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A R Padhani

Publications and source records attributed to A R Padhani.

63 records · Page 4Linked to original sources
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Probing tumor microvascularity by measurement, analysis and display of contrast agent uptake kinetics.

This paper describes a measurement protocol for acquiring quantitative dynamic MRI data and novel analysis and display software (Magnetic Resonance Imaging Workbench (MRIW)). Proton density-weighted and T1-weighted two-dimensional gradient echo images are used to quantify tissue contrast agent concentration. The dynamic studies last approximately 7 minutes, with 10-second temporal resolution. Analyses of signal and concentration changes with time are performed, allowing capillary permeability-surface area product, tissue leakage space, enhancement onset time, mean enhancement gradient and maximum enhancement level to be mapped as false-color parametric overlays registered with anatomic images. Quantification of permeability and leakage space provides a method for comparing physiology in patients between visits or for intersite comparisons.

Astrocytoma↗
PubMedDate not supplied

Antivascular cancer treatments: functional assessments by dynamic contrast-enhanced magnetic resonance imaging.

New anticancer therapeutics that target tumor blood vessels promise improved efficacy and tolerability in humans. Early phase 1 drug trials have shown that the maximum tolerated dose may be inappropriate for more advanced clinical studies with efficacy endpoints. More advanced clinical trials have demonstrated that morphologic assessments of tumor response are of limited value for gauging the efficacy of treatment. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can serve as pharmacodynamic indicator of biological activity for antivascular cancer drugs by helping to define the biologically active dose. DCE-MRI studies may also predict the efficacy of treatment on the basis of changes observed. If DCE-MRI is to be used for the selection of antivascular drugs that advance into efficacy trials, then it will be necessary to develop standardized approaches to measurement and robust analytic approaches with clear accepted endpoints specified prospectively that have biological validity. Such developments will be essential for multicenter trials in which it will be necessary to establish effective cross-site standardization of measurements and evaluation.

Angiogenesis Inhibitors↗
PubMedDate not supplied

Imaging tumor angiogenesis: functional assessment using MDCT or MRI?

Functional imaging using multidetector row computed tomography and dynamic contrast-enhanced magnetic resonance imaging are increasingly advocated for assessment of tumor vascularity because these techniques provide excellent anatomic imaging and reliable quantitative perfusion data and are easily incorporated into routine examinations. However, differences in acquisition techniques, mathematical analysis, measurement parameters, and propensity to artifacts influence the choice of imaging modality, which is explored in this review.

Contrast Media↗
PubMedDate not supplied

Multiplanar display of spiral CT data of the pulmonary hila in patients with lung cancer. Preliminary observations.

Spiral or helical computed tomography (CT)-generated multiplanar reconstructions were used in the radiological assessment of the pulmonary hila in patients with central lung cancer. Twelve patients with non-small-cell lung cancer and hilar abnormalities were examined with contrast-enhanced spiral CT. Studies were performed on a Siemens Somatom S or Plus-S scanner using either a 24- or 32-second spiral. The study volume was from the arch of the aorta to the inferior pulmonary veins done in a single breath-hold, using 4-mm collimation, and reconstructed at 2-mm intervals. We assessed the quality of vascular enhancement and of multiplanar reconstructions. Bronchoscopic, surgical, and pathological findings were correlated. Excellent vascular opacification and good-quality reconstructions were obtained in all patients. No interscan motion was detected. No problems were encountered with the breathholding technique or in the reconstruction of images, even in patients with poor respiratory function. Multiplanar reconstructions were useful for the evaluation of mediastinal including vascular and airways invasion, for optimal definition of lymph node groups, for the planning of bronchoscopically guided biopsy, as well as for endobronchoscopic laser coagulation therapy and surgical treatment. Spiral CT-generated multiplanar reconstructions of the hila are helpful for staging, solving problems, guiding bronchoscopy, and planning surgery. Even patients with limited respiratory reserve can successfully complete the examination.

