Optimising (18)F-Choline PET/CT Acquisition Protocol in Prostate Cancer Patients

Assessment and Comparison of 18F-Fluorocholine PET and 99mTc-Sestamibi Scans in Identifying Parathyroid Adenomas: A Metaanalysis

Hyperparathyroidism is an endocrine disorder caused by one or more hyperfunctioning parathyroid glands. Current imaging consisting of ultrasound and 99mTc-sestamibi is imprecise, making localization difficult. 18F-fluorocholine (18F-FCH) PET has recently shown promise in presurgical localization of parathyroid adenomas. The primary aim of this study was to summarize the sensitivities and specificities of studies using 18F-FCH PET to localize hyperparathyroidism. A secondary aim was to summarize a subset of studies in which 99mTc-sestamibi scans were also used and to compare the performance of the 2 modalities. Methods: We searched the MEDLINE and EMBASE databases following the PRISMA (Preferred Reporting Items for Systematic Review and Metaanalysis) statement. Quality was assessed using the QUADAS-2 tool (Quality Assessment of Diagnostic Accuracy Studies). Twenty studies were included for quantitative assessment in our metaanalysis. A random-effects model and a hierarchic summary receiver-operating-characteristic model was used to summarize the sensitivity of 18F-FCH PET in detecting abnormal parathyroid adenomas. We used the same methodology to assess sensitivity of 99mTc-sestamibi, as a comparison to 18F-FCH PET. Results:18F-FCH PET had a high sensitivity, 0.97 (range, 0.96-0.98), for the detection of abnormal parathyroid adenomas. In the subpopulation for which both 18F-FCH and 99mTc-sestamibi were reported, 18F-FCH also had a higher sensitivity, 0.96 (0.94-0.98), than the 0.54 (0.29-0.79) reported for 99mTc-sestamibi (P < 0.001). Conclusion:18F-FCH PET demonstrates high localization accuracy in patients with hyperparathyroidism. This metaanalysis supports the use of 18F-FCH over 99mTc-sestamibi in patients with hyperparathyroidism.

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.

Biologically-Based Mathematical Modeling of Tumor Vasculature and Angiogenesis via Time-Resolved Imaging Data

Tumor-associated vasculature is responsible for the delivery of nutrients, removal of waste, and allowing growth beyond 2-3 mm3. Additionally, the vascular network, which is changing in both space and time, fundamentally influences tumor response to both systemic and radiation therapy. Thus, a robust understanding of vascular dynamics is necessary to accurately predict tumor growth, as well as establish optimal treatment protocols to achieve optimal tumor control. Such a goal requires the intimate integration of both theory and experiment. Quantitative and time-resolved imaging methods have emerged as technologies able to visualize and characterize tumor vascular properties before and during therapy at the tissue and cell scale. Parallel to, but separate from those developments, mathematical modeling techniques have been developed to enable in silico investigations into theoretical tumor and vascular dynamics. In particular, recent efforts have sought to integrate both theory and experiment to enable data-driven mathematical modeling. Such mathematical models are calibrated by data obtained from individual tumor-vascular systems to predict future vascular growth, delivery of systemic agents, and response to radiotherapy. In this review, we discuss experimental techniques for visualizing and quantifying vascular dynamics including magnetic resonance imaging, microfluidic devices, and confocal microscopy. We then focus on the integration of these experimental measures with biologically based mathematical models to generate testable predictions.

A Retrospective Comparative Study of Sodium Fluoride (NaF-18)-PET/CT and Fluorocholine (F-18-CH) PET/CT in the Evaluation of Skeletal Metastases in Metastatic Prostate Cancer Using a Volumetric 3-D Radiomics Analysis

