Biomedical subjects

C J Keith

Publications and source records attributed to C J Keith.

6 recordsLinked to original sources

PubMed2005

Blood flow-metabolic relationships are dependent on tumour size in non-small cell lung cancer: a study using quantitative contrast-enhanced computer tomography and positron emission tomography.

PURPOSE: The purpose of this study was to undertake dual assessment of tumour blood flow and glucose metabolism in non-small cell lung cancer (NSCLC) using contrast-enhanced computed tomography (CE-CT) and (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in order to assess how the relationships between these parameters vary with tumour size and stage. METHODS: Tumour blood flow and glucose metabolism were assessed in 18 NSCLCs using quantitative CE-CT and FDG-PET respectively. Contrast enhancement and FDG uptake were both normalised to injected dose and patient weight to yield correspondingly the standardised perfusion value (SPV) and standardised uptake value (SUV). Tumour area was measured from conventional CT images. RESULTS: The ratio of SUV to SVP and the metabolic-flow difference (SUV-SVP) correlated with tumour size (r=0.56, p=0.015 and r=0.60 and p=0.008 respectively). A metabolic-flow difference of greater than 4 was more common amongst tumours of stages III and IV (odds ratio 10.5; 95% confidence limits 0.24-32.1). A significant correlation between SUV and SPV was found only for tumours smaller than 4.5 cm2 (r=0.85, p=0.03). CONCLUSION: Blood flow-metabolic relationships are not consistent in NSCLC but depend upon tumour size and stage. Quantitative CE-CT as an adjunct to an FDG study undertaken using integrated PET-CT offers an efficient way to augment the assessment of tumour biology with possible future application as part of clinical care.

Blood Flow Velocity↗

PubMed2003

Solitary pulmonary nodules: impact of quantitative contrast-enhanced CT on the cost-effectiveness of FDG-PET.

AIM: To determine the impact of quantitative contrast-enhanced computed tomography (QECT) on the cost-effectiveness of diagnostic strategies for the assessment of solitary pulmonary nodules (SPNs). MATERIALS AND METHODS: Four diagnostic strategies were evaluated using decision tree analysis: conventional CT alone; conventional CT followed by QECT; conventional CT followed positron emission tomography (PET); and conventional CT followed by QECT and PET (QECT+PET). The average cost per patient, accuracy of management and incremental cost:accuracy ratio (ICAR) were determined for each strategy. Although baseline assumptions reflected the Australian setting, sensitivity analysis was used to extrapolate the results to the UK. RESULTS: At the baseline prevalence of malignancy (54%) and cost of PET relative to surgery (16%), the QECT strategy incurs the least cost (5560 dollars/patient) but the QECT+PET strategy is the most cost-effective (ICAR 12,059 dollars/patient). At reported levels of disease prevalence (68.5%) and cost of PET relative to surgery (29.9%) in the UK, the QECT strategy is the most cost-effective. CONCLUSION: QECT offers a cost-effective approach to evaluation of SPNs. Whether QECT is used alone or in combination with PET will depend upon local availability and regional values for prior probability of malignancy within SPNs and the cost of PET relative to surgery.

Cost-Benefit Analysis↗

PubMed2003

Pancreatic cancer: preliminary experience with sodium iodide fluorodeoxyglucose positron emission tomography in Australia.

Previous studies of fluorodeoxyglucose positron emission tomography (FDG-PET) in pancreatic cancer have used Bismuth Germinate detector systems. This preliminary Australian study aims to confirm the accuracy of FDG-PET in pancreatic cancer using a dedicated sodium iodide (NaI) PET system. Fifteen consecutive patients underwent FDG-PET using a GE QUEST dedicated NaI PET scanner. The indications were the characterization of a pancreatic mass seen on CT or ultrasonographic imaging (nine cases), diagnosis or exclusion of recurrent disease following surgery and adjuvant therapy (four cases) and presurgical staging of primary pancreatic cancer (two cases). The final diagnosis was determined from histology or, when no histology was available, by radiological and clinical follow up. The FDG-PET accurately characterized eight out of nine pancreatic masses (seven were true negative, one was true positive and one was false positive). Of the four cases performed to determine recurrent disease, three were accurately diagnosed (two true negatives and one true positive). In the fourth case, PET accurately detected a liver metastasis but did not detect the local recurrence. Results in the two cases where PET was performed for preoperative staging comprised one true positive and one false negative. Sodium iodide FDG-PET is useful in the diagnosis of pancreatic cancer, particularly in the presence of a previously detected mass.

