Dual-time-point <Superscript>18</Superscript>F-FDG PET/CT in the diagnosis of solitary pulmonary lesions in a region with endemic granulomatous diseases

Objective

Granulomatous diseases (GDs) can be metabolically active and indistinguishable from lung cancer on ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) imaging. Evaluation of solitary pulmonary lesions remains a diagnostic challenge in regions with endemic GD. This study sought to determine the efficacy of dual-time-point (DTP) ¹⁸F-FDG PET/computed tomography (CT) imaging in diagnosing solitary pulmonary lesions from such regions.

Methods

A total of 50 patients with solitary pulmonary nodules or masses with confirmed histopathological diagnoses underwent DTP ¹⁸F-FDG PET/CT imaging at 1 and 3 h after tracer injection. The maximum standardized uptake value (SUV_max) on early and delayed scans (SUV_1h and SUV_3h, respectively) and retention index (RI) were calculated for each pulmonary lesion. Receiver operating characteristic analysis was performed to evaluate the discriminating validity of the parameters.

Results

There were 37 malignant and 13 benign solitary pulmonary lesions. Eight of the 13 (62 %) benign lesions were GDs. The sensitivity/specificity/accuracy of SUV_1h, SUV_3h and RI were 84/69/80 %, 84/85/84 %, and 81/54/74 %, respectively. SUV_3h had the best diagnostic performance, especially regarding specificity. The values of SUV_1h and SUV_3h were significantly different between malignant lesions and GD, while the RI values of malignant lesions and GD were both high (18.6 ± 19.5 and 18.7 ± 15.3 %, respectively; P = not significant).

Conclusion

SUV_3h appeared to improve the diagnostic specificity of ¹⁸F-FDG PET/CT in evaluating solitary pulmonary lesions from regions with endemic GD.

     

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 intratumoural heterogeneity on 18F-FDG PET/CT for characterization of peripheral nerve sheath tumours in neurofibromatosis type 1

Purpose

The aim of the study was to evaluate the potential usefulness of intratumoural tracer uptake heterogeneity on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT as compared to a cut-off maximum standardized uptake value (SUV_max) for characterization of peripheral nerve sheath tumours (PNSTs) in neurofibromatosis type 1 (NF1).

Methods

Fifty patients suffering from NF1 were examined by ¹⁸F-FDG PET/CT. Intralesional tracer uptake was analysed qualitatively and semi-quantitatively by measuring the mean and maximum SUV. Uptake heterogeneity was graded qualitatively using a three-point scale and semi-quantitatively by calculating an SUV-based heterogeneity index (HI_SUV). Cohen’s κ was used to determine inter- and intra-rater agreement. Histopathological evaluation and clinical as well as radiological follow-up examinations served as the reference standards.

Results

A highly significant correlation between the degree of intratumoural uptake heterogeneity on ¹⁸F-FDG PET and malignant transformation of PNSTs was observed (p?<?0.0001). Semi-quantitative HI_SUV was significantly higher in malignant PNSTs (MPNSTs) than in benign tumours (p?=?0.0002). Both intralesional heterogeneity and SUV_max could be used to identify malignant tumours with a sensitivity of 100 %. Cohen’s κ was 0.86 for inter-rater agreement and 0.88 for intra-rater agreement on heterogeneity.

Conclusion

MPNSTs in patients with NF1 demonstrate considerable intratumoural uptake heterogeneity on ¹⁸F-FDG PET/CT. Assessment of tumour heterogeneity is highly reproducible. Both tumour heterogeneity and a cut-off SUV_max may be used to sensitively identify malignant PNSTs, but the specificity is higher for the latter. A combination of both methods leads to a non-significant improvement in diagnostic performance.     

Anatomical and functional volume concordance between FDG PET,and T2 and diffusion-weighted MRI for cervical cancer: a hybrid PET/MR study

Purpose

To evaluate the concordance among ¹⁸F-FDG PET imaging, MR T2-weighted (T2-W) imaging and apparent diffusion coefficient (ADC) maps with diffusion-weighted (DW) imaging in cervical cancer using hybrid whole-body PET/MR.