Bone metastases are common in prostate cancer (PCa). Fluorocholine-18 (FCH) and sodium fluoride-18 (NaF) have been used to assess PCa associated skeletal disease in thousands of patients by demonstrating different mechanism of uptake-cell membrane (lipid) synthesis and bone mineralization. Here, this difference is characterized quantitatively in detail. Our study cohort consisted of 12 patients with advanced disease (> 5 lesions) (M) and of five PCa patients with no skeletal disease (N). They had routine PET/CT with FCH and NaF on consecutive days. Skeletal regions in CT were used to co-register the two PET/CT scans. Bone 3-D volume of interest (VOI) was defined on the CT of PET with a threshold of HU > 150, and sclerotic/dense bone as HU > 600, respectively. Additional VOIs were defined on PET uptake with the threshold values on both FCH (SUV > 3.5) and NaF (SUV > 10). The pathologic skeletal volumes for each technique (CT, HU > 600), NaF (SUV > 10) and FCH (SUV > 3.5) were developed and analyzed. The skeletal VOIs varied from 5.03 L to 7.31 L, whereas sclerotic bone VOIs were from 0.88 L to 2.99 L. Total choline kinase (cell membrane synthesis) activity for FCH (TCA) varied from 0.008 to 4.85 [kg] in M group and from 0.0006 to 0.085 [kg] in N group. Total accelerated osteoblastic (bone demineralization) activity for NaF (TBA varied from 0.25 to 13.6 [kg] in M group and varied from 0.000 to 1.09 [kg] in N group. The sclerotic bone volume represented only 1.86 ± 1.71% of the pathologic FCH volume and 4.07 ± 3.21% of the pathologic NaF volume in M group, and only 0.08 ± 0.09% and 0.18 ± 0.19% in N group, respectively. Our results suggest that CT alone cannot be used for the assessment of the extent of active metastatic skeletal disease in PCa. NaF and FCH give complementary information about the activity of the skeletal disease, improving diagnosis and disease staging.

Standardization of acquisition protocols using PET/CT with 18F-Choline in prostate cancer

AIM

To standardize acquisition protocols for ¹⁸F-Choline PET/CT to prevent from urine interference, to determine the best time point for the whole-body study, and to assess whether "dual point" acquisition allows for differentiating malignant vs. benign lesions.

METHODS

One hundred consecutive patients with prostate cancer were prospectively studied. Immediately after ¹⁸F-Choline injection, a pelvis study was acquired, and a whole-body was subsequently obtained 1 and 2 hours p.i. Mean SUVmax was obtained in regions and for every sequential imaging. Mean analysis (χ²) and SUV percentage change (2/1 hours; 1 hours/0 min) were obtained. Metabolic pattern dynamics were assessed: accumulative vs. clearance. Patient follow-up after therapy and directed classification whenever ethically possible were performed.

RESULTS

Fifty-three prostate foci, without disturbing urinary activity was ever found on early images. Accumulative pattern in 42, with percentage increase was: 0 min/1 hour: +16.7% (χ²0.94); 1/2 hours: +10,0% (χ² 0.83). Clearance pattern in 11, with percentage decrease: 0 min/1 hour: -21.4% (χ²0.91): -7.7% (χ²0.85), corresponding in 7 to initial staging and in 4 post-radiotherapy biochemical recurrence. Every infradiaphragmatic uptake (n: 24) showed accumulative pattern, with percentage increase of +9.1% (χ²0.97), all of them depicted on early imaging. As for 12 supradiaphragmantic uptake, 8 of them showed clearance pattern with percentage decrease: -13.0% (χ²0.95). Accumulative pattern showed in 4 of them with percentage increase +13.0% (χ² 0.96), thus being assessed as invasive/malignant. Every bone uptake (n: 18) showed accumulative pattern, with percentage increase: +17.1% (χ²0.95), all of them depicted on 1 hour imaging.

CONCLUSIONS

As for prostate assessment is concerned, dual point at 0 min/1 hour proved to be the best procedure. As for supradiaphragmatic lymph-nodes detection, dual point with 1/2 hours performed best. As for infradiaphragmatic and bone involvement, as well as for inconclusive findings, the 2 hour imaging increased our diagnostic confidence.

Comparison of 18F-Choline PET/CT and MRI functional parameters in prostate cancer

AIM

¹⁸F-Choline (FCH) uptake parameters are strong indicators of aggressive disease in prostate cancer. Functional parameters derived by magnetic resonance imaging (MRI) are also correlated to aggressive disease. The aim of this work was to evaluate the relationship between metabolic parameters derived by FCH PET/CT and functional parameters derived by MRI.

MATERIALS AND METHODS

Fourteen patients with proven prostate cancer who underwent FCH PET/CT and multiparametric MRI were enrolled. FCH PET/CT consisted in a dual phase: early pelvic list-mode acquisition and late whole-body acquisition. FCH PET/CT and multiparametric MRI examinations were registered and tumoral volume-of-interest were drawn on the largest lesion visualized on the apparent diffusion coefficient (ADC) map and projected onto the different multiparametric MR images and FCH PET/CT images. Concerning the FCH uptake, kinetic parameters were extracted with the best model selected using the Akaike information criterion between the one- and two-tissue compartment models with an imaging-derived plasma input function. Other FCH uptake parameters (early SUVmean and late SUVmean) were extracted. Concerning functional parameters derived by MRI scan, cell density (ADC from diffusion weighting imaging) and vessel permeability (K_trans and V_e using the Tofts pharmakinetic model from dynamic contrast-enhanced imaging) parameters were extracted. Spearman's correlation coefficients were calculated to compare parameters.

