(C): Correlation of

both methods: calculation of tumor growth by calliper measurement LY333531 (V) and pixel extension analyses based on NMR images (A) of all 12 tumors. Discussion MRI as a non-invasive imaging technology plays a key role in preclinical in vivo evaluation of tumor therapies. The development of a BT-MRI system for small animal imaging could lead to easy detection of tumor mass and progression with little effort and low costs. Additionally, MRI provides an insight into organs and tissues of laboratory animals. The experimental results clearly proof that BT-MRI can be used to visualise organs and tumors in nude mouse xenograft models. Subcutaneous xenografts were easily identified as relative hypointense areas in Selleck Ipatasertib transaxial slices of NMR images. In addition BT-MRI system is suitable for following xenograft tumor growth. Monitoring of tumor progression evaluated by pixel extension analyses based on NMR images correlated with increasing tumor volume calculated by calliper measurement. This is an important requirement for application of BT-MRI system in orthotopic/metastatic tumor models to evaluate the whole tumor check details burden. For this purpose it is necessary to take serial slices of NMR images to get the largest dimension of the tumor as basis for calculation. In addition the whole tumor shape can be reconstituted. One critical aspect

using orthotopic/metastatic tumor models RVX-208 could be the visualization of metastasis in tissues and organs depending on the model. This may require application of contrast agent for differentiation between

tumor and normal tissue. In this study we used Gd-BOPTA as one of the clinically used low molecular weight gadolinium chelates. Gd chelates are commonly used as MRI contrast agents for the detection of solid tumors in patients where an initial tumor rim enhancement is usually observed [12–18]. Thereby the characteristic enhancement of the tumor rim can be used for the differentiation between malignant and benign masses [15]. Initially most tumors in our study showed no peripheral contrast enhancement on NMR images. Applying a higher but well tolerated dose of Gd-BOPTA such an effect could be observed, albeit not in each case. This may be due to the artificial location of the tumor as subcutaneous xenograft. Moreover, it was observed that low molar mass Gd chelates show an initial rim enhancement, followed by a washout effect, which requires that the images are obtained within the first 2 min after injection [19]. This probably explains the lack of initial rim enhancement in our models after application of low dose Gd-BOPTA. In this regard the application of macromolecular MRI contrast agents could be useful [20]. They have a longer circulation time and are more confined to the blood pool, therefore giving a longer time window for imaging in mice models.