Abstract
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 < 0.001). The mean malignant-to-benign ratio increased significantly, from 1.4 on the initial scan to 1.8 on the delayed scan (P = 0.003). The areas under the receiver operating characteristic curves for distinguishing dominant malignant regions from probable benign regions based on initial SUVmax, delayed SUVmax, and retention index were 0.81, 0.92, and 0.93, respectively. Conclusion: On dual-phase PET of the prostate, areas of malignancy consistently demonstrated stable or increasing 18F-fluorocholine uptake, whereas most areas containing benign tissue demonstrated decreasing uptake. Delayed or dual-phase imaging after injection of 18F-fluorocholine may improve the performance of 18F-fluorocholine PET for localizing malignant areas of the prostate.
Prostate cancer is the second leading cause of cancer death in American men older than 50 y. Potentially curative treatment options for organ-confined prostate cancer include radical prostatectomy and radiation therapy. However, these definitive treatments are not without significant clinical side effects. To optimally treat subjects at this early stage, knowledge of the location and extent of cancer within the prostate may prove useful. For example, the locations of malignant sites within the prostate could be incorporated into a radiation therapy strategy to augment radiation dose to malignant areas while maintaining a safer dose to sensitive critical structures (1,2). Because the success rate and morbidity of prostate radiation therapy is directly related to radiation dose (3), such an individualized approach could conceivably improve both the safety and the efficacy of this method of treatment.
Unfortunately, despite advances in the technology of ultrasound, CT, and MRI, it remains difficult to locate malignant sites within the prostate (4). This difficulty in localization extends to sampling of the prostate at biopsy, which may detect only 50% of the malignant areas found on histologic examination of the whole prostate (5). A false-negative cancer detection rate exceeding 20% for transrectal ultrasound-guided prostate sextant (i.e., 6 regions) biopsy often makes it necessary to consider repeating biopsies in subjects with persistently elevated serum levels of prostate-specific antigen (PSA) and negative initial biopsy results (6,7). Unfortunately, simply increasing the number of biopsy samples does not necessarily result in higher detection rates (8). Because structure-based imaging methods seem limited in their ability to locate cancer in the prostate, it is worthwhile to explore imaging methods that have a molecular or biochemical basis.
Several lines of research suggest the choline metabolic pathway to be a promising imaging target for prostate cancer (9–15). The detection of primary and metastatic prostate cancer using PET and radiolabeled analogs of choline was first demonstrated by Hara et al. using 11C-choline and 18F-fluoroethylcholine (16,17). Another 18F-labeled compound, fluorocholine, has also shown potential as an imaging agent for prostate cancer, with in vitro phosphorylation rates comparable to those of natural choline (18–22). In comparison to the commonly used oncologic tracer 18F-FDG, 18F-fluorocholine has demonstrated higher avidity for both androgen-dependent and androgen-independent prostate cancer (21). Areas of increased 18F-fluorocholine uptake within the prostate have also correlated well with areas of malignancy on prostate biopsy (20). On the basis of these preliminary results, PET with 18F-labeled choline analogs offers potential clinical value for localizing and staging prostate cancer.
In studies of 18F-fluorocholine PET, scanning usually commences after a relatively brief delay (2–10 min) after tracer injection. (18–21). The use of relatively short uptake intervals is supported by studies demonstrating rapid blood-pool clearance and tissue uptake of 18F-fluorocholine, as well as rapid phosphorylation by the enzyme choline kinase (18,19). Immediate imaging may also avoid potential imaging artifacts caused by accumulated 18F radioactivity in the urinary bladder. However, the optimal timing for prostate PET using 18F-fluorocholine has not yet been systematically evaluated, and the metabolism and clearance of 18F-fluorocholine in benign and malignant tissue is not yet fully understood. For example, the cause of transient uptake and clearance of 18F-fluorocholine from benign lymph nodes, in contrast to more durable retention in malignant sites, is not known (21). Although the rapid distribution of 18F-fluorocholine may permit PET to be performed almost immediately after injection, delayed imaging could potentially improve lesion contrast in some areas of the body. The aim of this study was to evaluate whether 1-h delayed 18F-fluorocholine PET could increase contrast between benign and malignant areas in the prostate.
