James V. Rogers

Positron Emission Mammography: Correlation of Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor 2 Status and 18F-FDG

OBJECTIVE The study objective was to assess the correlation between (18)F-FDG uptake values on positron emission mammography (PEM), expressed as maximum uptake value and lesion-to-background ratio, and receptor status (i.e., estrogen receptor [ER], progesterone receptor [PR], and human epidermal growth factor receptor 2 [HER2]), tumor histology, and tumor grade. We also evaluated for the correlation between maximum uptake value on PEM and maximum uptake value on a whole-body PET/CT. MATERIALS AND METHODS We retrospectively reviewed our database for patients with newly diagnosed breast cancer who were referred for PEM between June 2007 and September 2009. A subset of patients also underwent a whole-body PET/CT scan. The original pathology reports were reviewed to establish the histologic type, grade, and receptor status. RESULTS The study involved 98 patients with 100 lesions. ER-negative tumors and PR-negative tumors had significantly higher mean lesion-to-background ratio than did their respective receptor-positive tumors (p = 0.02). Triple-negative tumors (i.e., ER-negative, PR-negative, and HER2-negative tumors) had statistically higher mean lesion-to-background ratio than did ER-positive PR-positive HER2-negative tumors (p = 0.04). Infiltrating ductal carcinomas had significantly higher PEM FDG uptake values than did infiltrating lobular carcinomas (p = 0.02-0.04). Breast tumors with higher histologic grade also had significantly higher PEM FDG uptake values than did those with lower grade (p = 0.03 and p < 0.001). A moderately high correlation (0.76-0.79) was seen between whole-body PET/CT and PEM uptake values. CONCLUSION This study shows a correlation between PEM FDG uptake values and the prognostic factors that have been shown to predict breast cancer survival.

Intraoperative Ultrasound Detection of Metastatic Tumors in the Central Cortex

Real-time sector ultrasonography precisely located metastatic tumors of the central motor cortex during craniotomy in two patients. In these two cases, the only surface abnormality was swelling of several overlying gyri. Intraoperative ultrasonography precisely located the 1.5- and 2.5-cm-diameter tumors to a position below a specific gyrus, enabling the surgeon to excise the tumors through small, accurately placed cortical windows. The precise location minimized exploratory probing and the size of the cortical incision required to identify and remove the tumors. This technique will have general application in similar situations when the cortical surface gives no indication of underlying tumor location. By charting the best trajectory for the surgical approach, this technique may replace a variety of stereotactic and computed tomography-guided techniques for biopsy of deep brain tumors.

(18)F-FDG PET/CT-positive internal mammary lymph nodes: pathologic correlation by ultrasound-guided fine-needle aspiration and assessment of associated risk factors.

OBJECTIVE Metastatic breast cancer in internal mammary (IM) lymph nodes is associated with a poor prognosis. This study correlates (18)F-FDG PET/CT-positive IM lymph nodes with ultrasound-guided fine-needle aspiration (FNA) cytopathologic results and determines risk factors for IM node positivity on PET/CT. MATERIALS AND METHODS For this retrospective study, a database search was performed to identify patients referred for whole-body (18)F-FDG PET/CT for initial staging or restaging of breast cancer from January 1, 2005, through December 31, 2010. The radiology reports and images were reviewed for patients with (18)F-FDG-avid IM lymph nodes on PET/ CT and correlated with the cytopathologic results from FNA of selected PET/CT-positive IM lymph nodes. The patients with positive IM nodes on PET/CT who underwent PET/CT for initial staging were compared against age-matched and tumor size-matched patients to identify risk factors for IM node positivity on PET/CT. RESULTS One hundred ten of 1259 patients (9%) had an (18)F-FDG-avid IM lymph node on PET/CT. Twenty-five patients underwent ultrasound-guided FNA of a suspicious IM node, and 20 IM lymph nodes (80%) were cytologically proven metastases from the primary breast malignancy. High tumor grade, the presence of lymphovascular invasion (LVI), and triple receptor-negative hormonal receptor status were found to be significant risk factors for IM node positivity on PET/CT (p < 0.05). CONCLUSION Although fewer than 10% of breast cancer patients have positive IM nodes on (18)F-FDG PET/CT performed for initial staging or restaging, a positive IM node indicates a very high likelihood of malignant involvement on ultrasound-guided FNA. The presences of high tumor grade, LVI, or triple receptor-negative status are risk factors for IM node positivity on (18)F-FDG PET/CT.

