Representative endpoint MRI, fluorescence microscopy, and immunohistochemistry acquired at 10x magnification from both implant models.

<p>(A) By day 16, 5/7 immune competent mice had no ¹⁹F signal remaining as shown by the representative MRI. The reference tube is marked by “R”. (B) Fluorescence microscopy of the muscle tissue revealed little red fluorescence remaining in the immune competent mice. No GFP+ mMSC were detectable by fluorescence microscopy, suggesting the original mMSC are no longer present. (C) H&E staining reveals the presence of cells at the implant site which correlate well with the remaining ¹⁹F red fluorescence. (D) Immunohistochemistry staining of adjacent tissue sections with the anti-F4/80 antibody reveals the presence of a few macrophages at this location in the immune competent model. (E) At endpoint, all immune compromised mice had detectable ¹⁹F-MRI signal remaining. (F) We observed more red fluorescence from the ¹⁹F-label at the transplant site in the immune compromised mice. (G) Once again, H&E staining in the immune compromised model correlates well with the regions of red fluorescence. (H) Macrophage staining of the immune compromised model reveals many more F4/80 positive cells at the site of implantation. Furthermore, the fluorescence microscopy of neighboring tissue sections reveals that the red fluorescence from the ¹⁹F agent is in the same location as the macrophages. Once again, scale bars represent 250μm.</p

Representative Day 0 MRI, fluorescence microscopy, and histology acquired as 10x magnification from both implant models.

<p>(A, E) Representative MRI from mice receiving either 2x10⁶ mMSC or 1.5x10⁶ hMSC respectively. The day 0 <i>in vivo</i>¹⁹F-MRI quantification correlates very well with the number of implanted cells. The reference tube is marked by “R”. (B) The red fluorescent fluorine agent is clearly visible in the tissue of the immune competent model, (F) as well as in the immune-compromised model. (C) Furthermore, the GFP+ mMSC are observable within the tissue section. (D) Overlaying the two fluorescent images, reveals the ¹⁹F agent colocalized with the GFP+ mMSC, as expected. (G, H) H&E stained tissue sections corresponding to the fluorescence microscopy clearly show the implant site of the mMSC and hMSC respectively. Scale bars in all images represent 250μm.</p

Cellular viability and loading with the ¹⁹F-agent.

<p>(A) Cellular viability was investigated before and after labeling with the ¹⁹F-agent, Cell Sense. Although a statistically significant difference was observed in hMSC after labeling, the viability remained high (>80%) in all experiments. There was no significant difference in mMSC viability. (B) Cellular loading was determined by performing NMR on a known number of cells alongside a reference peak with a known number of ¹⁹F atoms. We observed variation in cellular loading of both hMSC and mMSC between experiments. However, this variation does not affect in vivo ¹⁹F quantification since each transplant was only compared to its specific cellular loading.</p

Comparison of ¹⁹F-labeled cell detection in two transplantation models over time.

<p>(A) Following implantation of 2x10⁶ mMSC, ¹⁹F-MRI was used to quantify the number of cells remaining over 16 days. By day 16, only 2/7 mice had any detectable signal remaining. A significant difference from day 0 is denoted by <b>+</b>, from day 3 by ◆, and from day 9 by ■. (B) The number of detectable cells over a similar time period following a transplant of 1.5x10⁶ hMSC. ¹⁹F signal was found to decrease at a slower rate, with observable signal in all mice at endpoint. Statistical significance is denoted in the same way as A.</p

<i>In vitro</i> validation of ¹⁹F-MRI quantification accuracy.

<p>Quantification was validated in a phantom study using cell pellets ranging from 2x10⁵ to 2x10⁶ MSC. Pellets were imaged three times, with the error bars representing the standard deviation between scans. The ¹⁹F-MRI quantification is in very strong agreement with the true number of cells, and has a Pearson correlation coefficient of 0.99. The red line represents the ideal result of a 1:1 correlation.</p

SNR of human sub-cutaneous fat tissue, bone marrow, joint fluid, cartilage and leg muscle in standard bSSFP and WS-bSSFP images at 3T.

<p>The values were measured when the frequency excitation was shifted by 107Hz (corresponding to (3/4TR) with TR = 7ms) or not (OR) and for SOS2 or SOS4 reconstruction. The WS-bSSFP sequence was also combined with parallel imaging (SENSE 2 or 4) to reduce acquisition time. Acquisition time is shown in brackets under the sequence name.</p><p>* represents p<0.01 compared to fat and bone marrow SNR on standard images.</p><p>° represents p<0.05 compared to SNR on WS-SOS4 images.</p><p>^# represents p<0.05 compared to SNR on WS-SOS2 images.</p><p>^† represents p<0.05 compared to SNR on WS-SOS4 SENSE2 images.</p><p>SNR of human sub-cutaneous fat tissue, bone marrow, joint fluid, cartilage and leg muscle in standard bSSFP and WS-bSSFP images at 3T.</p

Small-animal applications of the 3D WS-bSSFP sequence at 7T.

<p>Coronal mouse whole-body images using standard bSSFP (B) and WS-bSSFP (A) sequences. Sagittal standard bSSFP (D,F) and WS-bSSFP (C,E) images showing the inguinal lymph node (C,D) and its corresponding lymphatic vessel (arrow) and a primary tumor (E,F) developing into the renal cortex (arrowhead).</p

Excitation profile of the WS pulses combined with the frequency-shift method.

<p>Proton spectrums measured at 7T (water linewidth = 180Hz) or 3T (water linewidth = 40Hz). The frequency profiles of 1-2-3-2-1 or 1-3-3-1 binomial pulses are overlaid to show the selectivity of the frequency excitations. In these cases, the binomial pulses were centered on the water frequency (grey lines). The binomial profiles applied when their excitations are shifted by (3/4TR) are also overlaid (dotted lines) to demonstrate that the selectivity of excitation is preserved.</p

3D human knee images acquired at 3T using standard bSSFP and WS-bSSFP sequences in combination with parallel imaging.

<p>The sagittal and axial images shown were either acquired On Resonance (OR + 0Hz), OR + (3/4TR) apart from the resonance (for TR = 7ms, the shift equals 107Hz), or summed using SOS technique (SOS2 or SOS4) and in combination with parallel imaging (SENSE 4). Arrows point at banding artifacts altering cartilage measurements. The arrowhead indicates a banding artifact in the muscle at the edge of the FOV.</p

3D coronal images of mouse abdomen acquired at 7T using standard bSSFP or WS-bSSFP sequences.

<p>The images shown were either acquired On Resonance (OR), OR + (3/4TR) apart from the resonance (for TR = 4.5ms, the shift equals 166.7Hz), or summed using the SOS technique (SOS4). Arrows point at banding artifacts. Arrowheads indicate the inguinal lymph node location.</p