Methods

This study prospectively included 35 patients with cervical cancer who underwent pretreatment ¹⁸F-FDG PET/MR imaging. ¹⁸F-FDG PET and MR images were fused using standard software. The percent of the maximum standardized uptake values (SUV_max) was used to contour tumours on PET images, and volumes were calculated automatically. Tumour volumes measured on T2-W and DW images were calculated with standard techniques of tumour area multiplied by the slice profile. Parametric statistics were used for data analysis.

Results

FDG PET tumour volumes calculated using SUV_max (14.30?±?4.70) and T2-W imaging volume (33.81?±?27.32 cm³) were similar (P?>?0.05) at 35 % and 40 % of SUV_max (32.91?±?18.90 cm³ and 27.56?±?17.19 cm³ respectively) and significantly correlated (P?<?0.001; r?=?0.735 and 0.766). The mean DW volume was 30.48?±?22.41 cm³. DW volumes were not significantly different from FDG PET volumes at either 35 % SUV_max or 40 % SUV_max or from T2-W imaging volumes (P?>?0.05). PET subvolumes with increasing SUV_max cut-off percentage showed an inverse change in mean ADC values on DW imaging (P?<?0.001, ANOVA).

Conclusion

Hybrid PET/MR showed strong volume concordance between FDG PET, and T2-W and DW imaging in cervical cancer. Cut-off at 35 % or 40 % of SUV_max is recommended for ¹⁸F-FDG PET/MR SUV-based tumour volume estimation. The linear tumour subvolume concordance between FDG PET and DW imaging demonstrates individual regional concordance of metabolic activity and cell density.     

Current generation time-of-flight <Superscript>18</Superscript>F-FDG PET/CT provides higher SUVs for normal adrenal glands,while maintaining an accurate characterization of benign and malignant glands

Objective

Modern PET/CT scanners have significantly improved detectors and fast time-of-flight (TOF) performance and this may improve clinical performance. The aim of this study was to analyze the impact of a current generation TOF PET/CT scanner on standardized uptake values (SUV), lesion-background contrast and characterization of the adrenal glands in patients with suspected lung cancer, in comparison with literature data and commonly used SUV cut-off levels.

Methods

We included 149 adrenal glands from 88 patients with suspected lung cancer, who underwent ¹⁸F-FDG PET/CT. We measured the SUV_max in the adrenal gland and compared this with liver SUV_mean to calculate the adrenal-to-liver ratio (AL ratio). Results were compared with literature derived with older scanners, with SUV_max values of 1.0 and 1.8 for normal glands [1, 2]. Final diagnosis was based on histological proof or follow-up imaging. We proposed cut-off values for optimal separation of benign from malignant glands.

Results

In 127 benign and 22 malignant adrenal glands, SUV_max values were 2.3 ± 0.7 (mean ± SD) and 7.8 ± 3.2 respectively (p < 0.01). Corresponding AL ratios were 1.0 ± 0.3 and 3.5 ± 1.4 respectively (p < 0.01). With a SUV_max cut-off value of 3.7, 96 % sensitivity and 96 % specificity was reached. An AL ratio cut-off value of 1.8 resulted in 91 % sensitivity and 97 % specificity. The ability of both SUV_max and AL ratio to separate benign from malignant glands was similar (AUC 0.989 vs. 0.993, p = 0.22).

Conclusions

Compared with literature based on the previous generation of PET scanners, current generation TOF ¹⁸F-FDG PET/CT imaging provides higher SUVs for benign adrenal glands, while it maintains a highly accurate distinction between benign and malignant glands. Clinical implementation of current generation TOF PET/CT requires not only the use of higher cut-off levels but also visual adaptation by PET readers.

