Optimal Standardized Uptake Value Research Articles

Quantitative assessment of 99mTc-methylene diphosphonate bone SPECT/CT for assessing bone metastatic burden and its prognostic value in patients with castration-resistant prostate cancers: initial results in a single-center retrospective study

To evaluate the prognostic value of the quantitative assessment of 99mTc-methylene diphosphonate (99mTc-MDP) bone SPECT/CT in castration-resistant prostate cancer (CRPC) patients with bone metastases. A total of 103 patients who underwent 99mTc-MDP bone SPECT/CT imaging from the neck to the proximal femur were included. First, in 65 patients without bone metastases, the normal range of standardized uptake value (SUV) of non-pathological bone was evaluated to determine an SUV threshold to reliably exclude most normal osseous activity. Then, in 38 CRPC patients with bone metastases, lesion uptake volume (LUV), which is the extracted volume of bone metastases exhibiting high accumulation above the SUV threshold, was calculated. The relation between LUV and prostate-related mortality was statistically evaluated. Based on the SUV measurements of non-pathological bones, the optimal SUV threshold, which defines abnormal bone SPECT uptake, was determined to be 8. Median LUV was 39mL (interquartile range 4.0-104.3mL) in the CRPC subjects with bone metastases. Kaplan-Meier survival analysis showed a significant relation between prostate cancer-specific survival and LUV (cut-off value, 19.95mL; P = 0.001). Multivariate analysis revealed LUV as an independent prognostic factor for the survival (P = 0.008, hazard ratio 23.424). Global chi-square test showed that LUV had significant incremental prognostic value in addition to prostate-specific antigen and the interval from progression to CRPC until bone SPECT/CT (P = 0.022). Quantitative assessment of 99mTc-MDP bone SPECT images can provide valuable prognostic information in CRPC patients with bone metastases.

Diagnostic value of integrated 18F-PSMA-1007 PET/MRI compared with that of biparametric MRI for the detection of prostate cancer.

ObjectiveTo assess the diagnostic value of fluorine 18 (18F)-labeled prostate-specific membrane antigen (PSMA)-1007 Positron emission tomography/Magnetic resonance imaging (PET/MRI) and compared with that of biparametric MRI (bpMRI) for the detection of prostate cancer (PCa).Materials and methodsThe study enrolled 29 patients with suspected PCa preoperatively who underwent 18F-PSMA-1007 PET/MRI and subsequent targeted biopsy for suspected PCa lesions. Two readers independently assessed the images of each suspected PCa lesion and determined their overall assessment category on bpMRI and 18F-PSMA-1007 PET/MRI. By using biopsy histopathology as the reference standard, the accuracies of 18F-PSMA-1007 PET/MRI and bpMRI for the detection of PCa lesion were determined. Furthermore, the receiver-operating characteristic (ROC) curves of their semi-quantitative parameters of the optimal standardized uptake value (SUVmax) and apparent diffusion coefficient (ADC) for detecting PCa lesions were derived, and their correlations with the International Society of Urological Pathology (ISUP) grade were reported.ResultsOf the 48 suspected PCa lesions in 29 patients, 38 were pathologically diagnosed with clinically significant PCa and 10 with nonprostate cancer (non-PCa) lesions. Compared with the pathological results, 18F-PSMA-1007 PET/MRI demonstrated much greater diagnostic accuracy (area under the curve, AUC), sensitivity, specificity, positive predictive value, and negative predictive value than bpMRI: 0.974 versus 0.711, 94.74% versus 92.11%, 100% versus 50%, 100% versus 87.50%, and 83.33% versus 62.50%, respectively. The semi-quantitative parameters of SUVmax demonstrated a higher AUC of 0.874 than that of ADC with 0.776 for detecting PCa. The ISUP grade was positively associated with SUVmax at spearman’s rho correlation coefficient (Rho) = 0.539, p = 0), but not associated with ADC (Rho = −0.105, p = 0.529).ConclusionThe diagnostic value of 18F-PSMA-1007 PET/MRI for the detection of PCa is better than that of bpMRI, and a high SUVmax may indicate a lesion with a high ISUP grade.

18F-FDG-PET/CT Evaluation of Indeterminate Adrenal Masses in Noncancer Patients.