RESULTS

The one-tissue compartment model for kinetic analysis of PET images was selected. Concerning correlation analysis between PET parameters, K₁ was highly correlated with early SUVmean (r = 0.83, p < 0.001) and moderately correlated with late SUVmean (r = 0.66, p = 0.010) and early SUVmean was highly correlated with late SUVmean (r = 0.90, p < 0.001). No significant correlation was found between functional MRI parameters. Concerning correlation analysis between PET and functional MRI parameters, K₁ (from FCH PET/CT imaging) was moderately correlated with K_trans (from perfusion MR imaging) (r = 0.55, p = 0.041).

CONCLUSIONS

No significant correlation was found between FCH PET/CT and multiparametric MRI metrics except FCH influx which is moderately linked to the vessel permeability in prostate cancer.

Optimization of temporal sampling for 18F-choline uptake quantification in prostate cancer assessment

Background

Suboptimal temporal sampling of time-activity curves (TAC) from dynamic ¹⁸F-fluoromethylcholine (FCH) PET images may introduce bias in quantification of FCH uptake in prostate cancer assessment. We sought to define an optimal temporal sampling protocol for dynamic FCH PET imaging.

Seven different time samplings were tested: 5 × 60″, 10 × 30″, 15 × 15″–1 × 75″, 6 × 10″–8 × 30″, 12 × 5″–8 × 30″; 10 × 5″–4 × 10″–3 × 20″–5 × 30″, and 8 × 3″–8 × 12″–6 × 30″. First, the irreversible and reversible one-tissue compartment model with blood volume parameter (VB) (respectively, 1T1K+VB and 1T2k+VB, with K1 = transfer coefficient from the arterial blood to the tissue compartment and k2 = transfer coefficient from the tissue compartment to the arterial blood) were compared for 37 lesions from 32 patients who underwent FCH PET imaging for initial or recurrence assessment of prostate cancer, and the model was selected using the Akaike information criterion. To determine the optimal time sampling, K1 values extracted from 1000 noisy-simulated TAC using Monte Carlo method from the seven different time samplings were compared to a target K1 value which is the average of the K1 values extracted from the 37 lesions using an imaging-derived input function for each patient. K1 values extracted with the optimal time sampling for each tumoral lesion were compared to K1 values extracted from each of the other time samplings for the 37 lesions.

Results

The 1T2k + VB model was selected. The target K1 value as the objective was 0.506 mL/ccm/min (range 0.216–1.246). Results showed a significant difference between K1 values from the simulated TAC with the seven different time samplings analyzed. The closest K1 value from the simulated TAC to the target K1 value was obtained by the 12 × 5″–8 × 30″ time sampling. Concerning the clinical validation, K1 values extracted from the optimal time sampling (12 × 5″–8 × 30″) were significantly different with K1 values extracted from the other time samplings, except for the comparison with K1 values extracted from the 10 × 5″–4 × 10″–3 × 20″–5 × 30″ time sampling.

Conclusions

A two-phase framing of dynamic PET reconstruction with frame durations of 5 s (blood phase) and 30 s (tissue phase) could be used to sample the TAC for uptake quantification in prostate cancer assessment.

[18F]Fluoromisonidazole PET in rectal cancer

BACKGROUND

There is an increasing interest in developing predictive biomarkers of tissue hypoxia using functional imaging for personalised radiotherapy in patients with rectal cancer that are considered for neoadjuvant chemoradiotherapy (CRT). The study explores [18F]fluoromisonidazole ([18F]FMISO) positron emission tomography (PET) scans for predicting clinical response in rectal cancer patients receiving neoadjuvant CRT.