     

<Superscript>18</Superscript>F-FDG and <Superscript>18</Superscript>F-FLT PET/CT imaging in the characterization of mediastinal lymph nodes

Purpose

There is currently no single modality for accurate characterization of enlarged mediastinal lymph nodes into benign or malignant. Recently ¹⁸F-fluorothymidine (FLT) has been used as a proliferation marker. In this prospective study, we examined the role of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and ¹⁸F-FLT PET/CT in categorizing mediastinal lymph nodes as benign or malignant.

Materials and methods

A total of 70 consecutive patients with mediastinal lymphadenopathy detected on computed tomography (CT) or chest radiograph underwent whole body ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT (within 1 week of each other). Lymph nodal tracer uptake was determined by calculation of standardized uptake value (SUV) with both the tracers. Results of PET/CT were compared with histopathology of the lymph nodes.

Results

Histopathology results showed thirty-seven patients with sarcoidosis, seven patients with tuberculosis, nine patients with non-small cell lung cancer, five patients with Hodgkin’s lymphoma and twelve patients with non-Hodgkin’s lymphoma. The mean FDG SUV_max of sarcoidosis, tuberculosis, Hodgkin’s and non-Hodgkin’s lymphoma was 12.7, 13.4, 8.2, and 8.8, respectively, and the mean FLT SUV_max was 6.0, 5.4, 4.4, and 3.8, respectively. It was not possible to characterize mediastinal lymphadenopathy as benign or malignant solely based on FDG SUV_max values (p > 0.05) or FLT SUV_max values (p > 0.05). There was no significant difference in FDG uptake (p > 0.9) or FLT uptake (p > 0.9) between sarcoidosis and tuberculosis. In lung cancer patients, the FDG SUV_max and FLT SUV_max of those lymph nodes with tumor infiltration on biopsy was 6.7 and 3.9, respectively, and those without nodal infiltration was 6.4 and 3.7, respectively, and both the tracers were not able to characterize the nodal status as malignant or benign (p > 0.05).

Conclusion

Though ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT reflect different aspects of biology, i.e., proliferation and metabolism, respectively, neither tracer could provide satisfactory categorization of benign and malignant lymph nodes. The results of this study clearly suggest that differentiation of mediastinal nodes into benign and malignant solely based on SUV_max values cannot be relied upon, especially in settings where tuberculosis and sarcoidosis are common.

     

The value of 18F-FDG PET/CT in the management of malignant peripheral nerve sheath tumors

Purpose

Our objective was to determine how positron emission tomography (PET)/CT had been used in the clinical treatment of malignant peripheral nerve sheath tumor (MPNST) patients at The University of Texas MD Anderson Cancer Center.

Methods

We reviewed a database of MPNST patients referred to MD Anderson Cancer Center during 1995–2011. We enrolled 47 patients who underwent PET/CT imaging. Disease stage was based on conventional imaging and PET/CT findings using National Comprehensive Cancer Network (NCCN) guidelines. Treatment strategies based on PET/CT and conventional imaging were determined by chart review. The maximum and mean standardized uptake values (SUV_max, SUV_mean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), change in SUV_max, change in MTV, and change in TLG were calculated from the PET/CT studies before and after treatment. Response prediction was based on imaging studies performed before and after therapy and categorized as positive or negative for residual tumor. Clinical outcome was determined from chart review.

Results

PET/CT was performed for staging in 16 patients, for restaging in 29 patients, and for surveillance in 2 patients. Of the patients, 88 % were correctly staged with PET/CT, whereas 75 % were correctly staged with conventional imaging. The sensitivity to detect local recurrence and distant metastasis at restaging was 100 and 100 % for PET/CT compared to 86 and 83 % for conventional imaging, respectively. PET/CT findings resulted in treatment changes in 31 % (5/16) and 14 % (4/29) of patients at staging and restaging, respectively. Recurrence, MTV, and TLG were prognostic factors for survival, whereas SUV_max and SUV_mean were not predictive. For 21 patients who had imaging studies performed both before and after treatment, PET/CT was better at predicting outcome (overall survival, progression-free survival) than conventional imaging. A decreasing SUV_max ≥ 30 % and decrease in TLG and MTV were significant predictors for overall and progression-free survival.

