Does 18F-Fluorocholine PET/CT add value to positive parathyroid scintigraphy in the presurgical assessment of primary hyperparathyroidism?

Introduction: To investigate the value of presurgical 18F-FCH PET/CT in detecting additional hyperfunctioning parathyroids despite a positive 99mTc-sestamibi parathyroid scintigraphy in patients with primary hyperparathyroidism (pHPT). Methods: This is a retrospective study involving patients with pHPT, positive parathyroid scintigraphy performed before 18F-FCH PET/CT, and parathyroid surgery achieved after PET/CT. Imaging procedures were performed according to the EANM practice guidelines. Images were qualitatively interpreted as positive or negative. The number of pathological findings, their topography, and ectopic location were recorded. Histopathology, Miami criterion, and biological follow-up were considered to ensure effective parathyroidectomy confirming the complete excision of all hyperfunctioning glands. The impact of 18F-FCH PET/CT on therapeutic strategy was recorded. Results: 64/632 scanned pHPT patients (10%) were included in the analysis. According to a per lesion-based analysis, sensitivity, specificity, positive predictive value, and negative predictive value of 99mTc-sestamibi scintigraphy were 82, 95, 87, and 93%, respectively. The same values for 18F-FCH PET/CT were 93, 99, 99, and 97%, respectively. 18F-FCH PET/CT showed a significantly higher global accuracy than 99mTc-sestamibi scintigraphy: 98% (CI: 95-99) vs. 91% (CI: 87-94%). Youden Index was 0.79 and 0.92 for 99mTc-sestamibi scintigraphy and 18F-FCH PET/CT, respectively. Scintigraphy and PET/CT were discordant in 13/64 (20%) patients (49 glands). 18F-FCH PET/CT identified nine pathologic parathyroids not detected by 99mTc-sestamibi scintigraphy in 8 patients (12.5%). Moreover, 18F-FCH PET/CT allowed the reconsideration of false-positive scintigraphic diagnosis (scinti+/PET-) for 8 parathyroids in 7 patients (11%). The 18F-FCH PET/CT influenced the surgical strategy in 7 cases (11% of the study population). Conclusion: In a preoperative setting, 18F-FCH PET/CT seems more accurate and useful than 99mTc-sestamibi scan in pHPT patients with positive scintigraphic results. Positive parathyroid scintigraphy could be not satisfactory before neck surgery particularly in patients with multiglandular disease, suggesting a need to evolve the practice and define new preoperative imaging algorithms including 18F-FCH PET/CT at the fore-front in pHPT patients.

Hyperfunctioning Intrathyroidal Parathyroid: a Misleading Preoperative Diagnosis.

Hyperfunctioning parathyroid glands may be rarely located in the thyroidal parenchyma and not identified by imaging or during surgical procedures. We present three patients with primary hyperparathyroidism related to hyperfunctioning intrathyroidal parathyroid retrospectively selected among 732 cases from own Institutional parathyroid PET/CT registry from 2018 to 2022. Intrathyroidal parathyroids showed intense 18F-fluorocholine uptake but a variable echographic pattern, inconstant 99mTc-MIBI uptake, and atypic iodine-contrast enhancement. Although rare, the possibility of an intrathyroidal parathyroid should be considered when no hyperfunctioning gland is found on preoperative imaging and thorough bilateral neck exploration.

Impact of pelvic dynamic acquisition on final reading of 18 F-Fluorocholine positron emission tomography in patients with prostate adenocarcinoma: True need or unnecessary burden?

INTRODUCTION: Despite the increasing use of 18 F-fluorocholine (18 F-FCH) positron emission tomography (PET) in patients with prostate cancer, the acquisition protocol remains debated. We have evaluated the influence of the pelvic dynamic phase on the final reading of whole-body 18 F-FCH PET, to assess the need for a two-stage protocol. Reading the physician's experience and patient's previous treatment profile was also considered as potential influencing factors on final PET interpretation. METHODS: All 18 F-FCH PET/CT performed from January 2018 to September 2019 in patients with prostate cancer and including a pelvic dynamic phase followed by a delayed whole-body acquisition were retrospectively retrieved. PET/CT were analysed by one expert nuclear medicine physician and one resident. The whole-body scan was analysed blinded (first reading) and nonblinded from the results of the dynamic phase. RESULTS: 221 consecutive PET/CT were selected from 201 patients previously treated by radical prostatectomy (n = 31), pelvic radiation therapy (n = 60), or both (n = 94). 24 patients had no previous treatments, and 12 benefited from other focal treatments. In the whole population, dynamic acquisition modified final interpretation of 32/221 scans (14.5%) for residents, 26 (11.8%) for experts and 19 (8.6%) for consensual reading. No influence of previous treatments was found. The availability of a dynamic phase would have been responsible for treatment modification in 5/221 scans (2.3%). Considering only the prostate bed, dynamic acquisition modified the final interpretation in 7/125 (5.6%) studies (consensual reading) from patients with previous prostatic surgery and 4/84 (4.8%) scans from patients without a history of prostatic surgical intervention. No significant influence of dynamic acquisition was found on the final PET interpretation on prostate lodge accordingly to previous prostatic surgery. CONCLUSION: The dynamic phase changes the interpretation of 18 F-FCH PET in about 9% of cases and the therapeutic strategy in <3% of patients. The influence of the early phase reduces with physician experience. Patient's treatment profile does not appear to have a significant influence on the variability of interpretation, also including the prostate bed.

