Variability in the amount of fluorine-18 fluorodeoxyglucose excreted in urine measured from oncology patients during PET/computed tomography imaging.

The objectives of this work were to estimate the amount of fluorine-18 fluorodeoxyglucose (F-FDG) excreted (AFE) in the patient urine during the uptake phase as percentage of the injected activity and to examine the effect of blood glucose levels (BGL) on the excreted amount and whether it varies among men and women using statistical analysis methods. Radiation dose rates were measured at 1 m from 50 patients, 24 men and 26 women, before and after the first void using a calibrated ionization chamber. The F-FDG was injected in the patients using a calibrated automatic dose injection system. Statistical analysis using hypothesis testing was carried out. Patients with BGL above 5 mmol/l had a higher AFE of 12.3% in comparison with 8.3% of the patients with BGL below 5 mmol/l. A statistically nonsignificant correlation (r=0.183, P<0.249) between AFE and BGL was found; a nonsignificant difference was found in the AFE measured among the male and female patients. The AFE measured was 12±6%, with a range of (2-30%). There was a wide variation in the first void time of 39±8 min, with a range of (17-68) min. A simple noninvasive measurement method is presented that enabled the estimation of the amount of F-FDG excreted from the patient during voiding. Statistical analysis concluded that the amount of F-FDG excreted does not depend on sex, but is perhaps influenced by BGL.

A Mimic of Intra-abdominal Malignancy: Physiological Urinary Excretion of FDG in the Rare Adult Vesicourachal Diverticulum.

Urachal remnant anomalies are rare, and vesicourachal diverticulum is the most uncommon subtype of these anomalies. We present such a rare case of vesicourachal diverticulum that is incidentally discovered during the staging surveillance of a known esophageal cancer with F-FDG PET/CT. The physiological urinary excretion of radiopharmaceutical in the vesicourachal diverticulum mimics intra-abdominal malignancy, which resolves spontaneously in the follow-up FDG PET/CT.

Internal dosimetry for intake of 18FDG using spot urine sample.

In nuclear medicine, workers handle unsealed radioactive materials. Among the materials, (18)FDG is the most widely used in PET/CT technique. Because of the short half-life of (18)F, it is very challenging to monitor internal exposure of nuclear medicine workers using in vitro bioassay. Thus, the authors developed the new in vitro bioassay methodology for short half-life nuclides. In the methodology, spot urine sample is directly used without normalisation to 1-d urine sample and the spot urinary excretion function was newly proposed. In order to estimate the intake and committed dose for workers dealing (18)FDG, biokinetic models for FDG was also developed. Using the new methodology and biokinetic model, the in vitro bioassay for workers dealing (18)FDG was successfully performed. The authors expect that this methodology will be very useful for internal monitoring of workers who deal short-lived radionuclides in the all field as well as the nuclear medicine field.

Evaluation of PET quantification accuracy in vivo. Comparison of measured FDG concentration in the bladder with urine samples.

UNLABELLED: Quantitative positron emission tomography (PET) requires accurate scanner calibration, which is commonly performed using phantoms. It is not clear to what extent this procedure ensures quantitatively correct results in vivo, since certain conditions differ between phantom and patient scans. AIM: We, therefore, have evaluated the actual quantification accuracy in vivo of PET under clinical routine conditions. PATIENTS, METHODS: We determined the activity concentration in the bladder in patients undergoing routine [18F]FDG whole body investigations with three different PET scanners (Siemens ECAT EXACT HR+ PET: n = 21; Siemens Biograph 16 PET/CT: n = 16; Philips Gemini-TF PET/CT: n = 19). Urine samples were collected immediately after scan. Activity concentration in the samples was determined in well counters cross-calibrated against the respective scanner. The PET (bladder) to well counter (urine sample) activity concentration ratio was determined. RESULTS: Activity concentration in the bladder (PET) was systematically lower than in the urine samples (well counter). The patient-averaged PET to well counter ratios for the investigated scanners are (mean ± SEM): 0.881 ± 0.015 (ECAT HR+), 0.898 ± 0.024 (Biograph 16), 0.932 ± 0.024 (Gemini-TF). These values correspond to underestimates by PET of 11.9%, 10.2%, and 6.8%, respectively. CONCLUSIONS: The investigated PET systems consistently underestimate activity concentration in the bladder. The comparison of urine samples with PET scans of the bladder is a straightforward means for in vivo evaluation of the expectable quantification accuracy. The method might be interesting for multi-center trials, for additional quality assurance in PET and for investigation of PET/MR systems for which clear proof of sufficient quantitative accuracy in vivo is still missing.