Conclusion

PET/CT is valuable in MPNST management because of its high accuracy in staging and high sensitivity and accuracy in restaging as well as improvements in treatment planning. MTV from baseline staging studies is predictive of survival. Additionally, change in SUV_max, TLG, and MTV accurately predicted outcomes after treatment.     

Shorter-time dual-phase FDG PET/CT in characterizing solid or ground-glass nodules based on surgical results

ObjectivesWe compared the accuracy of shorter-time dual-phase ¹⁸F-FDG PET/CT in evaluating 94 different lung nodules classified as solid or ground-glass nodules (GGNs).Materials and MethodsEarly and delayed maximum standardized uptake values (SUV_max) as well as the retention index (RI) of each nodule were determined in 75 solid nodules and 19 GGNs.ResultsIn solid nodules, early SUV_max, delayed SUV_max, and RI were higher in malignant than in benign lesions. In GGNs, these values were not significantly lower in the malignant than in the benign lesions.ConclusionIn the patient group with solid nodules, shorter-time dual-phase ¹⁸F-FDG PET/CT could significantly differentiate the malignant from the benign ones.     

Differentiation of adrenal incidentalomas by qualitative and quantitative analytical data obtained by 18F-FDG positron emission tomography/computed tomography in cancer patients

Aim of the work

To evaluate the diagnostic reliability of qualitative and quantitative data of 18F-FDG PET/CT scanning in the identification and differentiation of adrenal incidentalomas discovered in cancer patients.

Positron-emission tomography CT to identify local recurrence in stage I lung cancer patients 1 year after stereotactic body radiation therapy

Purpose

To evaluate the diagnostic value of positron-emission tomography/computed tomography (PET/CT) in stage I lung cancer patients treated with stereotactic body radiation therapy (SBRT), who have suspicious or unclear local recurrence findings in CT 1 year after treatment.

Patients and methods

A group of 29 patients with unclear or suspicious CT findings 1 year after SBRT were examined with PET/CT. The ability of standard uptake values (SUV_max, SUV_mean and posttherapeutic reduction in SUV) to detect local failure and identify patients at a high risk of disease-specific death was evaluated using logrank statistics. Histology and clinical follow-up were the gold standards for local recurrence.

Results

SUV_mean greater than 3.44 (p?=?0.001); SUV_max greater than 5.48 (p?=?0.009) or a relative reduction in SUV_mean or SUV_max of less than 43 (p?=?0.030) or 52?% (p?=?0.025), respectively, was indicative of local recurrence. These parameters also correlated with an increased risk of disease-specific death: SUV_mean greater than 2.81 (p?=?0.023); SUV_max greater than 3.45 (p?=?0.007) or a relative reduction in SUV_mean or SUV_max of less than 32 (p?=?0.015) or 52?% (p?=?0.013), respectively, was indicative of an increased risk of disease-specific death.

Conclusion

PET/CT performed 1 year after SBRT can reliably identify local recurrence and therefore help to clarify unclear CT findings. As posttherapeutic glucose metabolism also correlates with disease-specific survival, PET/CT may help to stratify lung cancer patients for additional treatment 1 year after SBRT.     

18F-FDG PET/CT is a valuable tool for relapsing polychondritis diagnose and therapeutic response monitoring

Objectives

To retrospectively investigate the role of ¹⁸ F–fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for the diagnosis and therapeutic response in relapsing polychondritis (RP) patients.

Methods

¹⁸F-FDG PET/CT findings were reviewed in six RP patients. The initial scans were performed for all patients, follow-up scans were performed during steroid therapy for five patients. Changes in the abnormal lesions and the maximal standard uptake value (SUV_max) were analyzed.