METHODS

Patients with biopsy-proven rectal adenocarcinoma were imaged at 0-45 min, 2 and 4 h, at baseline and after 8-10 fractions of CRT (week 2). The first 6 patients did not receive an enema (the non-enema group) and the last 4 patients received an enema before PET-CT scan (the enema group). [18F]FMISO production failed on 2 occasions. Static PET images at 4 h were analysed using tumour-to-muscle (T:M) SUVmax and tumour-to-blood (T:B) SUVmax. The 0-45 min dynamic PET scans were analysed using Casciari model to report hypoxia and perfusion. Akaike information criteria (AIC) were used to compare data fittings for different pharmacokinetic models. Pathological tumour regression grade was scored using American Joint Committee on Cancer (AJCC) 7.0. Shapiro-Wilk test was used to evaluate the normality of the data.

RESULTS

Five out of eleven (5/11) patients were classed as good responders (AJCC 0/1 or good clinical response) and 6/11 as poor responders (AJCC 2/3 or poor clinical response). The median T:M SUVmax was 2.14 (IQR 0.58) at baseline and 1.30 (IQR 0.19) at week 2, and the corresponding median tumour hypoxia volume was 1.08 (IQR 1.31) cm3 and 0 (IQR 0.15) cm3, respectively. The median T:B SUVmax was 2.46 (IQR 1.50) at baseline and 1.61 (IQR 0.14) at week 2, and the corresponding median tumour hypoxia volume was 5.68 (IQR 5.86) cm3 and 0.76 (IQR 0.78) cm3, respectively. For 0-45 min tumour modelling, the median hypoxia was 0.92 (IQR 0.41) min-1 at baseline and 0.70 (IQR 0.10) min-1 at week 2. The median perfusion was 4.10 (IQR 1.71) ml g-1 min-1 at baseline and 2.48 (IQR 3.62) ml g-1 min-1 at week 2. In 9/11 patients with both PET scans, tumour perfusion decreased in non-responders and increased in responders except in one patient. None of the changes in other PET parameters showed any clear trend with clinical outcome.

CONCLUSIONS

This pilot study with small number of datasets revealed significant challenges in delivery and interpretation of [18F]FMISO PET scans of rectal cancer. There are two principal problems namely spill-in from non-tumour tracer activity from rectal and bladder contents. Emphasis should be made on reducing spill-in effects from the bladder to improve data quality. This preliminary study has shown fundamental difficulties in the interpretation of [18F]FMISO PET scans for rectal cancer, limiting its clinical applicability.

The Use of Published Clinical Study Reports to Support U.S. Food and Drug Administration Approval of Imaging Agents

Pharmaceutical companies typically perform prospective, multicenter phase 3 clinical studies to support approval of a new imaging agent by the U.S. Food and Drug Administration (FDA). In uncommon situations, the FDA has approved imaging agents based solely, or in large part, on the clinical study experience described in published reports, including reports of exploratory (i.e., phase 1 or 2) studies performed at a single clinical site. We performed a survey of published reports to assess the potential of the reported information to support FDA approval of a commonly cited investigational imaging agent. Our survey revealed critical data limitations in most publications, all of which reported exploratory clinical studies. Here we summarize the precedent for FDA approval of imaging agents using effectiveness data from publications, FDA guidance, and our experience in reviewing publications. We also present a key-data checklist for investigators to consider in the design, conduct, and reporting of exploratory clinical studies for publication. We encourage editors and peer reviewers to consider requiring these key data when reviewing these reports for publication.

Acquisition with (11)C-choline and (18)F-fluorocholine PET/CT for patients with biochemical recurrence of prostate cancer: a systematic review and meta-analysis

The objective of the systematic review and meta-analysis was to evaluate whether the choice between two radiotracers, (11)C-choline ((11)C-cho) and (18)F-fluorocholine ((18)F-FCH) for PET/CT, and different acquisition protocols contributed to detect metastases for patients with biochemical recurrence of prostate cancer after radical prostatectomy or radiotherapy. We searched in January 2016 in Pubmed and Embase for articles that had used radiolabeled choline PET/CT in restaging. The meta-analysis evaluated technical and clinical aspects. Across 18 articles 1 219 of 2 213 patients (54.9 %) had a positive radiolabeled PET/CT image. Mean of the mean/median restaging PSA levels was 3.6 ± 2.7 ng/mL (range 0.5-10.7 ng/mL). Six articles with (11)C-cho PET/CT had a radiation activity of 561 ± 122 MBq and it was 293 ± 47 MBq in 12 articles with (18)F-FCH PET/CT. The difference was significant (P = 0.007, t test). Uptake time was 5 min in articles with (11)C-cho PET/CT and it was 29 ± 24 min in articles with (18)F-FCH PET/CT. The difference was significant (P = 0.02, t test). Thereby the detection rates of metastatic sites in articles with (11)C-cho (30 ± 5 %) and (18)F-FCH (39 ± 5 %) did not differ significantly (P = 0.26, t test). In linear regression analyses of the articles, the radiation activity of (11)C-cho and (18)F-FCH was not significantly associated with the detection rate of metastatic sites (P = 0.75 and P = 0.60). Restaging with radiolabeled choline PET/CT detected metastatic sites for patients with biochemical recurrence and PSA levels of 1-10 ng/mL at clinically relevant level. The choice between the two choline radiotracers and different acquisition protocols had no significant impact on detection.

