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.

A case of portal hypertension by presumed as plexiform neurofibroma at the hepatic hilum

Neurofibromas can occur anywhere in the body, but they usually involve the head, neck, pelvis, and extremities. Abdominal visceral involvement is rare, and intrahepatic involvement is even less common. We describe a patient who suffered from plexiform neurofibromatosis with liver involvement. A 49-year-old man, who had previously been diagnosed with neurofibromatosis, underwent esophagogastroduodenoscopy and abdominal ultrasonography for screening purposes. Esophagogastroduodenoscopy showed grade 2 esophageal varices and abdominal ultrasonography showed conglomerated nodules with echogenic appearances in the perihepatic space. Magnetic resonance imaging showed presumed plexiform neurofibroma involving the lesser sac and hepatic hilum and encasing the common hepatic artery celiac trunk and superior mesenteric artery left portal triad. We report an unusual case of portal hypertension attributed to the compressive narrowing of the portal vein by presumed as plexiform neurofibroma at the lesser sac and hepatic hilum.

Pulmonary epithelioid hemangioendothelioma misconceived as pulmonary metastasis of other malignancies / 영남의대학술지

Pulmonary epithelioid hemangioendothelioma (PEH) is a rare, low-to-intermediate malignant tumor of endothelial origin. Computed tomography (CT) findings of PEH demonstrate multiple small bilateral nodules; however, to the best of our knowledge, there were no reports on PEH coexisting with other malignancies. Here, we reported on a case involving PEH in a patient with colon cancer and breast cancer which was misconceived as pulmonary meta-stasis. A 63-year-old woman who suffered from constipation for 2 weeks visited our hospital. Colonoscopy showed a large mass with obstruction on hepatic flexure. The histological diagnosis was adenocarcinoma of the ascending colon. Multiple nodules in both lungs and breast were observed on a chest CT scan. A core biopsy of a breast nodule was performed and a diagnosis of invasive ductal carcinoma of the left breast was made. Pulmonary nodules observed on the chest CT scan was considered as pulmonary metastasis from colon or breast cancer. Laparoscopic right hemicolectomy was performed. At the same time, wedge resection of the lung was performed and pathological diagnosis was PEH. Radiologic features of PEH were difficult to distinguish from lung metastasis. Therefore the author reported a rare case involving PEH in a patient with primary malignancy of colon and breast.

The Prevalence of Sarcopenia in Korean Hospitalized Elderly

BACKGROUND: Sarcopenia is a syndrome characterized by the progressive loss of skeletal muscle mass and muscle strength. Although data exist on the prevalence of sarcopenia among the community-dwelling elderly, there is no systematic research on hospitalized elderly patients in Korea, in accordance with the newly developed criteria. METHODS: A cross-sectional study was conducted at the Daejin Medical Center, Bundang Jesaeng Hospital, Korea, from May 2013 to March 2015. In this study, we evaluated the levels of hemoglobin, total cholesterol, serum albumin, serum prealbumin, and serum zinc. Handgrip strength was measured with a hand grip dynamometer (FT-7110). Furthermore, the skeletal muscle mass was measured by bioelectrical impedance analysis (BIA). Sarcopenia was defined by skeletal muscle mass as measured with BIA, according to the Asian Working Group for Sarcopenia. RESULTS: Of the hospitalized elderly subjects, 40 (46.5%) had a definite diagnosis of sarcopenia and 46 (53.5%) had no sarcopenia. The prevalence of sarcopenia of the subjects was higher in males than females (males, 46.9% vs. females, 46.3%). The correlation analysis showed that the score of skeletal muscle index (SMI) was negatively correlated with age; whereas, it was positively correlated with the BMI, body weight, and serum prealbumin level. CONCLUSION: The results of the study showed that sarcopenia was associated with several factors, including age, BMI, serum prealbumin level, among the study subjects. Sarcopenia can be used as a sensitive predictive marker for prognosis of the hospitalized elderly.

