Computed diffusion-weighted imaging with a low-apparent diffusion coefficient-pixel cut-off technique for breast cancer detection.

OBJECTIVE: This study aimed to compare the image quality and diagnostic performance of computed diffusion-weighted imaging (DWI) with low-apparent diffusion coefficient (ADC)-pixel cut-off technique (cDWI cut-off) and actual measured DWI (mDWI). METHODS: Eighty-seven consecutive patients with malignant breast lesions and 72 with negative breast lesions who underwent breast MRI were retrospectively evaluated. Computed DWI with high b-values of 800, 1200, and 1500 s/mm2 and ADC cut-off thresholds of none, 0, 0.3, and 0.6 (×10-3 mm2/s) were generated from DWI with two b-values (0 and 800 s/mm2). To identify the optimal conditions, two radiologists evaluated the fat suppression and lesion reduction failure using a cut-off technique. The contrast between breast cancer and glandular tissue was evaluated using region of interest analysis. Three other board-certified radiologists independently assessed the optimised cDWI cut-off and mDWI data sets. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis. RESULTS: When an ADC cut-off threshold of 0.3 or 0.6 (× 10-3 mm2/s) was applied, fat suppression improved significantly (p < .05). The contrast of the cDWI cut-off with a b-value of 1200 or 1500 s/mm2 was better than the mDWI (p < .01). The ROC area under the curve for breast cancer detection was 0.837 for the mDWI and 0.909 for the cDWI cut-off (p < .01). CONCLUSION: The cDWI cut-off provided better diagnostic performance than mDWI for breast cancer detection. ADVANCES IN KNOWLEDGE: Using the low-ADC-pixel cut-off technique, computed DWI can improve diagnostic performance by increasing contrast and eliminating un-suppressed fat signals.

Automatic detection of punctate white matter lesions in infants using deep learning of composite images from two cases.

Punctate white matter lesions (PWMLs) in infants may be related to neurodevelopmental outcomes based on the location or number of lesions. This study aimed to assess the automatic detectability of PWMLs in infants on deep learning using composite images created from several cases. To create the initial composite images, magnetic resonance (MR) images of two infants with the most PWMLs were used; their PWMLs were extracted and pasted onto MR images of infants without abnormality, creating many composite PWML images. Deep learning models based on a convolutional neural network, You Only Look Once v3 (YOLOv3), were constructed using the training set of 600, 1200, 2400, and 3600 composite images. As a result, a threshold of detection probability of 20% and 30% for all deep learning model sets yielded a relatively high sensitivity for automatic PWML detection (0.908-0.957). Although relatively high false-positive detections occurred with the lower threshold of detection probability, primarily, in the partial volume of the cerebral cortex (≥ 85.8%), those can be easily distinguished from the white matter lesions. Relatively highly sensitive automatic detection of PWMLs was achieved by creating composite images from two cases using deep learning.

Diffusion-weighted MRI as an adjunct to mammography in women under 50 years of age: an initial study.

PURPOSE: To evaluate diffusion-weighted magnetic resonance (DW) imaging as an adjunct to mammography for the detection of small invasive breast cancer. MATERIALS AND METHODS: Institutional review board standards were followed for this retrospective study. We performed both breast DW imaging and mammography on 25 women under 50 years of age with pathologically proven T1 breast cancer and on 21 healthy women under 50 years of age. Four offsite radiologists blind to the clinical information independently interpreted the mammograms and DW images and then classified their confidence level regarding the presence of breast cancer. The composite area under receiver operating characteristic curve (AUC), of mammography alone, DW imaging alone, and the combination of DW imaging and mammography (DWI/Cal) were calculated. RESULTS: The AUC of composite ROC curves of mammography, DW imaging, DWI/Cal combination, was 0.79 (95% CI, 0.72-0.87), 0.86 (95% CI, 0.84-0.87), and 0.96 (95% CI, 0.92-1.00), respectively. CONCLUSION: DW imaging may be a useful adjunct to mammography in the detection of small invasive breast cancer in women under 50 years of age.

Apparent diffusion coefficient correlation with oesophageal tumour stroma and angiogenesis.

