Dual-phase 68Ga-PSMA-11 PET/CT may increase the rate of detected lesions in prostate cancer patients

Background: This study was conducted to compare the early static (3–6 min post-injection (p.i.)) and standard whole body (1 h, p.i.) 68Ga-PSMA-11 PET/CT imaging for detection of lesions in prostate cancer (PC) patients. Materials and methods: In this study, PC patients suspected of recurrence underwent 68Ga-PSMA-11 PET/CT. Early static images were acquired from the pelvis and the lower abdomen 3-5 minutes after radiotracer injection and, a routine whole body scan was performed from the skull to the mid-thigh 1 h after injection. Quantitative analysis (SUVmax) was evaluated in suspicious lesions. Results: Of 19 evaluated PC patients with a median age of 72 ± 1.66 years (range: 55–85 years) and prostate-specific antigen (PSA) of 1.72 ± 6.11 ng/ml (range: 0.1–100 ng/ml) (median ± SE), 16 showed positive in the whole body PET/CT. All of the patients with positive whole body scans due to pelvic involvement had positive early scan results. Totally, 22 lesions were detected in both early and delay scans in the pelvic which 16 were related to prostate involvement, 4 were related to lymph node involvement, and 2 were related to bone involvement. Moreover, in addition to the mentioned 22 lesions, early PET imaging successfully detected local recurrence in a patient who was negative on WB PET/ CT; this lesion was masked in the delay scan due to bladder activity. The median SUVmax values of the early and delay scans were 3.69 ± 1.07 (median ± SE) (range: 1.2–14.5) and 5.85 ± 1.69 (range: 3.1–23.4), respectively. ( p = 0.005). Conclusion: Early static 68Ga-PSMA-11 PET/CT imaging might discriminate metastases from urinary bladder activity. Therefore, early static imaging in combination with whole body 60-min p.i. imaging can improve the detection of local involvement pelvic disease.

Influence of Cation Transporters (OCTs and MATEs) on the Renal and Hepatobiliary Disposition of [11C]Metoclopramide in Mice

Purpose To investigate the role of cation transporters (OCTs, MATEs) in the renal and hepatic disposition of the radiolabeled antiemetic drug [11C]metoclopramide in mice with PET. Methods PET was performed in wild-type mice after administration of an intravenous microdose (<1 μg) of [11C]metoclopramide without and with co-administration of either unlabeled metoclopramide (5 or 10 mg/kg) or the prototypical cation transporter inhibitors cimetidine (150 mg/kg) or sulpiride (25 mg/kg). [11C]Metoclopramide PET was also performed in wild-type and Slc22a1/2(−/−) mice. Radiolabeled metabolites were measured at 15 min after radiotracer injection and PET data were corrected for radiolabeled metabolites. Results [11C]Metoclopramide was highly metabolized and [11C]metoclopramide-derived radioactivity was excreted into the urine. The different investigated treatments decreased (~2.5-fold) the uptake of [11C]metoclopramide from plasma into the kidney and liver, inhibited metabolism and decreased (up to 3.8-fold) urinary excretion, which resulted in increased plasma concentrations of [11C]metoclopramide. Kidney and liver uptake were moderately (~1.3-fold) reduced in Slc22a1/2(−/−) mice. Conclusions Our results suggest a contribution of OCT1/2 to the kidney and liver uptake and of MATEs to the urinary excretion of [11C]metoclopramide in mice. Cation transporters may contribute, next to variability in the activity of metabolizing enzymes, to variability in metoclopramide pharmacokinetics and side effects.

Feasibility of dual phase 99mTc-MDP SPECT/CT imaging in rheumatoid arthritis evaluation

ObjectivesTo prospectively demonstrate the feasibility of performing dual-phase SPECT/CT for the assessment of the small joints of the hands of rheumatoid arthritis (RA) patients, and to evaluate the reliability of the quantitative and qualitative measures derived from the resulting images.MethodsA SPECT/CT imaging protocol was developed in this pilot study to scan both hands simultaneously in RA patients, in two phases of 99mTc-MDP radiotracer uptake; namely the soft-tissue blood pool phase (within 15 minutes after radiotracer injection) and osseous phase (after 3 hours). Joints were evaluated qualitatively (normal vs. abnormal uptake) and quantitatively (by measuring the maximum corrected count ratio [MCCR]). Qualitative and quantitative evaluations were repeated to assess reliability.ResultsFour participants completed seven studies (all four were imaged at baseline, and three of them at follow-up after 1-month of arthritis therapy). A total of 280 joints (20 per hand) were evaluated. The MCCR from soft-tissue phase scans was significantly higher for clinically abnormal joints compared to clinically normal ones; p<0.001, however the MCCR from the osseous phase scans were not different between the two groups. Intraclass Correlation Coefficient (ICC) for MCCR was excellent (0.9789, 95% confidence interval [CI]: 0.9734-0.9833). Intra-observer agreement for qualitative SPECT findings was good for both the soft-tissue phase (kappa=0.78, 95%CI: 0.72-0.83) and osseous-phase (kappa=0.70, 95%CI: 0.64-0.76) scans.ConclusionExtracting reliable quantitative and qualitative measures from dual-phase 99mTc-MDP SPECT/CT hand scans is feasible in RA patients. SPECT/CT may provide a unique means for assessing both synovitis and osseous involvement in RA joints using the same radiotracer injection.

Visualization rate of internal mammary sentinel lymph nodes with modified technique of radiotracer injection.

99 Background: Even though the 2009 AJCC incorporated the internal mammary sentinel lymph node biopsy (IM-SLNB) concept, there has been limited change in surgeons practice patterns due to the low visualization rate of the internal mammary sentinel lymph nodes (IM-SLNs) with the conventional injection technique (average 13%, 0~37%). In this prospective study, different radiotracer injection techniques were evaluated to achieve a relative high visualization and detection rate of IM-SLNs (NCT01642511). Methods: The 190 patients enrolled in this study were divided into three groups according to the study period and radiotracer (99mTc-labeled sulfur colloid) injection technique. Group A: conventional technique (radiotracer injection only into the tumor quadrant) for the initial 58 cases; Group B: two-quadrant injection at the 6 and 12 o’clock positions, 2.0~3.0 cm from nipple in the latter 132 cases. Group B was then separated into two groups according to the radiotracer injection volume: Group B1, low volume (<0.5ml/point, n=41); Group B2, high volume (≥0.5ml/point, n=91). Radiotracer was injected into the parenchyma under the ultrasonographic guidance for all patients. IM-SLNB was performed for patients with IM-SLNs visualized on preoperative lymphoscintigraphy and/or detected by intraoperative gamma probe. Results: Group B was associated with a significantly higher IM-SLNs visualization rate (76.5%, 101/132) compared to Group A (15.5%, 9/58, P=0.000), and Group B2 with the highest visualization rate (86.8% vs. 53.7% Group B1, P=0.000). All techniques had the same visualization rate of the axillary SLNs (P=0.915). The visualization rate of IM-SLNs was related to the patient’s age (P=0.037) and injection volume (P=0.000). The successful rate of IM-SLNB was 92.3%, and arrived 100% after 20 cases learning curve. The postoperative IM-SLNB complications were 0. Conclusions: Modified technique of radiotracer injection (Qiu's injection technique: two-quadrant, high volume and ultrasonographic guidance) significantly improved the visualization rate of IM-SLNs, provided an effective technique to evaluate the status of internal mammary, and would promote research on the IM-SLNB.