Acquired Immunodeficiency Syndrome Presenting with Abdominal Tuberculosis / 이화의대지

The incidence of tuberculosis (TB) had gradually been declining all over the world, but in recent years, TB has been increasing due to the spread of the human immunodeficiency virus (HIV). When immune-suppression status deteriorates further, extrapulmonary TB generally appears more often. Abdominal TB is one type of extra-pulmonary TB, which may involve the gastrointestinal tract, peritoneum, lymph nodes or solid viscera. We encountered a case who had initially been diagnosed as having abdominal TB, had progressed to acute respiratory distress syndrome and was eventually confirmed as having developed acquired immune deficiency syndrome. In cases of coinfection of TB and HIV, it is reported that immunological responses become poor and complications with higher morbidity frequently occur. Therefore, the Korean guidelines for TB should be revised to ensure whether HIV infection exists in TB patients.

Molecular Imaging in the Era of Personalized Medicine

Clinical imaging creates visual representations of the body interior for disease assessment. The role of clinical imaging significantly overlaps with that of pathology, and diagnostic workflows largely depend on both fields. The field of clinical imaging is presently undergoing a radical change through the emergence of a new field called molecular imaging. This new technology, which lies at the intersection between imaging and molecular biology, enables noninvasive visualization of biochemical processes at the molecular level within living bodies. Molecular imaging differs from traditional anatomical imaging in that biomarkers known as imaging probes are used to visualize target molecules-of-interest. This ability opens up exciting new possibilities for applications in oncologic, neurological and cardiovascular diseases. Molecular imaging is expected to make major contributions to personalized medicine by allowing earlier diagnosis and predicting treatment response. The technique is also making a huge impact on pharmaceutical development by optimizing preclinical and clinical tests for new drug candidates. This review will describe the basic principles of molecular imaging and will briefly touch on three examples (from an immense list of new techniques) that may contribute to personalized medicine: receptor imaging, angiogenesis imaging, and apoptosis imaging.

Decreased Metabolism in the Cerebral Cortex in Early-Stage Huntington's Disease: A Possible Biomarker of Disease Progression?

BACKGROUND AND PURPOSE: Huntington's disease (HD) is an autosomal-dominant inherited neurodegenerative disorder. Genetic analysis of abnormal CAG expansion in the IT15 gene allows disease confirmation even in the preclinical stage. However, because there is no treatment to cure or delay the progression of this disease, monitoring of biological markers that predict progression is warranted. METHODS: FDG-PET was applied to 13 patients with genetically confirmed HD in the early stage of the disease. We recorded the initial and follow-up statuses of patients using the Independence Scale (IS) of the Unified Huntington's Disease Rating Scale. The progression rate (PR) was calculated as the annual change in the IS. The patients were divided into two groups with faster and slower progression, using the median value of the PR as the cut-off. FDG-PET data were analyzed using regions of interest, and compared among the two patient groups and 11 age- and sex-matched controls. RESULTS: The mean CAG repeat size in patients was 44.7. The CAG repeat length was inversely correlated with the age at onset as reported previously, but was not correlated with the clinical PR. Compared with normal controls, hypometabolism was observed even at very early stages of the disease in the bilateral frontal, temporal, and parietal cortices on FDG-PET. The decreases in metabolism in the bilateral frontal, parietal, and right temporal cortices were much greater in the faster-progression group than in the slower-progression group. CONCLUSIONS: A decrease in cortical glucose metabolism is suggested as a predictor for identifying a more rapid form of progression in patients with early-stage HD.

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.

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.

(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.

Cardiovascular Molecular Imaging / 핵의학분자영상

Molecular imaging strives to visualize processes in living subjects at the molecular level. Monitoring biochemical processes at this level will allow us to directly track biological processes and signaling events that lead to pathophysiological abnormalities, and help make personalized medicine a reality by allowing evaluation of therapeutic efficacies on an individual basis. Although most molecular imaging techniques emerged from the field of oncology, they have now gradually gained acceptance by the cardiovascular community. Hence, the availability of dedicated high-resolution small animal imaging systems and specific targeting imaging probes is now enhancing our understanding of cardiovascular diseases and expediting the development of newer therapies. Examples include imaging approaches to evaluate and track the progress of recent genetic and cellular therapies for treatment of myocardial ischemia. Other areas include in vivo monitoring of such key molecular processes as angiogenesis and apoptosis. Cardiovascular molecular imaging is already an important research tool in preclinical experiments. The challenge that lies ahead is to implement these techniques into the clinics so that they may help fulfill the promise of molecular therapies and personalized medicine, as well as to resolve disappointments and controversies surrounding the field.

