Optimization of the Balanced Steady State Free Precession (bSSFP) Pulse Sequence for Magnetic Resonance Imaging of the Mouse Prostate at 3T

Christiane L Mallett,Paula J Foster,Yi Wang

doi:10.1371/journal.pone.0018361

Christiane L Mallett, Paula J Foster + Show 1 more

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https://doi.org/10.1371/journal.pone.0018361

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Journal: PloS one	Publication Date: Apr 8, 2011
Citations: 17	License type: CC BY 4.0

Affiliation: Western University, Robarts Clinical Trials

Abstract

IntroductionMRI can be used to non-invasively monitor tumour growth and response to treatment in mouse models of prostate cancer, particularly for longitudinal studies of orthotopically-implanted models. We have optimized the balanced steady-state free precession (bSSFP) pulse sequence for mouse prostate imaging.MethodsPhase cycling, excitations, flip angle and receiver bandwidth parameters were optimized for signal to noise ratio and contrast to noise ratio of the prostate. The optimized bSSFP sequence was compared to T1- and T2-weighted spin echo sequences.ResultsSNR and CNR increased with flip angle. As bandwidth increased, SNR, CNR and artifacts such as chemical shift decreased. The final optimized sequence was 4 PC, 2 NEX, FA 50°, BW ±62.5 kHz and took 14–26 minutes with 200 µm isotropic resolution. The SNR efficiency of the bSSFP images was higher than for T1WSE and T2WSE. CNR was highest for T1WSE, followed closely by bSSFP, with the T2WSE having the lowest CNR. With the bSSFP images the whole body and organs of interest including renal, iliac, inguinal and popliteal lymph nodes were visible.ConclusionWe were able to obtain fast, high-resolution, high CNR images of the healthy mouse prostate with an optimized bSSFP sequence.

Highlights

magnetic resonance imaging (MRI) can be used to non-invasively monitor tumour growth and response to treatment in mouse models of prostate cancer, for longitudinal studies of orthotopically-implanted models
Mouse models of prostate cancer are valuable for pre-clinical studies of prostate cancer and include transgenic models such as the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model [2], and xenograft models [3,4,5] that typically involve subcutaneous or orthotopic injection of cancer cells
The prostate is adjacent to the bladder and surrounded by fatty tissue, which must be taken into account when determining which imaging pulse sequence and parameters to use

Summary

Introduction

MRI can be used to non-invasively monitor tumour growth and response to treatment in mouse models of prostate cancer, for longitudinal studies of orthotopically-implanted models. Mouse models of prostate cancer are valuable for pre-clinical studies of prostate cancer and include transgenic models such as the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model [2], and xenograft models [3,4,5] that typically involve subcutaneous or orthotopic (intra-prostatic) injection of cancer cells. Subcutaneous tumours are easy to implant and measurable with calipers, but orthotopic tumours are superior for studies in which metastasis is desired [6,7,8,9]. MRI has been used to monitor prostate tumour growth in mice, primarily at high field strengths (.4T), and at clinical field strengths (1.5T and 3T). Most investigations have used 2D T1- or T2-weighted spin echo sequences (T1wSE and T2wSE), but 3D imaging sequences have been used [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]

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