Solitary Nodular Invasive Mucinous Adenocarcinoma of the Lung: Imaging Diagnosis Using the Morphologic-Metabolic Dissociation Sign

OBJECTIVE: To evaluate the efficacy of the morphologic-metabolic (M-M) dissociation sign based on computed tomography (CT) and fluorine-18-fluorodeoxyglucose positron emission tomography (PET)/CT in discriminating invasive mucinous adenocarcinoma (IMA) from invasive non-mucinous adenocarcinomas (ADCs) of the lung. MATERIALS AND METHODS: The Institutional Review Board approved this retrospective study. Among surgically resected solitary pulmonary nodule (SPN)-type ADCs (< 3 cm in diameter), 35 patients with IMAs and 329 with invasive non-mucinous ADCs were included. Morphologic malignancy was established if the tumor with lobulated or spiculated margin on CT presented a tumor shadow disappearance rate of < 0.5. The M-M dissociation sign was determined when a malignant-morphologic nodule on CT showed maximum standardized uptake value (SUVmax) < 3.5 on PET/CT. RESULTS: Among 35 IMAs (size: 21 ± 7 mm, SUVmax: 1.8 ± 2.0) and 329 invasive non-mucinous ADCs (size: 21 ± 6 mm, SUVmax: 4.6 ± 4.2), the M-M dissociation sign was observed in 54% of IMAs (19/35) and 10% of invasive non-mucinous ADCs (34/329) (p < 0.001). The diagnostic performance of the sign in discriminating IMA from invasive non-mucinous ADCs showed a sensitivity of 54.3% (95% confidence interval [CI], 36.7–71.2), specificity 89.7% (95% CI, 85.9–92.7), positive predictive value 35.8% (95% CI, 26.5–46.5), and negative predictive value 94.9% (95% CI, 92.8–96.4). Multivariate analyses revealed metabolic benignity (odds ratio [OR] 2.99; 95% CI, 1.01–8.93; p = 0.047) and M-M dissociation sign (OR 6.35; 95% CI, 2.76–14.62; p < 0.001) to be significant predictors of SPN-type IMAs. CONCLUSION: Identification of the absence of M-M dissociation sign is an accurate indicator for excluding IMA from SPN-type lung ADCs.

Development of Predictive Models in Patients with Epiphora Using Lacrimal Scintigraphy and Machine Learning / 대한핵의학회잡지

PURPOSE: We developed predictive models using different programming languages and different computing platforms for machine learning (ML) and deep learning (DL) that classify clinical diagnoses in patients with epiphora. We evaluated the diagnostic performance of these models.METHODS: Between January 2016 and September 2017, 250 patients with epiphora who underwent dacryocystography (DCG) and lacrimal scintigraphy (LS) were included in the study. We developed five different predictive models using ML tools, Python-based TensorFlow, R, and Microsoft Azure Machine Learning Studio (MAMLS). A total of 27 clinical characteristics and parameters including variables related to epiphora (VE) and variables related to dacryocystography (VDCG) were used as input data. Apart from this, we developed two predictive convolutional neural network (CNN) models for diagnosing LS images. We conducted this study using supervised learning.RESULTS: Among 500 eyes of 250 patients, 59 eyes had anatomical obstruction, 338 eyes had functional obstruction, and the remaining 103 eyes were normal. For the data set that excluded VE and VDCG, the test accuracies in Python-based TensorFlow, R, multiclass logistic regression in MAMLS, multiclass neural network in MAMLS, and nuclear medicine physician were 81.70%, 80.60%, 81.70%, 73.10%, and 80.60%, respectively. The test accuracies of CNN models in three-class classification diagnosis and binary classification diagnosis were 72.00% and 77.42%, respectively.CONCLUSIONS: ML-based predictive models using different programming languages and different computing platforms were useful for classifying clinical diagnoses in patients with epiphora and were similar to a clinician's diagnostic ability.

