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M J Fulham

Publications and source records attributed to M J Fulham.

At least 37 records · Page 2Linked to original sources
PubMed1996

Validation of postinjection transmission measurements for attenuation correction in neurological FDG-PET studies.

UNLABELLED: Accurate estimation of local cerebral metabolic rate of glucose utilization (LCMRGlu) with PET requires a separate measurement of photon attenuation using a transmission source that extends study duration. The feasibility of postinjection transmission, (PIT) scanning has been demonstrated but not previously validated in humans. METHODS: Preinjection and postinjection transmission scans were performed in 26 patients undergoing routine [18F]fluorodeoxyglucose (FDG) neurological PET. The PIT data were processed with two methods: One estimated emission contamination using an independent emission scan (PITind); the other estimated the contamination directly from the PIT scan, using simultaneously acquired emission data for subtraction (PITsim). These methods were compared with measured attenuation correction (AC) using preinjection transmission data (ACpre) and calculated AC (ACcalc). After reconstruction, image data were reformatted to fit a standard brain atlas to facilitate analysis of the region of interest and to allow subtraction of datasets averaged over all subjects. RESULTS: The ratios of LCMRGlu values with respect to those obtained by the ACpre method ranged from 0.98 to 1.06 (mean +/- s.d., 1.01 +/- 0.02) for PITind, from 0.96 to 1.04 (mean 0.99 +/- 0.02) for PITsim and from 0.77 to 1.12 (mean 0.96 +/- 0.07) for ACcalc. Both PIT methods agreed well with the ACpre method, whereas ACcalc gave rise to appreciable bias in structures near thick bone or sinuses. CONCLUSION: Accurate quantitative estimates of LCMRGlu can be obtained using PIT measurements. The PIT methods shorten study duration and increase patient throughput. The PITsim method has the further advantage that it is not affected by tracer redistribution and can therefore be applied to tracers with relatively rapid kinetics in vivo.

Brain↗
PubMed1996

Automated interstudy image registration technique for SPECT and PET.

UNLABELLED: We report the extended application of an automated computer technique for three-dimensional spatial registration of SPECT and PET studies. METHODS: The technique iteratively reslices a misaligned data set until the sum of the absolute differences (SAD) from a reference data set is minimized. The registration accuracy was assessed in Hoffman brain phantom studies collected with known misalignments and transmission studies of a thorax phantom with fiducial markers. The SAD was compared with three other cost functions: stochastic sign change criterion, sum of products and standard deviation (s.d.) of ratios. In clinical neurological and myocardial perfusion studies, registration accuracy was estimated from the relative locations of landmarks in the reference and registered data sets. RESULTS: Registration accuracy in the Hoffman brain phantom studies was -0.07 +/- 0.46 mm (mean +/- s.d.) for translations and -0.01 +/- 0.20 degrees for rotations, with maximum translation and rotation errors of 1.2 mm and 0.8 degree, respectively. The SAD was the most accurate and reliable cost function. Registration errors in the thorax phantom were 3.1 +/- 1.7 mm. Mean accuracy in the neurological studies, estimated from landmark pairs, was 2.0 +/- 1.1 mm for SPECT to SPECT and 1.8 +/- 1.1 mm for PET to SPECT registrations. Average registration accuracy in 201Tl myocardial perfusion studies was 2.1 +/- 1.2 mm. CONCLUSION: Our registration method (a) provided accurate registrations for phantom and clinical SPECT and PET studies, (b) is fully automated, (c) simplifies comparison of data sets obtained at different times and with different modalities, and (d) can be applied retrospectively.

Algorithms↗
PubMed1995

Decreased cerebral glucose metabolism in patients with brain tumors: an effect of corticosteroids.