MATERIALS AND METHODS
Subjects
The institutional review board approved the study before it began. Informed consent was obtained from all subjects before they entered the study. Twenty-six sequential subjects underwent dual-phase PET with 18F-fluorocholine at our institution between July 2004 and June 2005. Twenty-three subjects had a history of prostate cancer, and 15 of these subjects had not yet received treatment for prostate cancer before PET. Of the remainder, 2 had undergone previous external-beam radiation therapy but had biopsy-proven recurrence in the prostate, and 6 had no clinical or biochemical (i.e., increasing serum PSA levels) evidence of recurrent disease after treatments that included radical prostatectomy (subject 22), external-beam radiation therapy (subjects 18, 19, 20, 23), brachytherapy (subject 20), and androgen suppression (subjects 18, 22, 23). For subjects who had not yet been treated, PET was performed within 8 wk of diagnosis. With the exception of 1 subject with bone metastases (subject 17), no subject had clinical or radiographic evidence of extraprostatic disease at the time of PET. In addition, 3 subjects who did not have a history of prostate cancer underwent dual-phase PET with 18F-fluorocholine. Two of these subjects had a history of primary brain tumor, and 1 did not have a history of cancer.
Synthesis of 18F-Fluorocholine
The radioactive tracer 18F-fluorocholine was synthesized by fluorination of ditosylmethane with 18F, followed by alkylation of fluorotosylmethane with dimethyl ethanol amine. The synthesis was automated and performed at an on-site cyclotron laboratory using a chemical process control unit (CTI/Siemens) (23). The radiochemical purity was greater than 99%.
PET
PET was performed using an SHR-22000 whole-body PET instrument (Hamamatsu Photonics). Subjects were positioned supine in the PET scanner. Whole-body transmission scans were acquired using two 68Ge rod sources over 5 fields of view (FOVs) starting at the pelvis and proceeding cephalad. Transmission scanning at each FOV lasted 3 min. A 3.3–4 MBq/kg dose of 18F-fluorocholine was then administered intravenously. After a delay of approximately 7 min, 2-dimensional emission scans were acquired over the same FOVs for 7 min each. On each scan, the first FOV was centered at the level of the pubic symphysis to include the prostate. After the whole-body scanning, the subjects voided in the restroom and then were repositioned in the scanner with the FOV centered over the pelvis. A single-FOV postinjection transmission scan was then acquired over 3 min. Approximately 1 h after tracer injection, a single-FOV emission scan of the pelvis was acquired over 7 min. Both initial whole-body and delayed pelvic images were reconstructed using ordered-subsets expectation maximization. Segmented attenuation correction was applied using the measured transmission data. Reconstruction resulted in voxels measuring 4 by 4 by 3.6 mm. Images were viewed and analyzed on a computer workstation using PET image analysis software (Medasys Data Systems).
Analysis
PET images were evaluated by 2 independent readers for tracer uptake in the prostate region. Neither reader was aware of the histopathology results at the initial reading. On PET images, the prostate was identified as a discrete region of uptake inferior and slightly posterior to the urinary bladder (Fig. 1). Visualized prostate volumes were segmented according to a sextant biopsy template into an upper (basal) one third, middle one third, and lower (apical) one third on each side. Region-of-interest analysis identified the sextant with highest measured activity on the initial whole-body and delayed pelvic images. The maximum standardized uptake value (SUVmax) in that sextant on both initial and delayed images was recorded. SUVmax was defined as the maximum measured activity divided by the injected radioactivity normalized to body weight. A retention index (%) was calculated as 100 × (SUVmax [at 1 h after injection] − SUVmax [at 7 min after injection])/SUVmax [at 7 min after injection].
Subject 3, with histologically proven malignancy in left prostate lobe. (A) Coronal whole-body 18F-fluorocholine PET image 7 min after injection shows focal uptake in left lobe of prostate (large arrow) corresponding to malignant lesion on biopsy. Increasing bladder activity is evident in second FOV of this image (small arrow). (B) Coronal image of pelvis 1 h after injection shows increasing activity in prostate lesion. Images are shown at same intensity. (C) Graph depicts distribution of SUVmax increase in transverse slice of prostate at midsection (inset: delayed transverse image). SUVmax in lesion increased by 22% (+4.4), whereas SUVmax in contralateral benign area decreased by 6% (−0.4).