Adrenal tumors in noncancer patients are common. Evaluate performance of 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG-PET/CT) in distinguishing between benign and malignant adrenal tumors. Retrospective chart review 2010-2019. Academic institution. One hundred and seventeen noncancer patients, defined as having no history of cancer or with cancer in remission for ≥5 years, completed 18F-FDG-PET/CT to evaluate adrenal masses, with pathologic diagnoses or imaging follow-up (≥12 months). 18F-FDG-PET/CT of 117 indeterminate adrenal masses. Receiver operator characteristic curve of the ratios of adrenal lesion standardized uptake value (SUV)max to liver SUVmean and of adrenal lesion SUVmax to aortic arch blood pool SUVmean were constructed. Seventy benign and 47 malignant masses (35 adrenocortical carcinomas [ACCs], 12 adrenal metastases) were identified. Malignant masses had higher median liver SUV and blood pool SUV ratios than benign masses (6.2 and 7.4 vs 1.4 and 2.0, P < .001). Median liver and blood pool SUV ratios of ACC (6.1 and 7.3, respectively) and metastases (6.7 and 7.7, respectively) were higher than those of than adenomas (1.4 and 2.2, P < .05 for all comparisons). Optimal liver SUV ratio to discern between benign and malignant masses was 2.5, yielding 85% sensitivity, 90% specificity, and 7 false negative results (including 3 ACCs). Optimal blood pool SUV ratio was 3.4, yielding 83% sensitivity, 90% specificity, and 8 false negative results (including 4 ACCs). When used in conjunction with other clinical assessments, 18F-FDG-PET/CT can be a valuable tool in evaluating adrenal masses in noncancer patients.

Optimal Standardized Uptake Value Threshold for Auto contouring of Gross Tumor Volume using Positron Emission Tomography/Computed Tomography in Patients with Operable Nonsmall-Cell Lung Cancer: Comparison with Pathological Tumor Size.

Purpose:Incorporating 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG-PET/CT) for gross tumor volume (GTV) delineation is challenging due to varying tumor edge based on the set threshold of the standardized uptake value (SUV). This study aims to determine an optimal SUV threshold that correlates best with the pathological tumor size.Materials and Methods:From January 2013 to July 2014, 25 consecutive patients of operable nonsmall-cell lung cancer (NSCLC) who underwent staging18F-FDG-PET/CT before surgical resection were included in the test cohort and 12 patients in the validation cohort. GTVs were delineated on the staging PET/CT by automatic delineation using various percentage threshold of maximum SUV (SUVmax) and absolute SUV. The maximum pathological tumor diameter was then matched with the maximum auto-delineated tumor diameter with varying SUV thresholds. First-order linear regression and Bland–Altman plots were used to obtain an optimal SUV threshold for each patient. Three radiation oncologists with varying degrees of experiences also delineated GTVs with the visual aid of PET/CT to assess interobserver variation in delineation.Results:In the test set, the mean optimal percentage threshold for GTV was SUVmax of 35.6%±18.6% and absolute SUV of 4.35 ± 1.7. In the validation set, the mean optimal percentage threshold SUV and absolute SUV were 36.9 ± 16.9 and 4.1 ± 1.6, respectively. After a combined analysis of all 37 patients, the mean optimal threshold was 36% ± 17.9% and 4.27 ± 1.7, respectively. Using Bland–Altman plots, auto-contouring with 40% SUVmax and SUV 4 was in greater agreement with the pathological tumor diameter.Conclusion:Automatic GTV delineation on PETCT in NSCLC with percentage threshold SUV of 40% and absolute SUV of 4 correlated best with pathological tumor size. Auto-contouring using these thresholds will increase the precision of radiotherapy contouring of GTV and will save time.

Comparison of histopathology and preoperative 18F-FDG-PET/CT of osteomyelitis aiming for image guided surgery: A preliminary trial

ObjectiveThere are currently no robust methods for accurately localizing the infection focus of osteomyelitis. Accumulation of fluorodeoxyglucose (FDG) is nonspecific, and it is well-known that it can indicate inflammatory cells and sites of inflammation, and its effectiveness in detecting osteomyelitis has been reported recently. However, the optimal cut-off value for the Standardized Uptake Value (SUV) in detecting the focus of osteomyelitis through 18F-FDG-PET/CT is not known. We investigated the optimal SUV cut-off values using 18F-FDG positron emission tomography (PET)computed tomography (CT) to visualize the infection focus of osteomyelitis accurately. Patients and MethodsInitially, we investigated a case where osteomyelitis was bacteriologically detected after orthopedic surgery on lower limb. Based on the surgical pathology, we explored the optimal SUV cut-off value of the 18F-FDG PET/CT image taken before surgery. The SUV cut-off value was varied, using the GE Rainbow Color Scale on a dedicated workstation. We searched for the most accurate visualization of the extent of the infectious lesion. Subsequently, using the SUV cut-off value decided on the basis of the first case studied, we investigated the accuracy for diagnosing osteomyelitis. A total of sixteen patients underwent 18F-FDG PET/CT for suspected osteomyelitis (one case involved the upper extremity and 15 cases the lower one). All patients underwent surgery. The final diagnosis was made by means of bacteriologic culture of surgical specimens and histopathologic analysis. We compared surgical pathology and preoperative 18F-FDG PET/CT. ResultsIn the first case studied, the infection was most accurately localized with a SUV with a lower level of 2.00 and an upper of 8.00. Upon comparing the pathological findings and the 18F-FDG PET/CT, we set a SUV with a lower level of 2.00 and an upper level of 8.00. In thirteen cases, infection was detected with positive pathological findings. Preoperative 18F-FDG PET/CT showed high accumulation in these cases. In the remaining three cases, no infection was detected on either pathological findings nor 18F-FDG PET/CT findings. ConclusionsThe infection focus of osteomyelitis was accurately visualized by setting the SUV cut-off lower level to 2.00 and upper level to 8.00. We believe that this 18F-FDG PET/CT technique is helpful for image guided surgery of osteomyelitis.

