Quantitative evaluation of bone metastases from prostate cancer with simultaneous [18F] choline PET/MRI: combined SUV and ADC analysis

Objective

To quantitatively analyze bone metastases from prostate cancer and correlate the apparent diffusion coefficients (ADCs) and standardized uptake values (SUVs).

Methods

Fifty-five patients with biopsy-proven prostate cancer or suspected recurrent prostate cancer were examined with simultaneous [¹⁸F] choline Positron emission tomography (PET)/MRI at 3 T. In 11 patients, thirty-two PET-positive bone lesions could be identified that were located in the field-of-view of the Diffusion weighted imaging-sequence. Region-of-interest and volume-of-interest analyses were performed to measure the mean and minimal ADCs and to assess maximum and mean SUVs of every bone lesion. Correlations between maximum and mean SUVs and mean and minimal ADCs were calculated.

Results

The SUV_max of all lesions was 5.5 ± 3.1 (mean ± SD). The SUV_mean was 1.8 ± 0.9. The mean ADC (ADC_mean) of all lesions was 0.67 ± 0.13 × 10^?3 mm²/s. The minimal ADC (ADC_min) of all lesions was 0.56 ± 0.14 × 10^?3 mm²/s. There was a moderate but significant inverse correlation of SUV_max vs. ADC_mean with a correlation coefficient of ?0.4 (p = 0.02). There was also a significant inverse correlation of SUV_max vs. ADC_min with r = ?0.41 (p = 0.02).

Conclusion

Our initial results demonstrate a moderate but significant inverse correlation between increased choline metabolism and ADC values of bone metastases from prostate cancer. Further research on a multimodality approach using simultaneous PET/MRI in bone metastasis of prostate cancer seems to be justified.     

Dual-time-point [18F]-FDG PET/CT in the diagnostic evaluation of suspicious breast lesions

Purpose

The authors sought to evaluate whether the reacquisition of images 3 h after administration of radiotracer improves the sensitivity of fluorine-18 fluorodeoxyglucose positron emission tomography computed tomography ([¹⁸F]-FDG PET/CT) in patients with suspicious breast lesions.

Materials and methods

Forty-eight patients with 59 breast lesions underwent an [¹⁸F]-FDG PET/CT study in the prone position with a dual-time-point acquisition performed in the early phase 1 h after FDG administration (PET-1) and in the delayed phase 3 h after FDG administration (PET-2). Both examinations were evaluated qualitatively and semiquantitatively with calculation of the mean percentage variation of the standard uptake values (Δ% SUV_max) between PET-1 and PET-2. All lesions with an SUV_max ≥2.5 at PET-1 or a reduction in SUV between PET-1 and PET-2 were considered benign. The definitive histopathological diagnosis was available for all patients included in the study.

Results

The dual-time-point acquisition of [¹⁸F]-FDG PET/CT displayed an accuracy of 85% for lesions with an SUV_max ≥2.5 and/or positive Δ% SUV_max, with sensitivity and specificity values of 81% and 100% compared with 69%, 63% (both p<0.001) and 100% (p=n.s.), respectively, for the single-time-point acquisition. Malignant lesions showed an increase in FDG uptake between PET-1 and PET-2, with a Δ% SUV_max of 10±7 (p<0.04). In contrast, benign lesions showed a decrease in SUV between PET-1 and PET-2, with aΔ% SUV_max of ?21±7 (p<0.001).

Conclusions

The delayed repeat acquisition of PET images improves the accuracy of [¹⁸F]-FDG PET/CT in patients with suspicious breast lesions with respect to the single-time-point acquisition. In addition, malignant breast lesions displayed an increase in FDG uptake over time, whereas benign lesions showed a reduction. These variations in FDG uptake between PET-1 and PET-2 are a reliable parameter that can be used for differentiating between benign and malignant breast lesions.     

Repeatability of hypoxia PET imaging using [<Superscript>18</Superscript>F]HX4 in lung and head and neck cancer patients: a prospective multicenter trial

Purpose

Hypoxia is an important factor influencing tumor progression and treatment efficacy. The aim of this study was to investigate the repeatability of hypoxia PET imaging with [¹⁸F]HX4 in patients with head and neck and lung cancer.