The pathology results corresponding to sextant or whole-prostate analysis were reviewed to determine malignant involvement in each sextant. The malignant sextant having the highest standardized uptake value on initial and delayed images was classified as the dominant malignant region. In 5 subjects who subsequently underwent radical prostatectomy, the prostate was histologically examined using the step-section technique. The formalin-fixed whole prostate was sectioned at regular 2.2-mm intervals. Thin slices from each section were mounted on large glass slides and stained with hematoxylin and eosin. Three alignment markers were placed on each slide to record the spatial orientation between slices. Areas of malignant tumor on each slide were manually segmented by a pathologist, and each slide was photographed to scale using a digital camera mounted on a stage. A model of each specimen showing the contour of the prostate surface and the location of tumors was created using surface-modeling software (3D-fit; i.Solutions, Inc.). A 3-dimensional model of the probable tumor volume based on PET images of the prostate was also rendered using software created for this purpose (SARGA; i.Solutions, Inc.) (Fig. 2). We compared these models to aid in correlating areas of uptake within the prostate on PET images to areas of malignancy in the specimen.
Histopathologic correlation of 18F-fluorocholine PET of prostate. (A) One-hour delayed PET scan of pelvis of subject 14 shows increased 18F-fluorocholine uptake in prostate (enclosed by white box). (B) Computer-rendered surface model based on PET images depicts 3-dimensional configuration of highest activity within prostate. (C) Low-power micrograph of prostate specimen shows left-sided tumor with contralateral tumor extension (outlined in black), morphologically resembling corresponding PET and computer-rendered images.
On PET images of the prostate, a probable benign region was defined either as a biopsy-negative sextant contralateral to the region of highest uptake or as the largest tumor-free region on whole-prostate step-section analysis. The SUVmax of the probable benign regions on the initial whole-body and delayed pelvic images was measured by region-of-interest analysis. It was not possible to define a probable benign region in 2 subjects because, at biopsy, malignancy was seen to involve all prostate sextants. The entire prostate was defined as a probable benign region in subjects who did not have a history of prostate cancer (n = 3) and subjects who had no evidence of disease after treatment for prostate cancer (n = 6). The SUVmax of each probable benign region and its corresponding location was recorded. In 15 subjects, both malignant and benign regions were identified within the prostate on the basis of histologic findings (i.e., a dominant malignant region and a probable benign region were present in the same prostate). A malignant-to-benign ratio for SUVmax was calculated for these subjects by dividing the SUVmax of the dominant malignant region by that of the probable benign region.
Differences in sample means were tested for significance using the Student t test. For paired measurements, differences in means were tested for significance using the paired t test. The linear relationship between 2 variables was assessed using the Pearson correlation coefficient. The ability of early and delayed uptake measurements to discriminate dominant malignant regions from probable benign regions was evaluated using receiver operating characteristic analysis. Statistical analysis was performed using JMP, version 5 (SAS Institute Inc.). All tests were 2-sided, and P values of less than 0.05 were considered significant.
RESULTS
Subject Characteristics
The characteristics of each subject are listed in Table 1. The average age of subjects with newly diagnosed or recurrent prostate cancer was 67 y (range, 38–83 y). The average age of subjects who had no evident disease after treatment was 71 y (range, 60–77 y). The median serum PSA in subjects with newly diagnosed or recurrent prostate cancer was 10 ng/dL (range, 1.2–272 ng/dL). The median Gleason sum was 7 (range, 6–10). No significant correlations were observed between SUVmax, age, serum PSA, and Gleason sum.
Subject Characteristics
PET Images
The average interval from injection to initial whole-body PET was 7 min. The average interval from injection to delayed pelvic imaging was 57 min. Six subjects (subjects 18−23; Table 1) had been previously treated for prostate cancer but had no clinical or biochemical evidence of recurrent disease at the time of PET. In these subjects, uptake in the prostate was relatively low and decreased over time. Mean SUVmax in the prostate on the initial and delayed PET images was 3.4 and 2.3, respectively, in these subjects. Three subjects (subjects 24−26) did not have a history of prostate cancer. Highest uptake in the prostate on initial and delayed PET images occurred in the same sextant in each of these subjects. Uptake within these regions decreased over time, with a mean SUVmax of 5.0 and 4.0 on initial and delayed images, respectively.
The remaining 17 subjects (subject 1−17) currently had prostate cancer but had not yet received treatment (n = 15) or had recurrent cancer after local external-beam radiation therapy (n = 2). In 1 subject with a serum PSA level of 272 ng/dL (subject 17), bone scintigraphic evidence of skeletal metastases corresponded to areas of increased skeletal uptake on the initial whole-body 18F-fluorocholine PET images. The remaining subjects did not show extraprostatic sites of increased 18F-fluorocholine uptake suggestive of metastases.
