<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.

     

Pictorial review of <Superscript>18</Superscript>F-FDG PET/CT findings in musculoskeletal lesions

We herein reviewed ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) findings in a number of musculoskeletal lesions including malignant tumors, benign tumors, and tumor-like lesions with correlations to other radiographic imaging modalities, and described the diversity of the ¹⁸F-FDG PET/CT findings of this entity. Malignant primary musculoskeletal tumors are typically ¹⁸F-FDG avid, whereas low-grade malignant tumors show mild uptake. Benign musculoskeletal tumors generally show a faint uptake of ¹⁸F-FDG, and tumor-like conditions also display various uptake patterns of ¹⁸F-FDG. Although musculoskeletal tumors show various uptakes of ¹⁸F-FDG on PET/CT, its addition to morphological imaging modalities such as CT and MRI is useful for the characterization and differentiation of musculoskeletal lesions.     

Usefulness of <Superscript>18</Superscript>F-FDG PET/CT to Detect Metastatic Mucinous Adenocarcinoma Within an Inguinal Hernia

Metastatic mucinous adenocarcinoma in an inguinal hernia is a rare disease and the image findings of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) are little known. Here, we introduce a 57-year-old man with metastatic mucinous adenocarcinoma in an inguinal hernia. On initial ¹⁸F-FDG PET/CT, hypermetabolism was observed in mucinous adenocarcinoma of the cecum, and adenocarcinomas of the transverse and ascending colon, respectively. Follow-up ¹⁸F-FDG PET/CT revealed newly developed multiple hypermetabolism in peritoneal seeding masses and nodules in the pelvic cavity and scrotum. Peritoneal carcinomatosis in the right pelvic side wall was extended to the incarcerated peritoneum and mesentery in the right inguinoscrotal hernia.¹⁸F-FDG PET/CT was useful to reveal unexpected peritoneal seeding within the inguinal hernia. Also, this case demonstrated that metastatic mucinous adenocarcinomas had variably intense FDG uptake.     

<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.     

Different predictive values of interim <Superscript>18</Superscript>F-FDG PET/CT in germinal center like and non-germinal center like diffuse large B-cell lymphoma

Purpose

Diffuse large B-cell lymphoma (DLBCL) is a pathologically heterogeneous disease with different prognoses according to its molecular profiles. Despite the broad usage of ¹⁸F-fluoro-2-dexoxy-d-glucose (FDG) positron emission tomography/computed tomography (PET/CT), previous studies that have investigated the value of interim ¹⁸F-FDG PET/CT in DLBCL have given the controversial results. The purpose of this study was to evaluate the prognostic value of interim ¹⁸F-FDG PET/CT in DLBCL according to germinal center B cell-like (GCB) and non-GCB molecular profiling.

Methods

We enrolled 118 newly diagnosed DLBCL patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP). Interim ¹⁸F-FDG PET/CT scans performed after 2 or 3 cycles of R-CHOP treatment were evaluated based on the Lugano response criteria. Patients were grouped as GCB or non-GCB molecular subtypes according to immunohistochemistry results of CD10, BCL6, and MUM1, based on Hans’ algorithm.

Results

In total 118 DLBCL patients, 35 % were classified as GCB, and 65 % were classified as non-GCB. Interim PET/CT was negative in 70 %, and positive in 30 %. During the median follow-up period of 23 months, the positive interim ¹⁸F-FDG PET/CT group showed significantly inferior progression free survival (PFS) compared to the negative interim ¹⁸F-FDG PET/CT group (P = 0.0004) in entire patients. A subgroup analysis according to molecular profiling demonstrated significant difference of PFS between the positive and negative interim ¹⁸F-FDG PET groups in GCB subtype of DLBCL (P = 0.0001), but there was no significant difference of PFS between the positive and negative interim ¹⁸F-FDG PET groups in non-GCB subtype of DLBCL.

Conclusions

Interim ¹⁸F-FDG PET/CT scanning had a significant predictive value for disease progression in patients with the GCB subtype of DLBCL treated with R-CHOP, but not in those with the non-GCB subtype. Therefore, molecular profiles of DLBCL should be considered for interim ¹⁸F-FDG PET/CT practice.