Impact and correction of the bladder uptake on 18 F-FCH PET quantification: a simulation study using the XCAT2 phantom

The spill-in counts from neighbouring regions can significantly bias the quantification over small regions close to high activity extended sources. This effect can be a drawback for (18)F-based radiotracers positron emission tomography (PET) when quantitatively evaluating the bladder area for diseases such as prostate cancer. In this work, we use Monte Carlo simulations to investigate the impact of the spill-in counts from the bladder on the quantitative evaluation of prostate cancer when using (18)F-Fluorcholine (FCH) PET and we propose a novel reconstruction-based correction method. Monte Carlo simulations of a modified version of the XCAT2 anthropomorphic phantom with (18)F-FCH biological distribution, variable bladder uptake and inserted prostatic tumours were used in order to obtain simulated realistic (18)F-FCH data. We evaluated possible variations of the measured tumour Standardized Uptake Value (SUV) for different values of bladder uptake and propose a novel correction by appropriately adapting image reconstruction methodology. The correction is based on the introduction of physiological background terms on the reconstruction, removing the contribution of the bladder to the final image. The bladder is segmented from the reconstructed image and then forward-projected to the sinogram space. The resulting sinograms are used as background terms for the reconstruction. SUV max and SUV mean could be overestimated by 41% and 22% respectively due to the accumulation of radiotracer in the bladder, with strong dependence on bladder-to-lesion ratio. While the SUVs measured under these conditions are not reliable, images corrected using the proposed methodology provide better repeatability of SUVs, with biases below 6%. Results also showed remarkable improvements on visual detectability. The spill-in counts from the bladder can affect prostatic SUV measurements of (18)F-FCH images, which can be corrected to less than 6% using the proposed methodology, providing reliable SUV values even in the presence of high radioactivity accumulation in the bladder.

Optimized protocol for (18)F-choline PET/CT in patients with biochemically relapsed prostate cancer: experiences on 250 consecutive cases

PURPOSE

We review acquisition F-choline PET/CT methodology, evaluate a new F-choline acquisition protocol for prostate cancer (PC), and propose a standardized acquisition protocol on F-choline in PC patients.

MATERIALS

Two hundred fifty consecutive PC patients (mean age 72 years, mean PSA 7.9 ng/mL) were prospectively evaluated with F-choline PET/CT. An early scan of the pelvis (1 bed position of 4 minutes) was followed by a whole-body scan at 1 hour. Early and 1 delayed hour images of the pelvis were compared.

RESULTS

Twenty-one percent of patients (n = 57) with positive F-choline demonstrated abnormal local uptake; 18% of patients (n = 45) showed distant localization only; 23% of patients (n = 53) had both local and distant localization; 38% of patients (n = 38) did not show any pathological uptake. All early images showed absence of radioactive urine in ureters, bladder, or urethra with satisfactory visualization of the prostatic region. Considering the group of patients with local uptake only, the prostatic region uptake, confirmed by late images, was better visualized in the early phase in 32/57 cases (SUVmax 12.4 ± 3.2 vs. 7.3 ± 5.2, P <0.01). Instead distant lesions were visualized on both early and late images with similar uptakes values (SUVmax 9.8 ± 4.1 vs. 10.3 ± 4.5, P = N.S.).

CONCLUSION

Early F-choline images improve pelvic prostate cancer lesion clarity. All pathologic pelvic deposits (prostate, lymph nodes, bone) were visualized both in the early and late images.

Detection of local recurrence of prostate cancer after radical prostatectomy: Is there a role for early ¹⁸F-FCH PET/CT?

AIM

To investigate the diagnostic performance of early acquisition compared to late imaging for the detection of local recurrence of prostate cancer by means of ¹⁸F-FCH PET/CT.