[18F-FDG PET/CT with retrograde filling of the urinary bladder in the assessment of malignant pelvic disease]. / PET-TAC con (18)F-FDG tras llenado retrógrado vesical en el estudio de patología pélvica maligna.

AIM: To assess the role of PET/CT with retrograde filling of urinary bladder (RFUB) in the assessment of pelvic malignancy in patients with urothelial or gynecological tumors. MATERIAL AND METHODS: A retrospective longitudinal analysis based on 62 studies belonging to 52 patients was performed. All of them had a history of pelvic malignancy (29 urothelial and 23 gynecological) and 42 had undergone previous treatments. All patients underwent a standard PET/CT protocol. Inclusion criteria were radiological alterations in pelvic organs or increased urinary activity of (18)F-FDG that hindered evaluation of the pelvic structures. Pathological pelvic locations were assessed as the additional value of PET/CT with RFUB. The pathologic lesions were histologically or clinically evaluated with a minimum follow-up of 12 months. RESULTS: Pelvic malignancy was confirmed in 33 cases, 16 of which were of urothelial origin. A total of 35/62 studies showed a pathologic PET/CT in pelvis, 4 of them were false positive and 2 false negative. In 19 cases, malignancy was detected in the bladder wall, 16 of which were true positive. No false negative was detected. Regarding standard imaging acquisition, RFUB helped to confirm or rule out bladder and/or gynecological disease in 54 cases. CONCLUSION: Retrograde bladder filling is a highly recommended technique in the assessment of malignant pelvic disease, especially of bladder origin.

Mimicry of physiological urinary FDG excretion: squamous cell carcinoma of esophagus metastasizing to psoas muscle.

Skeletal muscle metastases are rare and usually occur with various malignancies at more advanced stages. FDG PET/CT has been known as a useful tool to detect these lesions because of the character of whole-body scanning and superior contrast between malignant and normal tissues, except in areas with abundant physiological FDG radioactivity, such as the urinary system. We present a patient with esophageal squamous cell carcinoma and an incidental, rare finding of psoas muscle metastasis that was initially omitted because of the similarity of its distribution to physiological urinary FDG excretion in the ureter.

Radiation protection for accompanying person and radiation workers in PET/CT.

The purposes of the present study are to measure the total radiation doses for the radiation workers and for the accompanying person to the patients in positron emission tomography (PET)/computed tomography (CT) imaging. Urines samples from the patients were collected at 43, 62, 87, 117, 238, 362 min after the 555-MBq (18)flour-fluorodeoxyglucose ((18)F-FDG) injection and activities were measured. Dose rates were recorded using a Geiger-Muller counter and the total radiation doses were measured with using an electronic personnel dosemeter. According to the results here, 18.4 % of (18)F-FDG was excreted in the urine in 117 min after injection. At 117th min after injection, dose rates were determined as 345, 220, 140, 50 and 15 µSv h(-1), at proposed distances. The radiation doses after 117 min were measured as 3.92 mSv at 0.1 m, 2.11 mSv at 0.25 m and 1.08 mSv at 0.5 m. In conclusion, radiation protection will be sufficient within 2 h after (18)F-FDG injection for PET/CT imaging in daily practice.

A focal pulmonary F-18 FDG uptake without pulmonary CT abnormality in PET/CT probably due to mislocation of the urine F-18 FDG in the left upper renal calyx.