The authors measured cerebral glucose metabolism (CMRglu) using [18F]fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in patients with brain tumors to evaluate the effect of exogenous corticosteroids (in this instance, dexamethasone) on glucose metabolism. Fifty-six FDG-PET studies obtained in 45 patients with unilateral supratentorial brain tumors were analyzed. Patients with brain tumors were divided into three groups: 1) patients with cushingoid symptoms, who had been treated with combinations of radiotherapy and chemotherapy taking oral dexamethasone; 2) patients not taking dexamethasone but treated with radiotherapy; and 3) patients not taking dexamethasone who had not been treated with radiotherapy. Serial FDG-PET scans were obtained in eight of the cushingoid patients. Glucose metabolism was measured in the contralateral cerebral and ipsilateral cerebellar hemispheres in patients and compared to measurements taken from 19 normal volunteers. The authors found that in the cushingoid brain tumor patients there was a marked reduction in CMRglu compared to normal volunteers and other brain tumor patients (Kruskal-Wallis test; p 0.001). In the majority of patients who had serial FDG-PET scans, there was a decline in glucose metabolism over time and in one patient, in whom dexamethasone was reduced in dosage, there was a subsequent increase in CMRglu. The authors conclude that there is a generalized reduction in CMRglu in brain tumor patients taking dexamethasone compared to other brain tumor patients and normal volunteers, and that this effect is independent of radiotherapy, concurrent anticonvulsant medication, and transhemispheric functional disconnection (transhemispheric diaschisis).

Adult↗
PubMed1995

Simultaneous emission and transmission measurements for attenuation correction in whole-body PET.

UNLABELLED: We describe a methodology for measuring and correcting for attenuation in whole-body PET using simultaneous emission and transmission (SET) measurements. METHODS: The main components of the methodology are: (a) sinogram windowing of low activity (< or = 50 MBq) rotating 68Ge/Ga rod sources, (b) segmented attenuation correction (SAC) and (c) maximum likelihood reconstruction using the ordered subsets EM (OS-EM) algorithm. The methods were implemented on a whole-body positron emission tomograph. Quantitative accuracy and the signal-to-noise ratio (SNR) were measured for a thorax-tumor phantom as functions of acquisition time (range: 2-20 min per position). RESULTS: When a typical rod source activity (200 MBq 68Ge/Ga) was used, emission SNR was 60% lower in simultaneous than in separate measurements. The difference was only 14% when the rods contained 45 MBq 68Ge/Ga. The SNR was further improved by SAC in conjunction with OS-EM reconstruction and the relative gain increased with increasing acquisition time. Quantitative estimates of tumor, liver and lung radioactivity agreed with values obtained from a separate high count measurement to within 8%, independent of acquisition time. CONCLUSION: Attenuation correction of whole-body PET images is feasible using SET measurements. There is good quantitative agreement with conventional methods and increased noise is offset by the use of SAC and OS-EM reconstruction.

Adult↗
PubMed1995

PET-FDG of pleomorphic xanthoastrocytoma.

A young patient with pleomorphic xanthoastrocytoma (PXA), a usually benign cerebral tumor, had two recurrences in a short time period. The clinical, pathological and neuroradiological features, including PET with [18F]-fluorodeoxyglucose (FDG), are presented. The PET-FDG study revealed the recurrent tumor to be hypermetabolic. The diagnosis was confirmed histopathologically. As the clinical outcome of patients harboring PXA is not easy to predict because of possible recurrence and/or transformation into more aggressive gliomas, we discuss the predictive indicators of more aggressive clinical behavior.

Adult↗
PubMed1994

Peripheral benzodiazepine receptors and glucose metabolism in human gliomas.

Peripheral benzodiazepine receptors (PBR) are increased in gliomas and augmented glucose metabolism is seen in malignant brain tumors. We investigated the relationship between PBR density (Bmax) and glucose utilization rate (GUR) in 17 patients with cerebral gliomas of different grades. PBR Bmax was assessed by [3H]PK-11195 in vitro binding in surgical specimens and GUR was measured by Positron Emission Tomography with [18F]2-Fluorodeoxyglucose before the surgery. In untreated tumors there was a positive correlation between PBR Bmax and GUR (2r = 0.84). This correlation was not observed in patients who had been treated with radiation and/or chemotherapy prior to surgery (r2 = 0.13). In addition, in untreated patients, the increase in PBR density and GUR appeared to be related to the degree of malignancy.