MATERIALS AND METHODS

99 patients with radical prostatectomy (mean PSA 3.9 ± 5.03) were subjected to early dynamic PET/CT acquisition of the pelvis and a whole body PET/CT in the same exam session. None of the patients examined was subjected to radiotherapy for local or distant recurrence. All the subjects were taken off hormonal therapy.

RESULTS

58 subjects did not show local recurrence in both early and late acquisition, 22 were positive in both modalities, 10 showed a positive early and a negative late acquisition while 9 showed a negative early and a positive late acquisition (Cohen's k = 0.558). When the results of imaging modalities were considered separately, sensitivity, specificity, positive predictive value and negative predictive value resulted: 78.9, 96.7, 93.8 and 88.1 % for early acquisition and 73.7, 95.1, 90.3 and 85.3 % for late acquisition, respectively. When the results of early and late acquisition were considered together, results were 97.4, 93.4, 90.2 and 98.3 %, respectively.

CONCLUSIONS

The combination of early acquisition with late acquisition lead to an increase of the diagnostic accuracy of ¹⁸F-FCH PET/CT for the diagnosis of local recurrence in prostate cancer.

Dual-phase 11C-choline PET/computed tomography in the early evaluation of prostate cancer recurrence

PURPOSE

The aim of this study was to assess dual-phase 11C-choline PET/computed tomography (CT) for differentiating benign from malignant lesions in patients with biochemical recurrence of prostate cancer.

MATERIALS AND METHODS

We prospectively studied 56 patients with prostate cancer treated by surgery (n=22) or radiotherapy (n=34) who had hypermetabolic foci on 11C-choline PET/CT determined for biochemical recurrence (prostate-specific antigen 1.23-9.9 ng/ml). We used the dual-phase technique, calculating the standardized uptake value (SUV) for early (SUVearly) and late (SUVdelay) acquisitions and the difference between the two (SUVvariation) to determine whether tracer uptake remained stable or increased (accumulative pattern) or decreased (washout pattern). We used t-tests to compare mean and receiver operating characteristic curve analysis (SUVearly/SUVdelay/SUVvariation vs. benign/malignant).

RESULTS

We identified 106 hypermetabolic foci (34 local, 10 inguinal, 34 infradiaphragmatic, 14 supradiaphragmatic, and 14 in bone). We identified 34 local foci (eight after prostatectomy and 26 after radiotherapy). The eight postsurgical foci had an accumulative pattern and recurrence was confirmed (three histology, five follow-up). Of the 26 postradiotherapy foci, three had a washout pattern and follow-up ruled out recurrence; 23 had an accumulative pattern and recurrence was confirmed (14 histology, nine follow-up). The 10 inguinal foci had a washout pattern and were reactive (three histology, seven follow-up). The 34 infradiaphragmatic foci had an accumulative pattern and were malignant (34 follow-up). Of the 14 supradiaphragmatic foci, the three with a washout pattern were benign (three histology) and the 11 with an accumulative pattern were malignant (11 histology). Of the 14 foci in bone, two had a washout pattern and corresponded with signs of spondyloarthropathy. On the receiver operating characteristic curve analysis, SUVvariation best discriminated benign from malignant lesions [area under the curve (AUC)=0.993], followed by SUVdelay (AUC=0.933) and finally SUVearly (AUC=0.665).

CONCLUSION

Dual-phase PET/CT with 11C-choline is technically feasible despite this tracer's short physical half-life and is useful for discriminating benign from malignant lesions. SUVvariation accurately discriminated between benign and malignant lesions.

F-18 Choline PET angiography of the pelvic arteries: evaluation of image quality and comparison with contrast-enhanced CT

PURPOSE

The purpose was to show the feasibility of F-18 choline positron emission tomography (PET) angiography for the evaluation of abdominal and iliac arteries.

METHODS

Thirty-five patients were examined and image quality was scored. Findings were correlated with contrast-enhanced computed tomography.

RESULTS

Image quality was best in the aorta and common iliac arteries (100% and 93% of vessels). Negative predictive values of PET angiography were excellent (100%), and positive predictive values were impaired by disease overestimation.

CONCLUSION

PET angiography is technically feasible and of good image quality in large arteries. In selected cases, it may become an alternative to established angiographic methods.