Development of Predictive Models in Patients with Epiphora Using Lacrimal Scintigraphy and Machine Learning / 대한핵의학회잡지

PURPOSE@#We developed predictive models using different programming languages and different computing platforms for machine learning (ML) and deep learning (DL) that classify clinical diagnoses in patients with epiphora. We evaluated the diagnostic performance of these models.@*METHODS@#Between January 2016 and September 2017, 250 patients with epiphora who underwent dacryocystography (DCG) and lacrimal scintigraphy (LS) were included in the study. We developed five different predictive models using ML tools, Python-based TensorFlow, R, and Microsoft Azure Machine Learning Studio (MAMLS). A total of 27 clinical characteristics and parameters including variables related to epiphora (VE) and variables related to dacryocystography (VDCG) were used as input data. Apart from this, we developed two predictive convolutional neural network (CNN) models for diagnosing LS images. We conducted this study using supervised learning.@*RESULTS@#Among 500 eyes of 250 patients, 59 eyes had anatomical obstruction, 338 eyes had functional obstruction, and the remaining 103 eyes were normal. For the data set that excluded VE and VDCG, the test accuracies in Python-based TensorFlow, R, multiclass logistic regression in MAMLS, multiclass neural network in MAMLS, and nuclear medicine physician were 81.70%, 80.60%, 81.70%, 73.10%, and 80.60%, respectively. The test accuracies of CNN models in three-class classification diagnosis and binary classification diagnosis were 72.00% and 77.42%, respectively.@*CONCLUSIONS@#ML-based predictive models using different programming languages and different computing platforms were useful for classifying clinical diagnoses in patients with epiphora and were similar to a clinician's diagnostic ability.

Inverse Prognostic Relationships of ¹⁸F-FDG PET/CT Metabolic Parameters in Patients with Distal Bile Duct Cancer Undergoing Curative Surgery / 대한핵의학회잡지

PURPOSE: As there were few previous studies with a small number of subjects, the purpose of this was to evaluate the prognostic significance of ¹⁸F-FDG PET/CT in patients with distal bile duct cancer undergoing curative surgery.METHODS: The study included 40 patients (M/F = 24:16; age 68.0 ± 8.0 years) who underwent preoperative ¹⁸F-FDG PET/CT followed by curative surgical resection. The participant's age, sex, Eastern Cooperative Oncology Group performance-status score, baseline serum CA 19-9 level, stage, pathologic T and N stages, tumor size, tumor grade, tumor growth pattern, R0 resection, and adjuvant therapy were included as clinicopathological variables for predicting overall survival. The PET variables were maximum standardized uptake value (SUV(max)), average SUV (SUV(avg)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the tumor. The Kaplan-Meyer method and Cox proportional hazards model were used for the survival analysis.RESULTS: A total of 15 of 40 patients (37.5%) died during the follow-up period. In univariate analysis, low SUVmax (≤ 2.7, p = 0.0005) and low SUV(avg) (≤ 2.6, p = 0.0034) were significant predictors of poor overall survival. In multivariate analyses, only low SUV(max) (HR = 6.7016, 95% CI 1.9961–22.4993, p = 0.0047) was an independent prognostic factor associated with poor overall survival.CONCLUSION: The SUVmax of the primary tumor measured by ¹⁸F-FDG PET/CT was an independent significant prognostic factor for overall survival in patients with distal bile duct cancer. However, different results from a previous study warrant further large sample-sized study.

Inverse Prognostic Relationships of ¹⁸F-FDG PET/CT Metabolic Parameters in Patients with Distal Bile Duct Cancer Undergoing Curative Surgery / 대한핵의학회잡지