Diagnostic accuracy of 68 Ga-prostate-specific membrane antigen (PSMA) positron-emission tomography (PET) and multiparametric (mp)MRI to detect intermediate-grade intra-prostatic prostate cancer using whole-mount pathology: impact of the addition of 68 Ga-PSMA PET to mpMRI.

To evaluate the ability of prostate-specific membrane antigen (PSMA)-positron-emission tomography (PET)/computed tomography (CT) to detect intermediate-grade intra-prostatic prostate cancer (PCa), and to determine if PSMA-PET improves the diagnostic accuracy of multiparametric magnetic resonance imaging (mpMRI). A total of 56 consecutive patients with International Society of Urological Pathology (ISUP) grade 2-3 PCa after radical prostatectomy, who underwent both mpMRI and PSMA-PET CT (hereafter PSMA-PET) preoperatively, were enrolled in this study. The accuracy of PSMA-PET, mpMRI alone, and the two procedures in combination was analysed for identifying ISUP grades 1-3 within a 12-segment model. The accuracy of a combined predictive model (PSMA-PET and mpMRI) was determined. Receiver-operating characteristic curve analysis to determine the optimal standardized uptake value (SUVmax ) for PSMA-PET in discriminating between ISUP grades 1 and ≥2 was performed. On a per-patient basis, the sensitivities for PSMA-PET and mpMRI in identifying ISUP grades 2-3 PCa were 100% and 97%, respectively. Assessing ISUP grade ≥2 PCa using a 12-segment analysis, PSMA-PET demonstrated greater diagnostic accuracy (area under the curve), sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV), with values of 0.91, 88%, 93%, 95% and 85%, respectively, than did mpMRI (Prostate Imaging Reporting and Data System [PI-RADS] 3-5), at 0.79, 68%, 91%, 87%, and 75%, respectively. When used in combination (PSMA-PET and mpMRI PIRADS 4-5), sensitivity, specificity, NPV and PPV were 92%, 90%, 96% and 81%, respectively. The sensitivity for both techniques reduced markedly when assessing ISUP grade 1 PCa (18% for PSMA-PET, 10% for mpMRI). An SUVmax value of 3.95 resulted in 94% sensitivity and 100% specificity. PSMA-PET is accurate in detecting segments containing intermediate-grade intra-prostatic PCa (ISUP grade ≥ 2), compared with and complementary to mpMRI. By contrast the detection rate for ISUP grade 1 disease for both PSMA-PET and mpMRI was low.

Comparison of Tumor Volumes as Determined by Pathologic Examination and FLT-PET/CT Images of Non–Small Cell Lung Cancer: A Pilot Study

To determine the cut-off standardized uptake value (SUV) on 3-deoxy-3-18F-fluorothymidine (FLT) positron emission tomography/computed tomography (FLT-PET/CT) images that generates the best volumetric match to pathologic gross tumor volume (GTVpath) for non–small cell lung cancer (NSCLC). Twelve patients with NSCLC who, without any antineoplastic therapy before, underwent FLT-PET/CT scans one or two days followed by lobectomy were enrolled. The surgical specimen was dissected into 5-7 μm sections at approximately 4-mm intervals and stained with hematoxylin and eosin. The tumor-containing area was outlined slice by slice and the GTVpath determined by summing over all the slices, taking into account the interslice thickness and fixation-induced volume reduction. The gross tumor volume from the PET images, GTVPET, was determined as a function of cut-off SUV. Then, the GTV PET(SUV) value was determined at different cut-off values of the absolute SUV, from 0.9 to 1.8 at 0.1 intervals. Similarly, GTVPET(%SUV) was determined at various percentage thresholds of the maximal SUV, from 15% to 60% at 5% intervals. The optimal threshold or optimal absolute SUV was defined as the value at which the GTVPET was the same as the GTVpath. The patients included 5 men and 7 women, with a median age of 62 years (range, 43–71). The pathologic classifications were 8 adenocarcinoma and 4 squamous cell carcinoma. The locations of the tumors were 3 superior lobe of left lung, 2 inferior lobe of left lung, 5 superior lobe of right lung, and 2 inferior lobe of right lung, respectively. The fixation process induced a volumetric reduction to 70.84% ± 5.71% (range, 60.4%-79.7%) of the original tumor volumes. The maximal SUV was 3.50 ± 0.97 (range, 1.96-5.05). The GTVpath was 11.07± 10.30 cm3 (range, 2.39-33.10cm3). The mean optimal threshold and absolute SUV that produced the best agreement between GTVpath and GTVPET were 56% ± 11% and 1.84 ± 0.33, respectively. The optimal absolute SUV had a positive correlation with maximal SUV (P=.037), whereas the optimal threshold had no significant correlation with it (P=.52). On the other hand, the optimal threshold was correlated with volume retraction (P<.05), but the optimal absolute SUV had no significant correlation with volume retraction (P>.05). This study evaluated the use of GTVpath as a criterion for determining the FLT-PET/CT images’ optimal cut-off SUV for NSCLC. Absolute SUV 1.8 and threshold 56% might be used as the optimal cut-off SUV for NSCLC target volume delineation.

