Although 18F-labeled NaF was the first widely used agent for skeletal scintigraphy, it quickly fell into disuse after the introduction of 99mTc-labeled bone-imaging agents. Recent comparative studies have demonstrated that 18F-fluoride PET is more accurate than 99mTc-diphosphonate SPECT for identifying both malignant and benign lesions of the skeleton. Combining 18F-fluoride PET with other imaging, such as CT, can improve the specificity and overall accuracy of skeletal 18F-fluoride PET and probably will become the routine clinical practice for 18F-fluoride PET. Although 18F-labeled NaF and 99mTc-diphosphonate have a similar patient dosimetry, 18F-fluoride PET offers shorter study times (typically less than 1 h), resulting in a more efficient workflow, improved patient convenience, and faster turnarounds of reports to the referring physicians. With the widespread availability of PET scanners and the improved logistics for the delivery of 18F radiopharmaceuticals, prior limitations to the routine use of 18F-fluoride bone imaging have largely been overcome. The favorable imaging performance and the clinical utility of 18F-fluoride PET, compared with 99mTc-diphosphonate scintigraphy, support the reconsideration of 18F-fluoride as a routine bone-imaging agent.

https://jnm.snmjournals.org/content/49/1/68.full.pdf

Skeletal PET with 18F-Fluoride: Applying New Technology to an Old Tracer

We evaluated the potential of PET/CT and [18F]fluoromethylcholine (FCH) in the assessment of suspected recurrence of prostate cancer after treatment. One hundred consecutive prostate cancer patients with a persistent increase in serum PSA (>0.1 ng/ml) after radical prostatectomy (58 cases), radiotherapy (21 cases) or hormonal therapy alone (21 cases) were investigated. After injection of 3.7–4.07 MBq/kg of FCH, both early (at 60 min) PET/CT scans were performed in 43 patients, delayed PET/CT scans in 53 patients and early PET/CT scans in four patients. Of the 100 patients, 54 (PSA 0.22–511.79 ng/ml) showed positive FCH PET/CT scans. Thirty-seven patients had bone and/or abdominal lymph node uptake, while 17 showed pelvic activity. Malignant disease was confirmed in all but one. Delayed SUVmax of bone metastases was significantly higher (p<0.0001 by paired t test) than that measured at <15 min, whereas no differences were observed between early and delayed SUVs of malignant lymph nodes or pelvic disease. Forty-six patients (PSA 0.12–14.3 ng/ml) showed negative FCH PET/CT scans. Of the negative PET/CT scans, 89% were obtained in patients with serum PSA <4 ng/ml and 87% in patients with a Gleason score <8. In none of these cases could recurrent tumour be proven clinically during a follow-up of 6 months. FCH PET/CT is not likely to have a significant impact on the care of prostate cancer patients with biochemical recurrence until PSA increases to above 4 ng/ml. However, in selected patients, FCH PET/CT helps to exclude distant metastases when salvage local treatment is intended.

[18F]fluorocholine PET/CT imaging for the detection of recurrent prostate cancer at PSA relapse: experience in 100 consecutive patients.

The aim of this prospective study was to compare the potential value of 18F fluorocholine (FCH) and 18F fluoride positron emission tomography (PET)–CT scanning for the detection of bony metastases from prostate cancer. Thirty-eight men (mean age, 69 ± 8 years) with biopsy-proven prostate cancer underwent both imaging modalities within a maximum interval of 2 weeks. Seventeen patients were evaluated preoperatively, and 21 patients were referred for post-operative evaluation of suspected recurrence or progression based on clinical algorithms. The number, sites and morphological patterns of bone lesions on 18F FCH and 18F fluoride PET–CT were correlated: Concordant lesions between the two modalities with corresponding changes on CT were considered to be positive for malignancy; discordant lesions were verified by follow-up examinations. The mean follow-up interval was 9.1 months. Overall, 321 lesions were evaluated in this study. In a lesion-based analysis, a relatively close agreement was found between these two imaging modalities for detection of malignant bone lesions (kappa = 0.57), as well as in a patient-based analysis (kappa = 0.76). Sixteen malignant sclerotic lesions with a high density were negative in both 18F FCH and 18F fluoride PET–CT [mean Hounsfield unit (HU), 1,148 ± 364]. There was also a significant correlation between tracer intensity by SUV and density of sclerotic lesions by HU both in 18F FCH PET–CT (r = −0.28, p < 0.006) and 18F fluoride PET–CT (r = −0.20, p < 0.05). The sensitivity, specificity and accuracy of PET–CT in the detection of bone metastases in prostate cancer was 81%, 93% and 86% for 18F fluoride, and 74% (p = 0.12), 99% (p = 0.01) and 85% for FCH, respectively. 18F FCH PET–CT led to a change in the management in two out of 38 patients due to the early detection of bone marrow metastases. 18F fluoride PET–CT identified more lesions in some patients when compared with 18F FCH PET–CT but did not change patient management. FCH PET–CT may be superior for the early detection (i.e. bone marrow involvement) of metastatic bone disease. In patients with FCH-negative suspicious sclerotic lesions, a second bone-seeking agent (e.g. 18F fluoride) is recommended. 18F fluoride PET–CT demonstrated a higher sensitivity than 18F FCH PET–CT, but the difference was not statistically significant. Furthermore, 18F fluoride PET could be also negative in highly dense sclerotic lesions, which presumably reflects the effect of treatment. It will be important to clarify in future studies whether these lesions are clinically relevant when compared with metabolically active bone metastases.