PURPOSE@#As there were few previous studies with a small number of subjects, the purpose of this was to evaluate the prognostic significance of ¹⁸F-FDG PET/CT in patients with distal bile duct cancer undergoing curative surgery.@*METHODS@#The study included 40 patients (M/F = 24:16; age 68.0 ± 8.0 years) who underwent preoperative ¹⁸F-FDG PET/CT followed by curative surgical resection. The participant's age, sex, Eastern Cooperative Oncology Group performance-status score, baseline serum CA 19-9 level, stage, pathologic T and N stages, tumor size, tumor grade, tumor growth pattern, R0 resection, and adjuvant therapy were included as clinicopathological variables for predicting overall survival. The PET variables were maximum standardized uptake value (SUV(max)), average SUV (SUV(avg)), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the tumor. The Kaplan-Meyer method and Cox proportional hazards model were used for the survival analysis.@*RESULTS@#A total of 15 of 40 patients (37.5%) died during the follow-up period. In univariate analysis, low SUVmax (≤ 2.7, p = 0.0005) and low SUV(avg) (≤ 2.6, p = 0.0034) were significant predictors of poor overall survival. In multivariate analyses, only low SUV(max) (HR = 6.7016, 95% CI 1.9961–22.4993, p = 0.0047) was an independent prognostic factor associated with poor overall survival.@*CONCLUSION@#The SUVmax of the primary tumor measured by ¹⁸F-FDG PET/CT was an independent significant prognostic factor for overall survival in patients with distal bile duct cancer. However, different results from a previous study warrant further large sample-sized study.

Clinical Significance of Incidental Focal ¹⁸F-FDG Uptake in the Spinal Cord of Patients with Cancer / 대한핵의학회잡지

PURPOSE: We investigated the incidence, location, and clinical significance of focal ¹⁸F-FDG uptake of the spinal cord in patients with cancer.METHODS: We reviewed the medical records of 22,937 consecutive adult patients with known or suspicious malignancy who underwent ¹⁸F-FDG PET/CT. PET/CT scans with incidental focal spinal cord uptake were selected and retrospectively reviewed to determine the presence, location, number, and maximum standardized uptake value (SUV(max)) of any focal hypermetabolic lesions of the spinal cord. In subjects with focal spinal uptake, clinical characteristics and clinical follow-up results, including follow-up PET/CT, were reviewed.RESULTS: Incidental focal spinal cord uptake was observed in 69 of 22,937 adult patients (incidence = 0.3%; M:F = 31:38; age, 55.8 ± 14.7 years). Seventy-eight focal hypermetabolic lesions on spinal cord in the PET/CT scans of the 69 study subjects were analyzed. The most common sites of focal spinal cord uptake were the T12 vertebra (47/78; 60.3%) and L1 vertebra (20/78; 25.6%). Multifocal cord uptake was found in 8 of 69 patients (11.6%). The average SUV(max) for cord uptake was 2.5 ± 0.5 (range, 1.4∼3.9). There was no clinical or imaging evidence of abnormalities in the spinal cord, both at the time of PET/CT and during clinical follow-up.CONCLUSIONS: Although incidental focal ¹⁸F-FDG uptake of the spinal cord is rare in patients with cancer, it may be physiological or benign, but it should not be considered as malignant involvement. Common sites for the uptake were in the T12 and L1 spine levels.

Prognostic Value of Volume-Based Positron Emission Tomography/Computed Tomography in Patients With Nasopharyngeal Carcinoma Treated With Concurrent Chemoradiotherapy

OBJECTIVES: The aim of this study was to evaluate the prognostic value of volume-based metabolic parameters measured by 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in patients with nasopharyngeal carcinoma (NPC). METHODS: Forty-four NPC patients who underwent 18F-FDG PET/CT for initial staging work-up before concurrent chemoradiotherapy (CCRT) were retrospectively evaluated. Maximum standardized uptake value (SUV), mean SUV, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary tumors were measured. The prognostic significance and predictive performance of these parameters were assessed by Cox proportional hazards regression analysis and time-dependent receiver operating characteristics (ROC) curve analysis. RESULTS: Multivariate analysis showed that American Joint Committee on Cancer stage 7th edition (hazard ratio [HR], 1.525; 95% confidence interval [CI], 1.062 to 2.188; P=0.022), and TLG (HR, 7.799; 95% CI, 2.622 to 23.198; P< or =0.001) were independent predictive factors associated with decreased disease-free survival (DFS). Time-dependent ROC curve analysis indicated that TLG was a better predictor of DFS than MTV (P=0.008). CONCLUSION: The TLG of the primary tumor was a significant independent metabolic prognostic factor of DFS in patients with NPC treated with CCRT.