     

The incremental value of <Superscript>18</Superscript>F-FDG PET/CT in paediatric malignancies

PURPOSE: (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) imaging has been used in the assessment of paediatric malignancies. PET/CT increases the diagnostic accuracy in adult cancer patients. The present study assesses the incremental value of FDG PET/CT in paediatric malignancies. METHODS: A total of 118 (18)FDG PET/CT studies of 46 paediatric patients were reviewed retrospectively. PET and PET/CT results were classified as malignant, equivocal or benign, compared on a site- and study-based analysis, and also compared with the clinical outcome. RESULTS: Three hundred and twenty-four sites of increased FDG uptake were detected. Discordant PET and PET/CT interpretations were found in 97 sites (30%) in 27 studies (22%). PET yielded a statistically significant higher proportion of equivocal and a lower proportion of benign lesion and study results (p<0.001) than PET/CT. With PET there were 153 benign (47%), 84 (26%) equivocal and 87 (27%) malignant sites, while PET/CT detected 226 benign (70%), 10 (3%) equivocal and 88 (27%) malignant lesions. PET/CT mainly improved the characterisation of uptake in brown fat (39%), bowel (17%), muscle (8%) and thymus (7%). The study-based analysis showed that 17 equivocal and seven positive PET studies (20%) were interpreted as benign on PET/CT, while three equivocal studies were interpreted as malignant. The study-based sensitivity and specificity of PET/CT were 92% and 78% respectively. CONCLUSION: PET/CT significantly improved the characterisation of abnormal (18)FDG foci in children with cancer, mainly by excluding the presence of active malignancy in sites of increased tracer activity.     

Differential uptake of <Superscript>18</Superscript>F-FDG in patients with synchronous lung cancers

¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG PET/CT) has developed into the standard of care for investigating patients with non-small cell lung cancer (NSCLC) to determine the optimal treatment. However, although the majority of patients with NSCLC do have intense uptake of tracer, false negatives do occur and should be considered. We report cases of patients that have synchronous NSCLCs. In both cases, there was intense uptake of FDG in one tumour type, with very low grade uptake in the separate tumour. Histology confirmed separate lung malignancies, demonstrating that differential FDG uptake may not always be inflammatory and should be considered to have a separate malignant aetiology.     

Assessing the role of <Superscript>18</Superscript>F-FDG PET and <Superscript>18</Superscript>F-FDG PET/CT in the diagnosis of soft tissue musculoskeletal malignancies: a systematic review and meta-analysis

Purpose

Twelve years ago a meta-analysis evaluated the diagnostic performance of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in assessing musculoskeletal soft tissue lesions (MsSTL). Currently, PET/CT has substituted PET imaging; however, there has not been any published meta-analysis on the use of PET/CT or a comparison of PET/CT with PET in the diagnosis of MsSTL. Therefore, we conducted a meta-analysis to identify the current diagnostic performance of ¹⁸F-FDG PET/CT and determine if there is added value when compared to PET.

Methods

A systematic review of English articles was conducted, and MEDLINE PubMed, the Cochrane Library, and Embase were searched from 1996 to March 2015. Studies exploring the diagnostic accuracy of ¹⁸F-FDG PET/CT (or dedicated PET) compared to histopathology in patients with MsSTL undergoing investigation for malignancy were included.

Results

Our meta-analysis included 14 articles composed of 755 patients with 757 soft tissue lesions. There were 451 (60 %) malignant tumors and 306 benign lesions. The ¹⁸F-FDG PET/CT (and dedicated PET) mean sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for diagnosing MsSTL were 0.96 (0.90, 1.00), 0.77 (0.67, 0.86), 0.88 (0.85, 0.91), 0.86 (0.78, 0.94), and 0.91 (0.83, 0.99), respectively. The posterior mean (95 % highest posterior density interval) for the AUC was 0.92 (0.88, 0.96). PET/CT had higher specificity, accuracy, and positive predictive value when compared to a dedicated PET (0.85, 0.89, and 0.91 vs 0.71, 0.85, and 0.82, respectively).

Conclusion

¹⁸F-FDG PET/CT and dedicated PET are both highly accurate in the diagnosis of MsSTL. PET/CT is more accurate and specific and has a higher positive predictive value than PET.

     

Prognostic implications of <Superscript>62</Superscript>Cu-diacetyl-bis (<Emphasis Type="Italic">N</Emphasis><Superscript>4</Superscript>-methylthiosemicarbazone) PET/CT in patients with glioma

Objective

The potential of positron emission tomography/computed tomography using ⁶²Cu-diacetyl-bis (N⁴-methylthiosemicarbazone) (⁶²Cu-ATSM PET/CT), which was originally developed as a hypoxic tracer, to predict therapeutic resistance and prognosis has been reported in various cancers. Our purpose was to investigate prognostic value of ⁶²Cu-ATSM PET/CT in patients with glioma, compared to PET/CT using 2-deoxy-2-[¹⁸F]fluoro-d-glucose (¹⁸F-FDG).