Visual interpretation of the initial and delayed PET images was not problematic. The 2 independent readers had experience with interpreting 18F-fluorocholine PET images (20,24). Identification of the prostate gland and the prostate sextant with highest uptake was facilitated by the consistent position of the prostate in the pelvis and the higher uptake in the prostate than in surrounding pelvic structures at the same level. For each subject, the readers agreed on the prostate sextant demonstrating highest uptake, and concordance in measured SUVmax was found by region-of-interest analysis.
A total of 17 dominant malignant regions and 24 probable benign regions were identified. The mean SUVmax for dominant malignant regions increased significantly between the initial and delayed 18F-fluorocholine PET scans, from 7.6 to 8.6 (mean retention index, +14%; 95% confidence interval, 6%–22%, P = 0.002) (Fig. 3A). The mean SUVmax for probable benign regions decreased significantly between the initial and delayed 18F-fluorocholine PET scans, from 4.8 to 3.9 (mean retention index, −17%; 95% confidence interval, −10% to −23%; P < 0.001) (Fig. 3B). SUVmax differed significantly between the dominant malignant and probable benign regions on the initial scan (mean difference, 2.8; 95% confidence interval, 1.0–4.7; P = 0.01) and on the delayed scan (mean difference, 4.7; 95% confidence interval, 2.6–6.9; P = 0.001).
Plots of SUVmax in probable benign regions (A) and dominant malignant regions (B) on initial (time point 1) and delayed (time point 2) 18F-fluorocholine PET images of prostate.
In subjects for whom histologic analysis found both benign and malignant regions in the prostate (subjects 1–15), the mean malignant-to-benign ratio increased from 1.4 on the initial images to 1.8 on the delayed images (Table 2). This increase was statistically significant (P = 0.003). In these subjects, the difference in mean SUVmax between dominant malignant regions and probable benign regions was statistically significant on delayed imaging (P = 0.009) but not on initial imaging (P = 0.09). Mean retention index also differed significantly between dominant malignant regions and probable benign regions in a paired analysis limited to these 15 subjects (+14% vs. −10%, respectively, P = 0.003).
Malignant-to-Benign Ratio of SUVmax at T1 and T2 in 15 Subjects
The area under the receiver operating characteristic curve for distinguishing dominant malignant regions from probable benign regions based on measured SUVmax on initial whole-body images was 0.81. The area under the curve for distinguishing dominant malignant regions from probable benign regions based on measured SUVmax on delayed pelvic images was 0.92. The area under the curve for distinguishing dominant malignant regions from probable benign regions based on the retention index was 0.93 (Fig. 4).
Relative accuracy of different SUVmax measurements. Receiver operating characteristic curve for distinguishing dominant malignant region from probable benign region is based on SUVmax measurements on initial and delayed PET scans and their percentage difference (i.e., retention index).
DISCUSSION
In vitro and in vivo studies have provided substantial evidence that increased choline metabolism is a prominent feature of prostate cancer (9–14). Prostate cancer cells appear to contain higher levels of choline metabolites (e.g., phosphocholine and phosphatidylcholine) than do normal prostate epithelial and stromal cells (11). In vivo studies using 3-dimensional MRI spectroscopy have shown choline metabolite levels to be almost twice as high in areas of cancer as in areas of benign prostatic hyperplasia and normal tissue (13). Increased levels of choline metabolites in malignant cells are attributable to alterations in the activity of the choline kinase enzyme. Choline kinase catalyzes the phosphorylation of choline to produce phosphocholine. In eukaryotic cells, this enzyme pathway serves as the primary source of phosphatidylcholine and other important cell membrane constituents. Human tumor–derived cell lines of breast, colon, lung, and prostate cancer have higher choline kinase activity than do appropriate nontumor cells (14,15). As an avid substrate for choline kinase, 18F-fluorocholine also undergoes phosphorylation to produce 18F-phosphorylfluorocholine (18). In cultured PC-3 (human prostate cancer) cells incubated with 18F-fluorocholine, most of the intracellular 18F radioactivity is accounted for by the production of 18F-phosphorylfluorocholine (18). The accumulation of 18F-fluorocholine over time in malignant lesions, as observed in this study, is explainable by the metabolic trapping of 18F-fluorocholine due to phosphorylation.