呼吸同期PET/CT を用いた横隔膜境界における肉眼的腫瘍体積の算出能の評価

The present study aimed to clarify gross tumor volume (GTV) contouring accuracy at the diaphragm boundary using respiratory-gated PET/CT. The lung/diaphragm boundary was simulated using a phantom containing 18F solution (10.6 kBq/mL). Tumors were simulated using spheres (diameter, 11-38 mm) containing 18F and located at the positions of the lungs and liver. The tumor background ratios (TBR) were 2, 4, and 8. The phantom was moved from the superior to inferior direction with a 20-mm motion displacement at 3.6 s intervals. The recovery coefficient (RC), volume RC (VRC), and standardized uptake value (SUV) threshold were calculated using stationary, non-gated (3D), and gated (4D) PET/CT. In lung cancer simulation, RC and VRC in 3D PET images were, respectively, underestimated and overestimated in smaller tumors, whereas both improved in 4D PET images regardless of tumor size and TBR. The optimal SUV threshold was about 30% in 4D PET images. In liver cancer simulation, RC and VRC were, respectively, underestimated and overestimated in smaller tumors, and when the TBR was lower, but both improved in 4D PET images when tumors were >17 mm and the TBR was >4. The optimal SUV threshold tended to depend on the TBR. The contouring accuracy of GTV was improved by considering TBR and using an optimal SUV threshold acquired from 4D PET images.

Comparison of Tumor Volumes as Determined by Pathologic Examination and FLT-PET/CT Images of Non-Small Cell Lung Cancer: A Pilot Study

To determine the cut-off standardized uptake value (SUV) on 3-deoxy-3-18F-fluorothymidine (FLT) positron emission tomography/computed tomography (FLT-PET/CT) images that generates the best volumetric match to pathologic gross tumor volume (GTVpath) for non-small-cell lung cancer (NSCLC). Twelve patients with NSCLC who without any antineoplastic therapy before, underwent FLT-PET/CT scans one or two days followed by lobectomy were enrolled. The surgical specimen was dissected into 5-7 μm sections at approximately 4-mm intervals and stained with hematoxylin and eosin. The tumor-containing area was outlined slice by slice and the GTVpath determined by summing over all the slices, taking into account the interslice thickness and fixation-induced volume reduction. The gross tumor volume from the PET images, GTVPET, was determined as a function of cut-off SUV. Then, the GTV PET(SUV) value was determined at different cut-off values of the absolute SUV, from 1.0 to 2.0 at 0.1 intervals. Similarly, GTVPET(%SUV) was determined at various percentage thresholds of the maximal SUV, from 15% to 60% at 5% interval. The optimal threshold or optimal absolute SUV was defined as the value at which the GTVPET was the same as the GTVpath. The patients included 5 men and 7 women, with a median age of 62 years (range, 43-71). The pathologic classifications were 8 adenocarcinoma and 4 squamous cell carcinoma. The location of the tumors were 3 superior lobe of left lung, 2 inferior lobe of left lung, 5 superior lobe of right lung and 2 inferior lobe of right lung, respectively. The fixation process induced a volumetric reduction to 70.84% ± 5.71% (range, 60.4-79.7%) of the original tumor volumes. The maximal SUV was 3.50 ± 0.97 (range, 1.96-5.05). The GTVpath was 11.07± 10.30 cm3(range, 2.39-33.10cm3). The mean optimal threshold and absolute SUV that produced the best agreement between GTVpath and GTVPET were 56% ± 11% and 1.84 ± 0.33, respectively. The optimal absolute SUV had a positive correlation with maximal SUV (p = 0.037), whereas the optimal threshold had no significant correlation with it (p = 0.52). On the other hand, the optimal threshold was correlated with volume retraction (p<0.05), but the optimal absolute SUV had no significant correlation with volume retraction (p> 0.05). This study evaluated the use of GTVpath as a criterion for determining the FLT-PET/CT images optimal cut-off SUV for NSCLC. Absolute SUV 1.8 and threshold 56% might be used as the optimal cut-off SUV for NSCLC target volume delineation.

