Cardiac perfusion imaging using hyperpolarized ¹³c urea using flow sensitizing gradients

Abstract

PurposeTo demonstrate the feasibility of imaging the first passage of a bolus of hyperpolarized 13C urea through the rodent heart using flow-sensitizing gradients to reduce signal from the blood pool.MethodsA flow-sensitizing bipolar gradient was optimized to reduce the bright signal within the cardiac chambers, enabling improved contrast of the agent within the tissue capillary bed. The gradient was incorporated into a dynamic golden angle spiral 13C imaging sequence. Healthy rats were scanned during rest (n = 3) and under adenosine stress-induced hyperemia (n = 3).ResultsA two-fold increase in myocardial perfusion relative to rest was detected during adenosine stress-induced hyperemia, consistent with a myocardial perfusion reserve of two in rodents.ConclusionThe new pulse sequence was used to obtain dynamic images of the first passage of hyperpolarized 13C urea in the rodent heart, without contamination from bright signal within the neighboring cardiac lumen. This probe of myocardial perfusion is expected to enable new hyperpolarized 13C studies in which the cardiac metabolism/perfusion mismatch can be identified.

A referenceless Nyquist ghost correction workflow for echo planar imaging of hyperpolarized [1‐13C]pyruvate and [1‐13C]lactate

“…This is not the case for 13 C imaging because the 13 C signals are usually localized. This was the case here, where labelled lactate was observed predominantly in the tumour, but is also the case for other hyperpolarized 13 C‐labelled imaging agents, such as the perfusion markers 13 C‐labelled urea38, 39 and [1‐ 13 C]2‐methylpropan‐2‐ol (t‐butanol) 40, 41. For perfusion imaging, searches in early‐stage images may lead to biased correction coefficients because of rapid motion of the marker in the blood vessels, as is indicated by the results shown in Figure 8.…”

Renal MR angiography and perfusion in the pig using hyperpolarized water

“…In addition to the specific extravasation properties of water relative to any other molecule, the signal that can be created by hyperpolarized 1 H exceeds any other magnetic nucleus (e.g. 13 …”

“…By rapid dissolution in a hot medium, the hyperpolarized nuclei can be brought to liquid state and injected into the patient before the polarization is lost due to longitudinal relaxation (7). Alternatively, metabolically inert 13 C-labeled molecules can be used for angiographic imaging (9)(10)(11), as demonstrated in rodent and porcine models, and for perfusion of rodent organs (12)(13)(14)(15) or of tumor models (16,17). 13 C or 15 N labelled molecules for angiography and perfusion imaging exploits the long T 1 for selected 13 C and 15 N molecules and the low signal background (18).…”

Magnetic resonance imaging with hyperpolarized agents: methods and applications

“…Combined approaches using both [1- 13 C] and [2- 13 C] pyruvate [190, 191] or dual-enriched [1,2- 13 C 2 ] pyruvate allow for simultaneous investigation of pyruvate dehydrogenase flux, TCA cycle flux, and pH [192]. Other 13 C-labeled substrates applied to cardiac functional or metabolic imaging include [U- 13 C] α-ketobutyrate [193], [1- 13 C] lactic acid [194, 195], [1- 13 C] acetate [196–199], 13 C urea [200], and [1- 13 C] butyrate [201, 202]. Recently, co-polarization of 13 C urea and [1- 13 C] pyruvate was demonstrated to simultaneously assess myocardial perfusion and metabolism [80].…”