18F-FDOPA PET/CT Combined with MRI for Gross Tumor Volume Delineation in Patients with Skull Base Paraganglioma.

In this simulation study, we assessed differences in gross tumor volume (GTV) in a series of skull base paragangliomas (SBPGLs) using magnetic resonance imaging (MRI), 18F-dihydroxyphenylalanine (18F-FDOPA) combined positron emission tomography/computed tomography (PET/CT), and 18F-FDOPA PET/MRI images obtained by rigid alignment of PET and MRI. GTV was delineated in 16 patients with SBPGLs on MRI (GTVMRI), 18F-FDOPA PET/CT (GTVPET), and combined PET/MRI (GTVPET/MRI). GTVPET/MRI was the union of GTVMRI and GTVPET after visual adjustment. Three observers delineated GTVMRI and GTVPET/MRI independently. Excellent interobserver reproducibility was found for both GTVMRI and GTVPET/MRI. GTVPET and GTVMRI were not significantly different. However, there was some spatial difference between the locations of GTVMRI, GTVPET, and GTVPET/MRI. The Dice similarity coefficient median value was 0.4 between PET/CT and MRI, and 0.8 between MRI and PET/MRI. The combined use of PET/MRI produced a larger GTV than MRI alone. Nevertheless, both the target-delivered dose and organs-at-risk conservancy were respected when treatment was planned on the PET/MRI-matched data set. Future integration of 18F-FDOPA PET/CT into clinical practice will be necessary to evaluate the influence of this diagnostic modality on SBPGL therapeutic management. If the clinical utility of 18F-FDOPA PET/CT and/or PET/MRI is confirmed, GTVPET/MRI should be considered for tailored radiotherapy planning in patients with SBPGL.

Evaluation of Oxalate Osteopathy Secondary to Hyperoxaluria With 18F-FDG PET/CT and 99mTc-HMDP Bone Scan.

We report a case of a 69-year-old woman with primary hyperoxaluria type I, who developed a severe hypercalcemia despite controlled secondary hyperparathyroidism. Bone scintigraphy showed diffuse increased uptake in axial and peripheral skeleton. F-FDG PET/CT showed countless striking hypermetabolic foci, interesting 2 types of lesions (joint calcifications and periosteal resorptions). Bone biopsy demonstrated inflammatory changes around many calcium oxalate crystals; hypercalcemia was then related to oxalate osteopathy. Immunotherapy with denosumab was thus initiated. Eighteen months later, a second PET/CT showed decreased F-FDG uptake, reflecting treatment efficacy on inflammatory reaction secondary to calcium oxalosis skeletal deposits.

18F-FDOPA Uptake Reflects the Efficacy of Dopamine Agonists Treatment in Pituitary Prolactinoma.

We report the results of F-FDOPA PET/CT in an asymptomatic MEN-1 patient with secreting pituitary prolactinoma investigated before and during dopamine agonists treatment. PET/CT showed intense and focal F-FDOPA uptake in the right part of anterior pituitary corresponding to a microadenoma on MRI imaging. Six months after the beginning of cabergoline, prolactin secretion normalized, pituitary F-FDOPA uptake completely regressed, and tumor size reduced on follow-up PET/CT and MRI, respectively.

Positional Brain Single-Photon Emission Computed Tomography Findings in a Case of Limb-Shaking Syndrome.