Aged↗
PubMedDate not supplied

Screening with magnetic resonance imaging and mammography of a UK population at high familial risk of breast cancer: a prospective multicentre cohort study (MARIBS).

BACKGROUND: Women genetically predisposed to breast cancer often develop the disease at a young age when dense breast tissue reduces the sensitivity of X-ray mammography. Our aim was, therefore, to compare contrast enhanced magnetic resonance imaging (CE MRI) with mammography for screening. METHODS: We did a prospective multicentre cohort study in 649 women aged 35-49 years with a strong family history of breast cancer or a high probability of a BRCA1, BRCA2, or TP53 mutation. We recruited participants from 22 centres in the UK, and offered the women annual screening with CE MRI and mammography for 2-7 years. FINDINGS: We diagnosed 35 cancers in the 649 women screened with both mammography and CE MRI (1881 screens): 19 by CE MRI only, six by mammography only, and eight by both, with two interval cases. Sensitivity was significantly higher for CE MRI (77%, 95% CI 60-90) than for mammography (40%, 24-58; p=0.01), and was 94% (81-99) when both methods were used. Specificity was 93% (92-95) for mammography, 81% (80-83) for CE MRI (p<0.0001), and 77% (75-79) with both methods. The difference between CE MRI and mammography sensitivities was particularly pronounced in BRCA1 carriers (13 cancers; 92%vs 23%, p=0.004). INTERPRETATION: Our findings indicate that CE MRI is more sensitive than mammography for cancer detection. Specificity for both procedures was acceptable. Despite a high proportion of grade 3 cancers, tumours were small and few women were node positive. Annual screening, combining CE MRI and mammography, would detect most tumours in this risk group.

Adult↗
PubMedDate not supplied

CT features of pulmonary nocardiosis.

OBJECTIVE: Our goal was to identify the CT features of pulmonary nocardiosis, specifically in AIDS patients versus other immunocompromised hosts. MATERIALS AND METHODS: Twenty-four patients with pulmonary nocardiosis were identified; medical records, CT scans, and chest radiographs were reviewed. Five patients had HIV disease, 17 had other causes of immunosuppression, and 2 had normal immunity. RESULTS: CT features of pulmonary nocardiosis included one or more nodules/masses (20/24 cases, 83%), cavitation (8, 33%), consolidation/infiltrates (8, 33%), and pleural thickening (7, 29%). All AIDS patients with nocardiosis had multiple (four or more) nodules detected on CT and 80% (4/5) had cavitation compared with 21% each of non-AIDS patients (p < 0.01 for multiple nodules, p < 0.045 for cavitation). CONCLUSION: CT features of pulmonary nocardiosis are varied, and AIDS patients are more likely to display cavitation and multiple nodules. Although not widely recognized, Nocardia infection should be included in the differential diagnosis of an unexplained nodule or progressive cavitary process in HIV-positive patients.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

MRIW: parametric analysis software for contrast-enhanced dynamic MR imaging in cancer.

A software package called the Magnetic Resonance Imaging Workbench has been developed to characterize contrast agent uptake in vivo following T1-weighted magnetic resonance (MR) imaging with qualitative analysis of changes in signal intensity or quantitative analysis of changes in contrast agent concentration over time. Various descriptors may be calculated from the analysis of dynamic contrast agent-enhanced MR studies and visualized as false-color overlays, which allow the immediate display and interpretation of information taken from a series of images acquired over time. Qualitative descriptors include onset of enhancement, initial gradient, mean gradient, maximum enhancement, and washout. These parameters can be particularly useful in the investigation of multifocal or widespread disease. Quantitative descriptors include capillary permeability-surface area product, extracellular volume, and T1 and may be used to monitor changes in the disease state and to assess the efficacy of treatment. In addition, they allow comparison of data obtained from different patients, from independent MR studies, or from studies performed with different modalities. Analysis of contrast enhancement during MR imaging in terms of such qualitative or quantitative parameters is a promising new method of data analysis in radiology.

Computer Graphics↗