• Investigative Magnetic Resonance Imaging
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• v.14 no.2
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• pp.87-94
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• 2010

Purpose : To calculate the appearance of the image distortion from metallic artifacts and to determine the location of a metallic needle from a distorted MR image. Materials and Methods : To examine metal artifacts, an infinite metal cylinder in a strong magnetic field are assumed. The cylinder’s axis leaned toward the magnetic field along some arbitrary angle. The Laplace equation for this situation was solved to investigate the magnetic field distortion, and the simulation was performed to evaluation the image artifact caused by both readout and slice-selection gradient field. Using the result of the calculation, the exact locations of the metal cylinder were calculated from acquired images. Results : The distances between the center and the folded point are measured from images and calculated. Percentage errors between the measured and calculated distance were less than 5%, except for one case. Conclusion : The simulation was successfully performed when the metal cylinder was skewed at an arbitrary tilted angle relative to the main magnetic field. This method will make it possible to monitor and guide both biopsy and surgery with real time MRI.

• Investigative Magnetic Resonance Imaging
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• v.23 no.4
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• pp.283-295
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• 2019

Perirectal cystic lesions are rare entities, for which only a relatively few research publications are available. These lesions are heterogeneous in nature and can range from benign lesions to malignant lesions; thus, they are sometimes difficult to differentiate. Some studies have reported on retrorectal or presacral cystic lesions, but to our knowledge, there have been only a few reports on perirectal cystic lesions. Cystic lesions arise from the retrorectal space as well as the rectal lumen or adjacent organ, and they should be differentiated based on their characteristics and anatomic location. Thus, we comprehensively studied diseases with a cystic component around the rectum, which are perirectal cystic lesions. A clinical challenge with perirectal cystic lesions is that it is sometimes difficult to distinguish malignant lesions from benign lesions and is thus difficult to determine the extent for surgical excision. We thus attempted to identify benign and malignant imaging features of perirectal cystic lesions.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.155-163
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• 2020

To investigate the optimal detector material for prompt gamma imaging during boron neutron capture therapy, in this study, we evaluated the characteristic regarding radiation reaction of available detector materials using a Monte Carlo simulation. Sixteen detector materials used for radiation detection were investigated to assess their advantages and drawbacks. The estimations used previous experimental data to build the simulation codes. The energy resolution and detection efficiency of each material was investigated, and prompt gamma images during BNCT simulation were acquired using only the detectors that showed good performance in our preliminary data. From the simulation, we could evaluate the majority of detector materials in BNCT and also could acquire a prompt gamma image using the six high ranked-detector materials and lutetium yttrium oxyorthosilicate. We provide a strategy to select an optimal detector material for the prompt gamma imaging during BNCT with three conclusions.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.626-636
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• 2021

Boron-neutron capture therapy (BNCT) is a cancer treatment method that exploits the high neutron reactivity of boron. Monitoring the prompt gamma rays (PGs) produced during neutron irradiation is essential for ensuring the accuracy and safety of BNCT. We investigate the imaging of PGs produced by the boron-neutron capture reaction through Monte Carlo simulations of a gamma camera with a SrI₂ scintillator and parallel-hole collimator. GAGG scintillator is also used for a comparison. The simulations allow the shapes of the energy spectra, which exhibit a peak at 478 keV, to be determined along with the PG images from a boron-water phantom. It is found that increasing the size of the water phantom results in a greater number of image counts and lower contrast. Additionally, a higher septal penetration ratio results in poorer image quality, and a SrI₂ scintillator results in higher image contrast. Thus, we can simulate the BNCT process and obtain an energy spectrum with a reasonable shape, as well as suitable PG images. Both GAGG and SrI₂ crystals are suitable for PG imaging during BNCT. However, for higher imaging quality, SrI₂ and a collimator with a lower septal penetration ratio should be utilized.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.5 no.1
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• pp.54-60
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• 2019