Results

The initial PET/CT scans revealed intense FDG uptake in the cartilages for all six patients. The lesions of abnormal FDG uptake were tracheal/bronchial cartilage (n = 4), costicartilage (n = 4), nasal cartilage (n = 3), cricoid cartilage (n = 3), auricular cartilage (n = 3), arytenoid cartilage (n = 3), thyroid cartilage (n = 2), hyoid cartilage (n = 1) and mediastinum lymph node (n = 1). The mean visual score and the mean SUV_max were 2.96 ± 0.20 and 4.10 ± 0.6. The intense uptake reduced or disappeared during steroid therapy for five patients, the mean visual score and the mean SUV_max were 1.58 ± 1.4 and 1.51 ± 1.4.

Conclusions

¹⁸F-FDG PET/CT enables the acquisition of both morphologic and glucose metabolic of the related cartilage structures. It plays a valuable role in assessing almost all cartilage and detecting RP, which is a better selection of a biopsy site as well as therapeutic response monitoring.     

Standardized added metabolic activity (SAM) IN 18F-FDG PET assessment of treatment response in colorectal liver metastases

Purpose

Standardized added metabolic activity (SAM) is a PET parameter for assessing the total metabolic load of malignant processes, avoiding partial volume effects and lesion segmentation. The potential role of this parameter in the assessment of response to chemotherapy and bevacizumab was tested in patients with metastatic colorectal cancer with potentially resectable liver metastases (mCRC).

Methods

¹⁸F-FDG PET/CT was performed in 18 mCRC patients with liver metastases before treatment and after five cycles of FOLFOX/FOLFIRI and bevacizumab. Of the 18 patients, 16 subsequently underwent resection of liver metastases. Baseline and follow-up SUV_max, and SAM as well as reduction in SUV_max (?SUV_max) and SAM (?SAM) of all liver metastases were correlated with morphological response, and progression-free and overall survival (PFS and OS).

Results

A significant reduction in metabolic activity of the liver metastases was seen after chemotherapy with a median ?SUV_max of 25.3 % and ?SAM of 94.5 % (p?=?0.033 and 0.003). Median baseline SUV_max and SAM values were significantly different between morphological responders and nonresponders (3.8 vs. 7.2, p?=?0.021; and 34 vs. 211, p?=?0.002, respectively), but neither baseline PET parameters nor morphological response was correlated with PFS or OS. Follow-up SUV_max and SAM as well as ?SAM were found to be prognostic factors. The median PFS and OS in the patient group with a high follow-up SUV_max were 10.4 months and 32 months, compared to a median PFS of 14.7 months and a median OS which had not been reached in the group with a low follow-up SUV_max (p?=?0.01 and 0.003, respectively). The patient group with a high follow-up SAM and a low ?SAM had a median PFS and OS of 9.4 months and 32 months, whereas the other group had a median PFS of 14.7 months and a median OS which had not been reached (p?=?0.002 for both PFS and OS).

Conclusion

¹⁸F-FDG PET imaging is a useful tool to assess treatment response and predict clinical outcome in patients with mCRC who undergo chemotherapy before liver metastasectomy. Follow-up SUV_max, follow-up SAM and ?SAM were found to be significant prognostic factors for PFS and OS.     

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.     

FDG uptake heterogeneity evaluated by fractal analysis improves the differential diagnosis of pulmonary nodules

Purpose

The present study aimed to determine whether fractal analysis of morphological complexity and intratumoral heterogeneity of FDG uptake can help to differentiate malignant from benign pulmonary nodules.

Materials and methods

We retrospectively analyzed data from 54 patients with suspected non-small cell lung cancer (NSCLC) who were examined by FDG PET/CT. Pathological assessments of biopsy specimens confirmed 35 and 19 nodules as NSCLC and inflammatory lesions, respectively. The morphological fractal dimension (m-FD), maximum standardized uptake value (SUV_max) and density fractal dimension (d-FD) of target nodules were calculated from CT and PET images. Fractal dimension is a quantitative index of morphological complexity and tracer uptake heterogeneity; higher values indicate increased complexity and heterogeneity.

