Comparison of [<Superscript>68</Superscript>Ga]Ga-PSMA-11 PET/CT with [<Superscript>18</Superscript>F]NaF PET/CT in the evaluation of bone metastases in metastatic prostate cancer patients prior to radionuclide therapy

Aim

The purpose of this study was to investigate the diagnostic performance of ⁶⁸Ga-PSMA-11 PET/CT in the evaluation of bone metastases in metastatic prostate cancer (PC) patients scheduled for radionuclide therapy in comparison to [¹⁸F]sodium fluoride (¹⁸F-NaF) PET/CT.

Methods

Sixteen metastatic PC patients with known skeletal metastases, who underwent both ⁶⁸Ga-PSMA-11 PET/CT and ¹⁸F-NaF PET/CT for assessment of metastatic burden prior to radionuclide therapy, were analysed retrospectively. The performance of both tracers was calculated on a lesion-based comparison. Intensity of tracer accumulation of pathologic bone lesions on ¹⁸F-NaF PET and ⁶⁸Ga-PSMA-11 PET was measured with maximum standardized uptake values (SUV_max) and compared to background activity of normal bone. In addition, SUV_max values of PET-positive bone lesions were analysed with respect to morphologic characteristics on CT. Bone metastases were either confirmed by CT or follow-up PET scan.

Results

In contrast to 468 PET-positive lesions suggestive of bone metastases on ¹⁸F-NaF PET, only 351 of the lesions were also judged positive on ⁶⁸Ga-PSMA-11 PET (75.0%). Intensity of tracer accumulation of pathologic skeletal lesions was significantly higher on ¹⁸F-NaF PET compared to ⁶⁸Ga-PSMA-11 PET, showing a median SUV_max of 27.0 and 6.0, respectively (p?<?0.001). Background activity of normal bone was lower on ⁶⁸Ga-PSMA-11 PET, with a median SUV_max of 1.0 in comparison to 2.7 on ¹⁸F-NaF PET; however, tumour to background ratio was significantly higher on ¹⁸F-NaF PET (9.8 versus 5.9 on ⁶⁸Ga-PSMA-11 PET; p?=?0.042). Based on morphologic lesion characterisation on CT, ¹⁸F-NaF PET revealed median SUV_max values of 23.6 for osteosclerotic, 35.0 for osteolytic, and 19.0 for lesions not visible on CT, whereas on ⁶⁸Ga-PSMA-11 PET median SUV_max values of 5.0 in osteosclerotic, 29.5 in osteolytic, and 7.5 in lesions not seen on CT were measured. Intensity of tracer accumulation between¹⁸F-NaF PET and ⁶⁸Ga-PSMA-11 PET was significantly higher in osteosclerotic (p?<?0.001) and lesions not visible on CT (p?=?0.012).

Conclusion

In comparison to ⁶⁸Ga-PSMA-11 PET/CT, ¹⁸F-NaF PET/CT detects a higher number of pathologic bone lesions in advanced stage PC patients scheduled for radionuclide therapy. Our data suggest that ⁶⁸Ga-PSMA-11 PET should be combined with ¹⁸F-NaF PET in PC patients with skeletal metastases for restaging prior to initiation or modification of therapy.

     

Prospective comparison of <Superscript>68</Superscript>Ga-PSMA PET/CT, <Superscript>18</Superscript>F-sodium fluoride PET/CT and diffusion weighted-MRI at for the detection of bone metastases in biochemically recurrent prostate cancer

Purpose

To prospectively compare diagnostic accuracies for detection of bone metastases by ⁶⁸Ga-PSMA PET/CT, ¹⁸F-NaF PET/CT and diffusion-weighted MRI (DW₆₀₀-MRI) in prostate cancer (PCa) patients with biochemical recurrence (BCR).

Methods

Sixty-eight PCa patients with BCR participated in this prospective study. The patients underwent ⁶⁸Ga-PSMA PET/CT, a ¹⁸F-NaF PET/CT and a DW₆₀₀-MRI (performed in accordance with European Society of Urogenital Radiology guidelines, with b values of 0 and 600 s/mm²). Bone lesions were categorized using a three-point scale (benign, malignant or equivocal for metastases) and a dichotomous scale (benign or metastatic) for each imaging modality by at least two experienced observers. A best valuable comparator was defined for each patient based on study-specific imaging, at least 12 months of clinical follow-up and any imaging prior to the study and during follow-up. Diagnostic performance was assessed using a sensitivity analysis where equivocal lesions were handled as non-metastatic and then as metastatic.

Results

Ten of the 68 patients were diagnosed with bone metastases. On a patient level, sensitivity, specificity and the area under the curve (AUC) by receiver operating characteristic analysis were, respectively, 0.80, 0.98–1.00 and 0.89–0.90 for ⁶⁸Ga-PSMA PET/CT (n?=?68 patients); 0.90, 0.90–0.98 and 0.90–0.94 for ¹⁸NaF PET/CT (n?=?67 patients); and 0.25–0.38, 0.87–0.92 and 0.59–0.62 for DW₆₀₀-MRI (n?=?60 patients). The diagnostic performance of DW₆₀₀-MRI was significantly lower than that of ⁶⁸Ga-PSMA PET/CT and ¹⁸NaF PET/CT for diagnosing bone metastases (p?<?0.01), and no significant difference in the AUC was seen between ⁶⁸Ga-PSMA PET/CT and ¹⁸NaF PET/CT (p?=?0.65).

