Dynamic T₁ mapping predicts outcome of chemoradiation therapy in primary rectal carcinoma: Sequence implementation and data analysis

Abstract

Purpose:To describe details about the implementation of a dynamic T 1 -mapping technique and a simple data analysis strategy that can be used to predict therapy outcome in primary rectal carcinoma and to investigate the physiologic meaning of the obtained parameter. Materials and Methods:Contrast-enhanced dynamic T 1 mapping was achieved with a snapshot fast low-angle shot (FLASH) T 1 mapping sequence implemented on a 1.5T MR scanner. This method was applied to 58 patients with primary rectal cancer before onset of chemoradiation therapy. A simple data analysis strategy based on the calculation of the maximum slope of the tissue concentration-time curve divided by the maximum of the arterial input function (AIF) was used as a measure of tumor microcirculation (PI values). Results:The snapshot FLASH (SFL) T 1 -mapping technique is accurate and sensitive enough to detect inhomogeneous uptake kinetics within tumor tissue. Classifying the patients into two groups according to therapy response showed lower mean PI values for responders as compared to nonresponders. PI was found to combine information about permeability surface area product (PS) and blood volume. Conclusions:The described method based on dynamic T 1 mapping has the potential to be a clinical tool for predicting therapy outcome of preoperative chemoradiation in patients with primary rectal carcinoma.

Dynamic Contrast Enhanced Magnetic Resonance Imaging in Rectal Cancer

“…They showed the possible role of an increased angiogenic activity in aggressive tumour cell clusters that resulted in reduced nutrient supply and higher fraction of intratumoral necrosis. In line with these results, the same researchers published another paper (Kremser et al, 2007) in which they examined, using similar methodology, 58 patients before chemo-radiotherapy . Once again they found that PI is a good predictor of therapy outcome, being, before therapy, the PI of non-responders lower than responders.…”

“…For example, Henderson et al (1998) found that this interval should be approximately less than 16 s in the case of breast DCE-MRI. In the wash-out phase, this requirement could be relaxed (de Vries et al, 2003;Kremser et al, 2007). A high temporal resolution can be difficult to obtain because the acquisition of a single volume could require several seconds as a large part of the whole abdomen is scanned.…”

“…Another approach is to extract TIC features that are associated to tracer kinetics theory (see section 4.2). Within this framework de Lussanet et al (2005); de Vries et al (2000;2001;2003); Kremser et al (2007) used, as a first step in quantitative assessment of tumor perfusion, the steepest slope of the TIC during contrast medium uptake (WIS max ), and, on the base of the work by Miles (1991) they evaluated the Perfusion Index (PI) as:…”

“…Previous considerations support a Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI) approach that could gain a renewed role to MRI adding functional data to the morphological examination. DCE-MRI has been reported by many authors as a tool potentially able to permit an evaluation of pre-CRT effectiveness basing on the strict relationship between tumor growth and angiogenesis (Ceelen et al, 2006;de Lussanet et al, 2005;Kremser et al, 2007). DCE-MRI is gaining a large consensus as a technique for diagnosis, staging and assessment of therapy response for different types of tumours, due to its capability to detect highly active angiogenesis.…”

“…More specifically, in the case of rectal cancer, previous trials have provided the proof of principle that inhibition of angiogenesis has the potential to enhance the effectiveness of the treatment for this disease. In vivo imaging techniques capable to assess tumour perfusion have the potential to improve the management of treatment for patients with rectal cancer (Chen et al, 2005;de Vries et al, 2000;2001;2003;Kremser et al, 2007). The aim of this chapter is to review the main issues concerning the assessment of the angiogenic status of rectal cancer by means of DCE-MRI.…”