Clinical evaluation of 11C-Met-avid pituitary lesions using a ZTE-based AC method G. Delso, D. Gillett, W. Bashari, T. Matys, I. Mendichovszky & M. Gurnell

The pituitary gland The pituitary gland, or hypophysis, is an endocrine gland located at the base of the brain, suspended from the hypothalamus by a gray matter stalk. It is housed by the hypophysial fossa of the sphenoid bone, at the center of the middle cranial fossa. The pituitary gland is approximately 13 mm in diameter and 5 mm of height, weighting 500 mg. https://en.wikipedia.org/wiki/Pituitary_gland

Pituitary disease The pituitary gland consists of two main lobes, anterior and posterior, each releasing specific hormones that affect several bodily functions. Overproduction or underproduction of a pituitary hormone will affect the respective end-organ. https://en.wikipedia.org/wiki/Pituitary_disease

Pituitary disease Cushing’s (excess cortisol hormone) Acromegaly (excess growth hormone) Normal vs. acromegaly https://pituitarysociety.org https://en.wikipedia.org/wiki/Acromegaly

Pituitary lesions Pituitary adenomas are tumors that occur in the pituitary gland. Pituitary adenomas represent 10% to 25% of all intracranial neoplasms  and the estimated prevalence rate in the general population is approximately 17%. Most adenomas are benign, approximately 35% are invasive and just 0.1% to 0.2 are carcinomas. While pituitary adenomas are common, affecting ~1:6 of the population, clinically active adenomas that require surgical treatment affect ~1:1000 of the population. Images courtesy of Dr. Bashari & Prof. Gurnell https://en.wikipedia.org/wiki/Pituitary_adenoma

Treatment: Trans-sphenoidal surgery (TSS) https://www.mayfieldclinic.com/PE-EndoPitSurg.htm

Treatment: Trans-sphenoidal surgery (TSS) https://www.mayfieldclinic.com/PE-EndoPitSurg.htm

Value of 11C-Methionine PET Koulouri (2015). Eur J Endocrinol 173(4): M107-120. Koulouri (2016). Eur J Endocrinol 175(5): 485-498. Value of 11C-Methionine PET De novo Cushing’s disease Cor SPGR + Gd, 1mm slices [11C]-MET reflects amino acid transport

Value of 11C-Methionine PET De novo Cushing’s disease Cor SPGR + Gd, 1mm slices [11C]-MET reflects amino acid transport

The OPTIMUM Study “Optimising Pituitary Tumor Imaging with PET/MR Using 11C-Methionine.” Discovery 690 PET/CT SIGNA PET/MR

Patient summary 23 patients with clinically active pituitary lesions. 16 female, 7 male Weight: 84 ± 23 kg Age: 41 ± 14 kg 15 patients returned for a second session post-therapy. Delay: 28 ± 1 days.

Imaging protocol PET/CT imaging on GE Discovery 690 Dose: 409 ± 44 MBq 11C-Methionine (half-life 20 minutes) Start: 19 ± 2 minutes post-injection. Duration: 20 minutes. PET/MR imaging on GE SIGNA PET/MR No additional dose Start: 74 ± 22 minutes post-injection. Duration: 40 minutes.

MR protocol FOCUS DWI BRAVO T1 BRAVO T2 CUBE FIESTA-C DCE LAVA-FLEX FSPGR ZTE Contrast

PET results PET/CT PET/MR

Reconstruction pipeline ZTE MRI Reconstruction pipeline Denoising Intensity normalization LAVA-FLEX MRI Head atlas Non-rigid registration Head mask extraction Energy scaling Bias correction Atlas MRAC Resampling Partial volume mask extraction Hardware attenuation templates Template merging Sinus mask extraction Energy scaling Complete attenuation map In-vivo attenuation map Bone mask extraction Resampling Cavity mask extraction Hardware attenuation map Merging Density mapping Complete attenuation map Pseudo-CT

Qualitative results

Quantitative results

Quantitative results with normalization

Results with template-enhanced ZTE

Ongoing work: Reconstruction improvements

Ongoing work: Vascular imaging

Conclusion Clinically relevant, ideal indication for PET/MR. Successful PET/CT+PET/MR study, pre- & post- therapy. Marginal quantitation improvement with ZTE-AC. Preliminary evaluation of more advanced methods. Ongoing work to improve PET resolution. Ongoing work to improve anatomical context for surgery.

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