Conclusion

⁶⁸Ga-PSMA PET/CT and ¹⁸F-NaF PET/CT showed comparable and high diagnostic accuracies for detecting bone metastases in PCa patients with BCR. Both methods performed significantly better than DW₆₀₀-MRI, which was inadequate for diagnosing bone metastases when conducted in accordance with European Society of Urogenital Radiology guidelines.

     

Treatment response evaluation with <Superscript>18</Superscript>F-FDG PET/CT and <Superscript>18</Superscript>F-NaF PET/CT in multiple myeloma patients undergoing high-dose chemotherapy and autologous stem cell transplantation

Aim

The aim of this study was to assess the combined use of the radiotracers ¹⁸F-FDG and ¹⁸F-NaF in treatment response evaluation of a group of multiple myeloma (MM) patients undergoing high-dose chemotherapy (HDT) followed by autologous stem cell transplantation (ASCT) by means of static (whole-body) and dynamic PET/CT (dPET/CT).

Patients and methods

Thirty-four patients with primary, previously untreated MM scheduled for treatment with HDT followed by ASCT were enrolled in the study. All patients underwent PET/CT scanning with ¹⁸F-FDG and ¹⁸F-NaF before and after therapy. Treatment response by means of PET/CT was assessed according to the European Organization for Research and Treatment of Cancer (EORTC) 1999 criteria. The evaluation of dPET/CT studies was based on qualitative evaluation, semi-quantitative (SUV) calculation, and quantitative analysis based on two-tissue compartment modelling and a non-compartmental approach leading to the extraction of fractal dimension (FD).

Results

An analysis was possible in 29 patients: three with clinical complete response (CR) and 26 with non-CR (13 patients near complete response-nCR, four patients very good partial response-VGPR, nine patients partial response-PR). After treatment, ¹⁸F-FDG PET/CT was negative in 14/29 patients and positive in 15/29 patients, showing a sensitivity of 57.5 % and a specificity of 100 %. According to the EORTC 1999 criteria, ¹⁸F-FDG PET/CT-based treatment response revealed CR in 14 patients (¹⁸F-FDG PET/CT CR), PR in 11 patients (¹⁸F-FDG PET/CT PR) and progressive disease in four patients (¹⁸F-FDG PET/CT PD). In terms of ¹⁸F-NaF PET/CT, 4/29 patients (13.8 %) had a negative baseline scan, thus failed to depict MM. Regarding the patients for which a direct lesion-to-lesion comparison was feasible, ¹⁸F-NaF PET/CT depicted 56 of the 129 ¹⁸F-FDG positive lesions (43 %). Follow-up ¹⁸F-NaF PET/CT showed persistence of 81.5 % of the baseline ¹⁸F-NaF positive MM lesions after treatment, despite the fact that 64.7 % of them had turned to ¹⁸F-FDG negative. Treatment response according to ¹⁸F-NaF PET/CT revealed CR in one patient (¹⁸F-NaF PET/CT CR), PR in five patients (¹⁸F-NaF PET/CT PR), SD in 12 patients (¹⁸F-NaF PET/CT SD), and PD in seven patients (¹⁸F-NaF PET/CT PD). Dynamic ¹⁸F-FDG and ¹⁸F-NaF PET/CT studies showed that SUV_average, SUV_max, as well as the kinetic parameters K₁, influx and FD from reference bone marrow and skeleton responded to therapy with a significant decrease (p?<?0.001).

Conclusion

F-FDG PET/CT demonstrated a sensitivity of 57.7 % and a specificity of 100 % in treatment response evaluation of MM. Despite its limited sensitivity, the performance of ¹⁸F-FDG PET/CT was satisfactory, given that 6/9 false negative patients in follow-up scans (66.7 %) were clinically characterized as nCR, a disease stage with very low tumor mass. On the other hand, ¹⁸F-NaF PET/CT does not seem to add significantly to ¹⁸F-FDG PET/CT in treatment response evaluation of MM patients undergoing HDT and ASCT, at least shortly after therapy.

     

Prospective comparison of combined <Superscript>18</Superscript>F-FDG and <Superscript>18</Superscript>F-NaF PET/CT vs. <Superscript>18</Superscript>F-FDG PET/CT imaging for detection of malignancy

Purpose  

Typically, ¹⁸F-FDG PET/CT and ¹⁸F-NaF PET/CT scans are done as two separate studies on different days to allow sufficient time for the radiopharmaceutical from the first study to decay. This is inconvenient for the patients and exposes them to two doses of radiation from the CT component of the examinations. In the current study, we compared the clinical usefulness of a combined ¹⁸F-FDG/¹⁸F-NaF PET/CT scan with that of a separate ¹⁸F-FDG-only PET/CT scan.     