Methods

Nine patients with lung cancer and ten with head and neck cancer were included in the analysis (NCT01075399). Two sequential pretreatment [¹⁸F]HX4 PET/CT scans were acquired within 1 week. The maximal and mean standardized uptake values (SUV_max and SUV_mean) were defined and the tumor-to-background ratios (TBR) were calculated. In addition, hypoxic volumes were determined as the volume of the tumor with a TBR >1.2 (HV_1.2). Bland Altman analysis of the uptake parameters was performed and coefficients of repeatability were calculated. To evaluate the spatial repeatability of the uptake, the PET/CT images were registered and a voxel-wise comparison of the uptake was performed, providing a correlation coefficient.

Results

All parameters of [¹⁸F]HX4 uptake were significantly correlated between scans: SUV_max (r?=?0.958, p?<?0.001), SUV_mean (r?=?0.946, p?<?0.001), TBR_max (r?=?0.962, p?<?0.001) and HV_1.2 (r?=?0.995, p?<?0.001). The relative coefficients of repeatability were 15 % (SUV_mean), 17 % (SUV_max) and 17 % (TBR_max). Voxel-wise analysis of the spatial uptake pattern within the tumors provided an average correlation of 0.65?±?0.14.

Conclusion

Repeated hypoxia PET scans with [¹⁸F]HX4 provide reproducible and spatially stable results in patients with head and neck cancer and patients with lung cancer. [¹⁸F]HX4 PET imaging can be used to assess the hypoxic status of tumors and has the potential to aid hypoxia-targeted treatments.

     

Correlation between [18F]FDG PET/CT and volume perfusion CT in primary tumours and mediastinal lymph nodes of non-small-cell lung cancer

Purpose

The aim of this study was to investigate correlations between glucose metabolism as determined by [¹⁸F]FDG PET/CT and tumour perfusion as quantified by volume perfusion CT in primary tumours and mediastinal lymph nodes (MLN) of patients with non-small-cell lung cancer (NSCLC).

Methods

Enrolled in the study were 17 patients with NSCLC. [¹⁸F]FDG uptake was quantified in terms of SUV_max and SUV_avg. Blood flow (BF), blood volume (BV) and flow extraction product (K^trans) were determined as perfusion parameters. The correlations between the perfusion parameters and [¹⁸F]FDG uptake values were subsequently evaluated.

Results

For the primary tumours, no correlations were found between perfusion parameters and [¹⁸F]FDG uptake. In MLN, there were negative correlations between BF and SUV_avg (r?=??0.383), BV and SUV_avg (r?=??0.406), and BV and SUV_max (r?=??0.377), but not between BF and SUV_max, K^trans and SUV_avg, or K^trans and SUV_max. Additionally, in MLN with SUV_max >2.5 there were negative correlations between BF and SUV_avg (r?=??0.510), BV and SUV_avg (r?=??0.390), BF and SUV_max (r?=??0.536), as well as BV and SUV_max (r?=??0.346).

Conclusion

Perfusion and glucose metabolism seemed to be uncoupled in large primary tumours, but an inverse correlation was observed in MLN. This information may help improve therapy planning and response evaluation.     

Whole-body [18F]FDG PET/MRI vs. PET/CT in the assessment of bone lesions in oncological patients: initial results

Objectives

To compare [¹⁸?F]FDG PET/MRI with PET/CT for the assessment of bone lesions in oncologic patients.

Methods

This prospective study included 67 patients with solid tumours scheduled for PET/CT with [¹⁸?F]FDG who also underwent a whole-body PET/MRI scan. The datasets (PET/CT, PET/MRI) were rated by two readers regarding lesion conspicuity (four-point scale) and diagnostic confidence (five-point scale). Median scores were compared using the Wilcoxon test.

Results

Bone metastases were present in ten patients (15 %), and benign bone lesions in 15 patients (22 %). Bone metastases were predominantly localized in the pelvis (18 lesions, 38 %) and the spine (14 lesions, 29 %). Benign bone lesions were exclusively osteosclerotic and smaller than the metastases (mean size 6 mm vs. 23 mm). While PET/CT allowed identification of 45 of 48 bone metastases (94 %), PET/MRI allowed identification of all bone metastases (100 %). Conspicuity of metastases was high for both modalities with significantly better results using PET/MRI (p?<?0.05). Diagnostic confidence in lesion detection was high for both modalities without a significant difference. In benign lesions, conspicuity and diagnostic confidence were significantly higher with PET/CT (p?<?0.05).

