Radioiodine has served an important role in the diagnostic workup and treatment of patients with differentiated thyroid cancer for more than 6 decades. The interpretation of radioiodine scintigraphic studies should be performed in conjunction with a comprehensive history, histopathologic correlation, and pertinent laboratory values, as well as correlation with available anatomic images and the findings from physical examination. A thorough understanding of the physiology and biodistribution of radioiodine is critical when interpreting radioiodine scintigraphic studies to avoid misinterpretation of physiologic and nonthyroid pathologic variants as thyroid cancer metastases. Differentiating a false-positive finding from a true metastasis on pretherapy radioiodine scintigrams is important to determine the appropriate radioiodine treatment dose. The correct interpretation of posttherapy radioiodine scintigraphic studies is also important to determine if repeat radioiodine treatment will be necessary and for the future clinical and imaging followup of the patient. A variety of different factors, such as the presence of the sodium-iodide symporter and the passive diffusion or retention of radioiodine in normal and pathologic structures, can result in false-positive results on radioiodine scintigrams. Numerous false-positive findings have been reported in the literature and are further demonstrated with the increasing availability of single photon emission computed tomography (SPECT) integrated with computed tomography (CT) as true dual-modality imaging (SPECT/CT). SPECT/CT has been documented to be of incremental value in the accurate anatomic localization and characterization of radioiodine uptake as false-positive findings, particularly in cases with discordant findings of a low serum thyroglobulin level but positive findings on radioiodine whole-body planar scintigrams. The objectives of this review are to describe the physiology and biodistribution of radioiodine and to provide examples of false-positive results on radioiodine scintigrams, with clinical and anatomic correlation, in the following categories of radioiodine uptake: functional uptake secondary to sodium-iodide symporter expression, radioiodine retention, nonthyroid neoplasms, inflammatory or infectious uptake, contamination, and other causes. RSNA, 2017.

distributed among women with breast cancer [28-30]. Molecular subtypes are not only associated with different tumor phenotypes but also with distinct variations in response to therapy and patient survival. Accordingly, subtype-based recommendations for sys-temic therapies have now been implemented in clinical practice [28-31]. To match advanced therapeutic strategies in the era of precision medicine, diagnostic tests must be equally multilayered and complex to identify the underlying functional processes of cancer development and progression. However, with conventional imaging methods such as mam-mography, DBT, and sonography, which are qualitative tests that detect morphologic, non-specific tissue changes, the assessment and comprehension of breast cancer in all its diversity is not possible. To overcome these limitations, functional imaging techniques to improve breast cancer diagnosis have been explored. In this context , magnetic resonance imaging (MRI) has emerged as an exceptionally powerful, versatile, and precise imaging technique. MRI is an essential non-invasive technique in breast imaging with multiple established indications, such as pre-operative staging of breast cancer, evaluation of therapy response in patients receiving neoad-juvant treatment, differentiation between scar tissue and tumor recurrence , examination of patients with breast implants, and screening of high-risk patients [1, 5]. Dynamic contrast-enhanced MRI of the breast provides both high-resolution morphologic and functional quantitative information on neovascularity as a tumor-specific feature [32-35]. MRI is the most sensitive exam for the detection of breast cancer in women at any given risk [32-36] and often detects cancers that are occult in mammography, DBT and sonog-raphy [37, 38]. Due to these excellent results specific screening programs for high-risk women that include both annual mammogra-phy and MRI have been developed [32, 39] and there is discussion about screening of women at average of risk cancer with abbreviated MRI protocols [40-42]. In addition to breast cancer detection there is evidence that quantitative dynamic contrast enhanced (DCE)-MRI models are useful in the assessment and prediction of Breast cancer is the most common cancer in women, the 2nd leading cause of female cancer deaths and thus remains a major medical and socioeconomic burden. Medical imaging has always been an integral part in breast cancer care ranging from diagnosis and staging to therapy monitoring and post-therapeutic follow-up [1-5]. Screening mammography has significantly contributed to the detection of breast cancer especially at an early, prognostically favorable stage and mammography has been demonstrated to reduce breast cancer mortality [6-9]. Mammography is relatively inexpensive and widely available. However, its sensitivity is limited, ranging from 70 to 85% [10-12] overall but is significantly reduced to 30-50% in women with dense breasts, which can be attributed to the 'masking effect' of dense breast tissue. This effect is d...

AIM To compare the utility of breast magnetic resonance imaging (MRI) in determining the extent of disease in patients with newly diagnosed breast cancer detected on combination digital breast tomosynthesis (DBT) versus digital screening mammography (DM). MATERIALS AND METHODS Review of 24,563 DBT-screened patients and 10,751 DM-screened patients was performed. Two hundred and thirty-five DBT patients underwent subsequent MRI examinations; 82 to determine extent of disease after newly diagnosed breast cancer. Eighty-three DM patients underwent subsequent MRI examinations; 23 to determine extent of disease. MRI examinations performed to assess disease extent were considered true positives if additional disease was discovered in the contralateral breast or >2 cm away from the index malignancy. Differences in cancer subtypes and MRI outcomes between the DM and DBT cohorts were compared using chi-squared tests and post-hoc Bonferroni-adjusted tests for equal proportions. RESULTS No differences in cancer subtype findings were observed between the two cohorts; however, MRI outcomes were found to differ between the DBT and DM cohorts (p=0.024). Specifically, the DBT cohort had significantly (p=0.013) fewer true-positive findings (7/82, 8.5%) than did the DM cohort (7/23; 30%), whereas the false-positive rate was similar between the cohorts (not statistically significant). When stratifying by breast density, this difference in true-positive rates was primarily observed when evaluating women with non-dense breasts (p=0.001). CONCLUSION In both the DM- and DBT-screened populations with new cancer diagnoses, MRI is able to detect additional cancer; however, in those patients who have DBT screen-detected cancers the positive impact of preoperative MRI is diminished, particularly in those women with non-dense breasts.

FDG avid uterine cervical masses are most commonly due to primary cervical carcinoma; however, history and differential diagnoses are critical when interpreting FDG PET/CT studies. A 51-year-old woman with newly diagnosed moderately differentiated adenocarcinoma of the rectum underwent FDG PET/CT for staging, which revealed the hypermetabolic primary rectal tumor and nodal metastases. Additionally, FDG avid focus in the anterior cervix without a CT correlate was present. Cervical metastasis was suspected, and further evaluation with MRI and histopathologic correlation was recommended, which confirmed cervical metastasis. This case illustrates an unusual case of FDG-avid cervical metastasis from rectal adenocarcinoma.