OBJECTIVE: Because diffusion-weighted imaging (DWI) can predict the prognosis of patients with oesophageal squamous cell carcinoma (ESCC), we hypothesised that apparent diffusion coefficient (ADC) values might be correlated with the collagen content and tumour angiogenesis. The purpose of this study was to determine the correlation between ADC values of ESCC before treatment and oesophageal tumour stroma and angiogenesis. METHODS: Seventeen patients with ESCC were enrolled. The ADC values were calculated from the DWI score. Seventeen patients who had undergone oesophagectomy were analysed for tumour stroma, vascular endothelial growth factor (VEGF) and CD34. Tissue collagen was stained with azocarmine and aniline blue to quantitatively analyse the extracellular matrix in cancer stroma. Tissues were stained with VEGF and CD34 to analyse the angiogenesis. RESULTS: The ADC values decreased with stromal collagen growth. We found a negative correlation between the tumour ADC and the amount of stromal collagen (r = -0.729, P = 0.001), i.e. the ADC values decreased with growth of VEGF. We also found a negative correlation between the ADC of the tumours and the amount of VEGF (r = 0.538, P = 0.026). CONCLUSION: Our results indicated that the ADC value may be a novel prognostic factor and contribute to the treatment of oesophageal cancer. KEY POINTS: • Magnetic resonance apparent diffusion coefficient values inversely indicate tumour stromal collagen • There is also negative correlation between ADCs and vascular endothelial growth factor • ADC values may contribute to the treatment of oesophageal cancer.

Breast Cancer Subtypes and Quantitative Magnetic Resonance Imaging: A Systemic Review.

Magnetic resonance imaging (MRI) is the most sensitive imaging modality for breast cancer detection. This systematic review investigated the role of quantitative MRI features in classifying molecular subtypes of breast cancer. We performed a literature search of articles published on the application of quantitative MRI features in invasive breast cancer molecular subtype classification in PubMed from 1 January 2002 to 30 September 2021. Of the 1275 studies identified, 106 studies with a total of 12,989 patients fulfilled the inclusion criteria. Bias was assessed based using the Quality Assessment of Diagnostic Studies. All studies were case-controlled and research-based. Most studies assessed quantitative MRI features using dynamic contrast-enhanced (DCE) kinetic features and apparent diffusion coefficient (ADC) values. We present a summary of the quantitative MRI features and their correlations with breast cancer subtypes. In DCE studies, conflicting results have been reported; therefore, we performed a meta-analysis. Significant differences in the time intensity curve patterns were observed between receptor statuses. In 10 studies, including a total of 1276 lesions, the pooled difference in proportions of type Ⅲ curves (wash-out) between oestrogen receptor-positive and -negative cancers was not significant (95% confidence interval (CI): [-0.10, 0.03]). In nine studies, including a total of 1070 lesions, the pooled difference in proportions of type 3 curves between human epidermal growth factor receptor 2-positive and -negative cancers was significant (95% CI: [0.01, 0.14]). In six studies including a total of 622 lesions, the pooled difference in proportions of type 3 curves between the high and low Ki-67 groups was significant (95% CI: [0.17, 0.44]). However, the type 3 curve itself is a nonspecific finding in breast cancer. Many studies have examined the relationship between mean ADC and breast cancer subtypes; however, the ADC values overlapped significantly between subtypes. The heterogeneity of ADC using kurtosis or difference, diffusion tensor imaging parameters, and relaxation time was reported recently with promising results; however, current evidence is limited, and further studies are required to explore these potential applications.

Quantitative Values from Synthetic MRI Correlate with Breast Cancer Subtypes.

The purpose of this study is to correlate quantitative T1, T2, and proton density (PD) values with breast cancer subtypes. Twenty-eight breast cancer patients underwent MRI of the breast including synthetic MRI. T1, T2, and PD values were correlated with Ki-67 and were compared between ER-positive and ER-negative cancers, and between Luminal A and Luminal B cancers. The effectiveness of T1, T2, and PD in differentiating the ER-negative from the ER-positive group and Luminal A from Luminal B cancers was evaluated using receiver operating characteristic analysis. Mean T2 relaxation of ER-negative cancers was significantly higher than that of ER-positive cancers (p < 0.05). The T1, T2, and PD values exhibited a strong positive correlation with Ki-67 (Pearson's r = 0.75, 0.69, and 0.60 respectively; p < 0.001). Among ER-positive cancers, T1, T2, and PD values of Luminal A cancers were significantly lower than those of Luminal B cancers (p < 0.05). The area under the curve (AUC) of T2 for discriminating ER-negative from ER-positive cancers was 0.87 (95% CI: 0.69−0.97). The AUC of T1 for discriminating Luminal A from Luminal B cancers was 0.83 (95% CI: 0.61−0.95). In conclusion, quantitative values derived from synthetic MRI show potential for subtyping of invasive breast cancers.