Conclusions

[¹⁸?F]FDG PET/MRI shows high potential for the assessment of bone metastases by offering superior lesion conspicuity when compared to PET/CT. In hypersclerotic, benign bone lesions PET/CT still sets the reference.

Key Points

? PET/MRI and PET/CT are of equal value for the identification of disease-positive patients ? PET/MRI offers higher lesion conspicuity as well as diagnostic confidence ? PET/MRI is an attractive new alternative for the assessment of bone metastases     

Prospective evaluation of [<Superscript>11</Superscript>C]Choline PET/CT in therapy response assessment of standardized docetaxel first-line chemotherapy in patients with advanced castration refractory prostate cancer

Purpose

The aim of this study was to prospectively evaluate the value of [¹¹C] Choline PET/CT in monitoring early and late response to a standardized first-line docetaxel chemotherapy in castration refractory prostate cancer (mCRPC) patients.

Methods

Thirty-two patients were referred for [¹¹C] Choline PET/CT before the start of docetaxel chemotherapy, after one and ten chemotherapy cycles (or - in case of discontinuation - after the last administered cycle) for therapy response assessment. [¹¹C] Choline uptake (SUV_max, SUV_mean), CT derived Houndsfield units (HU_max, HU_mean), and volume of bone, lung, and nodal metastases and local recurrence were measured semi-automatically at these timepoints. Change in SUV_max, SUV_mean, HU_max, HU_mean, and volume was assessed between PET 2 and 1 (early response assessment, ERA) and PET 3 and 1 (late response assessment, LRA) on a patient and lesion basis. Results of PET/CT were compared to clinically used RECIST 1.1 and clinical criteria based therapy response assessment including PSA for defining progressive disease (PD) and non-progressive disease (nPD), respectively. Relationships between changes of SUV_max and SUV_mean (early and late) and changes of PSA_early and PSA_late were evaluated. Prognostic value of initial SUV_max and SUV_mean was assessed. Statistical analyses were performed using SPSS.

Results

In the patient-based ERA and LRA there were no statistically significant differences in change of choline uptake, HU, and volume between PD and nPD applying RECIST or clinical response criteria. In the lesion-based ERA, decrease in choline uptake of bone metastases was even higher in PD (applying RECIST criteria), whereas in LRA the decrease was higher in nPD (applying clinical criteria). There were only significant correlations between change in choline uptake and PSA in ERA in PD, in LRA no significant correlations were discovered. Initial SUV_max and SUV_mean were statistically significantly higher in nPD (applying clinical criteria).

Conclusion

There is no significant correlation between change in choline uptake in [¹¹C] Choline PET/CT and clinically routinely used objective response assessment during the early and late course of docetaxel chemotherapy. Therefore, [¹¹C] Choline PET/CT seems to be of limited use in therapy response assessment in standardized first-line chemotherapy in mCRPC patients.

     

Detection and quantification of focal uptake in head and neck tumours: 18F-FDG PET/MR versus PET/CT

Purpose

Our objectives were to assess the quality of PET images and coregistered anatomic images obtained with PET/MR, to evaluate the detection of focal uptake and SUV, and to compare these findings with those of PET/CT in patients with head and neck tumours.

Methods

The study group comprised 32 consecutive patients with malignant head and neck tumours who underwent whole-body ¹⁸F-FDG PET/MR and PET/CT. PET images were reconstructed using the attenuation correction sequence for PET/MR and CT for PET/CT. Two experienced observers evaluated the anonymized data. They evaluated image and fusion quality, lesion conspicuity, anatomic location, number and size of categorized (benign versus assumed malignant) lesions with focal uptake. Region of interest (ROI) analysis was performed to determine SUVs of lesions and organs for both modalities. Statistical analysis considered data clustering due to multiple lesions per patient.