Method

56 patients with glioma of World Health Organization grade 2–4 were enrolled. All participants had undergone both ⁶²Cu-ATSM PET/CT and ¹⁸F-FDG PET/CT within mean 33.5 days prior to treatment. Maximum standardized uptake value and tumor/background ratio were calculated within areas of increased radiotracer uptake. The prognostic significance for progression-free survival and overall survival were assessed by log-rank test and Cox’s proportional hazards model.

Results

Disease progression and death were confirmed in 37 and 27 patients in follow-up periods, respectively. In univariate analysis, there was significant difference of both progression-free survival and overall survival in age, tumor grade, history of chemoradiotherapy, maximum standardized uptake value and tumor/background ratio calculated using ⁶²Cu-ATSM PET/CT. Multivariate analysis revealed that maximum standardized uptake value calculated using ⁶²Cu-ATSM PET/CT was an independent predictor of both progression-free survival and overall survival (p?<?0.05). In a subgroup analysis including patients of grade 4 glioma, only the maximum standardized uptake values calculated using ⁶²Cu-ATSM PET/CT showed significant difference of progression-free survival (p?<?0.05).

Conclusions

⁶²Cu-ATSM PET/CT is a more promising imaging method to predict prognosis of patients with glioma compared to ¹⁸F-FDG PET/CT.

     

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.

     

Usefulness of <Superscript>18</Superscript>F-FDG PET in intrahepatic cholangiocarcinoma

Surgical resection is the only curative treatment strategy for intrahepatic cholangiocarcinoma (CC). Therefore, accurate staging is essential for appropriate management of patients with CC. We assessed the usefulness of 2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the staging of CC. We undertook a retrospective review of FDG PET images in 21 patients (10 female, 11 male; mean age 57 years) diagnosed with CC. Ten patients had hilar CC and 11, peripheral CC. Patients underwent abdominal magnetic resonance imaging (MRI) (n=20) and computed tomography (CT) (n=12) for the evaluation of primary tumours, and chest radiography and whole-body bone scintigraphy for work-up of distant metastases. For semi-quantitative analysis, the maximum voxel standardised uptake value (SUV_max) was obtained from the primary tumour. All peripheral CCs showed intensely increased FDG uptake, and some demonstrated ring-shaped uptake corresponding to peripheral rim enhancement on CT and/or MRI. In nine of the ten patients, hilar CCs demonstrated increased FDG uptake of a focal nodular or linear branching appearance. The remaining case was false negative on FDG PET. One patient with a false negative result on MRI demonstrated increased uptake on FDG PET. Among the ten hilar CCs, FDG uptake was intense in only two patients and was slightly higher than that of the hepatic parenchyma in the remaining patients. For the detection of lymph node metastasis, FDG PET and CT/MRI were concordant in 16 patients, and discordant in five (FDG PET was positive in three, and CT and MRI in two). FDG PET identified unsuspected distant metastases in four of the 21 patients; all of these patients had peripheral CC. FDG PET is useful in detecting the primary lesion in both hilar and peripheral CC and is of value in discovering unsuspected distant metastases in patients with peripheral CC. FDG PET could be useful in cases of suspected hilar CC with non-confirmatory biopsy and radiological findings.     

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.

     

Incidental focal <Superscript>18</Superscript>F-FDG uptake in the frontal process of the maxilla on PET/CT: prevalence and clinical significance

Objective

We investigated the prevalence and clinical significance of incidental focal ¹⁸F-FDG uptake in the frontal process of the maxilla, mimicking malignancy on PET/CT.

Methods

From a total of 32,834 patients who underwent ¹⁸F-FDG PET/CT, patients with focal uptake in the frontal process of the maxilla were selected by a database search. For those patients, medical records including relevant imaging studies were reviewed.

Results

Thirty-nine patients (0.12 %) demonstrated focal uptake on PET/CT. On CT of PET/CT, all lesions showed ground-glass attenuation with or without bony expansion, consistent with fibrous dysplasia. When comparing previous PET/CT, follow-up PET/CT, and CT, a significant difference in degree of ¹⁸F-FDG uptake was noted, with no associated change in the size of maxillary lesions. There were no patients who had symptoms or signs related to maxillary lesions during follow-up.

Conclusion

Focal ¹⁸F-FDG uptake in the frontal process of the maxilla is a rare, incidental, and persistent finding with variable uptake and can represent a benign condition.