Diffuse Thyroid Uptake Incidentally Found on 18F-Fluorodeoxyglucose Positron Emission Tomography in Subjects without Cancer History

OBJECTIVE: We investigated the clinical significance of incidental diffuse thyroid uptake (DTU) on 18F-FDG PET in subjects without a history of cancer. MATERIALS AND METHODS: This study included 2062 studies from adults who underwent 18F-FDG PET as a cancer screening program. Subjects were divided into the following two groups: with (group I) or without (group II) DTU. The presence of DTU and the thyroid visual grading score were compared with thyroid function tests, serum anti-microsomal antibody (AMA) levels, and the presence of diffuse parenchymal change (DPC) on ultrasonography (USG). RESULTS: DTU was found in 6.6% of the scans (137/2062). Serum thyroid stimulating hormone (TSH) and AMA levels were significantly higher in group I than in group II. Increased AMA level (55.1%) and DPC (48.7%) were more frequently found in group I (p < 0.001). The proportion of subjects with any abnormal results in serum free thyroxine, triiodothyronine, TSH, or AMA levels or DPC on USG was significantly higher in group I than in group II (71.5% vs. 10.6%, p < 0.001), and was significantly and gradually increased according to the visual grading score group (0 vs. 1-2 vs. 3-4 = 10.6% vs. 58.5% vs. 90.9%, p < 0.001). TSH and is AMA levels were significantly increased according to the visual grading score. CONCLUSION: The presence or degree of incidental DTU on 18F-FDG PET is closely correlated with increased serum AMA and TSH levels, and the presence of DPC on USG. Therefore, the most plausible pathological cause of DTU may be cell damage by an autoimmune mechanism.

Prognostic Value of Volume-Based 18F-Fluorodeoxyglucose PET/CT Parameters in Patients with Clinically Node-Negative Oral Tongue Squamous Cell Carcinoma

OBJECTIVE: To evaluate the prognostic value of volume-based metabolic parameters measured with 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) in patients with clinically node-negative (cN0) oral tongue squamous cell carcinoma (OTSCC) as compared with other prognostic factors. MATERIALS AND METHODS: In this study, we included a total of 57 patients who had been diagnosed with cN0 tongue cancer by radiologic, 18F-FDG PET/CT, and physical examinations. The maximum standardized uptake value (SUVmax), average SUV (SUVavg), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for primary tumors were measured with 18F-FDG PET. The prognostic significances of these parameters and other clinical variables were assessed by Cox proportional hazards regression analysis. RESULTS: In the univariate analysis, pathological node (pN) stage, American Joint Committee on Cancer (AJCC) stage, SUVmax, SUVavg, MTV, and TLG were significant predictors for survival. On a multivariate analysis, pN stage (hazard ratio = 10.555, p = 0.049), AJCC stage (hazard ratio = 13.220, p = 0.045), and MTV (hazard ratio = 2.698, p = 0.033) were significant prognostic factors in cN0 OTSCC patients. The patients with MTV > or = 7.78 cm3 showed a worse prognosis than those with MTV < 7.78 cm3 (p = 0.037). CONCLUSION: The MTV of primary tumor as a volumetric parameter of 18F-FDG PET, in addition to pN stage and AJCC stage, is an independent prognostic factor for survival in cN0 OTSCC.

18F-FDG PET/CT in Primary AL Hepatic Amyloidosis Associated with Multiple Myeloma

We report here on a rare case of primary AL hepatic amyloidosis associated with multiple myeloma in a 64-year-old woman. The patient was referred for evaluating her progressive jaundice and right upper quadrant pain. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) showed diffusely and markedly increased 18F-FDG uptake in the liver. Although there have been several case studies showing positive 18F-FDG uptake in pulmonary amyloidosis, to the best of our knowledge, the 18F-FDG PET/CT findings of hepatic amyloidosis or primary hepatic amyloidosis associated with multiple myeloma have not been reported previously.