Results

PET/MR coregistration and image fusion was feasible in all patients. The analysis included 66 malignant lesions (tumours, metastatic lymph nodes and distant metastases), 136 benign lesions and 470 organ ROIs. There was no statistically significant difference between PET/MR and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUV_mean and SUV_max measured on PET/MR and PET/CT for malignant lesions, benign lesions and organs (ρ?=?0.787 to 0.877, p?<?0.001). SUV_mean and SUV_max measured on PET/MR were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p?<?0.05). The main factor affecting the difference between SUVs in malignant lesions was tumour size (p?<?0.01).

Conclusion

In patients with head and neck tumours, PET/MR showed equivalent performance to PET/CT in terms of qualitative results. Comparison of SUVs revealed an excellent correlation for measurements on both modalities, but underestimation of SUVs measured on PET/MR as compared to PET/CT.     

Quantitative assessment of atherosclerotic plaques on <Superscript>18</Superscript>F-FDG PET/MRI: comparison with a PET/CT hybrid system

Purpose

PET with ¹⁸F-FDG has the potential to assess vascular macrophage metabolism. ¹⁸F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel ¹⁸F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior morphological conspicuity of plaque lesions. The purpose of this study was to evaluate the reliability and accuracy of ¹⁸F-FDG PET/MRI uptake quantification compared to PET/CT as a reference standard in patients with carotid atherosclerotic plaques.

Methods

The study group comprised 34 consecutive oncological patients with carotid plaques who underwent both PET/CT and PET/MRI with ¹⁸F-FDG on the same day. The presence of atherosclerotic plaques was confirmed by 3 T MRI scans. Maximum standardized uptake values (SUV_max) for carotid plaque lesions and the average SUV of the blood pool within the adjacent internal jugular vein were determined and target-to-blood ratios (TBRs, plaque to blood pool) were calculated.

Results

Atherosclerotic lesions with maximum colocalized focal FDG uptake were assessed in each patient. SUV_max values of carotid plaque lesions were significantly lower on PET/MRI than on PET/CT (2.3?±?0.6 vs. 3.1?±?0.6; P?<?0.01), but were significantly correlated between PET/CT and PET/MRI (Spearman’s r?=?0.67, P?<?0.01). In contrast, TBR_max values of plaque lesions were similar on PET/MRI and on PET/CT (2.2?±?0.3 vs. 2.2?±?0.3; P?=?0.4), and again were significantly correlated between PET/MRI and PET/CT (Spearman’s r?=?0.73, P?<?0.01). Considering the increasing trend in SUV_max and TBR_max values from early to delayed imaging time-points on PET/CT and PET/MRI, respectively, with continuous clearance of radioactivity from the blood, a slight underestimation of TBR_max values may also be expected with PET/MRI compared with PET/CT.

Conclusion

SUV_max and TBR_max values are widely accepted reference parameters for estimation of the radioactivity of atherosclerotic plaques on PET/CT. However, due to a systematic underestimation of SUV_max and TBR_max with PET/MRI, the optimal cut-off values indicating the presence of inflamed plaque tissue need to be newly defined for PET/MRI.

     

A PET/MRI study towards finding the optimal [<Superscript>18</Superscript>F]Fluciclovine PET protocol for detection and characterisation of primary prostate cancer

Purpose

[¹⁸F]Fluciclovine PET imaging shows promise for the assessment of prostate cancer. The purpose of this PET/MRI study is to optimise the PET imaging protocol for detection and characterisation of primary prostate cancer, by quantitative evaluation of the dynamic uptake of [¹⁸F]Fluciclovine in cancerous and benign tissue.

Methods

Patients diagnosed with high-risk primary prostate cancer underwent an integrated [¹⁸F]Fluciclovine PET/MRI exam before robot-assisted radical prostatectomy with extended pelvic lymph node dissection. Volumes-of-interest (VOIs) of selected organs (prostate, bladder, blood pool) and sub-glandular prostate structures (tumour, benign prostatic hyperplasia (BPH), inflammation, healthy tissue) were delineated on T2-weighted MR images, using whole-mount histology samples as a reference. Three candidate windows for optimal PET imaging were identified based on the dynamic curves of the mean and maximum standardised uptake value (SUV_mean and SUV_max, respectively). The statistical significance of differences in SUV between VOIs were analysed using Wilcoxon rank sum tests (

