Arjan W. Simonetti

Nosologic imaging of the brain: segmentation and classification using MRI and MRSI.

A new technique is presented to create nosologic images of the brain based on magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI). A nosologic image summarizes the presence of different tissues and lesions in a single image by color coding each voxel or pixel according to the histopathological class it is assigned to. The proposed technique applies advanced methods from image processing as well as pattern recognition to segment and classify brain tumors. First, a registered brain atlas and a subject‐specific abnormal tissue prior, obtained from MRSI data, are used for the segmentation. Next, the detected abnormal tissue is classified based on supervised pattern recognition methods. Class probabilities are also calculated for the segmented abnormal region. Compared to previous approaches, the new framework is more flexible and able to better exploit spatial information leading to improved nosologic images. The combined scheme offers a new way to produce high‐resolution nosologic images, representing tumor heterogeneity and class probabilities, which may help clinicians in decision making. Copyright

Tumour hyperthermia and ablation in rats using a clinical MR-HIFU system equipped with a dedicated small animal set-up

Purpose: We report on the design, performance, and specifications of a dedicated set‐up for the treatment of rats on a clinical magnetic resonance high intensity focused ultrasound (MR‐HIFU) system. Materials and methods: The small animal HIFU‐compatible 4‐channel MR receiver volume coil and animal support were designed as add‐on to a clinical 3T Philips Sonalleve MR‐HIFU system. Prolonged hyperthermia (Tu2009≈u200942°C, 15u2009min) and thermal ablation (Tu2009=u200965°C) was performed in vivo on subcutaneous rat tumours using 1.44u2009MHz acoustic frequency. The direct treatment effect was assessed with T2‐weighted imaging and dynamic contrast enhanced (DCE‐) MRI as well as histology. Results: The developed HIFU‐compatible coil provided an image quality that was comparable to conventional small animal volume coils (i.e. without acoustic window), and a SNR increase by a factor of 10 as compared to the coil set‐up used for clinical MR‐HIFU therapy. The use of an animal support minimised far field heating and allowed precise regulation of the animal body core temperature, which varied <1°C during treatment. Conclusions: The results demonstrated that, by using a designated set‐up, both controlled hyperthermia and thermal ablation treatment of malignant tumours in rodents can be performed on a clinical MR‐HIFU system. This approach provides all the advantages of clinical MR‐HIFU, such as volumetric heating, temperature feedback control and a clinical software interface for use in rodent treatment. The use of a clinical system moreover facilitates a rapid translation of the developed protocols into the clinic.

Assessment of early response to concurrent chemoradiotherapy in cervical cancer: value of diffusion-weighted and dynamic contrast-enhanced MR imaging

PURPOSEnTo investigate diffusion-weighted (DWI) and dynamic contrast-enhanced MR imaging (DCE-MRI) as early response predictors in cervical cancer patients who received concurrent chemoradiotherapy (CCRT).nnnMATERIALS AND METHODSnSixteen patients with cervical cancer underwent DWI and DCE-MRI before CCRT (preTx), at 1week (postT1) and 4weeks (postT2) after initiating treatment, and 1month after the end of treatment (postT3). At each point, apparent diffusion coefficient (ADC) and DCE-MRI parameters were measured in tumors and gluteus muscles (GM). Tumor response was correlated with imaging parameters or changes in imaging parameters at each point.nnnRESULTSnAt each point, ADC, K(trans) and Ve in tumors showed significant changes (P<0.05), as compared with those of GM (P>0.05). PostT1 tumor ADCs showed a significant correlation with tumor size response at postT2 (P=0.041), and changes in tumor ADCs at postT1 had a significant correlation with tumor size (P=0.04) and volume response (P=0.003) at postT2. In tumors, preTx K(trans) and Ve showed significant correlations with tumor size at postT3 (P=0.011) and tumor size response at postT2 (P=0.019), respectively.nnnCONCLUSIONnDWI and DCE-MRI, as early biomarkers, have the potential to evaluate therapeutic responses to CCRT in cervical cancers.

Pharmacokinetic analysis based on dynamic contrast-enhanced MRI for evaluating tumor response to preoperative therapy for oral cancer

To evaluate whether a pharmacokinetic analysis is useful for monitoring the response of oral cancer to chemoradiotherapy (CRT).

Automated planning of scan geometries in spine MRI scans

Consistency of MR scan planning is very important for diagnosis, especially in multi-site trials and follow-up studies, where disease progress or response to treatment is evaluated. Accurate manual scan planning is tedious and requires skillful operators. On the other hand, automated scan planning is difficult due to relatively low quality of survey images (scouts) and strict processing time constraints. This paper presents a novel method for automated planning of MRI scans of the spine. Lumbar and cervical examinations are considered, although the proposed method is extendible to other types of spine examinations, such as thoracic or total spine imaging. The automated scan planning (ASP) system consists of an anatomy recognition part, which is able to automatically detect and label the spine anatomy in the scout scan, and a planning part, which performs scan geometry planning based on recognized anatomical landmarks. A validation study demonstrates the robustness of the proposed method and its feasibility for clinical use.

Does the combination of magnetic resonance imaging and spectroscopic imaging improve the classification of brain tumours

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) play an important role in the noninvasive diagnosis of brain tumours. We investigate the use of both MRI and MRSI, separately and in combination with each other for classification of brain tissue types. Many clinically relevant classification problems are considered; for example healthy versus tumour tissues, low- versus high-grade tumours. Linear as well as nonlinear techniques are compared. The classification performance is evaluated by the area under the receiver operating characteristic (ROC) curve (AUC). In general, all techniques achieve a high performance, except when using MRI alone. For example, for low- versus high-grade tumours, low- versus high-grade gliomas, gliomas versus meningiomas, respectively a test AUC higher than 0.91, 0.93 and 0.98 is reached, when both MRI and MRSI data are used.

The Principal of Dynamic Contrast Enhanced MRI, the Method of Pharmacokinetic Analysis, and Its Application in the Head and Neck Region

Many researchers have established the utility of the dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) in the differential diagnosis in the head and neck region, especially in the salivary gland tumors. The subjective assessment of the pattern of the time-intensity curve (TIC) or the simple quantification of the TIC, such as the time to peak enhancement (T peak) and the wash-out ratio (WR), is commonly used. Although the semiquantitative evaluations described above have been widely applied, they do not provide information on the underlying pharmacokinetic analysis in tissue. The quantification of DCE-MRI is preferable; therefore, many compartment model analyses have been proposed. The Toft and Kermode (TK) model is one of the most popular compartment models, which provide information about the influx forward volume transfer constant from plasma into the extravascular-extracellular space (EES) and the fractional volume of EES per unit volume of tissue is used in many clinical studies. This paper will introduce the method of pharmacokinetic analysis and also describe the clinical application of this technique in the head and neck region.