New acquisition protocol of 18F-choline PET/CT in prostate cancer patients: review of the literature about methodology and proposal of standardization

Purpose. (1) To evaluate a new acquisition protocol of ¹⁸F-choline (FCH) PET/CT for prostate cancer patients (PC), (2) to review acquisition ¹⁸F-choline PET/CT methodology, and (3) to propose a standardized acquisition protocol on FCH PET/CT in PC patients. Materials. 100 consecutive PC patients (mean age 70.5 years, mean PSA 21.35 ng/mL) were prospectively evaluated. New protocol consisted of an early scan of the pelvis immediately after the injection of the tracer (1 bed position of 4 min) followed by a whole body scan at one 1 hour. Early and 1 hour images were compared for interfering activity and pathologic findings. Results. The overall detection rate of FCH PET/CT was 64%. The early static images of the pelvis showed absence of radioactive urine in ureters, bladder, or urethra which allowed a clean evaluation of the prostatic fossae. Uptake in the prostatic region was better visualized in the early phase in 26% (7/30) of cases. Other pelvic pathologic findings (bone and lymph nodes) were visualized in both early and late images. Conclusion. Early ¹⁸F-choline images improve visualization of abnormal uptake in prostate fossae. All pathologic pelvic deposits (prostate, lymph nodes, and bone) were visualized in both early and late images.

Is the detection rate of 18F-choline PET/CT influenced by androgen-deprivation therapy?

PURPOSE

To evaluate if the detection rate (DR) of (18)F-choline (18F-CH) PET/CT is influenced by androgen-deprivation therapy (ADT) in patients with prostate cancer (PC) already treated with radical intent and presenting biochemical relapse.

MATERIALS AND METHODS

We have retrospectively evaluated (18)F-CH PET/CT scans of 325 consecutive PC patients enrolled in the period November 2009 to December 2012 previously treated with radical intent and referred to our centre to perform (18)F-CH PET/CT for biochemical relapse. Two different groups of patients were evaluated. group A included the whole sample of 325 patients (mean age 70 years, range: 49-86) who presented trigger PSA between 0.1 and 80 ng/ml (mean 5.5 ng/ml), and group B included 187 patients (mean age 70 years, range 49-86) with medium-low levels of trigger PSA ranging between 0.5 and 5 ng/ml (mean PSA 2.1 ng/ml); group B was chosen in order to obtain a more homogeneous group of patients in terms of PSA values also excluding both very low and very high PSA levels avoiding the "a priori" higher probability of negative or positive PET scan, respectively. At the time of examination, 139 patients from group A and 72 patients from group B were under ADT: these patients were considered to be hormone-resistant PC patients because from their oncologic history (>18 months) an increase of PSA levels emerged despite the ongoing ADT. The relationship between (18)F-CH PET/CT findings and possible clinical predictors was investigated using both univariate and multivariate binary logistic regression analyses, including trigger PSA and ADT.

RESULTS

Considering the whole population, overall DR of (18)F-CH PET was 58.2 % (189/325 patients). In the whole sample of patients (group A), both at the univariate and multivariate logistic regression analysis, trigger PSA and ADT were significantly correlated with the DR of (18)F-CH PET (p < 0.05). Moreover, the DR in patients under ADT (mean PSA 7.8 ng/ml) was higher than in patients not under ADT (mean PSA 3.9 ng/ml), (DR was 70.5 % and 48.9 %, respectively; p < 0.001), therefore, demonstrating the existence of a significant correlation between the DR of (18)F-CH PET and ADT. In group B patients only trigger PSA resulted a reliable predictor of the (18)F-CH positivity, since ADT was not correlated to the DR of (18)F-CH PET (p = 0.061). Also in group B the DR of (18)F-CH PET in patients under ADT was higher than in patients not under ADT (65.3 % and 51.3 %, respectively) but the difference was not significant without a statistically significant correlation in the Mann Whitney test (p = 0.456) therefore, suggesting the lack of correlation between DR (18)F-CH PET/CT and ADT.

CONCLUSION

Similarly to previous published studies, in our series the overall DR of (18)F-CH PET/CT was 58 % and was significantly correlated to trigger PSA. The most important finding of the present study is that ADT does not negatively influence DR of (18)F-CH PET/CT in PC patients with biochemical relapse; therefore, it can be suggested that it is not necessary to withdraw ADT before performing (18)F-CH PET/CT.

First imaging results of an intraindividual comparison of (11)C-acetate and (18)F-fluorocholine PET/CT in patients with prostate cancer at early biochemical first or second relapse after prostatectomy or radiotherapy

PURPOSE

(18)F-Fluorocholine (FCH) and (11)C-acetate (ACE) PET are widely used for detection of recurrent prostate cancer (PC). We present the first results of a comparative, prospective PET/CT study of both tracers evaluated in the same patients presenting with recurrence and low PSA to compare the diagnostic information provided by the two tracers.