Detection of bone metastases in patients with prostate cancer by 18F fluorocholine and 18F fluoride PET–CT: a comparative study

Fluorocholine PET/CT changed the therapeutic care of 20% of patients at high risk for extracapsular extension.

18F choline PET/CT in the preoperative staging of prostate cancer in patients with intermediate or high risk of extracapsular disease: a prospective study of 130 patients.

Conventional imaging techniques have serious limitations in the detection, staging, and restaging of prostate carcinoma. Anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid (anti-18F-FACBC)is a synthetic l-leucine analog that has excellent in vitro uptake within the DU-145 prostate carcinoma cell line and orthotopically implanted prostate tumor in nude rats. There is little renal excretion compared with 18F-FDG. The present study examines anti-18F-FACBC uptake in patients with newly diagnosed and recurrent prostate carcinoma. Methods: Fifteen patients with a recent diagnosis of prostate carcinoma (n = 9) or suspected recurrence (n = 6) underwent 65-min dynamic PET/CT of the pelvis after intravenous injection of 300–410 MBq anti-18F-FACBC followed by static body images. Each study was evaluated qualitatively and quantitatively. Maximum standardized uptake values were recorded in the prostate or prostate bed, and within lymph nodes at 4.5 min (early) and 20 min (delayed), and correlated with clinical, imaging and pathologic follow-up. Time–activity curves were also generated for benign and malignant tissue. Results: In the 8 patients with newly diagnosed prostate carcinoma who underwent dynamic scanning, visual analysis correctly identified the presence or absence of focal neoplastic involvement in 40 of 48 prostate sextants. Pelvic nodal status correlated with anti-18F-FACBC findings in 7 of 9 patients and was indeterminate in 2 of 9. In all 4 patients in whom there was proven recurrence, visual analysis was successful in identifying disease (1 prostate bed, 3 extraprostatic). In 3 of these patients, 111In-capromab-pendetide had no significant uptake at nodal and skeletal foci. Malignant lymph node uptake in both the staging and restaging patients was significantly higher than benign nodal uptake. Though uptake faded with time, in all 6 patients with either lymph node metastases or recurrent prostate bed carcinoma, there was intense persistent uptake at 65 min. Conclusion: Anti-18F-FACBC is a promising radiotracer for imaging prostate carcinoma. Radiotracer uptake was demonstrated in primary and metastatic disease. Future research should investigate the mechanism of radiotracer uptake in normal and pathologic tissue and develop a clinical imaging strategy for initial staging and restaging.

https://jnm.snmjournals.org/content/jnumed/48/1/56.full.pdf

Initial Experience with the Radiotracer Anti-1-Amino-3-18F-Fluorocyclobutane-1-Carboxylic Acid with PET/CT in Prostate Carcinoma