Apparent diffusion coefficient values measured by diffusion-weighted imaging predict chemoradiotherapeutic effect for advanced esophageal cancer.

BACKGROUND: The purpose of this study was to assess whether apparent diffusion coefficient (ADC) values of esophageal squamous cell carcinoma (ESCC) predict responses to chemoradiotherapy (CRT) and/or patient prognosis. METHODS: Magnetic resonance images were acquired to construct the diffusion-weighted images, and the ADC values were calculated before CRT in 80 patients with ESCC. A high-ADC group responded better to CRT than did a low-ADC group (p < 0.01). We divided the 80 patients into two groups based on the operating characteristic analysis: one group comprised patients with ADC values higher than the average ADC of the esophageal cancer tissue (1.10 × 10(-3) mm2/s), and the other group comprised those whose ADC values were less than the average value. A Kaplan-Meier analysis showed that the survival rate in the high-ADC group was significantly better than that in the low-ADC group (p = 0.04). CONCLUSION: Our results indicate that the ADC value may be a useful marker to predict treatment response as well as survival for patients with ESCC.

Response rate to neoadjuvant chemotherapy measured on imaging predicts early recurrence and death in breast cancer patients with lymph node involvements.

BACKGROUND: The use of neoadjuvant chemotherapy for breast cancer is effective as postoperative adjuvant therapy, permits more lumpectomies, and can be used to study breast cancer biology. Although pathological response is the strongest prognostic factor, response rates vary according to various parameters, such as dissociation between breast and axillary node responses. PURPOSE: To clarify the correlation of response rates between breast tumors and metastasized lymph nodes and to identify the clinical significance; response rates measured on imaging were evaluated among breast cancer patients with axillary lymph node involvement. MATERIAL AND METHODS: Subjects consisted of 98 patients diagnosed with node-positive breast cancer who received chemotherapy before surgery. The response to the therapy was evaluated by changes in the largest dimensions of the breast mass and of regional lymph nodes measured on a multidetector row helical CT before and after chemotherapy. The percent reduction was calculated as a response rate. The correlation between response rate and patient outcome was analyzed retrospectively. RESULTS: Breast tumor response rates correlated statistically well with those of lymph nodes (p < 0.001). Disease-free cases had a greater tumor and/or nodal response rates than recurrence cases (p = 0.021, p < 0.001, respectively), regardless of tumor size, histological grade and HER2 amplification. Cancer-associated death was observed more frequently in cases with lower response rates compared to surviving cases (p = 0.007, p = 0.021, respectively). The prognostic difference was found most strongly in nodal response rates (p = 0.001). CONCLUSION: The present series evaluated the therapeutic effect of NAC on breast tumors and metastasized lymph nodes, and a significant correlation with patient outcome was observed. Evaluating the response rate measured by imaging could be used as a surrogate marker for prognosis before assessment of the pathological response which is ordinarily obtained after surgery.

Evaluation of ulcerative colitis using diffusion-weighted imaging.

BACKGROUND/AIMS: The aims of this study were to determine the feasibility of diffusion-weighted imaging (DWI) for detecting bowel inflammation and to investigate the changes in the apparent diffusion coefficient (ADC) values in the inflamed bowel of patients with ulcerative colitis (UC). METHODOLOGY: Seven patients, who underwent DWI for UC and curative total colectomy because of insistence on conservative therapy, were enrolled in this study. The resected specimens were examined histopathologically to determine the degree of inflammation and the presence of malignancy. The ADC values of the lesions were calculated and compared among UC lesions. RESULTS: The mean ADC value of the active UC lesions was significantly (p < 0.01) lower than that of the normal colorectal tissue (1.12 +/- 0.14 x 10(-3) mm2/s vs. 1.60 +/- 0.21 x 10 (-3) mm2/s, respectively). The mean ADC value of the active lesions was significantly (p < 0.01) lower than that that of the healing lesions (1.12 +/- 0.14 x10(-3) mm2/s vs. 1.62 +/- 0.28 x 10(-3) mm2/s, respectively). CONCLUSIONS: DWI may be valuable for following patients with UC, and the stage of UC may be diagnosed easily based on the ADC values.

