Monica Ricci

Relationship between thallium-201 uptake by supratentorial glioblastomas and their morphological characteristics on magnetic resonance imaging

Single-photon emission tomography (SPET) with thallium-201 is used in the assessment of patients with gliomas because the amount of201Tl accumulated by the tumoral cells increases in proportion to the degree of tumour malignancy, thus making it possible to differentiate high-grade from low-grade gliomas or recurrences from radiation necrosis. However, in large areas of tissue such as those examined in201Tl SPET studies, the uptake of201Tl may vary considerably even in tumours with the same histological diagnosis, as occurs in glioblastomas (GBMs). In order to evaluate the possible influence of the macroscopic characteristics of tumours on201Tl uptake, we studied a series of 13 patients with histologically proven GBMs, comparing magnetic resonance imaging (MRI) parameters such as tumour dimensions, perilesional oedema, intratumoral necrosis and contrast enhancement with the degree of201Tl uptake. The patients underwent both201Tl SPET and MRI before surgery. The201Tl index (tumour/contralateral unaffected brain) was calculated using two different region of interest (ROI) methods: the first employed irregular large ROIs (3.2±13.9 cm2) including pixels with more than 50% maximum activity; the second employed regular square small ROls (2.7 cm2) centered on the maximum activity of the lesion. Of the MRI morphological parameters studied, only necrosis significantly reduced the degree of201Tl uptake in GBMs when larger ROIs were used. However, by using small regular ROIs the influence of necrosis on201Tl uptake was found to be less relevant. Since necrosis is related to tumour proliferative activity and represents a negative prognostic factor in astrocytoma, a possible underestimation of201Tl uptake due to intratumoral necrosis must be carefully evaluated.

Motor stimulation response by technetium-99m hexamethylpropylene amine oxime split-dose method and single photon emission tomography

We applied the technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) split-dose method in order to evaluate the feasibility of assessing cerebral blood flow (CBF) changes with single photon emission tomography (SPET) during a motor activation task. Eleven normal subjects were studied using the Tomomatic 564 (Medimatic, DK). Five subjects were studied twice at rest and 6 subjects at rest and during a motor task performance (finger opposition movements). A total of 28 mCi of 99mTc-HMPAO was injected in 2 doses with a 1:3 ratio. The first scan was obtained after injection of 7 mCi at rest in all subjects. The second scan was obtained a few minutes later, after injection of the remaining dose (21 mCi), under similar resting conditions or during a motor task performance. The mean brain uptake was proportional to the amount of tracer injected and to the acquisition time for both the first scan (5263±1266 counts × mCi × min) and the second (5034.4±966 counts × mCi × min). The grey/white matter ratio was 1.67±0.019 and 1.67±0.097 for the two scans, respectively. A three-way analysis of variance (ANOVA) for repeated measure showed no significant effects of side, slice and region of interest (ROI) on the CBF in the 5 subjects studied twice at rest, and the mean regional CBF change was −0.2%±5%. In the 6 subjects studied at rest and during motor activation, the image subtraction analysis showed a significant CBF increase in the primary motor cortex contralateral to the stimulated side (15%±7%, n=6) and medially in the supplementary motor area (22%±12%, n=4). Our results indicate that the split-dose method allows the detection of a local CBF response to motor activation using 99mTc-HMPAO in a single imaging session.

Prolonged Muscular Flaccidity in Stroke Patients Is Associated with Crossed Cerebellar Diaschisis

In order to evaluate whether hypotonia could be the clinical expression of crossed cerebellar diaschisis (CCD), we studied the occurrence and severity of CCD in two groups of hemiparetic stroke patien

Presurgical integrated MRI/SPECT localization of the sensorimotor cortex in a patient with a low-grade astrocytoma in the rolandic area

We describe the case of a young man who, despite the presence of a tumour in the left sensorimotor cortex, exhibited no motor deficit. Integrated MRI/SPECT-CBF study during motor activation was aimed at determining which cerebral areas were involved in movement execution in this patient and their relationship with the tumour. CBF changes during motor activation were located in two motor areas: anteriorly and medially to the tumour in the left frontal lobe (+29%) and in the right medial frontal cortex (+43%). Integrated MRI/SPECT images provided both an anatomical and functional definition of the motor areas in a patient with a rolandic tumour and could prove useful in determining preoperatively an appropriate surgical strategy.

Pathophysiology of Ischemic Brain Disease

In this article, we review and discuss the pathophysiology of brain ischemia, focusing on requirements of cerebral metabolism, biochemical characterization of the energy reserve, and autoradiographic and toraographic methods for in vivo evaluation of cerebral blood flow and metabolism. We propose new therapeutic strategies for the management of the acute phase of stroke, based on diagnostic protocols that include clinical evaluation, noninvasive study of neck and intracranial arteries, brain computed tomography, and single-photon emission computed tomography. The ideal therapeutic trial should combine early thrombolysis and active brain protection against those biochemical mechanisms leading to irreversible neuronal damage. (Stroke 1990; 21(suppl IV):IV-9-IV-ll)

Motor activation by single-photon emission computed tomography. A comparison of xenon-133 and technetium-99m HM-PAO "split-dose" methods.

Single‐photon emission computed tomography (SPECT) was used to investigate the feasibility of the technetium 99m‐hexamethylpropyleneamineoxime (99mTc HM‐PAO) split‐dose method to evidence changes in regional cerebral blood flow during a motor activation task, in comparison with a quantitative method using the inhalatory xenon‐133. Four subjects were studied twice with both methods, at rest and during finger opposition movements. On the activated cerebral hemisphere, a significant increase in regional cerebral blood flow was observed over the motor cortical areas. The average increases were + 28.1 ± 5.6% for the xenon‐133 method and + 12.3 ± 5.2% for the 99mTc HM‐PAO method. By using the linearization algorithm for the 99mTc HM‐PAO method, a mean increase of + 22.5 ± 8.9% was calculated. This study demonstrated that the split‐dose method allows the motor activation SPECT studies with 99mTc HM‐PAO to be done in a single session.

Pet and Spect for the Study of Atherosclerotic Diseases in Humans

Emission Tomography (ET) investigates physiological parameters and biochemical reactions in vivo in humans. Positron Emission Tomography (PET) is based on x-ray computerized tomography (CT) principles and provides a tomographic representation of tissue radioactivity due to positrons, such as carbon (C-11), oxygen (0-15), nitrogen (N-13), and fluorine (F-18).