Sentinel lymph node (SLN) imaging plays an important role in surgery of patients with breast cancer and melanoma. In this study, avidin (Av), a tetrameric protein glycosylated with mannose and N-acetylglucosamine molecules, was labeled with $^{64}Cu$ and then evaluated for LN imaging. $^{64}Cu$-Labeled $NeutrAvidin^{TM}$ (NAv), a non-glycosylated form of Av, was used for comparison. 1,4,7,10-Tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-conjugated Av and NAv were prepared from the corresponding proteins and DOTA-NHS ester, which were then labeled with copper-64 and purified using PD-10 columns. The numbers of DOTA molecules conjugated to Av and NAv were 4.9 and 3.3, respectively. [$^{64}Cu$]Cu-DOTA-conjugated Av and NAv were prepared in 93% and 73% radiochemical yields, respectively. In vitro serum stability study showed that copper-64 remained stable on all radiotracers for 24 h (>97%). MicroPET/CT images showed that high radioactivity was accumulated in LNs within 15 min after footpad-injection of radiotracers. Tissue distribution data of mice demonstrated significantly higher uptake in the popliteal (PO) LN than lumbar (LU) LN for $^{64}Cu$-labeled Av (relative % ID/g excluding the injection sites: 66.2% and 26.0%, respectively) compared with those of $^{64}Cu$-labeled NAv (43.0% and 49.2%, respectively). The results of this study suggest that mannose molecules on Av enabled the radiotracer to retain in the first LN after mouse footpad-injection.

• Korean Journal of Radiology
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• v.22 no.3
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• pp.297-307
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• 2021

Objective: To compare the performance of simulated abbreviated breast MRI (AB-MRI) and full diagnostic (FD)-MRI in distinguishing between benign and malignant lesions detected by MRI and investigate the features of discrepant lesions of the two protocols. Materials and Methods: An AB-MRI set with single first postcontrast images was retrospectively obtained from an FD-MRI cohort of 111 lesions (34 malignant, 77 benign) detected by contralateral breast MRI in 111 women (mean age, 49.8. ± 9.8; range, 28-75 years) with recently diagnosed breast cancer. Five blinded readers independently classified the likelihood of malignancy using Breast Imaging Reporting and Data System assessments. McNemar tests and area under the receiver operating characteristic curve (AUC) analyses were performed. The imaging and pathologic features of the discrepant lesions of the two protocols were analyzed. Results: The sensitivity of AB-MRI for lesion characterization tended to be lower than that of FD-MRI for all readers (58.8-82.4% vs. 79.4-100%), although the findings of only two readers were significantly different (p < 0.05). The specificity of AB-MRI for lesion characterization was higher than that of FD-MRI for 80% of readers (39.0-74.0% vs. 19.5-45.5%, p ≤ 0.001). The AUC of AB-MRI was comparable to that of FD-MRI for all readers (p > 0.05). Fifteen percent (5/34) of the cancers were false-negatives on AB-MRI. More suspicious margins or internal enhancement on the delayed phase images were related to the discrepancies. Conclusion: The overall performance of AB-MRI was similar to that of FD-MRI in distinguishing between benign and malignant lesions. AB-MRI showed lower sensitivity and higher specificity than FD-MRI, as 15% of the cancers were misclassified compared to FD-MRI.

• Korean Journal of Radiology
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• v.21 no.4
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• pp.442-449
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• 2020

Objective: To compare the diagnostic performance of contrast-enhanced spectral mammography (CESM) versus ultrasonography (US) in symptomatic patients with dense breasts, while using histology as the gold standard. Materials and Methods: After obtaining approval from the local ethics board, this prospective study collected data from patients with symptomatic breasts who underwent CESM and US examinations from May 1, 2017 to September 30, 2017. We then selected those with dense breasts and pathological results as our sample population. Both CESM and US results were classified by a radiologist through the Breast Imaging Reporting and Data System, and the results were compared with their corresponding histological results. The chi-square test was conducted to compare the diagnostic performance of CESM and US, and the receiver operating characteristic curves for the two imaging modalities were obtained. Results: A total of 131 lesions from 115 patients with dense breasts were included in this study. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 93.8%, 88.1%, 88.2%, 93.7%, and 90.8% for CESM, and 90.6%, 82.1%, 82.9%, 90.2%, and 86.3% for US, respectively. The p values for sensitivity, specificity, PPV, NPV, and accuracy were 0.687, 0.388, 0.370, 0.702, and 0.238, respectively. The area under the curve of CESM (0.917) was comparable with that of US (0.884); however, the differences between CESM and US were not statistically significant (p = 0.225). Eight false-positive cases and 4 false-negative cases for breast cancer were found in CESM, while 12 false-positive cases and 6 false-negative cases were found in US. Conclusion: The diagnostic performances of CESM and US are comparable in symptomatic women with dense breasts; however, the routine use of additional US imaging is questionable for lesions that can be detected by CESM.