Diagnostic Efficacy of PET/CT Plus Brain MR Imaging for Detection of Extrathoracic Metastases in Patients with Lung Adenocarcinoma

We aimed to evaluate prospectively the efficacy of positron emission tomography (PET)/computed tomography (CT) plus brain magnetic resonance imaging (MRI) for detecting extrathoracic metastases in lung adenocarcinoma. Metastatic evaluations were feasible for 442 consecutive patients (M:F=238:204; mean age, 54 yr) with a lung adenocarcinoma who underwent PET/CT (CT, without IV contrast medium injection) plus contrast-enhanced brain MRI. The presence of metastases in the brain was evaluated by assessing brain MRI or PET/CT, and in other organs by PET/CT. Diagnostic efficacies for metastasis detection with PET/CT plus brain MRI and with PET/CT only were calculated on a per-patient basis and compared from each other. Of 442 patients, 88 (20%, including 50 [11.3%] with brain metastasis) had metastasis. Regarding sensitivity of overall extrathoracic metastasis detection, a significant difference was found between PET/CT and PET/CT plus brain MRI (68% vs. 84%; P=0.03). As for brain metastasis detection sensitivity, brain MRI was significantly higher than PET/CT (88% vs. 24%; P<0.001). By adding MRI to PET/CT, brain metastases were detected in additional 32 (7% of 442 patients) patients. In lung adenocarcinoma patients, significant increase in sensitivity can be achieved for detecting extrathoracic metastases by adding dedicated brain MRI to PET/CT and thus enhancing brain metastasis detection.

Detection of Cancer with PET and PET/CT in Asymptomatic Volunteers / 핵의학분자영상

PURPOSE: We retrospectively investigated the diagnostic performance of (18)F-fluorodeoxyglucose positron emission tomography (PET) and PET/CT for cancer detection in asymptomatic health-check examinees. MATERIALS AND METHODS: This study consisted of 5091 PET or PET/CT conducted as part of annual health examination at one hospital from March 1998 to February 2008. To find the incidence of cancers, medical records of the subjects were thoroughly reviewed for a follow-up period of one year. The patterns of formal readings of PET and PET/CT were analyzed to assess the sensitivity and specificity for cancer detection. The histopathology and stage of the cancers were evaluated in relation to the results of PET. RESULTS: Eighty-six cancers (1.7%) were diagnosed within one year after PET or PET/CT. When PET and PET/CT results were combined, the sensitivity was 48.8% and specificity was 81.1% for cancer detection. PET only had a sensitivity of 46.2% and a specificity of 81.4%, and PET/CT only had a sensitivity of 75.0% and a specificity of 78.5% respectively. There were no significant differences in cancer site, stage and histopathology between PET positive and PET negative cancers. In 19.3% of formal readings of PET and PET/CT, further evaluation to exclude malignancy or significant disease was recommended. Head and neck area and upper gastrointestinal tract were commonly recommended sites for further evaluation. CONCLUSIONS: PET and PET/CT showed moderate performance for detecting cancers in asymptomatic adults in this study. More experience and further investigation are needed to overcome limitations of PET and PET/CT for cancer screening.

Current Status and Problems of PET/CT Data on CD for Inter-hospital Transfer / 핵의학분자영상

PURPOSE: This study was performed to find the current problems of positron emission tomography / computed tomography (PET/CT) data on CD for inter-hospital transfer. MATERIALS AND METHODS: The subjects were 746 consecutive 18F-fluorodeoxyglucose PET/CT data CDs from 56 hospitals referred to our department for image interpretation. The formats and contents of PET/CT data CDs were reviewed and the email questionnaire survey about this was performed. RESULTS: PET/CT data CDs from 21 of 56 hospitals (37.5%) included all transaxial CT and PET images with DICOM standard format which were required for authentic interpretation. PET/CT data from the others included only secondary capture images or fusion PET/CT images. According to this survey, the main reason of limited PET/CT data on CD for inter-hospital transfer was that the data volume of PET/CT was too large to upload to the Picture Archiving and Communication System. CONCLUSION: The majority of hospitals provided limited PET/CT data on CD for inter-hospital transfer, which could be inadequate for accurate interpretation and clinical decision making. It is necessary to standardize the format of PET/CT data on CD for inter-hospital transfer including all transaxial CT and PET images with DICOM standard format.