Positron emission mammography (PEM): Effect of activity concentration, object size, and object contrast on phantom lesion detection

PURPOSE To characterize the relationship between lesion detection sensitivity and injected activity as a function of lesion size and contrast on the PEM (positron emission mammography) Flex Solo II scanner using phantom experiments. METHODS Phantom lesions (spheres 4, 8, 12, 16, and 20 mm diameter) were randomly located in uniform background. Sphere activity concentrations were 3 to 21 times the background activity concentration (BGc). BGc was a surrogate for injected activity; BGc ranged from 0.44-4.1 kBq∕mL, corresponding to 46-400 MBq injections. Seven radiologists read 108 images containing zero, one, or two spheres. Readers used a 5-point confidence scale to score the presence of spheres. RESULTS Sensitivity was 100% for lesions ≥12 mm under all conditions except for one 12 mm sphere with the lowest contrast and lowest BGc (60% sensitivity). Sensitivity was 100% for 8 mm spheres when either contrast or BGc was high, and 100% for 4 mm spheres only when both contrast and BGc were highest. Sphere contrast recovery coefficients (CRC) were 49%, 34%, 26%, 14%, and 2.8% for the largest to smallest spheres. Cumulative specificity was 98%. CONCLUSIONS Phantom lesion detection sensitivity depends more on sphere size and contrast than on BGc. Detection sensitivity remained ≥90% for injected activities as low as 100 MBq, for lesions ≥8 mm. Low CRC in 4 mm objects results in moderate detection sensitivity even for 400 MBq injected activity, making it impractical to optimize injected activity for such lesions. Low CRC indicates that when lesions <8 mm are observed on PEM images they are highly tracer avid with greater potential of clinical significance. High specificity (98%) suggests that image statistical noise does not lead to false positive findings. These results apply to the 85 mm thick object used to obtain them; lesion detectability should be better (worse) for thinner (thicker) objects based on the reduced (increased) influence of photon attenuation.

Positron emission mammography (PEM): Effect of activity concentration, object size, and object contrast on phantom lesion detection: PEM phantom lesion detectability

PURPOSE To characterize the relationship between lesion detection sensitivity and injected activity as a function of lesion size and contrast on the PEM (positron emission mammography) Flex Solo II scanner using phantom experiments. METHODS Phantom lesions (spheres 4, 8, 12, 16, and 20 mm diameter) were randomly located in uniform background. Sphere activity concentrations were 3 to 21 times the background activity concentration (BGc). BGc was a surrogate for injected activity; BGc ranged from 0.44-4.1 kBq∕mL, corresponding to 46-400 MBq injections. Seven radiologists read 108 images containing zero, one, or two spheres. Readers used a 5-point confidence scale to score the presence of spheres. RESULTS Sensitivity was 100% for lesions ≥12 mm under all conditions except for one 12 mm sphere with the lowest contrast and lowest BGc (60% sensitivity). Sensitivity was 100% for 8 mm spheres when either contrast or BGc was high, and 100% for 4 mm spheres only when both contrast and BGc were highest. Sphere contrast recovery coefficients (CRC) were 49%, 34%, 26%, 14%, and 2.8% for the largest to smallest spheres. Cumulative specificity was 98%. CONCLUSIONS Phantom lesion detection sensitivity depends more on sphere size and contrast than on BGc. Detection sensitivity remained ≥90% for injected activities as low as 100 MBq, for lesions ≥8 mm. Low CRC in 4 mm objects results in moderate detection sensitivity even for 400 MBq injected activity, making it impractical to optimize injected activity for such lesions. Low CRC indicates that when lesions <8 mm are observed on PEM images they are highly tracer avid with greater potential of clinical significance. High specificity (98%) suggests that image statistical noise does not lead to false positive findings. These results apply to the 85 mm thick object used to obtain them; lesion detectability should be better (worse) for thinner (thicker) objects based on the reduced (increased) influence of photon attenuation.