Adult↗
PubMed1994

Accelerated EM reconstruction in total-body PET: potential for improving tumour detectability.

Total-body positron emission tomography (PET) is a useful diagnostic tool for evaluating malignant disease. However, tumour detection is limited by image artefacts due to the lack of attenuation correction and noise. Attenuation correction may be possible using transmission data acquired after or simultaneously with emission data. Despite the elimination of attenuation artefacts, however, tumour detection is still hampered by noise, which is amplified during image reconstruction by filtered backprojection (FBP). We have investigated, as an alternative to FBP, an accelerated expectation maximization (EM) algorithm for its potential to improve tumour detectability in total-body PET. Signal to noise ratio (SNR), calculated for a tumour with respect to the surrounding background, is used as a figure of merit. A software tumour phantom, with conditions typical of those encountered in a total-body PET study using simultaneous acquisition, is used to optimize and compare various reconstruction approaches. Accelerated EM reconstruction followed by two-dimensional filtering is shown to yield significantly higher SNR than FBP for a range of tumour sizes, concentrations and counting statistics (deltaSNR = 6.3 +/- 3.9, p < 0.001). The methods developed are illustrated by examples derived from physical phantom and patient data.

Algorithms↗
PubMed1994

Focal cerebral ischemia and antiphospholipid antibodies: a case for cardiac embolism.

We report clinical, neuroimaging and immunological findings in seven women with antiphospholipid antibodies (APLA) and cerebral ischemia. Two patients had systemic lupus erythematosus (SLE) and five had the antiphospholipid syndrome (APS). Autopsies were done in 3 women who died acutely with focal neurological deficits. Evidence for cerebral embolism was found in all patients: a) pathology demonstrated multiple cerebral infarctions and cerebral emboli from underlying non-bacterial thrombotic endocarditis (NBTE) in the patients who died. b) Three patients had thickened mitral valves and embolic cerebral occlusions were identified with cerebral angiography. c) In one patient, echocardiography detected a thrombus on the posterior leaflet of a prolapsing mitral valve at the time of ictus. Our data provide further evidence to implicate valvular endothelium in the genesis of cerebral ischemia in some patients with APLA.

Adult↗
PubMed1993

Neuroimaging of juvenile pilocytic astrocytomas: an enigma.

PURPOSE: To present the imaging, metabolic, and clinical data obtained in five patients with juvenile pilocytic astrocytomas (JPAs) and discuss the paradoxical neuroimaging findings. MATERIALS AND METHODS: Five patients with JPAs who had undergone structural imaging and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were studied. Normalized glucose utilization rates (GURs) in the tumor were compared with GURs in histopathologically verified low-grade astrocytomas and high-grade tumors. RESULTS: All JPAs enhanced markedly after administration of contrast medium. Their glucose metabolism was significantly (P < .001) higher than that of low-grade astrocytomas and was similar to that of anaplastic astrocytomas. All patients with JPAs were in stable condition and showed no evidence of disease progression despite contrast enhancement and high tumoral glucose metabolism. CONCLUSION: The paradoxical FDG PET findings and enhancement at structural imaging might reflect the unusual vascularity of pilocytic tumors, and the increased GUR might be related to expression of the glucose transporter.

Adolescent↗
PubMed1992

Mapping of brain tumor metabolites with proton MR spectroscopic imaging: clinical relevance.

Brain tumor metabolism was studied with hydrogen-1 magnetic resonance spectroscopy and positron emission tomography with fluorine-18 fluorodeoxyglucose in 50 patients. N-acetylaspartate (NAA) was generally decreased in tumors and radiation necrosis but was somewhat preserved at neoplasm margins. Choline was increased in most solid tumors. Solid high-grade gliomas had higher normalized choline values than did solid low-grade gliomas (P < .02), but the normalized choline value was not a discriminator of tumor grade, since necrotic high-grade lesions had reduced choline values. Serial studies in one case showed an increase in choline as the glioma underwent malignant degeneration. Choline values were lower in chronic radiation necrosis than in solid anaplastic tumors (P < .001). In two cases studied before and after treatment, clinical improvement and a reduction in choline followed therapy. Lactate is more likely to be found in high-grade gliomas, but its presence is not a reliable indicator of malignancy.