(18)F-FDG PET/CT in Patients with Initially Diagnosed Adenoid Cystic Carcinoma of the Head and Neck: Clinicoplathologic Correlation / 핵의학분자영상

PURPOSE: We evaluated (18)F-FDG PET/CT findings in initially diagnosed adenoid cystic carcinoma (ACC) of the head and neck in association with pathological subtype, staging, uptake comparison with squamous cell carcinoma (SqCC) and prognosis. MATERIALS AND METHODS: The subjects were 16 patients with initially diagnosed ACC of head and neck who underwent pretreatment (18)F-FDG PET/CT. Histological subtype (solid pattern vs. tubular/cribriform pattern), SUV(max) of size-matched SqCC of the head and neck as control group, disease-free survival (DFS) were compared with the SUV(max) of ACC of the head and neck. RESULTS: Of total 16 patients, 6 had solid pattern and the remaining 10 had tubular/cribriform pattern. The SUV(max) were significantly higher in solid pattern group than in tubular/cribriform pattern group (6.7+/-3.2 vs. 4.2+/-0.9, p=0.03). PET/CT found unexpected distant metastasis in 18.7% of patients (3/16) and changed the therapeutic plan in those patients. The SUV(max) of ACC was significantly lower than that of size-matched SqCC (5.1+/-2.4 vs. 13.6+/-6.0, p or =6.0) had significantly shorter DFS than those with low (18)F-FDG uptake (SUV(max) <6.0). CONCLUSION: (18)F-FDG uptake of ACC of the head and neck is significantly associated with histological subtype and DFS. (18)F-FDG PET/CT may be useful for detecting unexpected metastasis. Since (18)F-FDG uptake of tubular/cribriform ACC compared with SqCC is relatively low, it is necessary to interpret PET images carefully in patients without alleged ACC.

18F-FDG PET/CT in Multiple Myeloma: Is It Necessary to Include the Skull and Lower Extremity Distal to Mid-Thigh? / 핵의학분자영상

PURPOSE: We evaluated whether it was necessary to perform whole body acquisition of 18F-FDG PET/CT including whole skull and lower extremity (LE) distal to mid-thigh (MT) in patients with multiple myeloma (MM). MATERIAL AND METHODS: Thirty patients underwent 45 whole body 18F-FDG PET/CT scans including skull and LE distal to MT. PET scans were divided by 2 subgroups according to the presence of abnormal focal 18F-FDG uptake in skull or LE distal to MT. Clinical characteristics including age, sex, and stages were compared between the 2 subgroups. RESULTS: Of total 45 whole body PET/CT scans, focally increased abnormal FDG uptake in the skull or LE distal to MT suggesting myeloma involvement was found in 22 scans (48.9%) of 14 patients (46.7%). Skull lesions were more frequently observed than LE lesions distal to MT on PET (86.4% vs. 40.9%, p0.05). CONCLUSION: Abnormal lesions in the skull or LE distal to MT on 18F-FDG PET/CT did not affect significantly on the tumor burden and Durie/Salmon plus stage of MM. Therefore, torso PET acquisition including head may be sufficient for evaluating patients with MM.