An 84-year-old man, who presented lower limbs limb-shaking syndrome at orthostatism lasting a few seconds, was referred in our stroke unit. Magnetic resonance imaging showed an acute infarction in the right thalamus and the insular cortex, left extracranial carotid stenosis at 80%, and low flow in the right middle cerebral artery but did not explain limb-shaking syndrome symptomatology. We performed comparative positional brain perfusion single-photon emission computed tomography (SPECT), in the upright and in the supine position, to explore and localize hypoperfusion-endangered brain structures that may be involved in the presenting symptoms. Brain perfusion SPECT showed deep hypoperfusion in bilateral carotid territories in the upright position in favor of a hemodynamic mechanism, on which blood pressure was maintained higher to avoid hypoperfusion and the patient remained supine for a longer period of time than in the usual support. Late postoperative brain perfusion SPECT after left endarterectomy did not show significant abnormalities. Limb-shaking syndrome may be related to a transient decrease in blood pressure and cerebral blood flow caused by postural changes. Positional brain perfusion SPECT seems to be helpful to improve clinical care. Positional brain perfusion SPECT should be discussed in the acute phase of stroke and if there are involuntary movements.

18F-FDG PET/CT for the Diagnosis of Malignant and Infectious Complications After Solid Organ Transplantation.

PURPOSE: Infection and malignancy represent two common complications after solid organ transplantation, which are often characterized by poorly specific clinical symptomatology. Herein, we have evaluated the role of 18F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) in this clinical setting. METHODS: Fifty-eight consecutive patients who underwent FDG PET/CT after kidney, lung or heart transplantation were included in this retrospective analysis. Twelve patients underwent FDG PET/CT to strengthen or confirm a diagnostic suspicion of malignancies. The remaining 46 patients presented with unexplained inflammatory syndrome, fever of unknown origin (FUO), CMV or EBV seroconversion during post-transplant follow-up without conclusive conventional imaging. FDG PET/CT results were compared to histology or to the finding obtained during a clinical/imaging follow-up period of at least 6 months after PET/CT study. RESULTS: Positive FDG PET/CT results were obtained in 18 (31 %) patients. In the remaining 40 (69 %) cases, FDG PET/CT was negative, showing exclusively a physiological radiotracer distribution. On the basis of a patient-based analysis, FDG PET/CT's sensitivity, specificity, PPV and NPV were respectively 78 %, 90 %, 78 % and 90 %, with a global accuracy of 86 %. FDG PET/CT was true positive in 14 patients with bacterial pneumonias (n = 4), pulmonary fungal infection (n = 1), histoplasmosis (n = 1), cutaneous abscess (n = 1), inflammatory disorder (sacroiliitis) (n = 1), lymphoma (n = 3) and NSCLC (n = 3). On the other hand, FDG PET/CT failed to detect lung bronchoalveolar adenocarcinoma, septicemia, endocarditis and graft-versus-host disease (GVHD), respectively, in four patients. FDG PET/CT contributed to adjusting the patient therapeutic strategy in 40 % of cases. CONCLUSIONS: FDG PET/CT emerges as a valuable technique to manage complications in the post-transplantation period. FDG PET/CT should be considered in patients with severe unexplained inflammatory syndrome or FUO and inconclusive conventional imaging or to discriminate active from silent lesions previously detected by conventional imaging particularly when malignancy is suspected.

FDG PET to Diagnose Neurolymphomatosis in a Case of Triple-Hit B-Cell Lymphoma.

A 46-year-old man with stage IV triple-hit B-cell lymphoma diagnosed in February 2016 was treated with chemotherapy. He was followed classically with FDG PET/CT, which assessed the complete metabolic response in June 2016. In July 2016, he had autologous stem cell transplantation. Two months later, he underwent an FDG PET/CT for revaluation. It showed intense FDG uptake in the medullary canal from cervical 4 to thoracic 4, bilateral cervical 7 to thoracic 8, and right thoracic 9 to 12 nerve roots, leading to the diagnosis of neurolymphomatosis. A clinical cervical radiculopathy and spinal MRI results reinforced this diagnosis.

FDOPA PET-CT of Nonenhancing Brain Tumors.