Adolescent↗
PubMed1992

Cerebellar diaschisis revisited: pontine hypometabolism and dentate sparing.

A unilateral supratentorial lesion may cause hypometabolism in the contralateral cerebellar hemisphere (crossed cerebellar diaschisis). We analyzed glucose metabolism, measured by PET-FDG, in the posterior fossa in 67 patients (78 PET studies) with primary unilateral supratentorial brain tumors selected for visually obvious metabolic asymmetry in the cerebellar hemispheres. We found that glucose utilization was 17% lower in the contralateral cerebellar cortex (compared with the ipsilateral one), consistent with the selection criterion, and 19% lower in the ipsilateral pons, wherein lie the first order synapses of the corticopontocerebellar pathway. This finding helps to validate the prevalent view that cerebellar diaschisis is due to interruption of afferent input from the corticopontocerebellar pathway. However, glucose metabolism in the contralateral dentate nucleus was relatively preserved--only 2% less than the ipsilateral dentate. This "dentate sparing" suggests preservation of afferent input to the largest of the deep cerebellar nuclei from the Purkinje cells in the cortex, despite interruption of the major excitatory input to the Purkinje cells.

Adolescent↗
PubMed1992

PET-fluorodeoxyglucose of cranial and spinal neuromas.

Five patients with eighth nerve, one with ninth nerve and one with cervical neuromas were studied with PET and [18F] fluorodeoxyglucose (FDG). Four of the patients had had surgery prior to the PET study, and six patients had subsequent surgery. All tumors were well-visualized on the PET images. Only one patient with bilateral acoustic neuroma exhibited tumor recurrence or growth after the PET study; these two lesions showed the highest FDG uptakes in the PET studies (tumor-to-cerebellum ratio of 0.93-0.98). All other tumors were relatively hypometabolic (tumor-cerebellum ratios of 0.43-0.65) and showed no tumor growth or recurrence during follow-up periods ranging from 5 to 8 yr. These results suggest that PET-FDG may be of value in the evaluation of cranial and spinal schwannomas.

Adolescent↗
PubMed1991

Computed tomography, magnetic resonance imaging and positron emission tomography with [18F]fluorodeoxyglucose in multiple system atrophy and pure autonomic failure.

We studied 45 patients who had autonomic failure with computed tomography, magnetic resonance imaging and positron emission tomography with [18F]fluorodeoxyglucose to characterize the neuroimaging features of multiple system atrophy and pure autonomic failure and determine the utility of these techniques in distinguishing multiple system atrophy from pure autonomic failure. There were 30 patients with multiple system atrophy and 15 with pure autonomic failure. In the multiple system atrophy group, eight patients had mainly cerebellar signs, seven extrapyramidal and 15 had combinations of cerebellar and extrapyramidal signs. Cerebellar atrophy on computerized tomography and magnetic resonance imaging, signal hypointensity in the posterolateral putamen on magnetic resonance imaging and a generalized reduction in glucose utilization rate with positron emission tomography with [18F]fluorodeoxyglucose, were the main findings and were seen only in the patients with multiple system atrophy. Decreased glucose utilization (hypometabolism) was most prominent in the cerebellum, brainstem, striatum and frontal and motor cortices. These results indicate clear differences, using neuroimaging studies, between multiple system atrophy and pure autonomic failure.

Atrophy↗
PubMed1991

In vivo study of NMDA-sensitive glutamate receptor by fluorothienylcyclohexylpiperidine [correction of fluorothienylcycloexylpiperidine], a possible ligand for positron emission tomography.