     

<Superscript>18</Superscript>F-fluorodeoxyglucose positron emission tomography in uterine carcinosarcoma

Purpose Uterine carcinosarcomas clinically confined to the uterus usually harbor occult metastases. We conducted a pilot study to evaluate the value of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in uterine carcinosarcoma. Methods Patients with histologically confirmed uterine carcinosarcoma were enrolled. Abdominal and pelvic magnetic resonance imaging (MRI)/whole-body computed tomography (CT) scan, and whole-body ¹⁸F-FDG PET or PET/CT were undertaken for primary staging, evaluating response, and restaging/post-therapy surveillance. The clinical impact of ¹⁸F-FDG PET was determined on a scan basis. Results A total of 19 patients were recruited and 31 ¹⁸F-FDG PET scans (including 8 scans performed on a PET/CT scanner) were performed. Positive impacts of scans were found in 36.8% (7/19) for primary staging, 66.7% (2/3) for monitoring response, and 11.1% (1/9) for restaging/post-therapy surveillance. PET excluded falsely inoperable disease defined by MRI in two patients. Aggressive treatment applying to three patients with PET-defined resectable stage IVB disease seemed futile. Two patients died of disease shortly after salvage therapy restaged by PET. With PET monitoring, one stage IVB patient treated by targeted therapy only was alive with good performance. Using PET did not lead to improvement of overall survival of this series compared with the historical control (n = 35) (P = 0.779). Conclusions The preliminary results suggest that ¹⁸F-FDG PET is beneficial in excluding falsely inoperable disease for curative therapy and in making a decision on palliation for better quality of life instead of aggressive treatment under the guidance of PET. PET seems to have limited value in post-therapy surveillance or restaging after failure.     

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.     

Heterogeneity index evaluated by slope of linear regression on <Superscript>18</Superscript>F-FDG PET/CT as a prognostic marker for predicting tumor recurrence in pancreatic ductal adenocarcinoma

Purpose

¹⁸F-Fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) has been investigated as a method to predict pancreatic cancer recurrence after pancreatic surgery. We evaluated the recently introduced heterogeneity indices of ¹⁸F-FDG PET/CT used for predicting pancreatic cancer recurrence after surgery and compared them with current clinicopathologic and ¹⁸F-FDG PET/CT parameters.

Methods

A total of 93 pancreatic ductal adenocarcinoma patients (M:F = 60:33, mean age = 64.2 ± 9.1 years) who underwent preoperative ¹⁸F-FDG PET/CT following pancreatic surgery were retrospectively enrolled. The standardized uptake values (SUVs) and tumor-to-background ratios (TBR) were measured on each ¹⁸F-FDG PET/CT, as metabolic parameters. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were examined as volumetric parameters. The coefficient of variance (heterogeneity index-1; SUVmean divided by the standard deviation) and linear regression slopes (heterogeneity index-2) of the MTV, according to SUV thresholds of 2.0, 2.5 and 3.0, were evaluated as heterogeneity indices. Predictive values of clinicopathologic and ¹⁸F-FDG PET/CT parameters and heterogeneity indices were compared in terms of pancreatic cancer recurrence.

Results

Seventy patients (75.3%) showed recurrence after pancreatic cancer surgery (mean recurrence = 9.4 ± 8.4 months). Comparing the recurrence and no recurrence patients, all of the ¹⁸F-FDG PET/CT parameters and heterogeneity indices demonstrated significant differences. In univariate Cox-regression analyses, MTV (P = 0.013), TLG (P = 0.007), and heterogeneity index-2 (P = 0.027) were significant. Among the clinicopathologic parameters, CA19–9 (P = 0.025) and venous invasion (P = 0.002) were selected as significant parameters. In multivariate Cox-regression analyses, MTV (P = 0.005), TLG (P = 0.004), and heterogeneity index-2 (P = 0.016) with venous invasion (P < 0.001, 0.001, and 0.001, respectively) demonstrated significant results.

Conclusions

The heterogeneity index obtained using the linear regression slope, could be an effective predictor of pancreatic cancer recurrence after pancreatic cancer surgery, in addition to ¹⁸F-FDG PET/CT volumetric parameters and clinicopathologic parameters.

