Karim Farid

Normal cerebrovascular reactivity in Stroke-like Migraine Attacks after Radiation Therapy syndrome.

Stroke-like Migraine Attacks after Radiation Therapy (SMART) syndrome is a rare complication of cranial irradiation. Radiation is well-known to impair vascular vessel architecture and function. We investigated the hypothesis of radiation-induced cerebral vascular reserve dysfunction as the underlying mechanism of SMART. Interictal cerebrovascular reactivity was investigated using Tc-99m hexamethylpropyleneamine oxime-SPECT and acetazolamide challenge in 3 patients. We found interictal hypoperfusion and normal cerebrovascular reactivity in all patients. Neither ictal restriction of the apparent diffusion coefficient nor MR angiography abnormalities were observed. These findings do not support a vascular mechanism in SMART syndrome. Postradiation neuronal dysfunction may be the underlying mechanism. Further investigations on larger series are needed to confirm this hypothesis.

Brain Dopaminergic Modulation Associated with Executive Function in Parkinson's Disease

The progressive development of deficits in executive functions, including action planning, is a well‐known complication of Parkinsons disease. A dysfunction of the prefrontal lobe, which is known to be involved in the control of inhibitory processes, could explain the difficulties in initiating behavior or inhibiting ongoing actions in patients with PD. The strong dopaminergic innervation of the prefrontal cortex raises questions about the putative effects of dopa therapy on this cognitive impairment. In the present study, we used fMRI to examine the functional influence of dopa therapy on neural activity during a go/no‐go task in nine patients with and without levodopa treatment and in matched controls. Whereas the patient and control subjects exhibited the same performance during the go/no‐go task, different patterns of brain activation were observed depending on the dopaminergic status. The drug‐off state was characterized by more widely distributed brain activity, mainly in the bilateral caudate. Levodopa did not fully restore normal brain activation and induced changes in the pattern of cingulate cortex activity, which was more pronounced in the rostral part in the drug‐off state and in the caudal part after levodopa intake. These results support the idea of a critical role for dopamine in the control of executive functions in patients with PD.

SPECT-CT improves scintigraphic accuracy of osteoid osteoma diagnosis.

Abstract:A 34-year-old woman with a history of chronic foot pain was admitted for bone evaluation. Bone scan revealed focal foot uptake in the early and late images. SPECT images combined with low dose CT revealed uptake at the site of a nidus considered to be osteoid osteoma. CT images are usually

Is brain SPECT useful in degenerative dementia diagnosis

Cerebral blood flow assessment performed by single-photon emission computed tomography (SPECT) of the brain is used to detect early neuronal dysfunction associated with degenerative dementia. Patterns of perfusion abnormalities are different across dementia syndromes. These differences could be used for differential diagnoses and early detection of amnesic mild cognitive impairment in patients with a high risk of conversion to Alzheimer disease. This paper aimed to summarize the expected benefits of single-photon emission computed tomography of the brain in the exploration of degenerative dementias.

Correlation between serum 25-hydroxyvitamin D concentrations and regional cerebral blood flow in degenerative dementia.

BackgroundChronic low serum vitamin D concentrations are common among the elderly. Recent studies have suggested that its metabolite, 25-hydroxyvitamin D (25-OHD), might be important for preserving cognitive functions through specific brain protective effects. However, this hypothesis is still under discussion. The aim of this study was to assess the correlation between serum 25-OHD concentrations and regional cerebral blood flow in neurodegenerative diseases such as Alzheimer’s disease (AD) and dementia of Lewy bodies (DLB). Patients and methodsRadionuclide brain single-photon emission computed tomography/computed tomography (SPECT/CT) images and 25-OHD dosage in noninstitutionalized patients were obtained within 14 days. SPECT/CT examination was carried out using technetium-99m-ethyl cysteinate dimer in 20 consecutive patients (12 AD and eight DLB). Reconstructed images were spatially normalized using Statistical Parametric Mapping version 5 software to a default SPECT template. Voxel-based multiple regression correlation analyses, with age and mini mental state examination scores as confounding factors, were carried out. Findings were considered significant for a threshold P-value less than 0.01 (corrected at cluster level). ResultsA positive correlation was found between 25-OHD concentrations and regional cerebral blood flow in the left precuneus cortex (Talairach coordinates: −14, −42, 63) in AD patients. No correlation was detected in DLB patients. ConclusionThe results of this study confirm the relationship between 25-OHD concentrations and AD and therefore underline the hypothesis of a potential neuroprotective effect against brain degeneration. These encouraging findings need to be confirmed by larger prospective correlation series.

SPECT-CT improves detection of small peritoneal fistula.

A 51-year-old woman on peritoneal dialysis for chronic renal failure underwent laparotomy for kidney transplant. One month later, painful subcutaneous edema was observed within the abdominal wall especially apparent in the standing position. A peritoneal fistula was suspected. Peritoneal scintigraphy was performed after infusion of Tc-99m sulfur colloid into the peritoneal cavity followed by SPECT/CT. Tracer uptake was observed between the peritoneal cavity and the subcutaneous space suggesting a postsurgical peritoneal fistula. On static images, the origin of the slight uptake was difficult to determine and could be due to the presence of Tc-99m in the peritoneal catheter that projects into this area. SPECT/CT improved detection of a small peritoneal fistulas.