Results

The m-FD, SUV_max and d-FD significantly differed between malignant and benign pulmonary nodules (p < 0.05). Although the diagnostic ability was better for d-FD than m-FD and SUV_max, the difference did not reach statistical significance. Tumor size correlated significantly with SUV_max (r = 0.51, p < 0.05), but not with either m-FD or d-FD. Furthermore, m-FD combined with either SUV_max or d-FD improved diagnostic accuracy to 92.6% and 94.4%, respectively.

Conclusion

The d-FD of intratumoral heterogeneity of FDG uptake can help to differentially diagnose malignant and benign pulmonary nodules. The SUV_max and d-FD obtained from FDG-PET images provide different types of information that are equally useful for differential diagnoses. Furthermore, the morphological complexity determined by CT combined with heterogeneous FDG uptake determined by PET improved diagnostic accuracy.     

Role of <Superscript>18</Superscript>F-FDG PET/CT in patients affected by Langerhans cell histiocytosis

Purpose

Langerhans cell histiocytosis (LCH) is a rare hematological disorder for which the utility of¹⁸F-FDG PET/CT is unclear. Our aim was to explore the metabolic features of LCH and the possible role of¹⁸F-FDG PET/CT in LCH evaluation.

Materials and methods

We found 17 patients with histologically proven LCH who underwent 17¹⁸F-FDG PET/CT scans for staging and 42 scans for restaging/follow-up purposes. PET/CT results were compared with those obtained from other conventional imaging modalities (bone scintigraphy, plain radiogram, computed tomography, magnetic resonance).

Results

¹⁸F-FDG PET/CT was positive in 15/17 patients, and it detected 36/37 lesions; all bone and extraskeletal lesions, except for a cecal lesion, were¹⁸F-FDG-avid. Only 1/4 of the patients with lung LCH had hypermetabolic lesions. The average SUV_max of the FDG-avid lesions was 7.3 ± 6.7, the average lesion-to-liver SUV_max ratio was 3.4 ± 2.5, and the average lesion-to-blood pool SUV_max ratio was 4 ± 3.2. In comparison to other imaging methods,¹⁸F-FDG PET/CT detected additional lesions or was able to evaluate treatment response earlier in 33/74 cases; it was confirmatory in 38/74 and detected fewer lesions in 3/74 (all three with lung LCH).

Conclusions

¹⁸F-FDG PET/CT seems to be useful for evaluating LCH when compared to conventional imaging, except in pulmonary cases. It can be used both for staging and restaging purposes.

     

11C-Acetate as a new biomarker for PET/CT in patients with multiple myeloma: initial staging and postinduction response assessment

Purpose

We investigated the potential value of ¹¹C-acetate (ACT) PET/CT in characterizing multiple myeloma (MM) compared with ¹⁸F-FDG PET/CT. Bone marrow histological and whole-body (WB) MRI findings served as the reference standards.

Methods

In this prospective study, 15 untreated MM patients (10 men and 5 women, age range 48?69 years) underwent dual-tracer ¹¹C-ACT and ¹⁸F-FDG PET/CT and WB MRI for pretreatment staging, and 13 of them had repeated examinations after induction therapy. Diffuse and focal bone marrow uptake was assessed by visual and quantitative analyses, including measurement of the maximum standardized uptake value (SUV_max). Between-group differences and correlations were assessed with the Mann-Whitney U test and the Pearson test.

Results

At staging, all 15 patients had diffuse myeloma involvement upon bone marrow examination with 30–90 % of plasma cell infiltrates. Diffuse infiltration was detected in all of them (100 %) using ¹¹C-ACT with a positive correlation between bone marrow uptake values and percentages of plasma cell infiltrates (r = +0.63, p?=?0.01). In contrast, a diagnosis of diffuse infiltration could be established using ¹⁸F-FDG in only six patients (40 %). Focal lesions were shown in 13 patients on both ¹¹C-ACT PET/CT and WB MRI, and in 10 patients on ¹⁸F-FDG PET/CT. Focal lesions demonstrated ¹¹C-ACT uptake with a mean SUV_max of 11.4 ± 3.3 (range 4.6?19.6, n?=?59), which was significantly higher than the ¹⁸F-FDG uptake (mean SUV_max 6.6 ± 3.1, range 2.3?13.7, n?=?29; p?<?0.0001). After treatment, the diffuse bone marrow ¹¹C-ACT uptake showed a mean SUV_max reduction of 66 % in patients with at least a very good partial response versus 34 % in those with at most a partial response only (p?=?0.01).