Molecular Imaging of Angiogenesis

Angiogenesis, the process whereby new capillaries are formed by outgrowth from existing microvessels, is required for tumor growth and metastasis, as well as for healing of ischemic injuries. Because angiogenesis is a promising target for molecular therapies, there is a real need to develop molecular imaging methods to monitor angiogenesis activity. Direct imaging of angiogenesis can help define the pathophysiology of angiogenic processes in vivo, and foster personized medicine by identifying patients likely to respond to angiogenesis-targeted drugs and accurately monitor the therapeutic efficacy. Promising imaging targets include integrins, vascular endothelial growth factor (VEGF) receptors, and matrix metalloproteinases. While MRI and optical imaging modalities are also workable, radiolabeled RGD (arginine-glycine-aspartate) probes that target alpha(v)beta(3) integrins overexpressed on activated endothelia are the most extensively investigated and successful angiogenesis imaging technique to date. This technique has repeatedly been validated in preclinical models of cancers and ischemic diseases, and clinical studies are presently ongoing to elucidate the value of RGD positron image tomography (PET) imaging in human patients. Herein, we review the current status of angiogenesis imaging research with special emphasis on integrin-targeted techniques.

Molecular Imaging of Angiogenesis

Angiogenesis, the process whereby new capillaries are formed by outgrowth from existing microvessels, is required for tumor growth and metastasis, as well as for healing of ischemic injuries. Because angiogenesis is a promising target for molecular therapies, there is a real need to develop molecular imaging methods to monitor angiogenesis activity. Direct imaging of angiogenesis can help define the pathophysiology of angiogenic processes in vivo, and foster personized medicine by identifying patients likely to respond to angiogenesis-targeted drugs and accurately monitor the therapeutic efficacy. Promising imaging targets include integrins, vascular endothelial growth factor (VEGF) receptors, and matrix metalloproteinases. While MRI and optical imaging modalities are also workable, radiolabeled RGD (arginine-glycine-aspartate) probes that target alpha(v)beta(3) integrins overexpressed on activated endothelia are the most extensively investigated and successful angiogenesis imaging technique to date. This technique has repeatedly been validated in preclinical models of cancers and ischemic diseases, and clinical studies are presently ongoing to elucidate the value of RGD positron image tomography (PET) imaging in human patients. Herein, we review the current status of angiogenesis imaging research with special emphasis on integrin-targeted techniques.

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.

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.

Radiotracer Methods for Targeted Imaging of the Epidermal Growth Factor Receptor / 핵의학분자영상

While indirect targeting strategies using reporter-genes are taking center stage in current molecular imaging research, another vital strategy has long involved direct imaging of specific receptors using radiolabeled ligands. Recently, there is renewal of immense interest in this area with particular attention to the epidermal growth factor receptor (EGFR), a transmembrane glycoprotein critically involved in the regulation of many cellular functions and malignancies. Recently, two novel classes of EGFR-targeting anticancer drugs have entered clinical trials with great expectations. These are monoclonal antibodies such as cetuximab that target the extracellular domain, and small molecule tyrosine kinase inhibitors such as gefitinib (Iressa) and erlotinib (Tarceva) that target the catalytic domain of the receptor. However, early results have showed disappointing survival benefits, disclosing a major challenge for this therapeutic strategy; namely, the need to identify tumors that are most likely to respond to the agents. To address this important clinical issue, several noninvasive imaging techniques are under investigation including radiolabeled probes based on small molecule tyrosine kinase inhibitors, anti-EGFR antibodies, and EGF peptides. This review describes the current status, limitations, and future prospects in the development of radiotracer methods for EGFR imaging.