Performance of dedicated breast PET in breast cancer screening: comparison with digital mammography plus digital breast tomosynthesis and ultrasound.

OBJECTIVE: To compare the diagnostic performance of dedicated breast positron emission tomography (dbPET) in breast cancer screening with digital mammography plus digital breast tomosynthesis (DM-DBT) and breast ultrasound (US). METHODS: Women who participated in opportunistic whole-body PET/computed tomography cancer screening programs with breast examinations using dbPET, DM-DBT, and US between 2016-2020, whose results were determined pathologically or by follow-up for at least 1 year, were included. DbPET, DM-DBT, and US assessments were classified into four diagnostic categories: A (no abnormality), B (mild abnormality), C (need for follow-up), and D (recommend further examination). Category D was defined as screening positive. Each modality's recall rate, sensitivity, specificity, and positive predictive value (PPV) were calculated per examination to evaluate their diagnostic performance for breast cancer. RESULTS: Out of 2156 screenings, 18 breast cancer cases were diagnosed during the follow-up period (10 invasive cancers and eight ductal carcinomas in situ [DCIS]). The recall rates for dbPET, DM-DBT, and US were 17.8%, 19.2%, and 9.4%, respectively. The recall rate of dbPET was highest in the first year and subsequently decreased to 11.4%. dbPET, DM-DBT, and US had sensitivities of 72.2%, 88.9%, and 83.3%; specificities of 82.6%, 81.4%, and 91.2%; and PPVs of 3.4%, 3.9%, and 7.4%, respectively. The sensitivities of dbPET, DM-DBT, and US for invasive cancers were 90%, 100%, and 90%, respectively. There were no significant differences between the modalities. One case of dbPET-false-negative invasive cancer was identified in retrospect. DbPET had 50% sensitivity for DCIS, while that of both DM-DBT and US was 75%. Furthermore, the specificity of dbPET in the first year was the lowest among all periods, and modalities increased over the years to 88.7%. The specificity of dbPET was significantly higher than that of DM-DBT (p < 0.01) in the last 3 years. CONCLUSIONS: DbPET had a compatible sensitivity to DM-DBT and breast US for invasive breast cancer. The specificity of dbPET was improved and became higher than that of DM-DBT. DbPET may be a feasible screening modality.

Brain MRI with Quantitative Susceptibility Mapping: Relationship to CT Attenuation Values.

Background Quantitative susceptibility mapping (QSM) is used to differentiate between calcification and iron deposits. Few studies have examined the relationship between CT attenuation values and magnetic susceptibility in such materials. Purpose To assess the relationship among metal concentration, CT attenuation values, and magnetic susceptibility in paramagnetic and diamagnetic phantoms, and the relationship between CT attenuation values and susceptibility in brain structures that have paramagnetic or diamagnetic properties. Materials and Methods In this retrospective study, CT and MRI with QSM were performed in gadolinium and calcium phantoms, patients, and healthy volunteers between June 2016 and September 2017. In the phantom study, we evaluated correlations among metal concentration, CT attenuation values, and susceptibility. In the human study, Pearson and Spearman correlations were performed to assess the relationship between CT attenuation values and susceptibility in regions of interest placed in the globus pallidus (GP), putamen, caudate nucleus, substantia nigra, red nucleus, dentate nucleus, choroid plexus, and hemorrhagic and calcified lesions. Results Eighty-four patients (mean age, 64.8 years ± 19.6; 49 women) and 20 healthy volunteers (mean age, 72.0 years ± 7.6; 11 men) were evaluated. In the phantoms, strong linear correlations were identified between gadolinium concentration and CT and MRI QSM values (R 2 = 0.95 and 0.99, respectively; P < .001 for both) and between calcium concentration and CT and MRI QSM values (R 2 = 0.89 [P = .005] and R 2 = 0.98 [P < .001], respectively). In human studies, positive correlations between CT attenuation values and susceptibility were observed in the GP (R 2 = 0.52, P < .001) and in hemorrhagic lesions (R 2 = 0.38, P < .001), and negative correlations were found in the choroid plexus (R 2 = 0.53, P < .001) and in calcified lesions (R 2 = 0.38, P = .009). Conclusion CT attenuation values showed a positive correlation with susceptibility in the globus pallidus and hemorrhagic lesions and negative correlation in the choroid plexus and calcified lesions. © RSNA, 2020 Online supplemental material is available for this article.

Internal evaluation of impregnation treatment of waterlogged wood; relation between concentration of internal materials and relaxation time using magnetic resonance imaging.