METHODS

The study group comprised 23 patients studied for a rising PSA level after radical prostatectomy (RP, 7 patients, PSA ≤ 3 ng/ml), curative radiotherapy (RT, 7 patients, PSA ≤ 5 ng/ml) or RP and salvage RT (9 patients, PSA ≤ 5 ng/ml). Both FCH and ACE PET/CT scans were performed in a random sequence a median of 4 days (range 0 to 11 days) apart. FCH PET/CT was started at injection (307 ± 16 MBq) with a 10-min dynamic acquisition of the prostate bed, followed by a whole-body PET scan and late (45 min) imaging of the pelvis. ACE PET/CT was performed as a double whole-body PET scan starting 5 and 22 min after injection (994 ± 72 MBq), and a late view (45 min) of the prostate bed. PET/CT scans were blindly reviewed by two independent pairs of two experienced nuclear medicine physicians, discordant subgroup results being discussed to reach a consensus for positive, negative end equivocal results.

RESULTS

PET results were concordant in 88 out of 92 local, regional and distant findings (Cohen's kappa 0.929). In particular, results were concordant in all patients concerning local status, bone metastases and distant findings. Lymph-node results were concordant in 19 patients and different in 4 patients. On a per-patient basis results were concordant in 22 of 23 patients (14 positive, 5 negative and 3 equivocal). In only one patient was ACE PET/CT positive for nodal metastases while FCH PET/CT was overall negative; interestingly, the ACE-positive and FCH-negative lymph nodes became positive in a second FCH PET/CT scan performed a few months later.

CONCLUSION

Overall, ACE and FCH PET/CT showed excellent concordance, on both a per-lesion and a per-patient basis, suggesting that both tracers perform equally for recurrent prostate cancer staging.

Role of ¹⁸F-choline PET/CT in suspicion of relapse following definitive radiotherapy for prostate cancer

PURPOSE

The aims of the study were (a) to evaluate the diagnostic role, by means of positive detection rate (PDR), of ¹⁸F-choline (CH) positron emission tomography (PET)/CT in patients with prostate cancer treated with radiotherapy, with curative intent, and suspicion of relapse during follow-up, (b) to correlate the PDR with trigger prostate-specific antigen (PSA), (c) to investigate the possible influence of androgen deprivation therapy (ADT) at the time of scan on PDR and (d) to assess distribution of metastatic spread.

METHODS

¹⁸F-CH PET/CT exams from 46 consecutive patients (mean age 71.3 years, range 51-84 years) with prostate cancer (mean Gleason score 6.4, range 5-8) previously treated by definitive radiotherapy and with suspicion of relapse with negative or inconclusive conventional imaging were retrospectively evaluated. Of the 46 patients, 12 were treated with brachytherapy and 34 with external beam radiation therapy. Twenty-three patients were under ADT at the time of the examination. Trigger PSA was measured within 1 month before the exam (mean value 6.5 ng/ml, range 1.1-49.4 ng/ml). Patients were subdivided into four groups according to their PSA level: 1.0 < PSA ≤ 2.0 ng/ml (11 patients), 2.0 < PSA ≤ 4.0 ng/ml (16 patients), 4.0 < PSA ≤ 6.0 ng/ml (9 patients) and PSA > 6.0 ng/ml (10 patients). Correlation between ADT and PDR was investigated as well as between PSA and distribution of metastatic spread.

RESULTS

The overall PDR of ¹⁸F-CH PET/CT was 80.4% (37/46 patients), increasing with the increase of trigger PSA. PDR of ¹⁸F-CH PET/CT is not influenced by ADT (p = 0.710) even if PET performed under ADT demonstrated an overall higher PDR (82.6%). The majority of the patients (59%, 22/37 patients) showed local relapse only, confined to the prostatic bed; 22% of the PET/CT-positive patients (8/37 patients) showed distant relapse only (bone localizations in all of them), while the remaining 19% (7/37 patients) showed both local and distant (lymph node and bone) spread.

CONCLUSION

¹⁸F-CH PET/CT showed a high overall detection rate (80%), proportional to the trigger PSA (both for local and distant relapse) not influenced by ADT. ¹⁸F-CH PET/CT is proposed as a first-line imaging procedure in restaging prostate cancer patients primarily treated with radiotherapy.