Results

Twenty-eight (28) patients [median (range) age: 66 (55-72) years] were included. An early (W1: 5-10 minutes post-injection) and two late candidate windows (W2: 18-23; W3: 33-38 minutes post-injection) were selected. Late compared with early imaging was better able to distinguish between malignant and benign tissue [W3, SUV_mean: tumour vs. BPH 2.5 vs. 2.0 (p<0.001), tumour vs. healthy tissue 2.5 vs. 2.0 (p=0.771), tumour vs inflammation 3.1 vs. 2.2 (p<0.001)] as well as between high-grade and low/intermediate-grade tumours (W3, SUV_mean: 2.6 vs. 2.1 (p=0.173)). These differences were relevant to the peripheral zone, but not the central gland.

Conclusion

Late-window [¹⁸F]Fluciclovine PET imaging shows promise for distinguishing between prostate tumours and benign tissue and for assessment of tumour aggressiveness.

     

Incidental pituitary uptake on whole-body 18F-FDG PET/CT: a multicentre study

Purpose

The purpose of this study was to determine the incidence of incidental pituitary uptake on whole-body ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and to investigate its clinical significance.

Methods

The files of 40,967 patients who underwent whole-body FDG PET/CT were retrospectively reviewed. Quantification of pituitary metabolic activity was obtained by using the maximum standardized uptake value (SUV_max). Hormone assays and pituitary MRIs were performed to assess pituitary lesions.

Results

Focally increased pituitary FDG uptake on PET/CT was found in 30 of 40,967 patients, accounting for an incidence of 0.073%. The mean SUV_max of 30 patients was 8.9?±?6.6 (range: 3.2–32.6). Histological diagnosis was obtained in three patients and included two growth hormone-secreting adenomas and one non-functioning adenoma. Hormone assays were performed on serum samples from 11 patients, 2 of whom were shown to have hypersecretion of pituitary hormone. MRI was performed on 19 patients. Abnormal MRI findings suggesting a pituitary mass were found in 18 of 19 cases (94.7%). The mean SUV_max calculated without correction for partial volume effect for macroadenomas was significantly higher than the SUV_max for microadenomas (11.5?±?8.4 vs 4.8?±?1.3; p?<?0.05). There were no cases diagnosed with metastasis to the pituitary gland during clinical follow-up.

Conclusion

Incidental pituitary FDG uptake was a very rare finding. Cases with incidental pituitary FDG uptake were diagnosed primarily with clinically non-functioning adenomas, and there were also a few functioning adenomas. Further evaluations, including hormone assays and pituitary MRI, are warranted when pituitary uptake is found on FDG PET/CT.     

Predictive role of post-treatment [18F]FDG PET/CT in patients with uterine cervical cancer

Objective

To evaluate the efficacy of post-treatment positron emission tomography (PET)/computed tomography (CT) for identification of tumor recurrence, and to determine whether [¹⁸F]fluorodeoxyglucose (FDG) uptake measured as the maximum standardized uptake value (SUV_max) has predictive role regarding survival in patients with uterine cervical cancer.

Methods

Medical records from 276 women with uterine cervical cancer who had post-treatment [¹⁸F]FDG PET/CT performed were retrospectively reviewed. Results of PET/CT scans were compared with histological or clinical examination.

Results

Ninety-five (34.4%) of the 276 patients had documented recurrence by either surgical biopsy or clinical and imaging follow-up. Median duration from treatment to PET/CT scan was 24 months (range, 6–307). The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of post-treatment PET/CT were 94.7%, 87.8%, 80.4%, 97%, and 90.2%, respectively. The PET/CT scan modified both the diagnostic or treatment plan in 67 patients (24.3%). Patients were divided into two groups according to cut-off SUV_max established on the basis of ROC analysis (<5.25 vs. ≥5.25), and there was a significant difference in OS between groups (p = 0.001). In addition, the 5-year progression-free survival (PFS) and OS rates of patients with a negative PET/CT scan for recurrence were significantly better than those with a positive PET/CT (98.62% vs. 17.83%, p < 0.0001 for PFS, 99.31% vs. 85.38%, p = 0.0015 for OS).

Conclusion

Post-treatment PET/CT scan is a sensitive and accurate surveillance modality, and provides prognostic information in uterine cervical cancer. Furthermore, it may allow individualization of patient care.     