BACKGROUND: Primary brain tumor grading is crucial to rapidly determine the therapeutic impact and prognosis of a brain tumor as well as the tumors' aggressiveness profile. On magnetic resonance imaging, high-grade tumors are usually responsible for blood -brain barrier breakdowns, which result in tumor enhancement. However, this is not always the case. The main objective of this study was to evaluate the diagnostic value of FDOPA PET in the assessment of primary brain tumor aggressiveness with no contrast enhancement on MRI. METHODS: Fifty-three patients were prospectively included: 35 low-grade and 18 high-grade histologically proven gliomas, with no contrast enhancement. Each patient underwent static PET acquisitions at 30 minutes. All patients had MRSI with measurements of different metabolites ratio. RESULTS: FDOPA was useful in the subgroup of low-grade gliomas, discriminating between dysembryoplastic neuroepithelial tumor and grade II oligodendroglioma (P < 0.01). An optimal threshold of the maximum standardized uptake value at 30 minutes (SUVmax (T/N)30) = 2.16 to discriminated low- from high-grade gliomas with a sensitivity of 60%, specificity of 100%, PPV of 100%, and NPV of 83.33% (P < 0.01). The nCho/Cr and nCho/NAA ratios were significantly higher in high- than in low-grade gliomas (P < 0.03 and P < 0.04, respectively). A significant positive correlation between MRSI ratios and SUVmax was found. CONCLUSION: Including data from amino acid metabolism used alone or in association with MRSI allows us to discriminate between dysembryoplastic neuroepithelial tumor and grade II oligodendroglioma and between low- and high-grade gliomas with no contrast enhancement on MRI.

Head-to-head comparison between 18F-FDOPA PET/CT and MR/CT angiography in clinically recurrent head and neck paragangliomas.

PURPOSE: Head and neck paragangliomas (HNPGLs) can relapse after primary treatment. Optimal imaging protocols have not yet been established for posttreatment evaluation. The aim of the present study was to assess the diagnostic value of 18F-FDOPA PET/CT and MR/CT angiography (MRA/CTA) in HNPGL patients with clinical relapse during their follow-up. METHODS: Sixteen consecutive patients presenting with local pain, tinnitus, dysphagia, hoarse voice, cranial nerve involvement, deafness, or retrotympanic mass appearing during follow-up after the initial treatment of HNPGLs were retrospectively evaluated. Patients underwent both 18F-FDOPA PET/CT and MRA (15 patents) or CTA (1 patent). Both methods were first assessed under blinded conditions and afterwards correlated. Head and neck imaging abnormalities without histological confirmation were considered true-positive results based on a consensus between radiologists and nuclear physicians and on further 18F-FDOPA PET/CT and/or MRA. RESULTS: 18F-FDOPA PET/CT and MRA/CTA were concordant in 14 patients and in disagreement in 2 patients. 18F-FDOPA PET/CT and MRA/CTA identified, respectively, 12 and 10 presumed recurrent HNPGLs in 12 patients. The two lesions diagnosed by PET/CT only were confirmed during follow-up by otoscopic examination and MRA performed 29 and 17 months later. 18F-FDOPA PET/CT images were only slightly influenced by the posttreatment sequelae, showing a better interobserver reproducibility than MRA/CTA. Finally, in 2 of the 16 studied patients, 18F-FDOPA PET/CT detected two additional synchronous primary HNPGLs. CONCLUSION: 18F-FDOPA PET/CT is highly sensitive in posttreatment evaluation of patients with HNPGLs, and also offers better interobserver reproducibility than MRA/CTA and whole-body examination. We therefore suggest that 18F-FDOPA PET/CT is performed as the first diagnostic imaging modality in symptomatic patients with suspicion of HNPGL relapse after primary treatment when 68Ga-labeled somatostatin analogues are not available.

Small Bowel Carcinoid: The "Dancing Bowel Sign" on 18F-FDOPA PET/CT.

The localization of small bowel (SB) neuroendocrine tumors (NETs) remains a diagnostic challenge in clinical practice. In about a third of cases, SB-NETs are multiple at diagnosis. However, the sensitivity of conventional presurgical diagnostic investigations is not exhaustive. F-FDOPA (6-L-F-fluorodihydroxyphenylalanine) PET seems to be a valuable diagnostic technique for the detection of midgut NETs. According to our experience, a delayed PET/CT acquisition centered on abdominopelvic region and performed after oral hydration may improve the detection of primary tumor and the identification of patients with multifocal SB-NETs who could benefit from a more accurate intraoperative palpation of the entire SB.

Carbidopa-assisted 18F-fluorodihydroxyphenylalanine PET/CT for the localization and staging of non-functioning neuroendocrine pancreatic tumors.