• Korean Journal of Radiology
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• v.20 no.4
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• pp.649-661
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• 2019

Objective: To systematically review the evaluation of the diagnostic accuracy of pre-treatment apparent diffusion coefficient (ADC) and change in ADC during the intra- or post-treatment period, for the prediction of locoregional failure in patients with head and neck squamous cell carcinoma (HNSCC). Materials and Methods: Ovid-MEDLINE and Embase databases were searched up to September 8, 2018, for studies on the use of diffusion-weighted magnetic resonance imaging for the prediction of locoregional treatment response in patients with HNSCC treated with chemoradiation or radiation therapy. Risk of bias was assessed by using the Quality Assessment Tool for Diagnostic Accuracy Studies-2. Results: Twelve studies were included in the systematic review, and diagnostic accuracy assessment was performed using seven studies. High pre-treatment ADC showed inconsistent results with the tendency for locoregional failure, whereas all studies evaluating changes in ADC showed consistent results of a lower rise in ADC in patients with locoregional failure compared to those with locoregional control. The sensitivities and specificities of pre-treatment ADC and change in ADC for predicting locoregional failure were relatively high (range: 50-100% and 79-96%, 75-100% and 69-95%, respectively). Meta-analytic pooling was not performed due to the apparent heterogeneity in these values. Conclusion: High pre-treatment ADC and low rise in early intra-treatment or post-treatment ADC with chemoradiation, could be indicators of locoregional failure in patients with HNSCC. However, as the studies are few, heterogeneous, and at high risk for bias, the sensitivity and specificity of these parameters for predicting the treatment response are yet to be determined.

• Korean Journal of Radiology
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• v.21 no.8
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• pp.946-954
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• 2020

Objective: To investigate preoperative magnetic resonance imaging (MRI) findings associated with resection margin status in patients with invasive lobular carcinoma (ILC) who underwent breast-conserving surgery. Materials and Methods: One hundred and one patients with ILC who underwent preoperative MRI were included. MRI (tumor size, multifocality, type of enhancing lesion, distribution of non-mass enhancement [NME], and degree of background parenchymal enhancement) and clinicopathological features (age, pathologic tumor size, presence of ductal carcinoma in situ [DCIS] or lobular carcinoma in situ, presence of lymph node metastases, and estrogen receptor/progesterone receptor/human epidermal growth factor receptor type 2 status) were analyzed. A positive resection margin was defined as the presence of invasive cancer or DCIS at the inked surface. Logistic regression analysis was performed to determine pre- and postoperative variables associated with positive resection margins. Results: Among the 101 patients, 21 (20.8%) showed positive resection margins. In the univariable analysis, NME, multifocality, axillary lymph node metastasis, and pathologic tumor size were associated with positive resection margins. With respect to preoperative MRI findings, multifocality (odds ratio [OR] = 3.977, p = 0.009) and NME (OR = 2.741, p = 0.063) were associated with positive resection margins in the multivariable analysis, although NME showed borderline significance. Conclusion: In patients with ILC, multifocality and the presence of NME on preoperative breast MRI were associated with positive resection margins.

• Korean Journal of Radiology
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• v.1 no.2
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• pp.104-109
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• 2000

Objective: Multilocular cystic renal cell carcinoma (MCRCC) is a recently described variety of renal cell carcinoma with characteristic pathologic and clinical features. The purpose of this study was to analyze the imaging findings of MCRCCs. Materials and Methods: Ten adult patients with pathologically proven unilateral MCRCC who underwent renal US and CT were included in this study. The radiologic findings were retrospectively evaluated for cystic content, wall, septum, nodularity, calcification and solid portion by three radiologists who established a consensus. Imaging and postnephrectomy pathologic findings were compared. Results: All patients were adults (six males and four females) and their ages ranged from 33 to 68 years (mean, 46). On US and CT images, all tumors appeared as well-defined multilocular cystic masses composed of serous or complicated fluid. In all patients, unenhanced CT scans revealed hypodense cystic portions, and in four tumors, due to the presence of hemorrhage or gelatinous fluid, some hyperdense areas were also noted. In no tumor was an expansile solid nodule seen in the thin septa, and in only one was there dystrophic calcification in a septum. Small areas of solid portion constituting less than 10% of the entire lesion were found in six of the ten tumors, and these areas were slightly enhanced on enhanced CT scans. In all patients, imaging and pathologic findings correlated closely. Conclusion: On US and CT images, MCRCC appeared as a well-defined multilocular cystic mass with serous, proteinaceous or hemorrhagic fluid, with no expansile solid nodules in the thin septa, and sometimes with small slightly enhanced solid areas. Where radiologic examinations demonstrate a cystic renal mass of this kind in adult males, MCRCC should be included in the differential diagnosis.