As a preliminary to positron emission tomography (PET) studies of excitatory amino acid neurotransmission, N-methyl-D-aspartate (NMDA)-sensitive glutamate receptors of mice and rats were labelled in vivo with [3H]fluorothienylcyclohexylpiperidine [corrected] (FTCP), which binds to the phencyclidine site of the NMDA receptor. After intravenous injection, the half-life of clearance of authentic FTCP from blood was 4.2 min in mice, 12 min in rats and 45 min in a rhesus monkey. In rodent brain, the specific binding of [3H]FTCP, 10 min after intravenous injection, was 10-20% of the total binding and no regional differences were observed. However, if animals were treated with NMDA intraperitoneally (0.68 mmol/kg), 10 min before injection of [3H]FTCP, a three- to five-fold increase in specific binding was observed in hippocampus, cerebral cortex and striatum but not in cerebellum. Thus, specific binding of [3H]FTCP in vivo revealed the physiological status of the NMDA receptor; in fact, preliminary PET studies with [18F]FTCP in monkeys indicated increased binding after activation of NMDA receptors. These data suggest that PET with [18F]FTCP can be a tool to evaluate physiological or pathological modifications of the function of NMDA receptors.

Animals↗
PubMed1990

Pituitary microadenomas: a PET study.

Twenty cases of surgically verified pituitary microadenoma (17 with Cushing disease and three with acromegaly) were studied with positron emission tomography (PET) with use of fluorine-18-2-fluorodeoxyglucose (FDG). The diagnostic results were compared with those of other modalities, namely, computed tomography (CT), magnetic resonance (MR) imaging, and, in the cases of Cushing disease, simultaneous bilateral inferior petrosal sinus sampling (SIPS). The PET results showed 12 positive readings and one questionable reading, compared with seven positive readings and one questionable reading for CT (18 cases studied) and 13 positive and two questionable MR imaging readings. PET complemented MR imaging, in the sense that five of the positive PET readings were negative or questionable at MR imaging. PET studies of 20 healthy control subjects showed no false-positive cases, whereas other studies of healthy subjects with contrast material-enhanced CT and MR imaging have yielded, respectively, 20% and 15% positive readings, with findings suggestive of silent or occult adenomas.

Adenoma↗
PubMed1990

Metabolism of human gliomas: assessment with H-1 MR spectroscopy and F-18 fluorodeoxyglucose PET.

Localized hydrogen-1 magnetic resonance (MR) spectroscopy and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) were employed to obtain metabolic information from intracranial gliomas. Advantages and difficulties associated with comparison of results from the two modalities were realized. Forty patients were studied with H-1 MR spectroscopy. MR signal intensities from lactate, N-acetylaspartate (NAA), choline, and creatine from a volume of interest containing the tumor and a contralateral volume were obtained and evaluated. NAA signal intensities were generally decreased in the tumor spectra, and choline signal intensities were elevated. H-1 MR spectroscopy was unsuccessful in eight patients, and FDG PET scans were not obtained in four of the patients with successful MR spectroscopic examinations. Lactate signal intensity was detected in 10 of the 28 patients who had successful H-1 MR spectroscopic and FDG PET studies. Lactate signal intensities were observed in lesions shown at FDG PET to be hypermetabolic, as well as in lesions found to be hypometabolic.

Adult↗
PubMed1989

Reversal of brain metabolic abnormalities following treatment of AIDS dementia complex with 3'-azido-2',3'-dideoxythymidine (AZT, zidovudine): a PET-FDG study.

Brain glucose metabolism was evaluated in four patients with acquired immunodeficiency syndrome (AIDS) dementia complex using [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET) scans at the beginning of therapy with 3'-azido-2',3'-dideoxythymidine (AZT, zidovudine), and later in the course of therapy. In two patients, baseline, large focal cortical abnormalities of glucose utilization were reversed during the course of therapy. In the other two patients, the initial PET study did not reveal pronounced focal alterations, while the post-treatment scans showed markedly increased cortical glucose metabolism. The improved cortical glucose utilization was accompanied in all patients by immunologic and neurologic improvement. PET-FDG studies can detect cortical metabolic abnormalities associated with AIDS dementia complex, and may be used to monitor the metabolic improvement in response to AZT treatment.

Acquired Immunodeficiency Syndrome↗