<Superscript>68</Superscript>Ga-DOTATATE PET/CT in recurrent medullary thyroid carcinoma: a lesion-by-lesion comparison with <Superscript>111</Superscript>In-octreotide SPECT/CT and conventional imaging

Purpose

The aim of this study was to prospectively compare the detection rate of ⁶⁸Ga-DOTATATE PET-CT with ¹¹¹In-octreotide SPECT-CT and conventional imaging (CI) in medullary thyroid carcinoma (MTC) patients with increased calcitonin (Ctn) levels but negative CI after thyroidectomy.

Methods

Fifteen patients with raised Ctn levels and/or CI evidence of recurrence underwent ⁶⁸Ga-DOTATATE PET-CT, ¹¹¹In-octreotide SPECT-CT and CI. Histopathology, CI and biochemical/clinical/imaging follow-up were used as the reference standard. PET/CT, SPECT/CT and CI were compared in a lesion-based and organ-based analysis.

Results

PET/CT evidenced recurrence in 14 of 15 patients. There were 13 true positive (TP), 1 true negative (TN), 1 false positive (FP) and no false negative (FN) cases, resulting in a sensitivity and accuracy of 100% and 93%. SPECT/CT was positive in 6 of 15 cases. There were 6 TP, 2 TN, 7 FN and no FP cases, resulting in a sensitivity of 46% and accuracy of 53%. CI procedures detected tumor lesions in 14 of 15 patients. There were 13 TP, 1TN, 1 FP and no FN cases with a sensitivity of 100% and accuracy of 93%.A significantly higher number of lesions was detected by PET/CT (112 lesions, p = 0.005) and CI (109 lesions, p = 0.005) in comparison to SPECT/CT (16 lesions). There was no significant difference between PET/CT and CI for the total number of detected lesions (p = 0.734). PET/CT detected more lesions than SPECT/CT regardless of the organ. PET/CT detected more bone lesions but missed some neck nodal metastases evidenced by CI. The number of lesions per region demonstrated by PET/CT and CI were similar in the other sites.

Conclusion

⁶⁸Ga-DOTATATE PET/CT is superior to ¹¹¹In-octreotide SPECT/CT for the detection of recurrent MTC demonstrating a significantly higher number of lesions. ⁶⁸Ga-DOTATATE PET/CT showed a superior detection rate compared to CI in demonstrating bone metastases.

     

<Superscript>68</Superscript>Gallium-Arginine-Glycine-Aspartic Acid and <Superscript>18</Superscript>F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Chondroblastic Osteosarcoma of the Skull

We report the case of a 32 year-old male with Chondroblastic Osteosarcoma of the skull, which was imaged with both ¹⁸[F]fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and ⁶⁸Gallium-arginine-glycine-aspartic acid (⁶⁸Ga-RGD) PET/CT. The ¹⁸F-FDG PET/CT did not demonstrate the tumour, whereas the ⁶⁸Ga-RGD PET/CT clearly depicted a left-sided frontal tumour. ⁶⁸Ga-RGD PET/CT may be a clinically useful imaging modality for early detection of recurrent osteosarcoma, considering the limitations of ¹⁸F-FDG PET in a setting of low glycolytic activity.     

[<Superscript>68</Superscript>Ga]DOTATATE PET/MRI and [<Superscript>18</Superscript>F]FDG PET/CT are complementary and superior to diffusion-weighted MR imaging for radioactive-iodine-refractory differentiated thyroid cancer

Purpose

The purpose of this study was to determine whether [⁶⁸Ga]DOTATATE PET/MRI with diffusion-weighted imaging (DWI) can replace or complement [¹⁸F]FDG PET/CT in patients with radioactive-iodine (RAI)-refractory differentiated thyroid cancer (DTC).

Methods

The study population comprised 12 patients with elevated thyroglobulin and a negative RAI scan after thyroidectomy and RAI remnant ablation who underwent both [¹⁸F]FDG PET/CT and [⁶⁸Ga]DOTATATE PET/MRI within 8 weeks of each other. The presence of recurrent cancer was evaluated on a per-patient, per-organ and per-lesion basis. Histology, and prior and follow-up examinations served as the standard of reference.

Results

Recurrent or metastatic tumour was confirmed in 11 of the 12 patients. [⁶⁸Ga]DOTATATE PET(/MRI) correctly identified the tumour burden in all 11 patients, whereas in one patient local relapse was missed by [¹⁸F]FDG PET/CT. In the lesion-based analysis, overall lesion detection rates were 79/85 (93 %), 69/85 (81 %) and 27/82 (33 %) for [¹⁸F]FDG PET/CT, [⁶⁸Ga]DOTATATE PET/MRI and DWI, respectively. [¹⁸F]FDG PET(/CT) was superior to [⁶⁸Ga]DOTATATE PET(/MRI) in the overall evaluation and in the detection of pulmonary metastases. In the detection of extrapulmonary metastases, [⁶⁸Ga]DOTATATE PET(/MRI) showed a higher sensitivity than [¹⁸F]FDG PET(/CT), at the cost of lower specificity. DWI achieved only poor sensitivity and was significantly inferior to [¹⁸F]FDG PET in the lesion-based evaluation in the detection of both extrapulmonary and pulmonary metastases.

