PET with ¹⁸F-FDG has been considered of limited value for detection of bladder cancer because of the urinary excretion of the tracer. The purpose of this study was to investigate the role of PET/CT in the detection and restaging of bladder cancer using furosemide and oral hydration to remove the excreted ¹⁸F-FDG from the bladder. Methods: Seventeen patients with bladder cancer (11 without cystectomy, 6 with total cystectomy and urinary diversion) underwent ¹⁸F-FDG PET/CT from head to the upper thighs 60 min after the intravenous injection of 370 MBq of ¹⁸F-FDG. Additional pelvic images were acquired 1 h after the intravenous injection of furosemide and oral hydration. PET/CT findings were confirmed by MRI, cystoscopy, or biopsy. Results: PET/CT was able to detect bladder lesions in 6 of 11 patients who had not undergone cystectomy. These images changed the PET/CT final reading in 7 patients: Recurrent bladder lesions were detected in 6 patients, pelvic lymph node metastases in 2 patients, and prostate metastasis in 1. This technique overcame the difficulties posed by the urinary excretion of ¹⁸F-FDG. Hypermetabolic lesions could be easily detected by PET and precisely localized in the bladder wall, pelvic lymph nodes, or prostate by CT. Seven of 17 patients (41%) were upstaged only after delayed pelvic images. Conclusion: Detection of locally recurrent or residual bladder tumors can be dramatically improved using ¹⁸F-FDG PET/CT with delayed images after a diuretic and oral hydration.

The purpose of this study was to evaluate outcome after ²²³Ra dichloride therapy (²²³Ra) and to determine whether skeletal tumor burden on whole-body ¹⁸F-fluoride PET/CT can be used as a predictive biomarker of survival in patients treated with ²²³Ra. Methods: Forty-two patients with hormone-refractory prostate cancer underwent ²²³Ra and a baseline fluoride PET/CT scan. Fluoride PET/CT parameters were generated, including maximum standardized uptake value (SUV_max) of the hottest lesion (hSUV_max), average SUV of disease (Mean₁₀), and skeletal tumor burden indices of total fluoride skeletal metastatic lesion uptake (TLF₁₀) and total volume of fluoride avid bone metastases (FTV₁₀). Overall survival (OS) was the primary endpoint. Secondary endpoints were progression-free survival and skeletal-related event (SRE). Results: Skeletal tumor burden indices (TLF₁₀ and FTV₁₀) derived from fluoride PET/CT at baseline were highly correlated and significant independent predictors of OS (P = 0.0212; hazard ratio = 5.990; 95% confidence interval = 1.306–27.475). A TLF₁₀ cutoff value of 8,000 discriminated survivors from nonsurvivors after ²²³Ra (with TLF₁₀ values < 8,000, the median OS was not estimated, whereas with TLF₁₀ > 8,000, the median OS was 6.67 mo). Visual analysis, Mean₁₀, and hSUV_max were not predictors of OS or progression-free survival. Mean₁₀ was found to be a significant univariate predictor of the odds of having an SRE (P = 0.0445; odds ratio = 1.30; 95% confidence interval = 1.006–1.681), with a Mean₁₀ greater than 19 increasing the risk of SRE. Conclusion: Skeletal tumor burden on baseline fluoride PET/CT is a predictive biomarker of OS and the risk of an SRE in patients treated with ²²³Ra.