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.

     

Comparison of integrated whole-body [11C]choline PET/MR with PET/CT in patients with prostate cancer

Purpose

To evaluate the performance of conventional [¹¹C]choline PET/CT in comparison to that of simultaneous whole-body PET/MR.

Methods

The study population comprised 32 patients with prostate cancer who underwent a single-injection dual-imaging protocol with PET/CT and subsequent PET/MR. PET/CT scans were performed applying standard clinical protocols (5 min after injection of 793?±?69 MBq [¹¹C]choline, 3 min per bed position, intravenous contrast agent). Subsequently (52?±?15 min after injection) PET/MR was performed (4 min per bed position). PET images were reconstructed iteratively (OSEM 3D), scatter and attenuation correction of emission data and regional allocation of [¹¹C]choline foci were performed using CT data for PET/CT and segmented Dixon MR, T1 and T2 sequences for PET/MR. Image quality of the respective PET scans and PET alignment with the respective morphological imaging modality were compared using a four point scale (0–3). Furthermore, number, location and conspicuity of the detected lesions were evaluated. SUVs for suspicious lesions, lung, liver, spleen, vertebral bone and muscle were compared.

Results

Overall 80 lesions were scored visually in 29 of the 32 patients. There was no significant difference between the two PET scans concerning number or conspicuity of the detected lesions (p not significant). PET/MR with T1 and T2 sequences performed better than PET/CT in anatomical allocation of lesions (2.87?±?0.3 vs. 2.72?±?0.5; p?=?0.005). The quality of PET/CT images (2.97?±?0.2) was better than that of the respective PET scan of the PET/MR (2.69?±?0.5; p?=?0.007). Overall the maximum and mean lesional SUVs exhibited high correlations between PET/CT and PET/MR (ρ?=?0.87 and ρ?=?0.86, respectively; both p?<?0.001).

Conclusion

Despite a substantially later imaging time-point, the performance of simultaneous PET/MR was comparable to that of PET/CT in detecting lesions with increased [¹¹C]choline uptake in patients with prostate cancer. Anatomical allocation of lesions was better with simultaneous PET/MR than with PET/CT, especially in the bone and pelvis. These promising findings suggest that [¹¹C]choline PET/MR might have a diagnostic benefit compared to PET/CT in patients with prostate cancer, and now needs to be further evaluated in prospective trials.     

Diagnostic accuracy of 68Ga-DOTANOC PET/CT imaging in pheochromocytoma

Purpose

The purpose of the present study was to evaluate the diagnostic accuracy of ⁶⁸Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma.

Methods

Data of 62 patients [age 34.3?±?16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n?=?70), who had undergone ⁶⁸Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUV_max), SUV_mean, SUV_max/SUV_liver, and SUV_mean/SUV_liver. Results of PET/CT were compared with ¹³¹I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard.

Results

The sensitivity, specificity, and accuracy of ⁶⁸Ga-DOTANOC PET/CT was 90.4, 85, and 88.7 %, respectively, on patient-based analysis and 92, 85, and 90 %, respectively, on lesion-based analysis. ⁶⁸Ga-DOTANOC PET/CT showed 100 % accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of ⁶⁸Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than ¹³¹I-MIBG imaging (91.1 vs 66.6 %, p?=?0.035). SUV_max was higher for pheochromocytomas than other adrenal lesions (p?=?0.005), MEN2-associated vs sporadic pheochromocytoma (p?=?0.012), but no difference was seen between benign vs malignant pheochromocytoma (p?=?0.269).

Conclusion

⁶⁸Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to ¹³¹I-MIBG imaging for this purpose. Best results of ⁶⁸Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.     

Evaluation of contrast medium enhancement and [(18)F]-FDG uptake of liver metastasis in PET/CT prior to therapy

Objective

To evaluate the contrast medium enhancement and [¹⁸F]-FDG uptake of liver metastases in patients suffering from colon or breast carcinoma prior to therapy.

Material and methods

PET/CT (Philips Gemini) with 200 MBq [¹⁸F]-FDG and contrast medium was performed in 50 patients with colon and 39 patients with breast carcinoma. Lesions were characterized with the presence or the absence of a rim enhancement. The area size, the HU_mean, HU_max, SUV_mean, SUV_max of the lesion and of the liver were determined. The standard uptake values (SUVs) were correlated with the tumor markers CEA and CA 15-3.