(18)F-FDG PET versus (18)F-FDG PET/CT for Adrenal Gland Lesion Characterization: a Comparison of Diagnostic Efficacy in Lung Cancer Patients

OBJECTIVE: The aim of this study was to assess the diagnostic efficacy of integrated PET/CT using fluorodeoxyglucose (FDG) for the differentiation of benign and metastatic adrenal gland lesions in patients with lung cancer and to compare the diagnostic efficacy with the use of PET alone. MATERIALS AND METHODS: Sixty-one adrenal lesions (size range, 5-104 mm; mean size, 16 mm) were evaluated retrospectively in 42 lung cancer patients. Both PET images alone and integrated PET/CT images were assessed, respectively, at two-month intervals. PET findings were interpreted as positive if the FDG uptake of adrenal lesions was greater than or equal to that of the liver, and the PET/CT findings were interpreted as positive if an adrenal lesion show attenuation > 10 HU and showed increased FDG uptake. Final diagnoses of adrenal gland lesions were made at clinical follow-up (n = 52) or by a biopsy (n = 9) when available. The diagnostic accuracies of PET and PET/CT for the characterization of adrenal lesions were compared using the McNemar test. RESULTS: Thirty-five (57%) of the 61 adrenal lesions were metastatic and the remaining 26 lesions were benign. For the depiction of adrenal gland metastasis, the sensitivity, specificity, and accuracy of PET were 74%, 73%, and 74%, respectively, whereas those of integrated PET/CT were 80%, 89%, and 84%, respectively (p values; 0.5, 0.125, and 0.031, respectively). CONCLUSION: The use of integrated PET/CT is more accurate than the use of PET alone for differentiating benign and metastatic adrenal gland lesions in lung cancer patients.

The Usefulness of 18F-FDG PET as a Cancer Screening Test / 핵의학분자영상

PURPOSE: The aim of this study was to evaluate the usefulness of whole body positron emission tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) for cancer screening in asymptomatic subjects. MATERIALS AND METHODS: The subjects were 1,762 men and 259 women who voluntarily underwent 18F-FDG PET for cancer screening as a part of a routine health examination. Final diagnosis was decided by other diagnostic studies, pathological results or clinical follow-up for 1 year. RESULTS: Of 2,021 subjects, 40 (2.0%) were finally proved to have cancer. Abnormal focal 18F-FDG uptake suggesting malignancy was found in 102 subjects (5.0%). Among them, 21 subjects (1.0%) were proved to have cancer. Other tests in the routine health examination could not find 9 of 21 cancers (42.9%) detected by PET. The sensitivity, specificity, positive predictive value, and negative predictive value of PET for cancer screening were 52.5%, 95.9%, 20.6%, and 99.0%, respectively. Pathologies of cancers missed on PET were adenocarcinoma (n=9; 3 colon cancers, 3 prostate cancers, 2 stomach cancers, and 1 rectal cancer), differentiated thyroid carcinoma (n=6), bronchioalveolar cell carcinoma (n=2), urinary bladder cancer (n=1), and melanoma (n=1). More than half of cancers which were not detected by PET were smaller than 1 cm in diameter. CONCLUSION: 18F-FDG PET might be useful for cancer screening in asymptomatic subjects due to its high specificity and negative predictive value and play a supplementary role to the conventional health check-up, but it could not replace due to limited sensitivity for urological cancers, small-sized tumors and some hypometaboic cancers.

Clinical Significance of Focal Breast Lesions Incidentally Identified by 18F-FDG PET/CT / 핵의학분자영상

PURPOSE: We evaluated the incidence and malignant risk of focal breast lesions incidentally detected by 18F-FDG PET/CT. Various PET/CT findings of the breast lesions were also analyzed to improve the differentiation between benign from malignant focal breast lesions. MATERIALS AND METHODS: The subjects were 3,768 consecutive 18F-FDG PET/CT exams performed in adult females without a history of breast cancer. A focal breast lesion was defined as a focal 18F-FDG uptake or a focal nodular lesion on CT image irrespective of 18F-FDG uptake in the breasts. The maximum SUV and CT pattern of focal breast lesions were evaluated, and were compared with final diagnosis. RESULTS: The incidence of focal breast lesions on PET/CT in adult female subjects was 1.4% (58 lesions in 53 subjects). In finally confirmed 53 lesions of 48 subjects, 11 lesions of 8 subjects (20.8%) were proven to be malignant. When the PET/CT patterns suggesting benignancy (maximum attenuation value > 75 HU or 20) were added as diagnostic criteria of PET/CT to differentiate benign from malignant breast lesions along with maximum SUV, the area under ROC curve of PET/CT was significantly increased compared with maximum SUV alone (0.680+/-0.093 vs. 0.786+/-0.076, p<0.05). CONCLUSION: The malignant risk of focal breast lesions incidentally found on 18F-FDG PET/CT is not low, deserving further diagnostic confirmation. Image interpretation considering both 18F-FDG uptake and PET/CT pattern may be helpful to improve the differentiation from malignant and benign focal breast lesion.