Determination of an Optimal Standardized Uptake Value of Fluorodeoxyglucose for Positron Emission Tomography Imaging to Assess Pathological Volumes of Cervical Cancer: A Prospective Study

PurposeTo determine the optimal standardized uptake value (SUV) of 18F-fluorodeoxyglucose (18F-FDG) for positron emission tomography (PET) imaging, at which the PET-defined gross tumor volume (GTVPET) best matches with the pathological volume (GTVPATH) in the cervical cancer.Materials and MethodsTen patients with the cervical cancer who underwent surgery were enrolled in this study. The excised specimens were processed for whole-mount serial sections and H-E staining. The tumor borders were outlined in sections under a microscope, histopathological images were scanned and the GTVPATH calculated. The GTVPET was delineated automatically by using various percentages relative to the maximal SUV and absolute SUV. The optimal threshold SUV was further obtained as the value at which the GTVPET best matched with the GTVPATH.ResultsAn average of 85±10% shrinkage of tissue was observed after the formalin fixation. The GTVPATH was 13.38±2.80 cm3 on average. The optimal threshold on percentile SUV and absolute SUV were 40.50%±3.16% and 7.45±1.10, respectively. The correlation analysis showed that the optimal percentile SUV threshold was inversely correlated with GTVPATH (p<0.05) and tumor diameter (p<0.05). The absolute SUV was also positively correlated with SUVmax (p<0.05).ConclusionThe pathological volume could provide the more accurate tumor volume. The optimal SUV of FDG for PET imaging by use of GTVPATH as standard for cervical cancer target volume delineation was thus determined in this study, and more cases are being evaluated to substantiate this conclusion.

The use of 18F-fluoromethylcholine PET/CT in differentiating focal nodular hyperplasia from hepatocellular adenoma

Diagnosis of focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) using conventional imaging techniques can be difficult; however, it is important to differentiate between them as these benign liver tumors require different therapeutic strategies. The aim of our study was to prospectively evaluate the use of PET/computed tomography (CT) with F-fluoromethylcholine (F-FCH) as a novel diagnostic approach in the differentiation between HCA and FNH. Fifty-six consecutive patients with a suspicion of one or multiple HCAs or FNHs larger than 2 cm were prospectively included after written informed consent was obtained from them. All the patients underwent a PET/CT with F-FCH. Histopathology of the lesions was the standard of reference. The ratio of the standardized uptake value (SUV) of the lesions compared with normal liver uptake within the same patient was calculated. Statistical tests were evaluated at the 95% confidence interval. Forty-nine patients with 60 lesions and histopathological diagnosis of FNH or HCA completed the study and were analyzed. The mean SUV ratio for FNH was 1.67±0.31 (mean±SD, n=28), resulting in a positive likelihood ratio of 32.3 for PET-positive FNH. The mean SUV ratio for HCA was 0.82±0.17 (n=32), with a likelihood ratio of ∼100 for PET-negative HCA. Receiver operating characteristic curve analysis revealed an optimal SUV ratio cutoff value of 1.13, which reached 100% sensitivity and 97% specificity in differentiating FNH from HCA. This prospective study shows that PET/CT with F-FCH can accurately differentiate FNH from HCA and may become a valuable diagnostic tool when conventional imaging techniques fail to do so.

Correlation Between Radiation Dose to 18F-FDG-PET Defined Active Bone Marrow Subregions and Acute Hematologic Toxicity in Cervical Cancer Patients Treated With Chemoradiotherapy

To test the hypothesis that radiation dose to (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET)-defined active bone marrow (BM(ACT)) subregions is correlated with hematologic toxicity in cervical cancer patients treated with chemoradiotherapy. The conditions of 26 women with cervical cancer who underwent (18)F-FDG-PET before treatment with concurrent cisplatin and intensity-modulated radiation therapy were analyzed. BM(ACT) was defined as the subregion of total bone marrow (BM(TOT)) with a standardized uptake value (SUV) equal to or above the mean for that individual. Inactive bone marrow (BM(INACT)) was defined as BM(TOT) - BM(ACT). Generalized linear modeling was used to test the correlation between BM(ACT) and BM(INACT) dose-volume metrics and hematologic nadirs, particularly white blood cell count (WBC) and absolute neutrophil count (ANC). Increased BM(ACT) mean dose was significantly associated with decreased log(WBC) nadir (β = -0.04; 95% CI, -0.07 to -0.01; p = 0.009), decreased log(ANC) nadir (β = -0.05; 95% CI, -0.08 to -0.02; p = 0.006), decreased hemoglobin nadir (β = -0.16; 95% CI, -0.27 to -0.05; p = 0.010), and decreased platelet nadir (β = -6.16; 95% CI, -9.37 to -2.96; p < 0.001). By contrast, there was no association between BM(INACT) mean dose and log(WBC) nadir (β = -0.01; 95% CI, -0.06 to 0.05; p = 0.84), log(ANC) nadir (β = -0.03; 95% CI, -0.10 to 0.04; p = 0.40), hemoglobin nadir (β = -0.09; 95% CI, -0.31 to 0.14; p = 0.452), or platelet nadir (β = -3.47; 95% CI, -10.44 to 3.50; p = 0.339). Irradiation of BM subregions with higher (18)F-FDG-PET activity was associated with hematologic toxicity, supporting the hypothesis that reducing dose to BM(ACT) subregions could mitigate hematologic toxicity. Future investigation should seek to confirm these findings and to identify optimal SUV thresholds to define BM(ACT).