Although this mechanism explains the increase in 18F-fluorocholine uptake in dominant malignant regions, it does not necessarily explain the decrease in 18F-fluorocholine uptake over time in probable benign regions. In the current study, the decrease in 18F-fluorocholine uptake in probable benign regions was comparable in magnitude to the increase in uptake in dominant malignant regions. One potential explanation is the dephosphorylation of 18F-phosphorylfluorocholine by prostatic acid phosphatase, an enzyme specific to prostate tissues. Normal prostate tissue and tissue affected by benign prostatic hyperplasia contain higher levels of prostatic acid phosphatase than does malignant prostate tissue (25). Phosphocholine is known to be an avid substrate for prostatic acid phosphatase even though it is relatively resistant to other phosphatases (26). Because 18F-phosphorylfluorocholine is structurally similar to phosphocholine, it may have the potential to serve as a substrate for prostatic acid phosphatase as well. This catabolic pathway could therefore explain the decrease in 18F-fluorocholine uptake over time in areas of the prostate containing benign tissue. The fact that prostatic acid phosphatase activity is reduced in transformed prostate cells is also consistent with increases in 18F-fluorocholine uptake observed in areas of malignancy. Further research is necessary to determine the actual mechanisms responsible for these observations.
The larger areas under the receiver operating characteristic curve for delayed and dual-phase imaging suggest that imaging at these times may be superior to early imaging for distinguishing benign from malignant areas in the prostate. Although in many cases the sextant demonstrating the highest uptake on either the initial or delayed PET scan corresponded to an area of malignancy, our study had 3 subjects (subjects 1, 4, and 12) in whom the region of highest prostatic activity on early imaging corresponded to a histopathologically benign area. In each of these subjects, SUVmax in the corresponding sextant decreased over the 2 time points (i.e., retention index < 0%), indicating that these regions were indeed benign. In contrast, malignant areas consistently demonstrated stable or increasing uptake over time. In subjects in whom it was possible to identify both a benign and a malignant region within the prostate, the difference between the SUVmax of the dominant malignant region and that of the probable benign region was statistically significant on delayed imaging but not on initial imaging. On the basis of these results, optimal scanning of the prostate with 18F-fluorocholine PET may involve imaging at dual times or after a delay to improve the contrast between malignant and benign (and possibly hyperplastic) tissues.
One potential drawback to delayed imaging with 18F-fluorocholine is the accumulation of radioactivity in the bladder and the consequent potential for obscuring of the prostate gland. In contrast to 11C-labeled choline, 18F-fluorocholine undergoes relatively consistent excretion by the renal system, possibly leading to the accumulation of significant bladder radioactivity over time. Fortunately, accumulated radioactivity in the bladder can be minimized by several methods, such as timed voiding or hydration (to dilute the radioactivity), as well as the insertion of a urinary bladder catheter as has been used for 18F-FDG PET of the pelvis (27). In the current study, subjects had been asked to void before delayed imaging, and the presence of bladder radioactivity did not impair interpretation.
The intraprostatic localization of cancer has been attempted with other metabolic imaging techniques. For example, MRI spectroscopy has been used to characterize prostate lesions on the basis of choline and citrate content (5,13,28). For this procedure, an endorectal probe is typically required to obtain spectroscopic information of sufficient quality. Although the spatial resolution of this technique is similar to PET, only a small volume can be imaged at one time, making this technique impractical for oncologic staging. Further research is necessary to determine the relative accuracies of both imaging modalities and whether the information obtained by these modalities is complementary.