Conclusion

PET/CT using ¹¹C-ACT as a biomarker showed a higher detection rate for both diffuse and focal myeloma lesions at diagnosis than using ¹⁸F-FDG, and may be valuable for response assessment.     

Preoperative lymph node staging in patients with primary prostate cancer: comparison and correlation of quantitative imaging parameters in diffusion-weighted imaging and 11C-choline PET/CT

Purpose

To compare the diagnostic performance of DWI and 11C-choline PET/CT in the assessment of preoperative lymph node status in patients with primary prostate cancer.

Material and methods

Thirty-three patients underwent DWI and 11C-choline PET/CT prior to prostatectomy and extended pelvic lymph node dissection. Mean standardised uptake value (SUV_mean) and mean apparent diffusion coefficient (ADC) of 76 identified lymph nodes (LN) were measured and correlated with histopathology. ADC values and SUVs were compared using linear regression analysis.

Results

A significant difference between benign and malignant LN was observed for ADC values (1.17 vs. 0.96?×?10^-3 mm²/s; P?<?0.001) and SUV_mean (1.61 vs. 3.20; P?<?0.001). ROC analysis revealed an optimal ADC threshold of 1.01?×?10^-3 mm²/s for differentiating benign from malignant LN with corresponding sensitivity/specificity of 69.70 %/78.57 % and an area under the curve (AUC) of 0.785. The optimal threshold for SUV_mean was 2.5 with corresponding sensitivity/specificity of 69.72 %/90.48 % and with an AUC of 0.832. ADC values and SUV_mean showed a moderate significant inverse correlation (r?=?-0.63).

Conclusion

Both modalities reveal similar moderate diagnostic performance for preoperative lymph node staging of prostate cancer, not justifying their application in routine clinical practice at this time. The only moderate inverse correlation between ADC values and SUV_mean suggests that both imaging parameters might provide complementary information on tumour biology.

Key Points

? Conventional imaging shows low performance for lymph node staging in prostate cancer. ? DWI and 11C-choline PET/CT both provide additional functional information ? Both functional modalities reveal only moderate diagnostic performance.     

Detection of neck recurrence in patients with differentiated thyroid cancer: comparison of ultrasound, contrast-enhanced CT and 18F-FDG PET/CT using surgical pathology as a reference standard: (ultrasound vs. CT vs. 18F-FDG PET/CT in recurrent thyroid cancer)

Objectives

To compare the diagnostic performance of ultrasound, contrast-enhanced computed tomography (CT) and ¹⁸F-FDG positron emission tomography (PET)/CT for detecting recurrent differentiated thyroid cancer in the neck.

Methods

Twenty patients who had undergone previous surgery for differentiated thyroid cancer (19 papillary carcinomas; 1 medullary carcinoma) and presented with pathologically proven recurrence in the neck were included. All patients had undergone ultrasound, CT and PET/CT in the 2 months before further surgery. In each patient, ultrasound, CT and PET/CT images were retrospectively reviewed to determine the presence of loco-regional recurrence by level-by-level analysis. Imaging results were correlated with the histological evaluation of the neck dissection as a standard of reference.

Results

Recurrences were found at 52 out of 110 cervical nodal levels surgically explored. The sensitivity, specificity and accuracy were 69.2 %, 89.7 % and 80.0 % for ultrasound; 63.5 %, 94.8 % and 80.0 % for CT; and 53.8 %, 79.3 % and 67.3 % for PET/CT, respectively. ROC analysis revealed higher diagnostic performance with ultrasound than with PET/CT for detecting recurrent tumour.