Respiratory-gated 18F-FDG PET imaging in lung cancer: effects on sensitivity and specificity

Respiratory motion is known to deteriorate positron emission tomography (PET) images and may lead to potential diagnostic errors when a standardized uptake value (SUV) cut-off threshold is used to discriminate between benign and malignant lesions. To evaluate and compare ungated and respiratory-gated 18F-fluorodeoxyglucose PET/computed tomography (CT) methods for the characterization of pulmonary nodules. The list-mode acquisition during respiratory-gated PET was combined with a short breath-hold CT scan to form the CT-based images. We studied 48 lesions in 43 patients. PET images were analyzed in terms of the maximum SUV (SUV(max)) and the lesion location. Using receiver-operating characteristic (ROC) curves, the optimal SUV cut-off thresholds for the ungated and CT-based methods were calculated to be 2.0 and 2.2, respectively. The corresponding sensitivity values were 83% and 92%, respectively, with a specificity of 67% for both methods. The two methods gave equivalent performance levels for the upper and middle lobes (sensitivity 93%, specificity 62%). They differed for the lower lobes, where the CT-based method outperformed the ungated method (sensitivity values of 90% and 70%, respectively, and a specificity of 73% with both methods) - especially for lesions smaller than 15 mm. The CT-based method increased sensitivity and did not diminish specificity, compared with the ungated method. It was more efficient than the ungated method for imaging the lower lobes and smallest lesions, which are most affected by respiratory motion.

A Prospective Evaluation of Staging and Target Volume Definition of Lymph Nodes by 18FDG PET/CT in Patients With Squamous Cell Carcinoma of Thoracic Esophagus

To determine an optimal standardized uptake value (SUV) threshold for detecting lymph node (LN) metastases in esophageal cancer using (18)F-Fluorodeoxyglucose positron emission tomography/computer tomography (18FDG PET/CT) and to define the resulting nodal target volume, using histopathology as a "gold standard." Sixteen patients with esophageal squamous cell carcinoma who underwent radical esophagectomy and three-field LN dissection after 18FDG PET/CT and CT scans were enrolled into this study. Locations of LN groups were recorded according to a uniform LN map. Diagnostic performance of different SUV thresholds was assessed by receiver operating characteristic analysis. The optimal cutoff SUV was determined by plotting the false-negative rate (FNR) and false-positive rate (FPR), the sum of both error rates (FNR+FPR), and accuracy against a hypothetical SUV threshold. For each patient, nodal gross tumor volumes (GTVNs) were generated with CT alone (GTVNCT), PET/CT (GTVNPET), and pathologic data (GTVNpath). GTVNCT or GTVNPET was compared with GTVNpath by means of a conformity index (CI), which is the intersection of the two GTVNs divided by the sum of them minus the intersection, e.g., CICT&path=GTVNCT&path/(GTVNCT+GTVNpath-GTVNCT&path). LN metastases occurred in 21 LN groups among the 144 specimens taken from the 16 patients. The area under the receiver operating characteristic curve was 0.9017±0.0410. The plot of error rates showed a minimum of FNR+FPR for an SUV of 2.36, at which the sensitivity, specificity, and accuracy were 76.19%, 95.93%, and 93.06%, respectively, whereas those of CT were 33.33%, 94.31%, and 85.42% (p values: 0.0117, 0.7539, and 0.0266). Mean GTVNCT, GTVNPET, and GTVNpath were 1.52±2.38, 2.82±4.51, and 2.68±4.16 cm3, respectively. Mean CICT&path and CIPET&path were 0.31 and 0.65 (p value=0.0352). Diagnostic superiority of PET/CT at an SUV threshold of 2.36 over CT has potential value in nodal target volume definition, but whether this can contribute to better treatment outcomes needs prospective analyses of recurrences in a larger cohort of patients.

The combination of [18F]fluorodeoxy-glucose and 16α-[18F]fluoro-17β-estradiol positron emission tomography for identifying leiomyosarcoma in uterine smooth muscle tumors.

5056 Background: Preoperative histologic examination of uterine myometrial lesions is not possible, and thus imaging plays an important role in the choice of treatment for uterine smooth muscle tumor (USMT). The aim of this study was to assess whether the positron emission tomography (PET) parameters of the [18F]fluorodeoxy-glucose (FDG) /16α-[18F]fluoro-17β-estradiol (FES) ratio predicts leiomyosarcoma, the most common malignant USMT. Methods: Over a 2-week period 28 patients suspected of having malignant USMT underwent FES-PET and FDG-PET. Regional values of tracer uptake were evaluated using the standardized uptake value (SUV). Receiver-operating-characteristic (ROC) analysis was performed to determine the optimal cut-off SUV value to differentiate malignant and benign USMTs. Sensitivity and specificity, and Cohen's kappa with 95% CI were computed to quantify the agreement between the SUV ratio of FDG/FES and the histopathological findings. Results: Of the 28 patients, 6 had a final diagnosis of malignant USMT, while 22 had benign USMT. The optimal cut-off SUV value for FDG/FES was 1.5 by ROC analysis. The overall accuracy of an FDG/FES ratio greater than 1.5 was 100% (95% CI 88%-100%), sensitivity was 100% (52%-100%), specificity was 100% (82%-100%), and the kappa value was 1.0, indicating very good correlation between malignant USMT and a high SUV ratio of FDG/FES. Conclusions: These findings support the potential clinical use of direct assessment of malignant USMT in patients with “suspected malignant” USMT. No significant financial relationships to disclose.