Two cases of oligometastatic castration-resistant prostate cancer detected by diffusion-weighted whole-body imaging with background body signal suppression.

INTRODUCTION: Treatment for oligometastasis in prostate cancer has changed from systemic therapy to metastatic lesion-targeted therapy. Early detection of metastatic lesions and assessment of the treatment response have become very important. Therefore, we started to perfume assessments with whole-body magnetic resonance imaging, especially diffusion-weighted imaging with background body signal suppression, as a modality to detect metastasis in patients with prostate cancer. CASE PRESENTATION: We encountered two cases of castration-resistant prostate cancer in which oligometastasis was detected by diffusion-weighted imaging with background body signal suppression. Metastasis-directed therapy was initiated for to treat the lesions in each case. The treatment was effective for disease control and symptom relief. Diffusion-weighted imaging with background body signal suppression could detect new lesions at an early phase and delineate changes in lesions immediately after therapy. CONCLUSION: Diffusion-weighted imaging with background body signal suppression enables early decision-making for metastasis-directed therapy compared with conventional imaging modalities. Further, metastasis-directed therapy targeting oligometastatic lesions detected by diffusion-weighted imaging with background body signal suppression may improve patients' overall survival and quality of life.

Cutaneous Metastases from Testicular Diffuse Large B-cell Malignant Lymphoma and Bowen Disease: 18F-FDG PET-CT Findings.

Here, we report the case of cutaneous metastases from testicular diffuse large B-cell malignant lymphoma (DLBCL) concurrent with Bowen disease evaluated with 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT). A 60-year-old male underwent orchiectomy to remove his left testicle because of DLBCL. Multiple skin lesions appeared 1 month postoperatively. Furthermore, an intractable erythematous plaque localized to the right lower leg was present from 2 years before the operation. 18F-FDG PET-CT images revealed multiple skin lesions with marked FDG uptakes in the face, neck, and thigh of this patient, as well as a lower leg lesion with minimal FDG uptake. Biopsy of both lesions revealed cutaneous metastases from DLBCL and Bowen disease (BD) of the lower leg lesion. 18F-FDG PET-CT images following chemotherapy and resection of BD demonstrated no FDG uptake.

Pulmonary drug toxicity: FDG-PET findings in patients with lymphoma.

OBJECTIVE: The objective of this study was to evaluate the prevalence and positron emission tomography (PET) imaging features of pulmonary drug toxicity in patients with lymphoma during or just following chemotherapy. METHODS: A total of 677 PET scans on 460 patients with lymphoma (351 non-Hodgkin's lymphoma, 92 Hodgkin's disease, and 17 both Hodgkin's and non-Hodgkin's lymphoma) were performed for the evaluation of chemotherapy response. In 51 patients, abnormal accumulation on both sides of the chest was reported. A review of medical records, (18)fluorodeoxyglucose ((18)FDG)-PET scans, and chest computed tomography (CT) was performed, and cases with probable drug toxicity were identified. Inclusion criteria of probable drug toxicity were abnormal but symmetrical FDG accumulation in both lungs seen during or just following the completion of chemotherapy, the abnormal accumulation or corresponding abnormal CT findings resolved on subsequent studies, exclusion of clinical diagnosis of pneumonia, radiation pneumonitis, or lymphoma involvement. RESULTS: In 10 patients (six men and four women, average age 47.3), 2.2% of cases, probable drug toxicity was identified. In all 10 cases, diffuse and subpleural-dominant FDG accumulation was seen on FDG-PET scans, and scattered or diffuse ground-glass opacities were observed on chest CT. Four patients reported symptoms, and six patients did not report any symptoms. CONCLUSIONS: Diffuse and peripheral-dominant FDG accumulation in the lung, which may represent pulmonary drug toxicity, was not uncommon in patients with lymphoma who underwent chemotherapy. FDG-PET scan might be able to detect pulmonary drug toxicity in asymptomatic patients.

Perfusion CT can predict the response to chemoradiation therapy and survival in esophageal squamous cell carcinoma: initial clinical results.