We experienced a case of a focal pulmonary F-18 fluoro-2-deoxy-D-glucose (FDG) uptake without pulmonary computed tomography (CT) abnormality probably due to the urine FDG in the upper pole calyx of the left kidney. A 76-year-old male patient was referred for evaluation of the postoperative right lung cancer. Positron emission tomography/CT was performed 1 hour after intravenous injection of FDG and showed a small focus of increased uptake in the left lower lung field accompanying no abnormality in the corresponding lung CT images. The lung uptake was not noted in repeated positron emission tomography/CT images taken after 1 hour, suggesting misplacement of the left renal upper calyx into the lower lung.

Modeling the excretion of FDG in human kidneys using dynamic PET.

In order to understand the excretion function of kidneys, dynamic scan was performed using the positron emission tomography (PET), the process of FDG's (2-[(18)F]fluoro-2-deoxy-D-glucose) excretion was detected, and the kidney model was established. The model in this study consisted of two parts: the fore part of the model described the transportation of FDG from plasma and the accumulation of FDG in kidney, and the latter part of the model described the transportation of FDG from kidney to ureter and then to bladder. Since there was a time delay between the fore part and the later part, which occurred when FDG was filtered into urine and accumulated in pelvis temporarily, a new parameter, delay constant t(0), was introduced in the model. Twelve healthy adult volunteers took part in the dynamic FDG-PET experiment. Ten subjects received dynamic scan on kidneys, and the data extracted from the PET scans were used for parameter estimation and model analysis. The other two subjects received dynamic scan on bladder in order to confirm the time delay constant. The output of the model fit well with the original curve, and the model built in this study could not only describe the excretion process of FDG, but also be used to quantitatively estimate urinary excretion of FDG and plasma clearance. Moreover, the model kept good accordance with physiological characteristics.

Urinary fluorine-18 fluorodeoxyglucose excretion with and without intravenous application of furosemide.

METHODS: Twenty patients suffering from malignancy received furosemide, twenty patients were examined by FDG-PET without diuretics. Urine volume and radioactivity were measured before and after acquisition. Bladder activity was evaluated qualitatively and quantitatively. RESULTS: Radioactivity in the bladder was lower and the image quality higher in the furosemide group. SUV values showed a median of 3.0 in the furosemide and 6.0 in the control group. With furosemide, a larger excreted volume was seen compared to the control group. The furosemide group showed a significantly higher ratio of excreted/ injected radioactivity early after injection. However, the totally excreted radioactivity was not significantly different (p = 0.93). CONCLUSION: Diuretics cause a higher urine volume with a diluted FDG concentration leading to an improved image quality. Furosemide accelerates early renal FDG elimination, reducing radiation exposure.

Unrecognized renal transplants as a potential source of false-positive interpretation of FDG PET.

Renal transplantation has become an effective therapy for patients with late-stage renal disease. Fluorodeoxyglucose (FDG) positron emission tomography (PET) is accepted as an important diagnostic technique in the evaluation of suspected or known malignancies or other disorders in the day-to-day practice of medicine. Because FDG is excreted from the kidneys into the urine, unrecognized renal transplants can appear as malignant lesions. Familiarity with the clinical history is a prerequisite in the correct interpretation of FDG PET images in this setting. In addition, FDG PET images should be correlated with anatomic images when such studies are available. When neither clinical history nor anatomic images are available, a combination of "abnormal" activity in the pelvis and absence of normal renal activity should raise suspicion of the existence of a renal transplant.

Dynamic evaluation of absorbed dose to the bladder wall with a balloon-bladder phantom during a study using [(18)F]fluorodeoxyglucose positron emission imaging.

