e permebilità di barriera nelle lesioni ischemiche con immagini funzionali derivate dall'angio-TC

Transit time, vascular volume, blood brain barrier permeability and rCBF images, obtained by computerized analysis of Angio-CT, were applied to the study of cerebral ischemic patients. Our results show a considerable increase in information with respect to conventional contrast examination.