Simultaneous hyperpolarized 13C-pyruvate MRI and 18F-FDG-PET in cancer (hyperPET):feasibility of a new imaging concept using a clinical PET/MRI scanner

In this paper we demonstrate, for the first time, the feasibility of a new imaging concept - combined hyperpolarized (13)C-pyruvate magnetic resonance spectroscopic imaging (MRSI) and (18)F-FDG-PET imaging. This procedure was performed in a clinical PET/MRI scanner with a canine cancer patient. We have named this concept hyper PET. Intravenous injection of the hyperpolarized (13)C-pyruvate results in an increase of (13)C-lactate, (13)C-alanine and (13)C-CO(2) ((13)C-HCO(3)) resonance peaks relative to the tissue, disease and the metabolic state probed. Accordingly, with dynamic nuclear polarization (DNP) and use of (13)C-pyruvate it is now possible to directly study the Warburg Effect through the rate of conversion of (13)C-pyruvate to (13)C-lactate. In this study, we combined it with (18)F-FDG-PET that studies uptake of glucose in the cells. A canine cancer patient with a histology verified local recurrence of a liposarcoma on the right forepaw was imaged using a combined PET/MR clinical scanner. PET was performed as a single-bed, 10 min acquisition, 107 min post injection of 310 MBq (18)F-FDG. (13)C-chemical shift imaging (CSI) was performed just after FDG-PET and 30 s post injection of 23 mL hyperpolarized (13)C-pyruvate. Peak heights of (13)C-pyruvate and (13)C-lactate were quantified using a general linear model. Anatomic (1)H-MRI included axial and coronal T1 vibe, coronal T2-tse and axial T1-tse with fat saturation following gadolinium injection. In the tumor we found clearly increased (13)C-lactate production, which also corresponded to high (18)F-FDG uptake on PET. This is in agreement with the fact that glycolysis and production of lactate are increased in tumor cells compared to normal cells. Yet, most interestingly, also in the muscle of the forepaw of the dog high (18)F-FDG uptake was observed. This was due to activity in these muscles prior to anesthesia, which was not accompanied by a similarly high (13)C-lactate production. Accordingly, this clearly demonstrates how the Warburg Effect directly can be demonstrated by hyperpolarized (13)C-pyruvate MRSI. This was not possible with (18)F-FDG-PET imaging due to inability to discriminate between causes of increased glucose uptake. We propose that this new concept of simultaneous hyperpolarized (13)C-pyruvate MRSI and PET may be highly valuable for image-based non-invasive phenotyping of tumors. This methods may be useful for treatment planning and therapy monitoring

Ultra-early apparent diffusion coefficient change indicates irradiation and predicts radiotherapy outcome in brain metastases

Ultra-early apparent diffusion coefficient change indicates irradiation and predicts radiotherapy outcome in brain metastase

The effect of region of interest strategies on apparent diffusion coefficient assessment in patients treated with palliative radiation therapy to brain metastases

<div><p>ABSTRACT</p><p><b>Background.</b> Although diffusion-weighted magnetic resonance imaging (DW-MRI) is widely used in radiation therapy (RT) response studies, no standard of delineating the region of interest (ROI) exists. In this retrospective study, we evaluate the effect of four ROI strategies on the apparent diffusion coefficients (ADC) in patients receiving palliative RT to brain metastases.</p><p><b>Material and methods.</b> Twenty-two metastases from nine patients, treated with whole-brain irradiation (30 Gy in 10 fractions) were analyzed. Patients were scanned with a 1T MR system to acquire DW- (eight b-values), T2*W-, T2W- and T1W scans, before start of RT (pre-RT) and at the 9th/10th fraction (end-RT). The following ROI strategies were applied. ROI_b800 and ROI_b0: Entire tumor volume visible on DW(b = 800 s/mm²) and DW(b = 0 s/mm²) images, respectively. ROI_b800vi: <i>Viable</i> tumor volume based on DW(b = 800 s/mm²). ROI_b800rep: ROI_b800 from pre-RT scan replicated to end-RT scan. Delineations were aided by co-registered T1W, T2W and T2*W images. ADC was estimated with two mono-exponential fits and one bi-exponential fit.</p><p><b>Results.</b> Differences in absolute ADC values were non-significant across ROI strategy independent of fitting method, while significantly different between fitting methods. Evaluation of individual metastases showed that ROI strategies disagreed on the relative ADC change (from pre-RT to end-RT) in 13 of the 22 metastases when all fitting methods were added up.</p><p><b>Conclusion.</b> The ROI strategies have an effect on the relative ADC change, which may be important for the assessment of individual patient's response to RT and the interpretation of the current literature.</p></div

Initial Experience with 64Cu-DOTATATE Digital PET of Patients with Neuroendocrine Neoplasms: Comparison with Analog PET

The recent introduction of solid-state detectors in clinical positron emission tomography (PET) scanners has significantly improved image quality and spatial resolution and shortened acquisition time compared to conventional analog PET scanners. In an initial evaluation of the performance of our newly acquired Siemens Biograph Vision 600 PET/CT (digital PET/CT) scanner for 64Cu-DOTATATE imaging, we compared PET/CT acquisitions from patients with neuroendocrine neoplasms (NENs) grades 1 and 2 and stable disease on CT who were scanned on both our Siemens Biograph 128 mCT PET/CT (analog PET/CT) and digital PET/CT within 6 months as part of their routine clinical management. Five patients fulfilled the criteria and were included in the analysis. The digital PET acquisition time was less than 1/3 of the analog PET acquisition time (digital PET, mean (min:s): 08:20 (range, 07:59–09:45); analog PET, 25:28 (24:39–28:44), p &lt; 0.001). All 44 lesions detected on the analog PET with corresponding structural correlates on the CT were also found on the digital PET performed 137 (107–176) days later. Our initial findings suggest that digital 64Cu-DOTATATE PET can successfully be performed in patients with NENs using an image acquisition time of only 1/3 of what is used for an analog 64Cu-DOTATATE PET