The ability to predict the response to chemoradiation therapy (CRT) by contrast-enhanced CT would be valuable for managing esophageal squamous cell carcinoma. The purpose of this study was to evaluate the usefulness of Perfusion CT to predict the response to CRT in patients with esophageal squamous cell carcinoma. Thirty-one consecutive patients with esophageal squamous cell carcinoma underwent Perfusion CT before CRT. We retrospectively investigated the correlations between Perfusion parameters and the response to CRT. Clinicopathological markers and blood flow were compared in terms of survival. There were 21 clinical responders and 10 non-responders. Clinical responders showed significantly higher pre-CRT blood flow (P=0.0004), significantly higher pre-CRT blood volume (P=0.03) and a significantly shorter pre-CRT mean transit time (P=0.002) than non-responders. For pre-CRT blood flow, accuracy was 90.3% for detection of clinical responders when the cut-off point was set at 50 ml/100 g/min. Patients with high blood flow tumors survived significantly longer than those with low blood flow tumors (P=0.006). Multivariate analysis identified blood flow as a significant independent prognostic factor (P=0.01). Therefore, Perfusion CT may help to identify patients with advanced esophageal squamous cell carcinoma who will benefit from CRT.

Dynamic enhanced MRI predicts chemosensitivity in breast cancer patients.

BACKGROUND: Primary chemotherapy for breast cancer is effective as postoperative adjuvant therapy. However, one of the critical disadvantages was a treatment delay for patients with progressive disease. The present study attempts to clarify quantitative parameters on MRI which can be used to predict the sensitivity to treatment in breast cancer patients. METHODS: The subjects consisted of 26 patients with invasive ductal breast cancer who received primary chemotherapy before surgery. The mean maximum tumor dimension was 3.3cm, and 21 cases had nodal involvements. Three cases demonstrated histological grade 3. Dynamic enhanced MRI was evaluated at three different time periods; prior to, in the midst of preoperative chemotherapy, and just before the initial operation. The signal intensity ratio (SIR) and early contrast uptake (ECU) were calculated, as well as the correlation between these dynamic data and the tumor reduction rates were analyzed retrospectively. P-values of less than 0.05 were considered to indicate statistically significant. RESULTS: Responders to chemotherapy had the significantly higher SIR and ECU values than non-responders (p=0.0454 and 0.0334, respectively). ECU value significantly decreased as tumor reduction by chemotherapy (p=0.0028). Pathological tumor dimension was significantly correlated with the tumor size estimated on presurgical MRI (p<0.0001). CONCLUSIONS: Our current series demonstrated the significant correlation between pretreatment MRI data and tumor reduction by chemotherapy in breast cancer patients. With these results, it seems possible to define good and non-responders prior to treatment.

Measurement of the apparent diffusion coefficient in the liver: is it a reliable index for hepatic disease diagnosis?

PURPOSE: The aim of this study was to determine the validity of the hepatic apparent diffusion coefficient (ADC) measurement. The influence of differences in measured location and administration of Buscopan (hyoscine butylbromide) for ADC were assessed. MATERIALS AND METHODS: SENSE-DWI (b = 0, 500) was obtained before and after Buscopan administration to 30 patients suspected of having a liver tumor. In this sequence, respiration gating was employed, but cardiac triggering was not. ADC measurement was performed in the hepatic parenchyma of both right and left lobes in selected slices. A statistical analysis was performed to estimate the correlation among ADC, measured location, Buscopan, and pulse rate. The images were visually evaluated to categorize the subcardiac signal loss in the left lobe. RESULTS: The ADC showed higher values in the left lobe than in the right lobe in both pre- and postloaded studies (P < 0.001). In a comparison between ADCs in the pre- and postloaded studies, the differences were not significant in the left lobe (P = 0.93) or the right lobe (P = 0.41). No correlation was noted between ADCs and the pulse rate. Visual evaluation revealed that the subcardiac signal loss was more prominent in the postloaded study. CONCLUSION: ADC measurement of the left hepatic lobe was far more incorrect than that of the right lobe if cardiac gating was not employed. The administration of Buscopan worsened the image quality of the left lobe and made visual evaluation difficult.

[Assessment of whole body PET/MRI fusion imaging using automated software: usefulness of partial body fusion].