Brain perfusion SPECT imaging and acetazolamide challenge in vascular cognitive impairment.

Cerebrovascular disease is recognized as a common cause of cognitive impairment and dementia, alone or coexisting with other neurodegenerative diseases, mostly Alzheimer’s disease. Vascular cognitive impairment (VCI) is a part of the heterogenous disorders group related to cerebral vessel disease. Although age is one of the most important risk factors for VCI, other common cardiovascular risk factors are also involved. By investigating these risk factors, a high proportion of these cognitive disorders can be prevented and/or delayed. Until now, only treatment of midlife arterial hypertension has been recognized as a preventing factor of vascular dementia. Brain MRI is becoming the method of choice to investigate cerebral vascular pathologies. However, this form of morphological imaging remains inadequate and does not provide useful functional information during VCI exploration, despite which functional imaging such as brain perfusion single-photon computed tomography, performed in baseline conditions and/or after an acetazolamide challenge, is underutilized in VCI exploration. The common strategies for VCI screening have not been standardized until now, and therefore further long-term imaging studies are needed to establish early diagnostic protocols. The present review summarizes the potential benefits of brain perfusion single-photon computed tomography imaging and possible scintigraphic quantification of cerebral hemodynamic reserves in investigation of VCI.

Delayed acquisition and hyperglycemia improve brain metastasis detection on F-18 FDG PET.

Abstract:A 60-year-old man with a history of lung cancer was admitted for a first partial epileptic seizure. Brain MRI demonstrated a right frontal lesion evoking a metastasis. F-18 FDG-PET-CT revealed this lesion only on delayed images obtained after oral hyperglycemia.Increased plasma glucose leve

Respiratory-gated imaging in metabolic evaluation of small solitary pulmonary nodules: 18F-FDG PET/CT and correlation with histology.

ObjectiveThe aim of the study was to evaluate the effect of 2-(18F)-fluoro-2-deoxy-D-glucose (18F-FDG)-PET/computed tomography (CT) respiratory-gated imaging [four-dimensional (4D)] in the metabolic evaluation of small solitary pulmonary nodules and analyze the cutoff maximum standardized uptake value (SUVmax) of 2.5 in classifying and distinguishing benign/malignant pulmonary pathologies in 4D studies. Materials and methodsThirty-two patients with pulmonary lesions measuring 2 cm or less were included during their scheduled 18F-FDG PET/CT examinations. The whole-body PET/CT acquisition (3D) was followed by a chest-centered PET/CT (4D) study synchronized with the respiratory cycle. The SUVmax percentage difference (%Diff SUVmax) was calculated. The nodule size, localization, and relationships with histological/cytological findings were studied. ResultsFifteen nodules were 10 mm or smaller and 17 were larger than 10 mm [mean size=12 mm (7–20)]. The mean 3D-SUVmax was 2.5 (0.7–6.1) and the mean 4D-SUVmax 3.2 (0.9–7.2) (P<0.001). The mean %Diff SUVmax was 38% for all patients (7–90), 45% in subcentimetric (7–90%) and 31% (7–75%) in supracentimetric lesions (P=NS). Histology was obtained in 23/32 (72%) cases and the pathologic benign/malignant ratio was 4/19. Malignancies were diagnosed as lung adenocarcinoma, solitary metastases, large cell lung carcinoma, and sarcoma in 13 (41%), 3 (9%), 2 (6%), and 1 (3%) case, respectively. Malignant lesions showed mean 4D-SUVmax of 3.8 (1.2–7.2). The cutoff SUVmax of 2.5 did not classify and distinguish between benign/malignant pulmonary pathologies, neither in 3D nor in 4D studies. ConclusionRespiratory gating improves the detectability and metabolic evaluation of solitary pulmonary nodules, mostly those that are subcentimetric. However, as expected, the cutoff SUVmax of 2.5 does not distinguish between benign/malignant lesions in either 4D or 3D studies.

Ct Nonuniform Attenuation and Tew Scatter Corrections in Brain Tc-99m Ecd Spect

Perfusion brain single photon emission computed tomography (SPECT) is currently used to evaluate patients with cognitive impairments. Although widely available, it has been reported to be significantly less sensitive than F-18 FDG positron emission tomography. Optimization of SPECT parameters using nonuniform attenuation correction (NUAC) and scatter correction (SC) might improve the accuracy of the method. This study assessed the effect of x-ray CT-based NUAC and triple-energy window (TEW-SC) on brain SPECT compared with Chang-uniform (UAC). A total of 31 patients with memory complaints underwent Tc-99m ECD SPECT/CT. CT-NUAC+TEW-SC and Chang-UAC were applied and compared. The images were spatially normalized to a default SPECT template supplied with Statistical Parametric Mapping software (SPM2). A paired t test image was then reconstructed. Regional cerebral blood flow measurements were apparently reduced in the frontal white-matter and in the frontotemporal cortex when CT-NUAC+TEW-SC were used. These findings need to be considered when interpreting Tc-99m ECD SPECT after applying CT-AC+TEW-SC. Further prospective studies with clinical correlations are needed.