Results

The lesions of colon carcinoma had HU_mean-values of 70.7 ± 19.2 and of breast carcinoma 88.1 ± 21.7 (p < 0.0001). In breast cancer the SUV_mean was 3.9 ± 1.3 versus 4.4 ± 1.9 in colon carcinoma (p = 0.0182). Lesion of colon carcinoma with rim enhancement had a significantly higher SUV_mean (4.4 ± 1.5 versus 3.6 ± 1.2; p = 0.001) and SUV_max (6.7 ± 2.6 versus 5.1 ± 2.1; p = 0.000) than lesions without a rim enhancement. A good correlation between tumor markers and SUVs_max could be found in both tumor groups; r = 0.83 (p < 0.01) for colon carcinoma and r = 0.82 (p < 0.01) for breast carcinoma.

Conclusions

The rim enhancement of the lesions in colon carcinoma indicate a significantly higher SUV.     

Integrated 18F-FDG PET/perfusion CT for the monitoring of neoadjuvant chemoradiotherapy in rectal carcinoma: correlation with histopathology

Purpose

The aim of this study was to prospectively monitor changes in the flow-metabolic phenotype (ΔFMP) of rectal carcinoma (RC) after neoadjuvant chemoradiotherapy (CRT) and to evaluate whether ΔFMP of RC correlate with histopathological prognostic factors including response to CRT.

Methods

Sixteen patients with RC (12 men, mean age 60.7?±?12.8 years) underwent integrated ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/perfusion CT (PET/PCT), followed by neoadjuvant CRT and surgery. In 13 patients, PET/PCT was repeated after CRT. Perfusion [blood flow (BF), blood volume (BV), mean transit time (MTT)] and metabolic [maximum and mean standardized uptake values (SUV_max, SUV_mean)] parameters as well as the FMP (BF × SUV_max) were determined before and after CRT by two independent readers and correlated to histopathological prognostic factors of RC (microvessel density, necrosis index, regression index, vascular invasion) derived from resected specimens. The diagnostic performance of ΔFMP for prediction of treatment response was determined.

Results

FMP significantly decreased after CRT (p?<?0.001), exploiting higher changes after CRT as compared to changes of perfusion and metabolic parameters alone. Before CRT, no significant correlations were found between integrated PET/PCT and any of the histopathological parameters (all p?>?0.05). After CRT, BV and SUV_max correlated positively with the necrosis index (r?=?0.67/0.70), SUV_max with the invasion of blood vessels (r?=?0.62) and ΔFMP with the regression index (r?=?0.88; all p?<?0.05). ΔFMP showed high accuracy for prediction of histopathological response to CRT (AUC 0.955, 95 % confidence interval 0.833–1.000, p?<?0.01) using a cut-off value of ?75 %.

Conclusion

In RC, ΔFMP derived from integrated ¹⁸F-FDG PET/PCT is useful for monitoring the effects of neoadjuvant CRT and allows prediction of histopathological response to CRT.     

Comparison of PET imaging with a 68Ga-labelled PSMA ligand and 18F-choline-based PET/CT for the diagnosis of recurrent prostate cancer

Purpose

Positron emission tomography (PET) with choline tracers has found widespread use for the diagnosis of prostate cancer (PC). However, choline metabolism is not increased in a considerable number of cases, whereas prostate-specific membrane antigen (PSMA) is overexpressed in most PCs. Therefore, a ⁶⁸Ga-labelled PSMA ligand could be superior to choline tracers by obtaining a high contrast. The aim of this study was to compare such a novel tracer with standard choline-based PET/CT.

Methods

Thirty-seven patients with biochemical relapse of PC [mean prostate-specific antigen (PSA) 11.1?±?24.1 ng/ml, range 0.01–116] were retrospectively analysed after ¹⁸F-fluoromethylcholine and ⁶⁸Ga-PSMA PET/CT within a time window of 30 days. Radiotracer uptake that was visually considered as PC was semi-quantitatively analysed by measuring the maximum standardized uptake values (SUV_max) of the scans acquired 1 h after injection of ⁶⁸Ga-PSMA complex solution (median 132 MBq, range 59–263 MBq) and ¹⁸F-fluoromethylcholine (median 237 MBq, range 114–374 MBq), respectively. In addition, tumour to background ratios were calculated.