Application of Machine Learning Methodology for Pet-Based Definition of Lung Cancer

We applied a learning methodology framework to assist in the threshold-based segmentation of non-small-cell lung cancer (NSCLC) tumours in positron-emission tomography-computed tomography (PET-CT) imaging for use in radiotherapy planning. Gated and standard free-breathing studies of two patients were independently analysed (four studies in total). Each study had a pet-ct and a treatment-planning ct image. The reference gross tumour volume (GTV) was identified by two experienced radiation oncologists who also determined reference standardized uptake value (SUV) thresholds that most closely approximated the GTV contour on each slice. A set of uptake distribution-related attributes was calculated for each PET slice. A machine learning algorithm was trained on a subset of the PET slices to cope with slice-to-slice variation in the optimal suv threshold: that is, to predict the most appropriate suv threshold from the calculated attributes for each slice. The algorithm's performance was evaluated using the remainder of the pet slices. A high degree of geometric similarity was achieved between the areas outlined by the predicted and the reference SUV thresholds (Jaccard index exceeding 0.82). No significant difference was found between the gated and the free-breathing results in the same patient. In this preliminary work, we demonstrated the potential applicability of a machine learning methodology as an auxiliary tool for radiation treatment planning in NSCLC.

Comparison of Tumor Volumes as Determined by Pathologic Examination and FDG-PET/CT Images of Non–Small-Cell Lung Cancer: A Pilot Study

To determine the cut-off standardized uptake value (SUV) on (18)F fluoro-2-deoxy-glucose (FDG) positron emission tomography/computed tomography (FDG-PET/CT) images that generates the best volumetric match to pathologic gross tumor volume (GTV(path)) for non-small-cell lung cancer (NSCLC). Fifteen patients with NSCLC who underwent FDG-PET/CT scans followed by lobectomy were enrolled. The surgical specimen was dissected into 5-7-mum sections at approximately 4-mm intervals and stained with hematoxylin and eosin. The tumor-containing area was outlined slice by slice and the GTV(path) determined by summing over all the slices, taking into account the interslice thickness and fixation-induced volume reduction. The gross tumor volume from the PET images, GTV(PET), was determined as a function of cut-off SUV. The optimal threshold or optimal absolute SUV was defined as the value at which the GTV(PET) was the same as the GTV(path). The fixation process induced a volumetric reduction to 82% +/- 10% (range, 62-100%) of the original. The maximal SUV was 10.1 +/- 3.6 (range, 4.2-18.7). The optimal threshold and absolute SUV were 31% +/- 11% and 3.0 +/- 1.6, respectively. The optimal threshold was inversely correlated with GTV(path) and tumor diameter (p < 0.05), but the optimal absolute SUV had no significant correlation with GTV(path) or tumor diameter (p > 0.05). This study evaluated the use of GTV(path) as a criterion for determining the optimal cut-off SUV for NSCLC target volume delineation. Confirmatory studies including more cases are being performed.

FDG-PET zur Lymphknoten-Diagnostik des Lungenkarzinoms: Welche SUV-Schwelle ist sinnvoll?

AIM: 18 F-FDG PET is the most accurate noninvasive modality for staging mediastinal lymph nodes in lung cancer. Beside using visual image interpretation, some institutions use standardized uptake value (SUV) measurements in lymph nodes. Mostly, an SUV of 2.5 is used as the cut-off, but this choice was never deduced from respective studies. Receiver operating characteristic (ROC) analyses demonstrated that SUV thresholds of more than 4 resulted in the highest accuracy. But these high cutoffs imply high false-negative rates (FNRs). The aim of our evaluation was to determine an optimal SUV threshold and to compare its diagnostic performance with the results of visual interpretation. METHODS: This retrospective study included 95 patients with suspected lung cancer who underwent mediastinoscopy / mediastinal lymphadenectomy after 18 F-FDG PET imaging (90-150 min after 250 MBq of 18 F-FDG). Maximum SUV was measured in 371 LN regions biopsied afterwards and visually interpreted using a 6-level score (--- through +++). Diagnostic performance was assessed by ROC analysis. FNR and false-positive rate (FPR), the sum of both error rates (FNR + FPR), and diagnostic accuracy were plotted against a hypothetical SUV threshold to determine the optimum SUV threshold. RESULTS: SUVs in metastatic lymph nodes were higher (mean ± SD, 7.1 ± 4.5; range, 1.4-26.9; n = 70) than in tumor-free lymph node stations (2.4 ± 1.7; range, 0.6-14.9; n = 301; p < 0.01). Inflammatory lymph nodes exhibited slightly increased SUVs (2.7 ± 2.0; range, 0.8-14.9; n = 146). The plot of error rates featured a minimum of the sum FNR + FPR for an SUV of 2.5. With increasing SUV threshold, the FPR decreased most prominently up to that value whereas a continuous rise of FNR was noticed. Highest diagnostic accuracy was achieved with an SUV of 4.5. The areas under the ROC curves demonstrated that visual interpretation tends to be more accurate than SUV quantification (visual, 0.930 ± 0.022; SUV, 0.899 ± 0.025; p = 0.241). Using an SUV of 2.5 as the threshold, the resulting sensitivity, specificity, and negative predictive value were 89, 84, and 96 %, respectively. CONCLUSIONS: For mediastinal staging, the choice of an SUV of 2.5 as the threshold is justified because FNR + FPR is minimized. The resulting high negative predictive value of 96 % allows the omission of mediastinoscopy in patients with negative mediastinal findings on 18 F-FDG PET images. For the experienced observer, visual analysis should be relied on primarily, with calculation of the SUV used, at most, as a secondary aid. For the less experienced observer, the SUV may be of greater value.