Several points should be considered when interpreting the study results. First, the evaluation of 18F-fluorocholine PET was limited to prostate imaging at 2 times. The optimal timing of 18F-fluorocholine PET for oncologic staging (to detect nodal and distant metastatic disease) was not addressed by this study. Furthermore, to maintain the tolerability of this procedure, 1-h dynamic imaging of the prostate was not performed. Presumably, similar results could be achieved using dynamic PET, although this remains to be tested. Second, there may be a question as to why an increase in the SUVmax of probable benign regions was observed in 3 of the subjects (subjects 5, 8, and 12). Although the SUVmax of these probable benign regions was relatively lower than the average SUVmax of dominant malignant regions, an interval increase in uptake in probable benign regions raises the possibility that some benign tissues can accumulate 18F-fluorocholine over time. However, because the pathology data for these 3 subjects were obtained from biopsy, it is also possible that sampling error could have resulted in a malignant sextant's being misclassified as a probable benign region. Unfortunately, whole-prostate histologic examination was not performed for these subjects, and therefore it is not possible to confirm this possibility. Finally, the current study used 18F-fluorocholine exclusively for prostate PET. It is conceivable that similar patterns of uptake can be observed using other choline analogs such as 18F-fluoroethylcholine and 11C-choline. Delayed PET of the prostate with these choline analogs deserves further study. However, with regard to 11C-choline, the short half-life of 11C (20 min) may limit its utility in delayed PET.
In this study, all prostate sextants with malignant involvement demonstrated stable or increasing 18F-fluorocholine uptake over time. On the basis of these results, dual-phase 18F-fluorocholine PET appears advantageous for identifying the most likely region of malignancy within the prostate. However, further study is needed to determine the overall accuracy of 18F-fluorocholine PET for mapping the extent of malignancy in the prostate. A larger study directly comparing 18F-fluorocholine PET findings with whole-prostate histopathologic findings is needed to evaluate 18F-fluorocholine PET as a technique for tumor mapping. Nevertheless, knowing the location of a single “dominant” malignant lesion in the prostate may still have clinical value. For example, knowing the most likely location of malignancy in the prostate may allow prostate biopsies to be directed toward those regions, thus potentially increasing the diagnostic accuracy of biopsy. For radiation therapy, it may be possible to target a region identified by 18F-fluorocholine PET to receive a higher radiation dose and thus increase the likelihood of tumor eradication. The advent of advanced conformal techniques for the planning and delivery of external-beam radiation therapy has made it possible to enhance the dose of radiation to specific lesions within the prostate while maintaining a safer therapeutic dose to the remainder of the gland (1,2). Further study of the appropriate subject populations (e.g., subjects with elevated levels of serum PSA) is necessary to determine the potential role of 18F-fluorocholine PET in these settings.
CONCLUSION
On dual-phase PET of the prostate, areas of malignancy demonstrated stable or increasing 18F-fluorocholine uptake over time, whereas most areas containing benign tissue demonstrated a corresponding decrease. Compared with 18F-fluorocholine PET at earlier times, 1-h delayed PET may improve differentiation between benign and malignant areas of the prostate. Decreases in 18F-fluorocholine uptake in areas that contain benign prostate tissue may be the result of higher phosphatase activity in these areas than in areas of malignant involvement.
Acknowledgments
This study was supported by NIH/NCI grant R41CA110121 and NIH grant RR-16467. The findings and conclusions expressed in this article do not necessarily represent the views of The Queen's Medical Center.
References
- Received for publication July 28, 2005.
- Accepted for publication November 7, 2005.
Jump to section
Related Articles
Cited By...
- Clinical Evaluation of (4S)-4-(3-[18F]Fluoropropyl)-L-glutamate (18F-FSPG) for PET/CT Imaging in Patients with Newly Diagnosed and Recurrent Prostate Cancer
- Ultrasonographic Follow-up of the Multistep Protocol for Prostate Cancer Induction in Wistar Rats
- Evaluation of Prostate Cancer with 11C- and 18F-Choline PET/CT: Diagnosis and Initial Staging
- Evaluation of Prostate Cancer Bone Metastases with 18F-NaF and 18F-Fluorocholine PET/CT
- AEG-1 Promoter-Mediated Imaging of Prostate Cancer
- Impact of 18F-Choline PET/CT in Prostate Cancer Patients with Biochemical Recurrence: Influence of Androgen Deprivation Therapy and Correlation with PSA Kinetics
- A Compartmental Model for Biokinetics and Dosimetry of 18F-Choline in Prostate Cancer Patients
- Choline phosphorylation and regulation of transcription of choline kinase {alpha} in hypoxia
- The Impact of Urinary Excretion of 18F-Labeled Choline Analogs
- Initial Experience with the Radiotracer Anti-1-Amino-3-18F-Fluorocyclobutane-1-Carboxylic Acid with PET/CT in Prostate Carcinoma
- PET of Human Prostate Cancer Xenografts in Mice with Increased Uptake of 64CuCl2
- Imaging Prostate Cancer with 11C-Choline PET/CT