OBJECTIVE: CD premedication was found to increase the value of 18F-fluorodihydroxyphenylalanine (18F-FDOPA) PET/CT imaging in the detection of adult insulinoma. The aim of this study was to evaluate the performance of CD-assisted 18F-FDOPA PET/CT in the diagnosis and staging of non-functioning pNETs. METHODS: Twenty consecutive patients with low-grade pNETs who underwent CD-assisted 18F-FDOPA PET/CT imaging and 111In-somatostatin receptor scintigraphy (SRS) were evaluated. Histology was considered as the gold standard. In case where no surgical resection was performed, the diagnosis of pNET was made by the confrontation of the different available imaging modalities. RESULTS: CD-assisted 18F-FDOPA PET/CT was positive in 18/20 cases (90 %), whereas SRS was positive in 13/19 cases (68 %). When considered the 19 patients underwent both nuclear medicine examinations, 18F-FDOPA PET/CT was significantly more sensitive then SRS for primary tumor detection (p = 0.049). False-negative results of both 18F-FDOPA PET/CT and SRS were observed in 2 cystic pNETs. SRS failed to detect one additional cystic tumor and 3 pNETs of 10, 12 and 17 mm, respectively. 18F-FDOPA PET/CT correctly identified all patients with lymphatic, visceral and bone metastases. SRS failed to detect lymphatic spread and was falsely negative in one patient with splenic metastasis. CONCLUSIONS: Contrary to widely held assumptions, our study further expands the application of CD-assisted 18F-FDOPA PET/CT for non-functioning pNETs when 68Ga-radiolabeled somatostatin analogs are not available.

Adrenal Metastasis of a Poorly Differentiated Adenocarcinoma Mimicking a Pheochromocytoma on 18F-FDOPA PET/CT.

We report the surprising intense uptake of F-FDOPA in a right adrenal metastasis of a poorly differentiated metastatic adenocarcinoma of unknown primary mimicking a pheochromocytoma in a hemodialyzed patient with the typical Menard's triad and increased serum catecholamines. Our observation emphasizes that F-FDOPA is not a specific radiotracer for pheochromocytoma and paraganglioma investigation, although it is currently and successfully used in this clinical setting. Moreover, we underline that kidney failure may be responsible for abnormally high serum catecholamines values even in subjects without pheochromocytoma, leading to erroneous diagnostic conclusions particularly in patients with adrenal masses.

FDG PET in Intracranial Carcinomatous Meningitis.

A 63-year-old white man, diagnosed with pT3N2 squamous cell lung carcinoma, underwent right upper lobectomy with adjuvant radiochemotherapy. After a partial epileptic seizure, MRI revealed a solitary right frontal metastasis that was treated with surgical resection followed by stereotaxic radiotherapy. Three months later, the patient presented weight loss, weakness, and headache. He underwent a whole-body FDG PET/CT for restaging. It showed intense FDG uptakes on the brain periphery corresponding to nodular meningeal contrast enhancement on MRI leading to the diagnosis of carcinomatous meningitis, despite negative cerebrospinal fluid cytology.

(18)F-DOPA PET/CT in the diagnosis and localization of persistent medullary thyroid carcinoma.

PURPOSE: To evaluate the performance of (18)F-L-dihydroxyphenylalanine ((18)F-DOPA) PET/CT in the detection of locoregional and distant medullary thyroid carcinoma (MTC) metastases and to compare imaging findings with histological data. METHODS: We retrospectively evaluated 86 MTC patients with persistently high serum calcitonin levels after initial surgery who had undergone (18)F-DOPA PET/CT between January 2007 and December 2014 in two referral centres. They were followed up for at least 6 months after the PET/CT assessment. The results were compared with histological data or with the findings obtained during follow-up using a complementary imaging modality. RESULTS: (18)F-DOPA PET/CT was positive in 65 of the 86 patients, corresponding to a patient-based sensitivity of 75.6 %. Distant metastatic disease (M1) was seen in 29 patients including 11 with previously unknown metastases revealed only by PET/CT. Among the 36 patients without distant metastatic spread, 25 had nodal involvement limited to the neck, and 10 of these 25 patients underwent reoperation. The lymph node compartment-based sensitivity of (18)F-DOPA PET/CT was 100 % in the two institutions but lesion-based sensitivity was only 24 %. Preoperative and postoperative median calcitonin levels were 405 pg/mL (range 128 - 1,960 pg/mL) and 259 pg/mL (range 33 - 1,516 pg/mL), respectively. None of the patients achieved normalization of serum calcitonin after reoperation. CONCLUSION: (18)F-DOPA PET/CT enables early diagnosis of a significant number of patients with distant metastasis. It has a limited sensitivity in the detection of residual disease but provides high performance for regional analysis. A surgical compartment-oriented approach could be the approach of choice whatever the number of nodes revealed by (18)F-DOPA PET/CT.