Conclusion

[¹⁸F]FDG PET/CT was more sensitive than [⁶⁸Ga]DOTATATE PET/MRI in the evaluation of RAI-refractory DTC, mostly because of its excellent ability to detect lung metastases. In the evaluation of extrapulmonary lesions, [⁶⁸Ga]DOTATATE PET(/MRI) was more sensitive and [¹⁸F]FDG PET(/CT) more specific. Furthermore, DWI did not provide additional information and cannot replace [¹⁸F]FDG PET for postoperative monitoring of patients with suspected RAI-refractory DTC.

     

Quantification of temporal changes in calcium score in active atherosclerotic plaque in major vessels by <Superscript>18</Superscript>F-sodium fluoride PET/CT

Purpose

Our aim was to assess whether ¹⁸F-NaF PET/CT is able to predict progression of the CT calcium score.

Methods

Between August 2007 and November 2015, 34 patients (18 women, 16 men; age, mean?±?standard deviation, 57.5?±?13.9 years; age range 19–78 years) with malignancy or orthopaedic disease were enrolled in this study, with approximately 1-year follow-up data. Baseline and follow-up CT images were retrospectively evaluated for the presence of calcification sites in major vessel walls. The maximum and mean CT values (CTmax and CTmean, in Hounsfield units), calcification volumetric score (CVS, in cubic millimetres) and Agatston units score (AU) were evaluated for each site. Subsequent changes in CTmax, CTmean, CVS and AU were calculated and expressed as ΔCTmax, ΔCTmean, ΔCVS and ΔAU, respectively. We then evaluated the relationship between ¹⁸F-NaF uptake (using the maximum target-to-background ratio, TBRmax, and the maximum blood-subtracted ¹⁸F-NaF activity, bsNaFmax, which was obtained by subtracting the SUVmax of each calcified plaque lesion and NaF-avid site from the SUVmean in the right atrium blood pool) and the change in calcified plaque volume and characteristics obtained after 1 year.

Results

We detected and analysed 182 calcified plaque sites and 96 hot spots on major vessel walls. ¹⁸F-NaF uptake showed very weak correlations with CTmax, CTmean, CVS, CVS after 1 year, AU and AU after 1 year on both baseline and follow-up PET/CT scans for each site. ¹⁸F-NaF uptake showed no correlation with ΔCTmax or ΔCTmean. However, there was a significant correlation between the intensity of ¹⁸F-NaF uptake and ΔCVS and ΔAU.

Conclusion

¹⁸F-NaF uptake has a strong correlation with calcium score progression which was a predictor of future cardiovascular disease risk. PET/CT using ¹⁸F-NaF may be able to predict calcium score progression which is known to be the major characteristic of atherosclerosis.

     

Comparison of 18F-NaF PET/CT with Other Imaging Methods in the Detection of Bone Metastases in Patients with Medullary Thyroid Cancer: a Report of a Series of 31 Cases

PurposeTo compare the ¹⁸F-NaF PET/CT studies (¹⁸F-NaF) with other imaging methods in the detection of skeletal metastases (SM) in patients with medullary thyroid cancer (MTC).MethodsWe retrospectively analyzed 31 patients with MTC who performed ¹⁸F-NaF to assess SM. The results of the ¹⁸F-NaF were compared with other imaging methods performed for metastasis detection: ⁹⁹Tc-MDP bone scan (BS), magnetic resonance imaging (MRI), contrast-enhanced CT (CT), and ⁶⁸Ga-Dotatate and ¹⁸F-FDG PET/CT studies. A qualitative analysis comparing the ¹⁸F-NaF findings with the ones of the other methods was performed, and the results were classified as superior (>), equal (=), and inferior (<).ResultsEleven patients had no bone metastases detected on any of the imaging methods used. Twenty patients presented SM depicted on ¹⁸F-NaF. Of these 20 patients, 12 performed bone scan (in 9 ¹⁸F-NaF > BS and in 3 ¹⁸F-NaF = BS), 1 performed ¹⁸F-FDG (¹⁸F-NaF > ¹⁸F-FDG), 4 performed ⁶⁸Ga-Dotatate (in 2 ¹⁸F-NaF > ⁶⁸Ga-Dotatate and in 2 ¹⁸F-NaF = ⁶⁸Ga-Dotatate), 20 performed CT of at least one body segment (in 15 ¹⁸F-NaF = CT and in 5 ¹⁸F-NaF > CT), and 16 performed MRI of at least one body segment, and in all of them, the ¹⁸F-NaF was equal to the MRI. Beside this, the ¹⁸F-NaF detected SM in body segments not routinely scanned in MRI and CT.ConclusionIn patients with MTC, the ¹⁸F-NaF seems to be equal or superior to other imaging modalities in the detection of SM and allows the analysis of the whole skeletal in a single study.     

