Visualization of Paget's disease during somatostatin receptor scintigraphy

Differentiating dural metastases from meningioma: role of 68Ga DOTA-NOC PET/CT

OBJECTIVE

To assess the ability of Ga DOTA-NOC PET/computed tomography (CT) to differentiate dural metastases from meningioma.

PATIENTS AND METHODS

Patients who underwent a Ga DOTA-NOC PET/CT for differentiating meningiomas from dural metastases were included in the study. A visual score was assigned to the dural lesions (visual score - 1 to 3) in relation to the uptake in liver and spleen and variation in the visual score was evaluated. SUVmax of the dural lesions was also noted and difference in the values of the two pathologies were compared for statistical significance using nonparametric statistical tests. Final diagnosis was decided by histopathological confirmation whenever available.

RESULTS

Imaging, histopathology or follow-up data of 42 patients was available for analysis. Meningioma was the final diagnosis in 31 (73.8%) patients, whereas dural metastases were diagnosed in 9 (21.4%) patients. In two patients, histopathology revealed inflammatory pseudotumor and hemangioblastoma. Meningiomas showed intense tracer uptake in 30/31 patients (visual score 3). All metastatic lesions showed some degree of tracer uptake though the intensity was lesser compared to meningioma (visual score 1, 2). Meningiomas showed a significantly higher median SUV max value compared to metastases (12.7 vs. 6.0, P = 0.001).

CONCLUSION

Meningiomas can be differentiated from dural metastases by virtue of their higher uptake of Ga-labeled DOTA peptides reflecting higher SSTR expression. An asymptomatic meningeal based lesion with a high visual score (Visual score 3) has a very high probability to be a meningioma rather than dural metastasis.

Paget's Disease Mimicking Bone Metastasis in a Patient with Neuroendocrine Tumor on 68Ga-DOTANOC PET/CT

Somatostatin (SST) is a neuropeptide present in neurons, endocrine cells, and a wide range of neuroendocrine tumors (NETs). ⁶⁸Ga-DOTATOC, ⁶⁸Ga-DOTANOC, and ⁶⁸Ga-DOTATATE are current SST analogues used for PET/CT which bind to SST receptors expressed in NETs. These SST analogues have been used successfully for diagnosis of SST-expressing tumors with a more sensitive detection technique than conventional scintigraphy. However, there is a lack of clinical data on the differentiation between NETs and other malignant tumors or benign pathological conditions. Here, we report a case of Paget’s disease mimicking bone metastasis of NET on PET/CT due to increased ⁶⁸Ga-DOTANOC uptake and review examples of similar cases in the literature.

Visualization of Gallbladder with In-111 Octreotide Scan

A 54-year-old woman underwent octreotide scintigraphy for evaluation of neuroendocrine tumor recurrence. The images demonstrated unusual uptake in gallbladder area in addition to physiologic uptake at other tissues. Whole-body planar and SPECT imaging were repeated after fatty meal ingestion at 28 hours in order to figure out whether this activity was physiologic or not. Since the unusual uptake in the gallbladder was still detected at these images, additional images were obtained 72 hours after radionuclide injection. The activity in the gallbladder disappeared at these images revealing the physiologic nature of this unusual accumulation.

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

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.

Increased 177Lu-DOTATATE uptake in Paget disease

A 45-year-old female patient was referred for peptide receptor radionuclide therapy of liver metastases of neuroendocrine origin; the patient had undergone 2 years earlier surgical resection of a grade 2 neuroendocrine neoplasm of ampulla of Vater infiltrating the duodenal submucosa and muscular layers and the neighboring pancreatic tissue. Post-therapy whole-body scan performed to evaluate in vivo radiopharmaceutical distribution confirmed high accumulation in liver lesions and revealed increased uptake in the hip bone. Bone scan and corresponding CT images demonstrated changes of Paget disease in the same district.

Detection of cranial meningiomas: comparison of ⁶⁸Ga-DOTATOC PET/CT and contrast-enhanced MRI

PURPOSE

PET imaging with somatostatin receptor ligands, such as (68)Ga-DOTATOC, is a well-established method for detection and target volume definition of meningiomas prior to radiotherapy. Since DOTATOC PET delivers a higher contrast between meningiomas and surrounding tissues than MRI, we conducted a retrospective analysis to compare the diagnostic accuracy of contrast-enhanced MRI (CE-MRI) with (68)Ga-DOTATOC PET/CT in patients with cranial meningiomas prior to radiotherapy.

METHODS

Over a period of 6 years, 134 patients (20-82 years of age, 107 women and 27 men) underwent cranial CE-MRI and (68)Ga-DOTATOC PET/CT. To compare the two methods, the lesions considered typical of meningiomas visually were counted and analysed with respect to their location and SUVmax.

RESULTS

In the 134 patients investigated by both modalities, 190 meningiomas were detected by (68)Ga-DOTATOC PET/CT and 171 by CE-MRI. With knowledge of the PET/CT data, the MRI scans were reinvestigated, which led to the detection of 4 of the 19 incidental meningiomas, resulting in an overall detection rate of 92 % of the meningioma lesions that were found by PET/CT.

CONCLUSION

Ga-DOTATOC PET/CT demonstrated an improved sensitivity in meningioma detection when compared to CE-MRI. Tumours adjacent to the falx cerebri, located at the skull base or obscured by imaging artefacts or calcification are particularly difficult to detect by MRI. Therefore (68)Ga-DOTATOC PET/CT may provide additional information in patients with uncertain or equivocal results on MRI or could help to confirm a diagnosis of meningioma based on MRI or could help to confirm MRI-based diagnosis of meningiomas in cases of biopsy limitations. It is possible that not only radiotherapy and surgical planning, but also follow-up strategies would benefit from this imaging modality.

Positive octreotide scintigraphy and determination of lanreotide activity in Paget's disease of bone associated with phosphate diabetes: a case report

A patient with Paget's disease developed phosphate diabetes (phosphate: 1.6 mg/dl (2.5-4.4 mg/dl), with 29 ml/min phosphate clearance (Nl<15ml/min) and a 65% phosphate reabsorption rate (Nl>85%). As previously demonstrated in tumor-induced osteomalacia, we hypothesized that osteoblasts might manifest somatostatin receptor activity. The patient underwent an octreotide scan which demonstrated increased uptake localized in affected bone. Under lanreotide treatment (40 mg i.m.), the patient's bone pain improved with a concomitant decrease in phosphate alkaline level. Phosphate clearance and tubular readsorption rate of phosphate did not change significantly. We reviewed previously reported cases of associated Paget's bone disease and phosphate diabetes.