Preoperative Diagnosis of Lymph Node Metastases of Colorectal Cancer by FDG-PET/CT

The purpose of this study was to assess the diagnostic value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) for lymph node (LN) metastasis of colorectal cancer. FDG-PET/CT was used to preoperatively evaluate 88 patients with colorectal cancer. In this study, LN sites were divided into proximal and distant according to their distance from the primary tumor. The FDG-PET/CT images were evaluated by three criteria; nodal diameter, abnormal uptake and maximum standardized uptake value (SUV). We compared the diagnostic ability of these methods for LN metastasis at proximal and distant sites. The mean SUV of the malignant LNs was significantly higher than that of the benign LNs. The sensitivity, specificity and accuracy of diagnosis by abnormal uptake were 28.6, 92.9 and 75.0%, those by nodal diameter using cutoff value of 10 mm were 30.6, 95.3 and 74.4% and those by SUV using cutoff value of 1.5 were 53.1, 90.6 and 80.1%, respectively. The sensitivity, specificity and accuracy of diagnosis based on optimal SUV were 51.2, 85.1 and 69.3% in the proximal site and 62.5, 92.5 and 89.7%, respectively, in the distant site. FDG-PET/CT is useful for preoperative diagnosis of distant LN metastases of colorectal cancers.

18F-FDG PET for Mediastinal Staging of Lung Cancer: Which SUV Threshold Makes Sense?

(18)F-FDG PET is the most accurate noninvasive modality for staging mediastinal lymph nodes in lung cancer. Besides using visual image interpretation, some institutions use standardized uptake value (SUV) measurements in lymph nodes. Mostly, an SUV of 2.5 is used as the cutoff, but this choice was never deduced from respective studies. Receiver operating characteristic (ROC) analyses demonstrated that SUV thresholds of more than 4 resulted in the highest accuracy. But these high cutoffs imply high false-negative rates (FNRs). The aim of our evaluation was to determine an optimal SUV threshold and to compare its diagnostic performance with the results of visual interpretation. This retrospective study included 95 patients with suspected lung cancer who underwent mediastinoscopy/mediastinal lymphadenectomy after (18)F-FDG PET (90-150 min after 250 MBq of (18)F-FDG). Maximum SUV was measured in 371 lymph node regions biopsied afterward and visually interpreted using a 6-level score (- - - through + + +). Diagnostic performance was assessed by ROC analysis. FNR and false-positive rate (FPR), the sum of both error rates (FNR + FPR), and diagnostic accuracy were plotted against a hypothetical SUV threshold to determine the optimum SUV threshold. SUVs in metastatic lymph nodes were higher (mean +/- SD, 7.1 +/- 4.5; range, 1.4-26.9; n = 70) than in tumor-free lymph node stations (2.4 +/- 1.7; range, 0.6-14.9; n = 301; P < 0.01). Inflammatory lymph nodes exhibited slightly increased SUVs (2.7 +/- 2.0; range, 0.8-14.9; n = 146). The plot of error rates featured a minimum of the sum FNR + FPR for an SUV of 2.5. With increasing SUV threshold, the FPR decreased most prominently up to that value whereas a continuous rise of FNR was noticed. Highest diagnostic accuracy was achieved with an SUV of 4.5. The areas under the ROC curves demonstrated that visual interpretation tends to be more accurate than SUV quantification (visual, 0.930 +/- 0.022; SUV, 0.899 +/- 0.025; P = 0.241). Using an SUV of 2.5 as the threshold, the resulting sensitivity, specificity, and negative predictive value were 89%, 84%, and 96%, respectively. For mediastinal staging, the choice of an SUV of 2.5 as the threshold is justified because FNR + FPR is minimized. The resulting high negative predictive value of 96% allows the omission of mediastinoscopy in patients with negative mediastinal findings on (18)F-FDG PET images. For the experienced observer, visual analysis should be relied on primarily, with calculation of the SUV used, at most, as a secondary aid. For the less experienced observer, the SUV may be of greater value.