Detection of bone metastases in patients with lung cancer: <Superscript>99m</Superscript>Tc-MDP planar bone scintigraphy, <Superscript>18</Superscript>F-fluoride PET or <Superscript>18</Superscript>F-FDG PET/CT

Purpose  

The aim of the study was to compare the diagnostic accuracy of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT versus standard planar bone scintigraphy (BS) and ¹⁸F-labelled NaF (¹⁸F) PET for the detection of bone metastases (BM) in non-small cell lung cancer (NSCLC).     

<Superscript>68</Superscript>Ga-PSMA PET/CT in the evaluation of bone metastases in prostate cancer

Purpose

The aims of this retrospective analysis were to compare ⁶⁸Ga-PSMA PET findings and low-dose CT findings (120 kV, 30 mA), and to obtain semiquantitative and quantitative ⁶⁸Ga-PSMA PET data in patients with prostate cancer (PC) bone metastases.

Methods

In total, 152 PET/CT scans from 140 patients were evaluated. Of these patients, 30 had previously untreated primary PC, and 110 had biochemical relapse after treatment of primary PC. All patients underwent dynamic PET/CT scanning of the pelvis and lower abdomen as well as whole-body PET/CT with ⁶⁸Ga-PSMA-11. The PET/CT scans were analysed qualitatively (visually), semiquantitatively (SUV), and quantitatively based on a two-tissue compartment model and a noncompartmental approach leading to the extraction of the fractal dimension. Differences were considered significant for p values <0.05.

Results

In total, 168 ⁶⁸Ga-PSMA-positive and 113 CT-positive skeletal lesions were detected in 37 patients (8 with primary PC, 29 with biochemical recurrence). Of these 168 lesions, 103 were both ⁶⁸Ga-PSMA PET-positive and CT-positive, 65 were only ⁶⁸Ga-PSMA-positive, and 10 were only CT-positive. The Yang test showed that there were significantly more ⁶⁸Ga-PSMA PET-positive lesions than CT-positive lesions. Association analysis showed that PSA plasma levels were significantly correlated with several ⁶⁸Ga-PSMA-11-associated parameters in bone metastases, including the degree of tracer uptake (SUV_average and SUV_max), its transport rate from plasma to the interstitial/intracellular compartment (K₁), its rate of binding to the PSMA receptor and its internalization (k₃), its influx rate (K_i), and its distribution heterogeneity.

Conclusion

⁶⁸Ga-PSMA PET/CT is a useful diagnostic tool in the detection of bone metastases in PC. ⁶⁸Ga-PSMA PET visualizes more bone metastases than low-dose CT. PSA plasma levels are significantly correlated with several ⁶⁸Ga-PSMA PET parameters.

     

<Superscript>18</Superscript>F-DOPA PET/CT in the diagnosis and localization of persistent medullary thyroid carcinoma

Purpose

To evaluate the performance of ¹⁸F-l-dihydroxyphenylalanine (¹⁸F-DOPA) PET/CT in the detection of locoregional and distant medullary thyroid carcinoma (MTC) metastases and to compare imaging findings with histological data.

Methods

We retrospectively evaluated 86 MTC patients with persistently high serum calcitonin levels after initial surgery who had undergone ¹⁸F-DOPA PET/CT between January 2007 and December 2014 in two referral centres. They were followed up for at least 6 months after the PET/CT assessment. The results were compared with histological data or with the findings obtained during follow-up using a complementary imaging modality.

Results

¹⁸F-DOPA PET/CT was positive in 65 of the 86 patients, corresponding to a patient-based sensitivity of 75.6 %. Distant metastatic disease (M1) was seen in 29 patients including 11 with previously unknown metastases revealed only by PET/CT. Among the 36 patients without distant metastatic spread, 25 had nodal involvement limited to the neck, and 10 of these 25 patients underwent reoperation. The lymph node compartment-based sensitivity of ¹⁸F-DOPA PET/CT was 100 % in the two institutions but lesion-based sensitivity was only 24 %. Preoperative and postoperative median calcitonin levels were 405 pg/mL (range 128 – 1,960 pg/mL) and 259 pg/mL (range 33 – 1,516 pg/mL), respectively. None of the patients achieved normalization of serum calcitonin after reoperation.

Conclusion

¹⁸F-DOPA PET/CT enables early diagnosis of a significant number of patients with distant metastasis. It has a limited sensitivity in the detection of residual disease but provides high performance for regional analysis. A surgical compartment-oriented approach could be the approach of choice whatever the number of nodes revealed by ¹⁸F-DOPA PET/CT.