PURPOSE: In this study, we created a whole body fusion image of PET and MRI using automated software for fusion imaging, and assessed the accuracy of the software. MATERIALS AND METHODS: Twenty patients with abnormal FDG-PET findings underwent whole body MRI. Images from both modalities were automatically fused in two ways using software (Fusion Viewer, Nihon Medi-Physics Co., Ltd., Nishinomiya, Japan) with a registration algorithm based on maximum mutual information. One was to create a whole body fusion image at once, named whole body fusion (WBF). The other was to create fusion images of the head and body separately, named partial body fusion (PBF). Two radiologists measured the misregistration between PET and MRI in the fusion images at nine landmarks (brain, cervical spine, chest, heart, liver, right kidney, left kidney, vertebra, base of bladder). RESULTS: When fusion images were created using WBF at once, misregistration was observed in the head and neck area in approximately half of the cases, whereas almost no misregistration was observed in the body. When fusion images were created using PBF, the misregistration in the head and neck areas was significantly smaller than in those using WBF, and misregistration in the body was very small. CONCLUSION: The PBF technique that creates highly accurate whole body PET/MRI fusion images is easy to use and may provide clinically useful information.

Balanced Turbo Field Echo with Extended k-space Sampling: A Fast Technique for the Thoracic Ductography.

We evaluated the visibility of the thoracic duct by fast balanced turbo field echo with extended k-space sampling (bTFEe). The thoracic duct of 10 healthy volunteers was scanned by bTFEe using a 1.5-T magnetic resonance imaging (MRI), which was acquired in approximately 2 minutes. Three-dimensional (3D) turbo spin-echo (TSE) was obtained for comparison. The thoracic duct including draining location of the venous system was overall well visualized on bTFEe, compared to TSE.

Diagnostic performance of (18)F-fluorodeoxyglucose PET/CT and bone scintigraphy in breast cancer patients with suspected bone metastasis.

BACKGROUND: We prospectively compared the diagnostic accuracies of PET/CT and BS in patients with suspected bone metastases from breast cancer. METHODS: This single-institution prospective study included consecutive patients with suspected bone metastases from biopsy-proven breast cancer seen at Tokai University Hospital between September 2011 and March 2014. Inclusion criteria included suspicions for bone metastases (bone pain, elevated alkaline phosphatase, elevated tumor markers, or suspected bone metastases by BS). Two nuclear medicine physicians evaluated PET/CT and BS images. RESULTS: Thirty patients were initially enrolled in this study. Two were excluded from the analyses because they declined to undergo imaging during follow-up. PET/CT successfully detected bone metastases in all 10 patients finally diagnosed with the condition, whereas BS identified 2. The two methods were not highly concordant in detecting osseous metastases. In 19 of 28 paired studies (68 %), 2 (10 %) were positive for metastasis, and 17 (90 %) were negative. Nine occurrences (32 %) were discordant; of these, 2 were PET/CT positive and BS negative; 5 were PET/CT positive and BS equivocal; one was PET/CT negative and BS equivocal, and one was PET/CT equivocal and BS negative. CONCLUSIONS: Our results indicated that PET/CT was superior to BS for the diagnosis of bone metastases. On the basis of the results of previous studies as well as ours, PET/CT could replace BS as the initial modality to detect bone metastases in patients suspected for the condition.

FDG PET in the evaluation of treatment for lymphoma: clinical usefulness and pitfalls.

Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-d-glucose (FDG) may play an important role in the evaluation and management of malignant lymphoma. FDG uptake is predictive of therapeutic response during the course of treatment. After completion of chemotherapy, residual abnormalities representing either residual tumor or necrotic or fibrotic tissue are not uncommon, and FDG PET may be more accurate than computed tomography (CT) or magnetic resonance imaging in assessing residual disease and identifying patients who require more intense treatment. However, posttreatment FDG PET does not help exclude the presence of minimal residual disease, which may lead to disease relapse. Furthermore, FDG is not a tumor-specific substance, and increased accumulation may be seen in a variety of benign entities and scenarios (eg, infection, drug toxicity, granulocyte colony-stimulating factor therapy, radiation therapy, physiologic activity, postoperative or postbiopsy changes, fracture, degenerative change, injection leakage), which may yield false-positive findings. Nevertheless, recognition of these entities and correlation of FDG PET findings with clinical and other radiologic findings-especially those at combined PET and CT or PET-CT fusion imaging-allows improved diagnostic accuracy. If the interpretation of positive findings is exceptionally difficult, short-term follow-up may be helpful.