Comparison of ⁶⁸Ga-DOTATOC-PET/CT and PET/MRI hybrid systems in patients with cranial meningioma: Initial results

Abstract

Background: (68)Ga-DOTATOC-PET/CT is a well-established method for detecting and targeting the volume definition of meningiomas prior to radiotherapy. Moreover, there is evidence that this method is able to detect meningiomas with higher sensitivity than the goldstandard MRI. Since the hybrid PET/MRI scanner became available in the past few years, the next stage of development could consequently evolve by evaluating the feasibility of a hybrid PET/MRI scanner using (68)Ga-DOTATOC for detecting meningiomas.

Methods: Fifteen patients received (68)Ga-DOTATOC-PET/CT (0.5 h post injection [p.i.]) followed by PET/MRI 2 hours p.i. Both investigations were analyzed separately and then compared with respect to image quality, detection of intracranial meningiomas, and radiotracer uptake values (RUVs). In addition, ratios between radiotracer uptake in meningiomas and pituitary glands were compared between both PET/CT and PET/MRI.

Results: Overall, 33 intracranial meningiomas were detected. All were visible with high contrast in both PET/CT and PET/MRI. (68)Ga-DOTATOC-PET/MRI provided flawless image quality without artefacts. Calculated RUV in meningiomas, as well as the ratios of RUVs in meningiomas to those of pituitary glands, were higher in PET/CT. As a result, meningiomas can be distinguished from pituitary glands better in early images.

Conclusions: (68)Ga-DOTATOC-PET/MRI provided flawless image quality and presented an ideal combination of high sensitivity/specificity (PET) and the best possible morphological visualization of meningiomas (MRI). In addition, excellent detection of meningiomas is already possible at 0.5 hours p.i. Later images do not improve the distinction between pituitary gland and adjacent meningiomas. However, RUVs need to be carefully compared between both imaging modalities.

Keywords: 68Ga-DOTATOC; MRI; PET/CT; PET/MRI; hybrid imaging; meningioma; somatostatin receptor.

Fig. 1.

⁶⁸Ga-DOTATOC-PET/MRI (A–C) and PET/CT (D–F) of patient 9 demonstrating a meningioma of the skull base (yellow arrows) adjacent to the pituitary gland (white arrows). Late images (PET/MRI) do not help to improve the distinction between the 2 types of tissues. (A) contrast enhanced T1-weighted MRI. (B) DOTATOC-PET 30 minutes p.i. (derived from the PET/CT). (C) fusion of a and b. (D) native CT. (E) DOTATOC-PET ∼2 hours p.i. (derived from the PET/MRI). (F) fusion of D and E.

Fig. 2.

⁶⁸Ga-DOTATOC-PET/MRI (A–C) and PET/CT (D–F) of patient 11. Extensive and inhomogeneous meningioma of the skull base infiltrating the nasal cavity. DOTATOC-PET can distinguish between vital meningioma and other tissues such as postoperative scarring or reactive tissue. (A) contrast-enhanced T1-weighted MRI. (B) DOTATOC-PET 30 minutes p.i. (derived from the PET/CT). (C) fusion of a and b. (D) native CT. (E) DOTATOC-PET ∼2 hours p.i. (derived from the PET/MRI). (F) fusion of D and E.

Fig. 3.

Mean and maximum uptake values (SUV_mean/max) of the 33 meningiomas in ⁶⁸Ga-DOTATOC-PET/CT (30 min p.i.) and PET/MRI (2 h p.i.). In the majority of the cases, radiotracer uptake was higher in early images.

Fig. 4.

Ratios between meningiomas and pituitary glands (hypophysis) in ⁶⁸Ga-DOTATOC-PET/CT (30 min p.i.) and PET/MRI (2 h p.i.). The majority of the ratios were higher in early images. Later scans therefore do not improve the distinction between meningiomas and adjacent pituitary glands.