Conclusions

Although no significant difference was found among the three techniques, the sensitivity and specificity of ultrasound and CT were higher than those of PET/CT for the evaluation of cervical recurrence in patients with differentiated thyroid cancer.

Key Points

? Ultrasound, CT and ¹⁸ F-FDG PET/CT can all detect recurrent thyroid cancer. ? Ultrasound and CT have higher sensitivity and specificity. ? Ultrasound, CT and ¹⁸ F-FDG PET/CT frequently demonstrated discordant findings     

18F-fluorodeoxyglucose positron emission tomography and computed tomography in anaplastic thyroid cancer

Purpose

Our aim was to evaluate in anaplastic thyroid carcinoma (ATC) patients the value of ¹⁸F-FDG PET/CT compared with total body computed tomography (CT) using intravenous contrast material for initial staging, prognostic assessment, therapeutic monitoring and follow-up.

Methods

Twenty consecutive ATC patients underwent PET/CT for initial staging. PET/CT was performed again during follow-up. The gold standard was progression on imaging follow-up (CT or PET/CT) or confirmation with another imaging modality.

Results

A total of 265 lesions in 63 organs were depicted in 18 patients. Thirty-five per cent of involved organs were demonstrated only with PET/CT and one involved organ only with CT. In three patients, the extent of disease was significantly changed with PET/CT that demonstrated unknown metastases. Initial treatment modalities were modified by PET/CT findings in 25% of cases. The volume of FDG uptake (≥300 ml) and the intensity of FDG uptake (SUV_max ≥18) were significant prognostic factors for survival. PET/CT permitted an earlier assessment of tumour response to treatment than CT in 4 of the 11 patients in whom both examinations were performed. After treatment with combined radiotherapy and chemotherapy, only the two patients with a negative control PET/CT had a confirmed complete remission at 14 and 38 months; all eight patients who had persistent FDG uptake during treatment had a clinical recurrence and died.

Conclusion

FDG PET/CT appears to be the reference imaging modality for ATC at initial staging and seems promising in the early evaluation of treatment response and follow-up.     

Quantitative assessment of shear-wave ultrasound elastography in thyroid nodules: diagnostic performance for predicting malignancy

Objectives

To evaluate the predictability of shear-wave ultrasound elastography (SWE) for thyroid malignancy and to compare the diagnostic performances of SWE and B-mode US.

Methods

Retrospective review of 99 patients who underwent SWE before US-guided fine-needle aspiration of thyroid nodules was performed. SWE elasticity indices of the mean (E_mean ), maximum (E_max), and minimum (E_min) of nodules were measured. Diagnostic performance of SWE was compared with that of B-mode US.

Results

Among a total of 99 nodules, 21 were papillary thyroid carcinoma (PTC) and 78 were benign. E_mean, E_max, and E_min were significantly higher in PTCs than in benign nodules (P?<?0.001). Sensitivity and specificity for predicting malignancy were 76.1 %, 64.1 % with E_max (65 kPa), 61.9 %, 76.1 % with E_min (53 kPa), and 66.6 %, 71.6 % with E_mean (62 kPa). Areas under the ROC curves (Az) of SWE values were not significantly different from those of US categories on B-mode US. However, combining E_mean and E_min with B-mode US of probably benign lesions improved the specificity (P?=?0.02, 0.007) for predicting PTC.

Conclusions

The quantitative parameter of SWE was significantly higher in PTC than in benign nodules, and combined use of quantitative SWE and B-mode US provided higher specificity for predicting malignancy.

Key Points

? Quantitative shear-wave elastography (SWE) helps differentiate benign from malignant nodules ? SWE and conventional ultrasound have comparable diagnostic performance for predicting thyroid malignancy ? Combined quantitative SWE and B-mode ultrasound is highly specific for thyroid malignancy