     

The clinical efficacy of <Superscript>18</Superscript>F-FDG-PET/CT in benign and malignant musculoskeletal tumors

Objective  Most of the current clinical data on the role of 2-[¹⁸F]fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG-PET) in musculoskeletal tumors come from patients studied with PET and less frequently with hardware fusion PET/computed tomography (CT). And the number of cases in each report is too small to clarify the exact clinical efficacy of PET or PET/CT. This prompted us to analyze our experience with ¹⁸F-FDG-PET/CT in a relatively large group of patients with musculoskeletal tumors. Methods   ¹⁸F-FDG-PET/CT was performed on 91 patients from May 2004 to June 2007. The final diagnosis was obtained from surgical biopsy in 83 patients (91%) and clinical follow-up in 8 (9%). We analyzed the characteristics and amount of ¹⁸F-FDG uptake in soft tissue and bone tumors, and investigated the ability of ¹⁸F-FDG-PET/CT to differentiate malignant from benign tumors. The cutoff maximum standardized uptake value (SUV_max) was calculated using the receiver-operation characteristic curve method. Sensitivity, specificity, and diagnostic accuracy were calculated with cutoff SUV_max and the final diagnosis. Unpaired t test was used for the statistical analysis. Results  Final diagnosis revealed 19 benign soft tissue tumors (mean SUV_max 4.7), 27 benign bone tumors (5.1), 25 malignant soft tissue tumors (8.8), and 20 malignant bone tumors (10.8). There was a significant difference in SUV_max between benign and malignant musculoskeletal tumors in total (P < 0.002), soft tissue tumors (P < 0.05), and bone tumors (P < 0.02). Sensitivity, specificity, and diagnostic accuracy were 80%, 65.2%, and 73% in total with cutoff SUV_max 3.8, 80%, 68.4%, and 75% in the soft tissue tumors with cutoff SUV_max 3.8, and 80%, 63%, and 70% in the bone tumors with cutoff SUV_max 3.7. Conclusions   ¹⁸F-FDG-PET/CT reliably differentiated malignant soft tissue and bone tumors from benign ones, although there were many false-positive and falsenegative lesions. Further studies with all kinds of musculoskeletal tumors in large numbers are needed to improve the diagnostic accuracy of ¹⁸F-FDG-PET/CT.     

Evaluation of [<Superscript>18</Superscript>F]-choline PET/CT for staging and restaging of prostate cancer

Purpose To evaluate the accuracy of [¹⁸F]-choline (FCH) positron emission tomography/computed tomography (PET/CT) for staging and restaging of prostate cancer. Methods FCH PET/CT was performed in 111 patients with prostate cancer using 200 MBq FCH: 43 patients [mean age 63 years; mean prostrate specific antigen (PSA) 11.58 μg/l] were examined for initial staging, and 68 patients (mean age 66.4 years) were examined for restaging (mean PSA 10.81 μg/l). FCH PET/CT results were correlated to histopathology, bone scan, morphology as revealed by magnetic resonance imaging (MRI) and CT, PET/CT follow-up and PSA follow-up after therapy. Results FCH PET/CT scans at initial staging correctly showed no metastases in 36/38 patients undergoing radical surgery, as confirmed by PSA levels <0.1 μg/l 6 months postoperatively. Lymphadenectomy was performed in 24 of these patients, revealing four false FCH-negative lymph nodes (LN). In one patient, only lymphadenectomy was performed since a FCH-positive LN was confirmed by histology. Four patients showed FCH-positive bone metastases, as proven by bone scan. FCH PET/CT scans at restaging correctly revealed local recurrence in 36 patients. No pathological FCH uptake was observed in 11 patients with biochemical recurrence. Twenty-three patients showed FCH-positive LN. Twenty LN were surgically removed in seven patients. Histopathology verified metastases in all LN, but revealed two additional metastastic, FCH-negative LN. Seventeen patients showed FCH-positive bone metastases, as proven by bone scan or MRI. Sensitivity to detect recurrent disease was 86%. Conclusion The results obtained using FCH PET/CT scans for initial N-staging were discouraging, especially in terms of its inability to detect small metastases. Recurrent disease can be localized reliably in patients with PSA levels of >2 μg/l.     

Diagnostic utility of PET/CT with <Superscript>18</Superscript>F-DOPA and <Superscript>18</Superscript>F-FDG in persistent or recurrent medullary thyroid carcinoma: the importance of calcitonin and carcinoembryonic antigen cutoff

Purpose

This study sought to evaluate and compare the utility of 18-F-fluorodihydroxyphenylalanine (¹⁸F-DOPA) and 18-F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) for identification of lesions in patients with recurrent medullary thyroid carcinoma (MTC). In addition, we analyzed the correlation between the calcitonin (Ct), carcinoembryonic antigen (CEA) levels, each doubling time (DT), and PET positivity. We evaluated the reliability of the 150 pg/mL Ct cutoff set by the American Thyroid Association guidelines for further imaging (including ¹⁸F-DOPA PET/CT).

Methods

We prospectively recruited 18 patients with recurrent MTC, identified by elevation of Ct or CEA. Each patient underwent a ¹⁸F-FDG PET/CT and a ¹⁸F-DOPA PET/CT.

