Water Exchange

In the discussion above, and indeed in many studies employing dynamic contrast-enhanced MRI in oncology, it has been assumed that tissues contain a single, homogenous, water population with well described MR properties that undergoes simple changes when subjected to a contrast agent. However, experiments from the early days of biomedical MR suggested that the situation is more complex than this (Hazlewood et al. 1974). Water is found in a number of different environments in a biological tissue....

Sources of Error

As mentioned in Sect. 6.4 of this chapter, major sources of error may include the common assumption of a straightforward signal change - contrast agent concentration relationship and of a standard arterial input function. Other factors that can significantly affect both the accuracy and the precision of kinetic modelling results include the blood haematocrit, contrast agent relaxivity, errors in T1 measurement, image artefact, in particular those caused by motion, model over-simplification and...

Reproducibility of Tumour Blood Volume and Transfer Coefficient Measurements

The development of anti-angiogenic therapies for tumours has led to a demand for imaging-based surrogate markers of the angiogenic process. The utility of such markers is highly dependent on their test-retest reproducibility. The use of these techniques in brain tumours can be expected to be associated with good reproducibility compared to applications in other anatomical areas since normal brain has no significant permeability and the area is not subject to physiological motion. To date only a...

References

Annet L, Materne R, Danse E, Jamart J, Horsmans Y, Van Beers BE (2003) Hepatic flow parameters measured with MR imaging and Doppler US correlations with degree of cirrhosis and portal hypertension. Radiology 229 409-414 Asahina Y, Izumi N, Uchihara M, Noguchi O, Ueda K, Inoue K, Nishimura Y, Tsuchiya K, Hamano K, Itakura J, Himeno Y, Koike M, Miyake S (2003) Assessment of Kupffer cells by ferumoxides-enhanced MR imaging is beneficial for diagnosis of hepatocellular carcinoma comparison of...

Issues for Single Centre Trials

Choice of field strength, imaging coils and patient set up - these must be appropriate to the trial. Does the manufacturer provide the sequences required for the trial This may be a particular problem when quantitative measurements are required, or when faster than usual measurements are needed, or when the protocol calls for an unusual combination of information, for example interleaved T1 and T2*-weighted information (d'Arcy et al. 2002). If a nonstandard sequence is required the...

Imaging Protocols

In the early clinical studies conducted at the University of Iowa, the first-pass method (Type I model) was employed. Pre-contrast MR examination used 5-mm sagittal T2-weighted images and 10-mm axial T1-weighted images for optimal localization and delineation of the tumor. Using the findings of the pre-contrast study, a sagittal slice with 1-cm thickness through the epicenter of the tumor mass was delineated for the dynamic studies. DCE imaging was obtained using T1-weighted fast spin-echo...

Conclusion s and Future Directions

DSC-MRI has long been adapted into daily clinical use with the rapid 2D or 3D GE EPI being the most predominant method due to its sensitivity to contrast agent in both capillaries and larger vessels (Weisskoff et al. 1994), whereas the SE method is more rarely used since it is sensitive only to contrast agent within the capillaries. However, singleshot, GE EPI techniques for bolus tracking of the brain suffer from a substantial loss of resolution at the maximum of the bolus associated with the...

Clinical Applications of Dscemri in Cerebral Tumours

Despite a large number of studies describing quantitative imaging of angiogenesis in brain tumours none of these techniques has yet passed into routine clinical use. There is however considerable evidence that these quantitative techniques can provide valuable clinical data concerning tumour type, tumour grade and therapeutic response. Tables 9.1 and 9.2 show maximum and mean literature values for rCBV derived from DSCE-MRI in brain tumours. In gliomas tumour capillary blood volumes measured by...

Hepatobiliary Contrast Agents

Hepatobiliary contrast agents utilise hepatic excretion mechanisms to produce hepatocyte uptake and biliary excretion of paramagnetic ions by binding them to appropriate ligands. Two agents, Mangafo-dipir trisodium (Mn-DPDP, Teslascan) and Gado-benate dimeglumine (Gd-BOPTA, Multihance) are commercially available and a third, gadoxetic acid (Gd-EOB-DTPA, Eovist) is in phase III clinical trials (see Tables 14.1 and 14.2). Mangafodipir is the first manganese complex that has been used as contrast...

Introduction and Role of Imaging

Prostate cancer is the most commonly diagnosed cancer in men in the United States of America with an estimated 198,000 new cases in 2001 (GreenleE et al. 2001). In the United Kingdom and the European Union, prostate cancer is the second most common cancer in men, with 20,000 new cases in the UK in 1997 (CRC 2001) and an estimated 134,000 new cases in the EU in 1996 (EUCAN). Substantial increases in incidence have been reported in recent years around the world, some of which can be attributed to...

MR Imaging of Bone and Soft Tissue Tumors

A broad consensus on diagnostic assessment of mus-culoskeletal tumors has emerged over the past decade. Radiographs, clinical data and MRI can narrow the differential diagnosis, and in some cases precisely diagnose the tumor type (Ma 1999 van der Woude et al. 1998a). However, biopsy is still required for accurate diagnosis of musculoskeletal lesions. Protocols for MR imaging and the intricacies of interpretation in diagnosing musculoskeletal lesions have been well described in recent reviews...