This study compared 18F-fluorocholine uptake in malignant and benign areas of the prostate at 2 time points to determine the suitability of delayed or dual-phase 18F-fluorocholine PET for localizing malignancy in the prostate gland. Methods: Twenty-six men (15 newly diagnosed with prostate cancer, 2 with recurrent prostate cancer, 6 with no evidence of prostate cancer recurrence after treatment, and 3 with no history of prostate cancer) underwent dual-phase PET consisting of initial whole-body PET starting 7 min after injection of 3.3–4 MBq/kg of 18F-fluorocholine followed by 1-h delayed PET of the pelvis. Tracer uptake in the prostate on the initial and delayed images was measured on a sextant basis. Prostate biopsy or whole-prostate histologic examination after radical prostatectomy was used to classify a prostate sextant as a dominant malignant region or probable benign region. For each sextant, a retention index based on the measured maximum standardized uptake value (SUVmax) was calculated on the initial and delayed images. In 15 prostates with both benign and malignant sextants on histologic examination, a malignant-to-benign ratio of SUVmax was also calculated for each time point. Results: A dominant malignant region was found in 17 subjects, and a probable benign region was found in 24 subjects. The mean SUVmax for dominant malignant regions increased significantly between initial and delayed scans, from 7.6 to 8.6 (mean retention index, +14%; 95% confidence interval, 6%–22%; P = 0.002). The mean SUVmax for probable benign regions decreased significantly between initial and delayed scans, from 4.8 to 3.9 (mean retention index, −17%; 95% confidence interval, −10% to −23%, P

https://jnm.snmjournals.org/content/jnumed/47/2/262.full.pdf

Localization of Primary Prostate Cancer with Dual-Phase 18F-Fluorocholine PET

We present a novel hybrid miniature dual-cavity Fabry-Perot sensor for simultaneous pressure and temperature measurements. The pressure sensing cavity is composed of an UV-molded cavity covered by a metal/polymer composite diaphragm for achieving a high pressure sensitivity while maintaining a miniature sensor size. Another intrinsic polymer/silica cavity is adopted for temperature sensing, which enables a high temperature sensitivity even with a short cavity length due to the large thermal expansion of the polymer. The sensor is fabricated by using a unique UV molding process with simple and safe procedures. The overall sensor size is around 150 μm in diameter and 343 μm in length. Experimental studies show that the sensor exhibits a good linearity over a pressure range of 6.89 to 27.58 kPa with a pressure sensitivity of 0.0122 μm/kPa at 26 °C, and a temperature range of 26.0 °C to 50.0 °C with a temperature sensitivity of 0.0029 μm/°C. An optical signal processing method is developed to retrieve the two cavity length changes, which is demonstrated to have a better resolution and a faster speed than the conventional method. The sensor is expected to benefit many fronts that require simultaneous pressure and temperature measurements with minimum intrusiveness, especially for biomedical applications.

Hybrid Miniature Fabry–Perot Sensor with Dual Optical Cavities for Simultaneous Pressure and Temperature Measurements

Intensity modulated radiation therapy for prostate cancer with radiation dose augmentation guided by 18F-FCH PET imaging

/pdf/supersonic-combustion-diagnostics-with-dual-comb-36o9hr5r.pdf

Supersonic combustion diagnostics with dual comb spectroscopy

As infrared telescopes are finding evidence of methane in hot exoplanet atmospheres, it is becoming increasingly important to have accurate high-temperature methane absorption models. To evaluate and update several spectroscopic databases (HITRAN2016, HITEMP, ExoMol), we collected laboratory spectra of the methane icosad (6770–7570 cm-1) using a 200 MHz (0.0067 cm-1) dual frequency comb spectrometer. The pure methane data span 18 to 300 Torr and 296 to 1000 K. We found good agreement with the HITRAN2016 model spectrum at room temperature, and substantial mismatch between our spectra and all absorption models at elevated temperature. We present several updates to HITRAN2016 to improve agreement with the measured high-temperature spectra. Specifically, we assign 4283 lower-state energies which had previously been given a default value in HITRAN2016 ( E H I T ″ = 999 cm-1), update existing lower-state energies for 92 features, and add 293 new high-temperature features in order to improve HITRAN2016 above 300 K. Additionally, we update the band-wide line positions by ∼ 0.001 cm-1, the self-widths by +7%, and we estimate band-averaged temperature-dependence exponents for self-width (0.85) and self-shift (0.58). These measurements are an important step towards merging empirical and theoretical high-temperature methane databases, with the goal of enabling better understanding of exoplanet atmospheres.

David Yun

Papers

Localization of Primary Prostate Cancer with Dual-Phase 18F-Fluorocholine PET

Hybrid Miniature Fabry–Perot Sensor with Dual Optical Cavities for Simultaneous Pressure and Temperature Measurements

Intensity modulated radiation therapy for prostate cancer with radiation dose augmentation guided by 18F-FCH PET imaging

Supersonic combustion diagnostics with dual comb spectroscopy

Dual frequency comb absorption spectroscopy of CH4 up to 1000 Kelvin from 6770 to 7570 cm-1