FDG PET/CT and Mediastinal Nodal Metastasis Detection in Stage T1 Non-Small Cell Lung Cancer: Prognostic Implications

OBJECTIVE: We aimed to compare the prognoses of patients with pathologically true negative (P-TN) N2 and PET/CT false negative (FN) results in stage T1 non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Our institutional review board approved this retrospective study with a waiver of informed consent. The study included 184 patients (124 men and 60 women; mean age, 59 years) with stage T1 NSCLC who underwent an integrated PET/CT and surgery. After estimating the efficacy of PET/CT for detecting N2 disease, we determined and compared disease-free survival (DFS) rates in three groups (P-TN [n = 161], PET/CT FN [n = 12], and PET/CT true positive [TP, n = 11]) using the Kaplan-Meier analysis and log-rank test. RESULTS: Pathologic N2 disease was observed in 23 (12%) patients. PET/CT had an N2 disease detection sensitivity of 48% (11 of 23 patients), a specificity of 95% (153 of 161), and an accuracy of 89% (164 of 184). The 3-year DFS rate in the PET/CT FN group (31%, 95% confidence interval [CI]; 13.6-48.0%) was similar to that of the TP group (16%, 95% CI; 1.7-29.5%) (p = 0.649), but both groups had significantly shorter DFS rates than the P-TN group (77%, 95% CI; 72.0-81.2%) (p < 0.001). CONCLUSION: The PET/CT shows a high specificity, but low sensitivity for detecting N2 disease in stage T1 NSCLC. Patients with PET/CT FN N2 disease have survival rates similar to PET/CT TP N2 disease patients, which are both substantially shorter than the survival rate of P-TN patients.

Quantitative Comparisons between CT and 68Ge Transmission Attenuation Corrected 18F-FDG PET Images: Measured Attenuation Correction vs. Segmented Attenuation Correction / 핵의학분자영상

PURPOSE: It was reported that CT-based measured attenuation correction (CT-MAC) produced radioactivity concentration values significantly higher than 68Ge-based segmented attenuation correction (Ge-SAC) in PET images. However, it was unknown whether the radioactivity concentration difference resulted from different sources (CT vs. Ge) or types (MAC vs. SAC) of attenuation correction (AC). We evaluated the influences of the source and type of AC on the radioactivity concentration differences between reconstructed PET images in normal subjects and patients. MATERIAL AND METHODS: Five normal subjects and 35 patients with a known or suspected cancer underwent 18F-FDG PET/CT. In each subject, attenuation corrected PET images using OSEM algorithm (28 subsets, 2 iterations) were reconstructed by 4 methods: CT-MAC, CT-SAC, Ge-MAC, and Ge-SAC. The physiological uptake in normal subjects and pathological uptake in patients were quantitatively compared between the PET images according to the source and type of AC. RESULTS: The SUVs of physiological uptake measured in CT-MAC PET images were significantly higher than other 3 differently corrected PET images. Maximum SUVs of the 145 foci with abnormal FDG uptake in CT-MAC images were significantly highest among 4 differently corrected PET images with a difference of 2.4% to 5.1% (p<0.001). The SUVs of pathological uptake in Ge-MAC images were significantly higher than those in CT-SAC and Ge-MAC PET images (p<0.001). CONCLUSION: Quantitative radioactivity values were highest in CT-MAC PET images. The adoption of MAC may make a more contribution than the adoption of CT attenuation map to such differences.