There are different metabolic imaging methods, various tracers, and emerging anatomic modalities to stage neuroendocrine tumor (NET). We aimed to compare NET lesion detectability among (99m)Tc-hydrazinonicotinamide (HYNIC)-octreotide (somatostatin receptor scintigraphy [SSRS]) SPECT/CT, (68)Ga-DOTATATE PET/CT, and whole-body diffusion-weighted MR imaging (WB DWI). Nineteen consecutive patients (34-77 y old; mean, 54.3 ± 10.4 y old; 10 men and 9 women) underwent SSRS SPECT/CT, (68)Ga-DOTATATE PET/CT, and WB DWI. Images were acquired with a maximum interval of 3 mo between them and were analyzed with masking by separate teams. Planar whole-body imaging and SPECT/CT were performed from thorax to pelvis using a double-head 16-slice SPECT/CT scanner 4 h after injection of 111-185 MBq of (99m)Tc-HYNIC-octreotide. (68)Ga-DOTATATE PET/CT was performed from head to feet using a 16-slice PET/CT scanner 45 min after injection of 185 MBq of tracer. WB DWI was performed in the coronal plane using a 1.5-T scanner and a body coil. The standard method of reference for evaluation of image performance was undertaken: consensus among investigators at the end of the study, clinical and imaging follow-up, and biopsy of suggestive lesions. McNemar testing was applied to evaluate the detectability of lesions using (68)Ga-DOTATATE PET/CT in comparison to SSRS SPECT/CT and WB DWI: a significant difference in detectability was noted for pancreas (P = 0.0455 and P = 0.0455, respectively), gastrointestinal tract (P = 0.0455 and P = 0.0455), and bones (P = 0.0082 and P = 0.0082). Two unknown primary lesions were identified solely by (68)Ga-DOTATATE PET/CT. (68)Ga-DOTATATE PET/CT, SSRS SPECT/CT, and WB DWI demonstrated, respectively, sensitivities of 0.96, 0.60, and 0.72; specificities of 0.97, 0.99, and 1.00; positive predictive values of 0.94, 0.96, and 1.00; negative predictive values of 0.98, 0.83, and 0.88; and accuracies of 0.97, 0.86, and 0.91. (68)Ga PET/CT seems to be more sensitive for detection of well-differentiated NET lesions, especially for bone and unknown primary lesions. NET can be staged with (68)Ga-DOTATATE PET/CT. WB DWI is an efficient new method with high accuracy and without ionizing radiation exposure. SSRS SPECT/CT should be used only when (68)Ga-DOTATATE PET/CT and WB DWI are not available.

Over the past several years, Positron Emission Tomography (PET) imaging agents labeled with ⁶⁸Gallium (⁶⁸Ga) have undergone a significant increase in clinical utilization. ⁶⁸Ga is conveniently produced from a germanium-68/gallium-68 (⁶⁸Ge/⁶⁸Ga) generator. Because of the compact size and ease of use of the generator, ⁶⁸Ga labeled compounds may be more cost-effective than PET radioisotopes that are cyclotron-produced. The convenient half-life of ⁶⁸Ga (T_1/2=68 min) provides sufficient radioactivity for various PET imaging applications, while delivering acceptable radiation doses to patients. This chapter summarizes the emerging clinical utilization of ⁶⁸Ga-based radiotracers in medical imaging.

The purpose of this study was to define a method to assess skeletal tumor burden with ¹⁸F-labeled sodium fluoride PET/CT (¹⁸F-fluoride PET/CT) and evaluate the reproducibility of these measurements. Methods: Ninety-eight consecutive patients (90 men; mean age ± SD, 65.7 ± 14.2 y) underwent 158 ¹⁸F-fluoride PET/CT scans for evaluation of skeletal metastatic disease. In order to determine the mean normal bone SUV, initially a 1-cm spheric volume of interest (VOI) was placed over 5 bone sites: T12, L5, sacrum, right iliac bone, and right femur. For each patient, the mean SUV_max for all sites was generated. Afterward, a threshold value of normal bone uptake was established. Subsequently, skeletal tumor burden was determined by generating volumetric data using a whole-body segmentation method. Any SUV_max below the normal threshold was excluded from analysis, as were VOIs not related to metastatic disease. Statistics for the remaining VOIs were then generated and defined as the skeletal metastatic tumor burden by 2 parameters: total lesion fluoride uptake above an SUV_max of 10 (TLF₁₀) and fluoride tumor volume above an SUV_max of 10 (FTV₁₀). TLF₁₀ and FTV₁₀ reproducibility was determined using 2 independent and experienced PET/CT interpreters analyzing a subset of 13 ¹⁸F-fluoride PET/CT scans. Results: Mean (±SD) normal bone SUV_max was 6.62 ± 1.55 for T12, 6.11 ± 1.73 for L5, 4.59 ± 1.74 for sacrum, 5.39 ± 1.72 for right iliac bone, and 3.90 ± 1.57 for right femur. The mean normal SUV_max for all 543 sites was 5.32 ± 0.99. On the basis of these values, an SUV_max threshold of 10 was chosen to exclude normal bone from the volumetric calculations. Semiautomated measurements of TLF₁₀ and FTV₁₀ exhibited high interobserver reproducibility, within ±0.77% and ±3.62% of the interinterpreter average for TLF₁₀ and FTV₁₀, respectively. Conclusion: Determination of skeletal tumor burden with ¹⁸F-fluoride PET/CT is feasible and highly reproducible. Using an SUV_max threshold of 10 excludes nearly all normal bone activity from volumetric calculations.