To investigate the use of binomial pulses in balanced steady-state free-precession (bSSFP) to aid in acquisition of spectroscopically selective images of hyperpolarized pyruvate and its metabolites.bSSFP is an attractive technique for hyperpolarized imaging because it provides good sensitivity and makes efficient use of the magnetization. Strategies for spectroscopically selective bSSFP imaging include techniques that acquire multiple echoes per TR [1,2], selectively excite a single metabolite [3,4], or make use of a variable RF phase advance to separate signals from different metabolites [5]. These techniques generally have a high sensitivity to off-resonance effects that requires careful shimming to reduce so-called ‘bright band’ bSSFP artifacts. Here we investigate the use of a simple binomial pulse to selectively null the signal from either pyruvate or lactate in alternate frames of a dynamic acquisition. In applications where the alanine and pyruvate hydrate signals are small, the resulting images provide an approximation of spectrally selective images of pyruvate and lactate.A bSSFP sequence was modified to include two successive slice-selective RF excitation pulses separated by a delay τ as shown in Fig. 1. The pulse sequence was implemented for dynamic imaging where the relative phase between the two RF pulses was alternated between 0 and 180 degrees in successive images. This binomial pulse modulates the signal of a metabolite at chemical shift Δ by an overall factor of either cos(πΔτ) or sin(πΔτ) for a phase difference of 0 or 180 degrees, respectively. For imaging of pyruvate and its metabolites at 9.4T, τ was set to 0.404ms and the center frequency of the scanner was placed at the chemical shift of pyruvate. With these parameters, the signals from pyruvate and lactate (approximately 1.24kHz off-resonance) are nulled in alternating frames. TR was set to 2.20ms, a value that minimizes the likelihood of bSSFP ‘bright band’ artifacts for pyruvate and all of its metabolites. To ensure smooth entry into the steady state, the RF pulse amplitude was modulated by a Fermi function during each frame. In vivo imaging was performed using a 9.4T horizontal bore scanner (Biospec 94/20, Bruker, Billerica MA) with IACUC approval. A mouse bearing a subcutaneous A498 tumor was anesthetized and situated for imaging as described previously [5] with a 28mm 13C coil situated around the tumor. Ultrasound gel was applied over the tumor to reduce the susceptibility mismatch at the air/tissue interface. Hyperpolarized pyruvate solution was prepared using a DNP hyperpolarizer (Hypersense, Oxford Instruments, Oxfordshire UK). T2 weighted anatomical images were used to select a 5mm slice for subsequent imaging. Local shimming was performed in the tumor and surrounding vessels to obtain approximately 100Hz proton linewidth. To confirm the scanner center frequency setting, a small 50 microliter bolus of 100mM pyruvate solution was administered by tail vein during acquisition of spectra from the imaging slice. Subsequently, a 150 microliter bolus was administered, and bSSFP images were acquired with 1.5mm in-plane resolution, (net) tip angle 15 degrees, and 1.1s per frame. Slice-selective spectra were analyzed using AMARES in jMRUI [6]. bSSFP images were reconstructed using standard Fourier methods and sorted into even and odd frames.Fig. 2 shows the bSSFP images overlaid on the proton reference images at several time points. Images on the left have relative RF phase 0, while those on the right have relative phase 180, values are chosen to null lactate and pyruvate respectively. Fig. 3 shows time courses from region of interest placed over the tumor in the bSSFP images, together data from the slice-selective spectra.The images on the left and right in Fig. 2 are expected to be dominated by pyruvate and lactate, respectively. The pyruvate-dominated images on the left show the expected features, including large intravascular signal (arrow in top frame) followed by rapid arrival in the tumor. Likewise, the lactate-dominated images on the right show low intravascular signal, late buildup in the tumor, and long signal persistence. Both sets of images include contributions alanine and pyruvate hydrate, which are expected to be small. Previous studies in A498 tumors have shown that signals from these metabolites are approximately an order of magnitude smaller than those from pyruvate and lactate [5]. Binomial pulses provide a simple method for nulling the signal from a chosen metabolite in bSSFP. This method is relatively robust against off-resonance errors, and can be used to obtain approximate spectrally selective images of pyruvate and lactate in applications where other metabolites are small. This technique can be readily combined with existing methods to improve their performance.