An accurate evaluation of the absorbed dose to the bladder wall from 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG) is clinically important because the bladder is considered as a critical organ in most positron emission tomography (PET) studies that cumulate about 20% of the total activity injection during image procedures. In the MIRD calculation, no allowance is made for the inclusion of all the dynamic parameters that affect the actual dose to the bladder wall to be taken in the dose assessment. The goal of the study is to propose a dose evaluation model by using a dynamic bladder phantom and time-activity curves from the bladder PET imaging. The proposed model takes all dynamic parameters into account and provides a much more accurate dose estimation to the bladder. In this study, the lowest dose to the bladder wall was obtained at the conditions of having a larger initial volume for the bladder contents and a higher production rate for urine. It is then advised patients to drink a bulk amount of water before the FDG injection or after urine voiding to facilitate urine production and to enlarge the bladder surface area, which are the most crucial steps in reducing the dose to the bladder wall. In our study, the voiding schedule in dose calculation plays certain roles although it is much more critical in the conventional MIRD calculation. The model estimated that the lowest dose to the bladder would occur at an initial void about 40 min after the FDG injection and the urine voiding was as complete as possible.

Optimization of urinary FDG excretion during PET imaging.

UNLABELLED: Accumulation of fluorodeoxyglucose (FDG) activity in the urine interferes with the visualization of pelvic and, sometimes, abdominal abnormalities. Although this is a major problem, there are few data on the physiological variables affecting FDG urinary excretion that are critical to minimizing urinary FDG interference during PET imaging. METHODS: The excretion of FDG in urine was determined during 90 min in four groups of rats (n = 24) under the following conditions: normal, hydrated, hydrochlorothiazide treated and phlorizin treated. FDG clearance rates were measured in both normal and phlorizin-treated animals and compared with the glomeruler filtration rate measured with 99mTc-diethylenetriamine pentaacetic acid. We measured FDG excretion in 10 patients who had no known renal disease and were undergoing PET scanning (divided into two groups: hydrated and dehydrated) to relate the animal data to humans. RESULTS: The hydrated and phlorizin-treated animals had the highest excretion of FDG (39.68+/-5.00 % injected dose (%ID) and 45.64+/-9.77 %ID, respectively). Animals given the hydrochlorothiazide had the highest urinary volume, but the percentage excreted was comparable with the normal rats. Measurement of the clearance of FDG in animals before and after the administration of phlorizin determined the amount of FDG reabsorbed in the proximal tubules to be 56%+/-9.15%. The hydrated patients had a higher excretion of FDG than dehydrated patients (16.98+/-1.99 %ID versus 14.27+/-1.00 %ID, P < 0.021), and the volume of urine voided was significantly higher (P < 0.020). CONCLUSION: Hydrochlorothiazide increases urine volume without enhancing FDG excretion. The hydration of patients before PET scanning may lead to more FDG reaching the bladder. Reduction of bladder activity by more frequent voiding facilitated by increased urine volume in hydrated patients may be offset by increased delivery of FDG to the bladder. A preferable means of increasing urinary volume without increasing delivery of FDG to the bladder may be the use of a diuretic.

Animal studies on the reduction and/or dilution of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) activity in the urinary system.

To evaluate two methods for decreasing and/or diluting the FDG activity in the urinary system, five rats were intraperitoneally given 1,000 micrograms/g of L-lysine 4 times, starting from 60 minutes before iv injection of FDG, and then at 30-minute intervals for 90 minutes. Five rats were used as controls. In a furosemide study, 12 rats were allocated to three groups. Group 1 received iv injection of FDG alone. Group 2 received saline before iv injection of FDG. Group 3 received furosemide (7 mg/kg) and saline (1/30 of body weight). Neither renal uptake nor urinary excretion of FDG had a statistically significant difference: renal uptake; 0.179 +/- 0.011 (L-lysine) vs. 0.119 +/- 0.003 (control) % kg injected dose/g. The % dose excreted and total urine volume were: 15.0 +/- 2.5 to 15.5 +/- 2.5 with 2.98 ml (L-lysine), 22.9 +/- 1.8 to 24.2 +/- 1.5 with 1.41 ml (control). The furosemide study revealed a statistically significant difference: Group 1; 7.57 +/- 4.73, Group 2; 0.686 +/- 0.638, Group 3; 2.37 +/- 2.33% kg injected dose/g (p < 0.01 for Group 1 vs. Group 2, p < 0.05 for Group 1 vs. Group 3). While pretreatment with L-lysine or furosemide failed to decrease renal activity of FDG, saline injection without furosemide markedly decreased urinary activity.