Fluorodeoxyglucose F18↗

PubMed2002

Solitary pulmonary nodules: accuracy and cost-effectiveness of sodium iodide FDG-PET using Australian data.

This study uses Australian data to confirm the accuracy of dedicated sodium iodide (NaI) fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in evaluating indeterminate solitary pulmonary nodules (SPNs) and to determine the conditions under which PET could play a cost-effective role in this evaluation. Ninety-two patients from two Australian hospitals in different states underwent FDG-PET for evaluation of an SPN. Observed values for prior probability of malignancy and diagnostic accuracy of PET were applied to previously published decision tree models using published Australian health care costs. The accuracy of FDG-PET was 93% with a sensitivity of 92% and a specificity of 95%. The prior probability of malignancy (0.54), PET sensitivity and PET specificity indicated cost savings per patient of up to EUR 455 (Adollars 774) based on a PET cost of EUR 706 (Adollars 1,200). PET would remain cost-effective for levels of prior probability up to 0.8-0.9 and a PET cost of EUR 736-1,161 (Adollars 1,252-Adollars 1,974). It is concluded that NaI PET is accurate, cost saving and cost-effective for the characterisation of indeterminate pulmonary nodules in Australia. Comparison with previous reports from the United States confirms that FDG-PET can remain cost-effective despite population differences in medical costs, disease prevalence and PET diagnostic performance.

Aged↗

PubMed2002

Computed tomography perfusion imaging in acute stroke.

The development of thrombolytic and neuroprotective agents for the treatment of acute stroke has created an imperative for improved imaging techniques in the assessment of acute stroke. Five cases are presented to illustrate the value of perfusion CT in the evaluation of suspected acute stroke. To obtain the perfusion data, a rapid series of images was acquired without table movement following a bolus of contrast medium. Cerebral blood flow, cerebral blood volume and mean transit time were determined by mathematically modelling the temporal changes in contrast enhancement in the brain and vascular system. Pixel-by-pixel analysis allowed generation of perfusion maps. In two cases, CT-perfusion imaging usefully excluded acute stroke, including one patient in whom a low-density area on conventional CT was subsequently proven to be tumour. Cerebral ischaemia was confirmed in three cases, one with an old and a new infarction, one with a large conventional CT abnormality but only a small perfusion defect, and one demonstrating infarct and penumbra. Perfusion CT offers the ability to positively identify patients with non-haemorrhagic stroke in the presence of a normal conventional CT, to select those cases where thrombolysis is appropriate, and to provide an indication for prognosis.

Acute Disease↗

PubMed2002

Hepatic haemodynamics: interrelationships between contrast enhancement and perfusion on CT and Doppler perfusion indices.

This study compares three techniques that evaluate hepatic haemodynamics for the detection of metastatic liver disease to determine the interrelationships between the techniques and to assess their equivalence. The three techniques studied were dedicated CT measurements of hepatic enhancement, CT measurements of perfusion and Doppler perfusion indices. 53 patients with proven malignancies of either breast or colon underwent a single location dynamic CT for measurement of hepatic perfusion and enhancement, whilst a subset of 12 patients underwent both CT perfusion and Doppler perfusion studies. Statistically significant correlations were found between CT arterial phase enhancement and CT arterial perfusion (r=0.612, p<0.001), and between both of these parameters and Doppler arterial flow (r=0.867, p<0.001 and r=0.842, p<0.001, respectively). Significant correlations were also found between both the ratio of CT arterial enhancement to peak enhancement and the CT arterial perfusion with the Doppler perfusion index (r=0.797, p=0.002 and r=0.725, p=0.008, respectively). Combined CT arterial and portal perfusion correlated with peak liver enhancement (r=0.614, p< 0.001), but Doppler measurements of portal flow did not correlate with any CT parameter. Increased arterial enhancement, perfusion or flow are valuable additional radiological signs for the presence of hepatic metastases that can be elicited by incorporating any one of these methods into existing imaging protocols.

Adult↗