The purpose of this study is to clarify the degree of impregnation resulting from treatment of internal waterlogged wood samples using MRI. On a 1.5T MR scanner, T1 and T2 measurements were performed using inversion recovery and spin-echo sequences, respectively. The samples were cut waterlogged pieces of wood treated with various impregnation techniques which were divided into different concentrations of trehalose (C12H22O11) and polyethylene glycol (PEG; HO-(C2H4O)n-H) solutions. Then these samples underwent impregnation treatment every two weeks. From the results, we found that the slope of the T1-concentration curve using linear fitting showed the value of the internal area for PEG to be higher than the external area; internal, -2.73ms/wt% (R2=0.880); external, -1.50ms/wt% (R2=0.887). Furthermore, the slope of the T1-concentration curve using linear fitting showed the values for trehalose to have almost no difference when comparing the internal and the external areas; internal, -2.79ms/wt% (R2=0.759); external, -3.02ms/wt% (R2=0.795). However, the slope of the T2-concentration curve using linear fitting for PEG showed that there was only a slight change between the internal and the external areas; internal, 0.26ms/wt% (R2=0.642); external, 0.18ms/wt% (R2=0.920). The slope of the T2-concentration curve did not show a change in linear relationship between the internal and the external areas; internal, 0.06ms/wt% (R2=0.175); external, -0.14ms/wt% (R2=0.043). In conclusion, using visualization of relaxation time T1, it is possible to obtain more detail information noninvasively concerning the state of impregnation treatment of internal waterlogged wood.

Evaluation of Appropriate Readout Sequence for Renal MRI Perfusion Using ASTAR (ASL) Technique.

The aim of this study was to compare true-steady state free precession (True-SSFP) with fast field echo (FFE) as readout imaging sequences for renal arterial spin labeling (ASL), and to optimize the imaging condition. Renal ASL perfusion images were acquired using signal targeting with alternated radio frequency using asymmetric inversion slab (ASTAR) technique with respiratory triggering at 3T MRI system, using either 3D True-SSFP or FFE as the readout sequence. Inversion time (TI) varied from 800 to 2400 ms. Appropriate flip angles were estimated for each sequence by simulating signal intensity (SI). The SI of the renal cortex, vertebral body, and intestinal tract were measured, and the contrast ratio of the cortex (CRcortex) or intestine (CRintestine) related to vertebra was calculated. The image quality of the kidneys, background signal suppression, and misregistration were evaluated by four-point scales. As a result, in quantitative evaluation, the average of CRcortex of each TI (800, 1200, 1600, 2000, and 2400 msec) were 0.49, 0.57, 0.63, 0.63, and 0.56 in FFE, and 0.59, 0.71, 0.73, 0.73, and 0.68 in True-SSFP, respectively. IN qualitative evaluation, ASL images with True-SSFP readout were significantly better than those with FFE readout. In conclusion, True-SSFP sequences will be recommended as read out imaging sequence for obtaining ASL image compared with FFE image.

Optimization of non-contrast-enhanced MR angiography of the renal artery with three-dimensional balanced steady-state free-precession and time-spatial labeling inversion pulse (time-SLIP) at 3T MRI, in relation to age and blood velocity.

PURPOSE: To determine the optimal inversion time (TI) value of three-dimensional (3D) balanced steady-state free-precession time-spatial labeling inversion pulse (time-SLIP) technique for visualization of the renal artery at 3T MRI, and to assess whether the optimal TI is affected by the subject's age and blood velocity. MATERIALS AND METHODS: Forty-two healthy volunteers (range 20-67 years) were enrolled in the study and subjected to non-contrast-enhanced renal MR angiography. Five different TI values (1200, 1400, 1600, 1800, and 2000 ms) were selected for evaluation. For quantitative evaluation, the relative signal intensity (SI) of the main renal artery was compared with that of the renal medulla (Vessel-to-Kidney ratio; VKR). Blood velocity of the abdominal aorta was measured using 2D phase contrast technique. For qualitative evaluation, two radiologists scored the depiction of the renal pelvis and the quality of visualization of the renal artery. RESULTS: VKR is the highest at TI = 1600 ms. A strong negative correlation between age and blood velocity was demonstrated. Regarding the qualitative evaluation, the overall image scores of renal arteries were the highest at a TI = 1800 ms for both readers. The optimal TI values in subjects below 50 years of age were 1600 and 1800 ms, whereas in subjects above 50 years of age, the optimal TI value was 1800 ms. CONCLUSION: The optimal TI value for the visualization of renal arteries using time-SLIP technique at 3T MRI was 1800 ms. Subjects' age affected optimal TI and this is likely due to differences in the blood velocity of the abdominal aorta.