Results

A total of 78 lesions characteristic for PC were detected in 32 patients using ⁶⁸Ga-PSMA PET/CT and 56 lesions were detected in 26 patients using choline PET/CT. The higher detection rate in ⁶⁸Ga-PSMA PET/CT was statistically significant (p?=?0.04). In five patients no lesion was found with both methods. All lesions detected by ¹⁸F-fluoromethylcholine PET/CT were also seen by ⁶⁸Ga-PSMA PET/CT. In ⁶⁸Ga-PSMA PET/CT SUV_max was clearly (>10 %) higher in 62 of 78 lesions (79.1 %) and the tumour to background ratio was clearly (>10 %) higher in 74 of 78 lesions (94.9 %) when compared to ¹⁸F-fluoromethylcholine PET/CT.

Conclusion

⁶⁸Ga-PSMA PET/CT can detect lesions characteristic for PC with improved contrast when compared to standard ¹⁸F-fluoromethylcholine PET/CT, especially at low PSA levels.     

Functional imaging of head and neck squamous cell carcinoma with diffusion-weighted MRI and FDG PET/CT: quantitative analysis of ADC and SUV

Purpose

Head and neck squamous cell carcinoma (HNSCC) may cause a decreased apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (DW MRI) and an increased standardized uptake value (SUV) on fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). We analysed the reproducibility of ADC and SUV measurements in HNSCC and evaluated whether these biomarkers are correlated or independent.

Methods

This retrospective analysis of DW MRI and FDG PET/CT data series included 34 HNSCC in 33 consecutive patients. Two experienced readers measured tumour ADC and SUV values independently. Statistical comparison and correlation with histopathology was done. Intra- and inter-observer agreement for ADC and SUV measurements was assessed.

Results

Intraclass correlation coefficient (ICC) analysis showed almost perfect reproducibility (>0.90) for ADC_mean, ADC_min, SUV_max and SUV_mean values for intra-observer and inter-observer agreement. Mean ADC_mean and ADC_min in HNSCC were 1.05?±?0.34 × 10^?3?mm²/s and 0.65?±?0.29 × 10^?3?mm²/s, respectively. Mean SUV_mean and mean SUV_max were 7.61?±?3.87 and 12.8?±?5.0, respectively. Although statistically not significant, a trend towards higher SUV and lower ADC was observed with increasing tumour dedifferentiation. Pearson’s correlation analysis showed no significant correlation between ADC and SUV measurements (r ?0.103, ?0.051; p 0.552, 0.777).

Conclusion

Our data suggest that ADC and SUV values are reproducible and independent biomarkers in HNSCC.     

Direct comparison of [18F]FDG PET/CT with PET alone and with side-by-side PET and CT in patients with malignant melanoma

Purpose

The purpose of this retrospective, blinded study was to evaluate the additional value of [¹⁸F]FDG PET/CT in comparison with PET alone and with side-by-side PET and CT in patients with malignant melanoma (MM).

Methods

A total of 127 consecutive studies of patients with known MM referred for a whole-body PET/CT examination were included in this study. PET alone, side-by-side PET and CT and integrated PET/CT study were independently and separately interpreted without awareness of the clinical information. One score each was applied for certainty of lesion localisation and for certainty of lesion characterisation. Verification of the findings was subsequently performed using all available clinical, pathological (n?=?30) and follow-up information.

Results

The number of lesions with an uncertain localisation was significantly (p?p?p?=?0.057) compared versus PET alone. Respectively, PET, side-by-side PET and CT and PET/CT showed a sensitivity of 86%, 89% and 91%, a specificity of 94%, 94% and 94%, a positive predictive value of 96%, 96% and 96% and a negative predictive value of 80%, 83% and 87%.

Conclusion

Integrated PET/CT offers a significant benefit in lesion localisation and an improvement in lesion characterisation compared with PET alone or with side-by-side PET and CT. The benefit is not as great as that reported for other tumour entities, which may be due to the high avidity of MM for [¹⁸F]FDG.