Results

Abnormal uptakes were detected with ¹⁸F-DOPA (n=12) and ¹⁸F-FDG (n=9), (sensitivity of 66.7% vs. 50%; p<0.01). Twenty-eight lesions were detected with ¹⁸F-DOPA vs. 16 lesions with ¹⁸F-FDG (1.56±1.5 vs. 0.89±1.18 lesions per patient; p=0.01). None of our patients showed additional lesions with ¹⁸F-FDG in comparison to ¹⁸F-DOPA. Patient-based detection rate increased significantly with Ct levels ≥150 pg/mL vs. Ct<150 pg/mL for both ¹⁸F-DOPA (sensitivity 90.9% vs. 28.6%; p=0.013) and ¹⁸F-FDG PET/CT (sensitivity 72.7% vs. 14.3%; p=0.025). Using a CEA cutoff of ≥5 ng/mL, detection rates of ¹⁸F-DOPA and ¹⁸F-FDG PET/CT were 81.1% and 72.7%, respectively. No correlation between Ct-DT or CEA-DT and PET positivity was found. Histological confirmation was obtained in eight patients.

Conclusions

¹⁸F-DOPA PET/CT appears to be superior to ¹⁸F-FDG PET/CT in detecting and locating lesions in patients with recurrent MTC. This technique tends to be especially useful in patients with negative results in other imaging modalities and Ct≥150 pg/mL or CEA≥5 ng/mL.

     

Usefulness of Respiratory-Gated <Superscript>18</Superscript>F-FDG PET/CT in Detecting Upper Abdominal Fever Focus

Respiratory-gated ¹⁸F-fluorodeoxygluocse (¹⁸F-FDG) PET/CT has been successfully used to better localize malignancies in the lung or upper abdominal organs. However, clinical usefulness of respiratory-gated ¹⁸F-FDG PET/CT in detection of fever focus has not been reported yet. A 68-year-old male patient with a history of living donor liver transplantation and biliary stenting was referred for ¹⁸F-FDG PET/CT due to fever of unknown origin (FUO). To find the accurate fever focus, respiratory-gated and non-gated ¹⁸F-FDG PET/CT was performed. Respiratory-gated PET/CT readily revealed prominent hypermetabolic lesion in the distal common bile duct (CBD) area where previous surgical graft was in situ. Maximum standardized uptake value (SUVmax) and SUV ratio (SUR) were greater in the gated PET/CT (SUVmax 5.4 and SUR 3.5) than in the non-gated PET/CT (SUVmax 4.6 and SUR 3.0). Fever dramatically subsided after removal of the graft in the CBD. This case report implies that respiratory-gated ¹⁸F-FDG PET/CT can visualize upper abdominal fever focus with better contrast than the conventional non-gated method.     

Impact of Nonosseous Findings on 18F-NaF PET/CT in a Patient with Ductal Breast Carcinoma

¹⁸F-NaF was used as a bone-seeking PET tracer for skeletal imaging until the introduction of the widely available ^99mTc-labeled bone agents. However, there is renewed clinical interest in ¹⁸F-NaF since prior technical and logistic limitations to its routine use are no longer present, and, as a consequence, it is likely that uptake unrelated to bone and non-osseous findings will be encountered more frequently. As a result of tumoral necrosis, soft tissue metastases may demonstrate ¹⁸F-NaF avidity due to dystrophic calcification. On the other hand, all non-osseous findings, whether ¹⁸F-NaF avid or not, may provide important diagnostic information that may alter the course of the disease, including treatment options. Herein we present a patient with ductal carcinoma of the breast in whom findings unrelated to the skeletal system in ¹⁸F-NaF PET/CT altered the treatment strategy.     

The impact of <Superscript>18</Superscript>F-FDG PET/CT in patients with liver metastases

Purpose The aim of this study was to assess the performance of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) versus dedicated contrast-enhanced CT (CECT) in the detection of metastatic liver disease. Methods All patients that presented to our Institution with suspected metastatic liver disease who underwent ¹⁸F-FDG PET/CT and CECT within 6 weeks of each other, were retrospectively analyzed, covering a 5-year period. One hundred and thirty-one patients (67 men, 64 women; mean age 62) were identified. Seventy-five had colorectal carcinoma and 56 had other malignancies. The performance of CECT and that of ¹⁸F-FDG-PET/CT in detecting liver metastases were compared. The ability of each to detect local recurrence, extrahepatic metastases and to alter patient management was recorded. The final diagnosis was based on histology, clinical and radiological follow-up (mean 23 months). Results In detecting hepatic metastases, ¹⁸F-FDG-PET/CT yielded 96% sensitivity and 75% specificity, whilst CECT showed 88% sensitivity and 25% specificity. ¹⁸F-FDG-PET/CT and CECT were concordant in 102 out of 131 patients (78%). In the colorectal group ¹⁸F-FDG-PET/CT showed 94% sensitivity and 75% specificity, whilst CECT had 91% sensitivity and 25% specificity. In the noncolorectal group ¹⁸F-FDG-PET/CT showed 98% sensitivity and 75% specificity whilst CECT had 85% sensitivity and 25% specificity. Overall, ¹⁸F-FDG-PET/CT altered patient management over CECT in 25% of patients. CECT did not alter patient management over ¹⁸F-FDG-PET/CT alone in any patients. Conclusion ¹⁸F-FDG-PET/CT performed better in detecting metastatic liver disease than CECT in both colorectal and noncolorectal malignancies, and frequently altered patient management. The future role of CECT in these patients may need to be re-evaluated to avoid potentially unnecessary duplication of investigation where ¹⁸F-PET/CT is readily available. Authors stated no financial relationship to disclose     