     

Usefulness of <Superscript>11</Superscript>C-methionine PET in the evaluation of brain lesions that are hypo- or isometabolic on <Superscript>18</Superscript>F-FDG PET

The fact that some brain tumors show hypo- or isometabolism on fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) has caused problems in the detection of primary or recurrent tumors and in the differentiation from benign lesions. We investigated the usefulness of carbon-11 methionine PET in characterizing brain lesions under these conditions. 11C-methionine PET was performed in 45 patients with brain lesions (in 34 for initial diagnosis and in 11 for detection of recurrence) that showed hypo- or isometabolism compared with normal brain tissue on FDG PET. Ten minutes after the injection of 555-740 MBq of 11C-methionine, attenuation-corrected brain images were obtained with a dedicated PET scanner. The brain lesions comprised 24 gliomas, five metastatic brain tumors, four meningiomas, two other brain tumors and ten benign lesions (including three cases of cysticercosis, two cases of radiation necrosis, one tuberculous granuloma, one hemangioma, one benign cyst, and one organizing infarction). Proliferative activity was measured using the Ki-67 immunostaining method in glioma tissues. Thirty-one of 35 brain tumors (89% sensitivity) showed increased 11C-methionine uptake despite iso- or hypometabolism on FDG PET. By contrast, all ten benign lesions showed decreased or normal 11C-methionine uptake (100% specificity). Twenty-two of 24 gliomas (92%) showed increased 11C-methionine uptake, the extent and degree of which exceeded 18F-FDG uptake, and the 11C-methionine uptake correlated with the proliferation index (r=0.67). The mean (+/-SD) uptake ratios of glioma to normal brain on FDG and 11C-methionine PET were 0.92+/-0.34 and 2.54+/-1.25, respectively. All metastatic tumors except one showed intense 11C-methionine uptake in the entire tumor or in the peripheral margin of the tumor. In meningiomas, 11C-methionine uptake showed a variable increase. In conclusion, brain lesions that show hypo- or isometabolism on FDG PET can be detected and differentiated with high sensitivity and good contrast using 11C-methionine PET. 11C-methionine PET can provide additional information when used in combination with FDG PET in the evaluation of these patients.     

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.

     

Preoperative prediction of microvascular invasion of hepatocellular carcinoma using <Superscript>18</Superscript>F-FDG PET/CT: a multicenter retrospective cohort study

Purpose

The aim of this study was to assess the potential of tumor ¹⁸F-fluorodeoxyglucose (FDG) avidity as a preoperative imaging biomarker for the prediction of microvascular invasion (MVI) of hepatocellular carcinoma (HCC).

Methods

One hundred and fifty-eight patients diagnosed with Barcelona Clinic Liver Cancer stages 0 or A HCC (median age, 57 years; interquartile range, 50–64 years) who underwent ¹⁸F-FDG positron emission tomography with computed tomography (PET/CT) before curative surgery at seven university hospitals were included. Tumor FDG avidity was measured by tumor-to-normal liver standardized uptake value ratio (TLR) of the primary tumor on FDG PET/CT imaging. Logistic regression analysis was performed to identify significant parameters associated with MVI. The predictive performance of TLR and other clinical variables was assessed using receiver operating characteristic (ROC) curve analysis.

Results

MVI was present in 76 of 158 patients with HCCs (48.1%). Multivariable logistic regression analysis revealed that TLR, serum alpha-fetoprotein (AFP) level, and tumor size were significantly associated with the presence of MVI (P?<?0.001). Multinodularity was not significantly associated with MVI (P?=?0.563). The area under the ROC curve (AUC) for predicting the presence of MVI was best with TLR (AUC?=?0.704), followed by tumor size (AUC?=?0.685) and AFP (AUC?=?0.670). We were able to build an improved prediction model combining TLR, tumor size, and AFP by using multivariable logistic regression modeling (AUC?=?0.756).

Conclusions

Tumor FDG avidity measured by TLR on FDG PET/CT is a preoperative imaging biomarker for the prediction of MVI in patients with HCC.

     

Incidentally Detected Small Intestine Intussusception Caused by Primary Small Intestine Carcinoma on <Superscript>18</Superscript>F-FDG PET/CT

Small intestine intussusception in adults is a rare condition mainly caused by primary or metastatic small intestine malignancy. Here, we present a 72-year-old male patient who was diagnosed with small intestine cancer that was presented as small intestine intussusception on hybrid ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT). The patient was initially referred for an abnormality on a chest radiography and severe anemia. FDG PET/CT showed the lung lesion in the right upper lobe of lung as a high FDG uptake mass. Accidentally, FDG PET demonstrated another intense hypermetabolic intraluminal lesion in the small intestine accompanied with intussusception shown as a circumferential hypermetabolic wall. By pathologic examination, the patient was diagnosed as primary small intestine cancer with lung metastasis. This case highlights usefulness of hybrid FDG PET/CT to identify unexpected malignancy.