Automated radiochemical synthesis of pharmaceutical grade [18 F]FLT using 3-N-Boc-5'-O-dimethoxytrityl-3'-O-nosyl-thymidine precursor and its Sep-Pak® purification employing selective elution from reversed phase.

Pharmaceutical grade 3'-deoxy-3'-[18 F]fluorothymidine [18 F]FLT was synthesized using 3-N-Boc-5'-O-dimethoxytrityl-3'-O-nosyl-thymidine (BOC-Nosyl) precursor, in the general purpose TRACERlab FX modules. Purification of [18 F]FLT, via solid phase extraction (SPE) after radiosynthesis, using a combination of different SPE cartridges, yielded satisfactory results, with radiochemical and chemical purity >99%. While the non-decay corrected radiochemical yield (RCY) with 20 mg (24 µmole) of BOC-Nosyl precursor was found to be 6.80 ± 0.16%, the decay corrected radiochemical yield (RCY) was 9.95 ± 0.24%. Residual acetone, acetonitrile, and ethanol levels were found to be 22.97 ± 0.76, 109.08 ± 0.93, and 7,666.45 ± 3.7 ppm, respectively. A simplified method for solid-phase purification of [18 F]FLT was developed, circumventing the need for HPLC purification. Biodistribution in C57BL/6 mice with B16F10 cell line-induced melanoma showed tumor to blood ratio of ~3.8 at 90 min. PET/CT imaging of normal rabbit injected with [18 F]FLT shows selective uptake in the bone marrow and small intestine. [18 F]FLT was found to be excreted through the kidneys and get collected in the urinary bladder, 120 min post injection. PET/CT imaging performed in rabbit model at 30, 60, 90, and 120 min post [18 F]FLT injections showed concordance with tissue distribution kinetics of mice tumor model.

Angiogenesis Imaging of Adrenocortical Carcinoma with Ga-68-NODAGA-RGD Positron Emission Tomography: Opening New Horizons in Multimodality Imaging from Theranostic Perspective.

A 53-year-old female, with a known case of adrenocortical carcinoma (ACC), underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for initial staging, which revealed FDG avid large left suprarenal mass contiguous with hypermetabolic tumor thrombus in the inferior vena cava (IVC) through the left renal vein. Thereafter, she underwent angiogenesis imaging using Ga-68-NODAGA-RGD PET/CT, which showed similar avid tracer uptake in both primary and IVC thrombus. Demonstration of RGD avidity in ACC in this case opens a new horizon for targeted radionuclide therapy (e.g., Lu-177 RGD) in selected patients, who may have limited therapeutic options.

68 Ga-PSMA-11 PET/CT Imaging in Brain Gliomas and Its Correlation With Clinicopathological Prognostic Parameters.

BACKGROUND: Gliomas are the most common primary central nervous system tumors, of which the malignant gliomas account for 60%-75%. The primary and secondary brain malignancies are highly treatment resistant, and their marked angiogenesis attracts interest as a potential therapeutic target. The grade of gliomas, Ki-67 index, and IDH mutation status are among the major prognostic markers in gliomas. Prostate-specific membrane antigen (PSMA) is a zinc-dependent peptidase that is not only expressed in prostate cancer cells but also in the tumor neovasculature. The initial PSMA PET studies in central nervous system tumors using 68 Ga-HBED-CC-PSMA ( 68 Ga-PSMA-11) PET tracer confirmed selective target expression in gliomas of different grades, with higher expression in high-grade glioma compared with low-grade glioma. AIMS AND OBJECTIVES: The aim of the present study was to correlate and compare the 68 Ga-PSMA-11 and 18 F-FDG uptake in brain tumors with their clinicopathological prognostic parameters, so as to study their prognostic implications. In addition, the study also aimed to identify patients who are likely to benefit from potential PSMA-targeted therapies. PATIENTS AND METHODS: This ongoing prospective study was approved by the institutional scientific and medical ethics committee. The patients with primary or recurrent glioma lesions on MRI underwent regional brain PET/CT scanning with 68 Ga-PSMA-11 and 18 F-FDG. The final histopathology of the brain lesions (glioma grade), Ki-67 index, and IDH mutation status were compared with SUV max values of the 68 Ga-PSMA-11 and 18 F-FDG PET/CT. RESULTS: A total of 15 patients (13 males and 2 females; age range, 21-73 years; median age, 58 years) were included in this study analysis. Among the 15 patients, 10 were treatment naive and 2 were patients with recurrent glioma. Three patients turned out to be WHO grade I-II, 6 belonged to grade III, and 6 grade IV (glioblastoma multiforme) on final histopathology. The 68 Ga-PSMA-11 PET/CT showed tracer uptake in all high-grade gliomas with good tumor-to-background ratio. It was PSMA nonavid in 2/3 low-grade gliomas, and it showed low-grade uptake in 1/3 patients. PSMA expression (as evaluated by SUV max values) was significantly higher in higher-grade tumors, those with IDH mutation wildtype status, and higher Ki-67 indices. FDG PET SUV max also showed significant correlation with these prognostic parameters. CONCLUSIONS: In these preliminary results, PSMA PET appears to be an important tool in the evaluation and prognosis of gliomas. PSMA-directed theranostics can be explored as a personalized approach in gliomas with high PSMA uptake. However, with the limitation of small sample size, larger clinical trials are warranted to draw conclusive evidence regarding the same.

Unilateral Breast Uptake of 99mTc-MIBI in a Lactating Woman During Myocardial Perfusion Imaging.

ABSTRACT: A 34-year-old woman, who was 11 months postpartum, underwent 99mTc-MIBI myocardial perfusion SPECT imaging for atypical symptomatology with normal baseline electrocardiogram and 2-dimensional echocardiography. She was lactating on and off, preferentially from the right breast. Analysis of the raw images revealed unilateral intense tracer uptake in the right breast region that persisted in the delayed spot views (24-hour postinjection). Although bilateral breast uptake of 99mTc-MIBI may be seen in postpartum scenario, unilateral breast uptake can also occur in patients with preferential lactation from 1 breast as seen in this case and should not be mistaken for pathology.