Diagnostic impact of PET with <Superscript>18</Superscript>F-FDG, <Superscript>18</Superscript>F-DOPA and 3-<Emphasis Type="Italic">O</Emphasis>-methyl-6-[<Superscript>18</Superscript>F]fluoro-DOPA in recurrent or metastatic medullary thyroid carcinoma

Purpose In patients with medullary thyroid carcinoma (MTC), rising levels of the tumour markers calcitonin and CEA after primary surgery indicate tumour recurrence or metastases. The only chance of cure is the resection of localised tumour tissue. For positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and ¹⁸F-dihydroxyphenylalanine (¹⁸F-DOPA), sensitivities of 78% and 63% have been reported, but in a considerable percentage of MTC patients the source of tumour marker elevation is not detected. The aim of this retrospective data evaluation was to compare the value of PET with ¹⁸F-FDG, ¹⁸F-DOPA and the amino acid tracer 3-O-methyl-6-[¹⁸F]fluoro-DOPA (¹⁸F-OMFD) in the detection of MTC recurrence. Methods Fifteen patients with elevated calcitonin were investigated with PET as part of their individual clinical work-up. All patients underwent ¹⁸F-FDG PET and ¹⁸F-DOPA PET, and ten patients underwent ¹⁸F-OMFD PET. Results With ¹⁸F-FDG, seven patients showed foci in the neck, mediastinum, upper abdomen or bone. In seven patients, ¹⁸F-DOPA revealed suspicious foci; five of these seven patients showed partially corresponding uptake of ¹⁸F-FDG in the neck and mediastinum. Two of these patients underwent surgery and metastases were verified. With ¹⁸F-OMFD, a small focus in the liver was suspected in one patient without a correlate on ¹⁸F-FDG PET, ¹⁸F-DOPA PET or conventional imaging. Conclusion ¹⁸F-FDG and ¹⁸F-DOPA showed foci that were highly suspicious for local recurrence or metastasis of MTC, although histological verification in these patients with numerous previous surgical interventions was performed in only two patients. The amino acid tracer ¹⁸F-OMFD had no diagnostic impact in these patients.     

Reproducibility of standardized uptake values of same-day randomized <Superscript>68</Superscript>Ga-PSMA-11 PET/CT and PET/MR scans in recurrent prostate cancer patients

Objective

Positron emission tomography in association with magnetic resonance imaging (PET/MR) and ⁶⁸Ga-PSMA-11 has shown superior detection in recurrent prostate cancer patients as compared to PET/computed tomography (PET/CT). There are, however, several technological differences between PET/CT and PET/MR systems which affect the PET image quality. The objective of this study was to assess the reproducibility of PET/CT and PET/MR SUV’s in recurrent prostate cancer patients. We randomized the patients regarding the order of the PET/CT and PET/MR scans to reduce the influence of tracer uptake as a function of time.

Methods

Thirty patients, all with biochemical recurrence after radical prostatectomy, underwent whole-body PET/CT and PET/MR scans after intravenous injection of a single dose of ⁶⁸Ga-PSMA-11. Fifteen patients underwent PET/CT first and 15 patients underwent PET/MR first. Volumes of interest on tumor lesions were outlined and maximum standardized uptake value (SUVmax) corrected for lean body mass was calculated. Correlation and agreement between scans were assessed by generalized linear mixed-effects models and Bland–Altman analysis. The association between SUV, patient characteristics and imaging parameters was assessed.

Results

Eighteen of the 30 evaluated patients had at least one positive lesion, giving an overall detection rate of 60%. In total, there were 34 visible lesions: 5 local recurrences, 22 lymph node metastases and 7 bone metastases. One group acquired PET/CT and PET/MR at median time points of 63.0 and 159.0 min, while the other group acquired PET/MR and PET/CT at median time points of 92.0 and 149.0 min. SUVmax between scans was linearly correlated, described by the equation Y(PET/CT SUVmax)?=?0.75?+?1.00?×?(PET/MR SUVmax), on average 20% higher on PET/CT than on PET/MR. SUV associated significantly only with type of lesion, scan time post-injection and acquisition time per bed position.

Conclusions

SUVmax from PET/CT and PET/MR are linearly correlated, on average 20% higher on PET/CT than on PET/MR and should, therefore, not be used interchangeably in patient follow-up.