Positron emission mammography (PEM)

PURPOSE To characterize the relationship between lesion detection sensitivity and injected activity as a function of lesion size and contrast on the PEM (positron emission mammography) Flex Solo II scanner using phantom experiments. METHODS Phantom lesions (spheres 4, 8, 12, 16, and 20 mm diameter) were randomly located in uniform background. Sphere activity concentrations were 3 to 21 times the background activity concentration (BGc). BGc was a surrogate for injected activity; BGc ranged from 0.44-4.1 kBq∕mL, corresponding to 46-400 MBq injections. Seven radiologists read 108 images containing zero, one, or two spheres. Readers used a 5-point confidence scale to score the presence of spheres. RESULTS Sensitivity was 100% for lesions ≥12 mm under all conditions except for one 12 mm sphere with the lowest contrast and lowest BGc (60% sensitivity). Sensitivity was 100% for 8 mm spheres when either contrast or BGc was high, and 100% for 4 mm spheres only when both contrast and BGc were highest. Sphere contrast recovery coefficients (CRC) were 49%, 34%, 26%, 14%, and 2.8% for the largest to smallest spheres. Cumulative specificity was 98%. CONCLUSIONS Phantom lesion detection sensitivity depends more on sphere size and contrast than on BGc. Detection sensitivity remained ≥90% for injected activities as low as 100 MBq, for lesions ≥8 mm. Low CRC in 4 mm objects results in moderate detection sensitivity even for 400 MBq injected activity, making it impractical to optimize injected activity for such lesions. Low CRC indicates that when lesions <8 mm are observed on PEM images they are highly tracer avid with greater potential of clinical significance. High specificity (98%) suggests that image statistical noise does not lead to false positive findings. These results apply to the 85 mm thick object used to obtain them; lesion detectability should be better (worse) for thinner (thicker) objects based on the reduced (increased) influence of photon attenuation.

TH‐D‐201B‐09: Low Dose Lesion Contrast on PEM Flex Solo II

Objective: The aim of this study was to investigate lesion detection with very low doses of radiotracer concentration using a PEM Flex Solo II breast PETscanner. Methods: We imaged a phantom with hot radioactive spheres in a warm background of known radiotracer concentration and lesion‐to‐background ratios (LBR) on a PEM Flex Solo IIpositron emission mammographyscanner (Naviscan Inc.). Two detectors with variable separation each 5.6cm X 16cm scan in unison to cover a 24cm × 16cm field. We tested two breast compression thicknesses of 55mm and 85mm. Sphere diameters were 3.9 7.8 16 and 20 mm and LBRs were 4‐to‐1 and 10‐to‐1. We imaged the phantom with between 0.1kBq/mL and 5.0kBq/mL background concentration of 18‐FDG solution. Image acquisition was 10min. Lesion uptake was characterized by lesion‐to‐background metrics used clinically; LBR equals the maximum of a lesion region of interest (ROI) divided by the mean of a background ROI. Overall image uniformity was measured as the coefficient of variation (COV) calculated from 72 ROIs placed throughout the image volume. Contrast‐to‐noise ratio (CNR) was calculated as LBR/COV and was compared for different activity concentrations and true LBRs. Results: Our phantom results show little change in measured LBR over the range of background activity of 0.5 to 5.0 kBq/mL. Image COV increased slowly from 5 kBq/mL to 1 kBq/mL and then increased rapidly below 1 kBq/mL. Resulting CNR decreased little between l‐5kBq/mL then fell to ∼50% of nominal value at ∼0.1–0.3kBq/mL. When true LBR = 4 the 3.9mm sphere was not visible for any tested concentration; the limits for visualizing the 7.8mm sphere were ∼0.2 and 0.4 kBq/mL for compression = 5.8cm and 8.5cm respectively. These tests require receiver operator analyses but suggest that PEMimaging may use significantly lower injected doses than routine clinical whole‐body PET.