• 디지털콘텐츠학회 논문지
• /
• 제11권3호
• /
• pp.283-290
• /
• 2010

1.5T에서 경직장 코일과 3.0T의 위상 배열 코일을 이용하여 신호대 잡음비를 비교하여 3.0T의 위상 배열 코일의 유용성을 제시한다. 전립선암으로 진단받은 환자 40명을 대상으로 1.5T MR scanner에서는 경직장 표면 코일과 3.0T MR scanner에서는 위상 배열 코일을 이용하여 T2 강조 영상, T1 강조영상, 확산 강조 영상을 각각 획득 후 전립선의 Central Zone(CZ)과 Peripheral Zone(PZ)에서 Right Peripheral Zone(PZ)과 Left Peripheral Zone(PZ) 세 부위에서 신호 강도(signal intensity)측정을 하였다. 정량적 분석방법으로 관심영역의 신호대 잡음비(signal to noise ratio)를 구하고 평균화 하여 1.5T MR scanner로 획득한 그룹과 3.0T MR scanner로 획득한 그룹에서의 신호대 잡음비를 비교하였다. 3.0T MR scanner에서 위상 배열 코일을 사용한 경우 1.5T MR scanner에서 경직장 코일을 사용한 경우보다 신호대 잡음비가 증가됨을 알 수 있었다.

• 한국방사선학회논문지
• /
• 제16권7호
• /
• pp.835-842
• /
• 2022

본 연구는 금속 인공물을 감소시키는 데 있어 synthetic MR 기법의 효과를 평가해보고자 하였다. 실험은 척추 수술용 나사로 제작된 팬텀을 대상으로 synthetic MR 기법과 고속 스핀 에코 기법을 적용하여 in-plane과 through-plane 영상을 획득하고 금속 인공물의 면적을 비교해 보았다. 금속 인공물은 signal-loss와 signal pile-up 영역으로 구분하여 측정하였고 둘의 합을 통해 최종 인공물의 면적을 계산하였다. 그 결과, in-plane, through-plane 모두 synthetic MR 기법을 적용했을 때 상대적으로 금속 인공물이 감소하였다. 시퀀스 별로 비교하면 in-plane의 경우 T1 영상은 23.45%, T2 영상은 20.85%, PD 영상은 19.67%, FLAIR 영상은 22.12% 감소하였다. 또한 through-plane의 경우 T1 영상은 62.95%, T2 영상은 73.93, PD 영상은 74.68%, FLAIR 영상은 66.43% 감소하였다. 이러한 결과의 원인은 synthetic MR 기법 적용 시 signal pile-up에 의한 왜곡이 발생하지 않아 전체 금속 인공물의 크기가 감소하였기 때문이다. 따라서 synthetic MR 기법은 매우 효과적으로 금속 인공물을 감소시킬 수 있어 영상의 진단적 가치를 높이는 데 도움을 줄 수 있다.

• Journal of Korean Neurosurgical Society
• /
• 제40권5호
• /
• pp.351-356
• /
• 2006

Objective : Spondylodiscitis has been diagnosed by clinical, radiological and laboratory methods. MR imaging is well known as an excellent diagnostic tool for spondylodiscitis. However, the changes in MR images throughout the treatment process has not been studied. Thus we have analyzed the serial changes of MR images throughout the stages of infection. Methods : Ten patients were selected for retrospective reviewed who had been treated at our institute for infectious spondylodiscitis between 2000 and 2005. These patients had been followed-up at least six months and had taken more than a couple of series of MR scans. We classified the MR images into four groups according to the stages of treatment for the infection and compared them to the clinical and laboratory findings. Results : MR image signals changed minimally or appeared to be normal in the early stages. The progression of spondylodiscitis was characterized by a low T1 WI signal and a high T2 WI signal in disc and vertebral body. The signal changes of the MR images were then propagated and the end plate was destructed. During the treatment, the destructed endplate became stabilized and the signal intensity of both T1 and T2 WI were fixed to low-or iso-intensity. Conclusion : We can determine the serial signal changes based on MR images according to the treatment of spondylodiscitis. We can therefore determine the status of the infection and the stage of treatment, as well as the diagnosis of spondylodiscitis using serial MR images.

• 한국멀티미디어학회논문지
• /
• 제19권4호
• /
• pp.736-746
• /
• 2016

In this paper, we propose an automatic prostate cancer detection method using position, signal intensity and texture feature based on SVM in multi-parametric MR images. First, to align the prostate on DWI and ADC map to T2wMR, the transformation parameters of DWI are estimated by normalized mutual information-based rigid registration. Then, to normalize the signal intensity range among inter-patient images, histogram stretching is performed. Second, to detect prostate cancer areas in T2wMR, SVM classification with position, signal intensity and texture features was performed on T2wMR, DWI and ADC map. Our feature classification using multi-parametric MR imaging can improve the prostate cancer detection rate on T2wMR.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.341-344
• /
• 2002

Neurodegenerative disorders, like Alzheimer's disease, are often accompanied by reduced brain perfusion (cerebral blood flow). Using the intrinsic magnetic properties of water, arterial spin labeling magnetic resonance imaging (ASLMRI) can map brain perfusion without injection of radioactive tracers or contrast agents. However, accuracy in measuring perfusion with ASL-MRI can be limited because of contributions to the signal from stationary spins and because of signal modulations due to transient magnetic field effects. The goal was to optimize ASL-MRI for perfusion measurements in the aging human brain, including brains with Alzheimer's disease. A new ASL-MRI sequence was designed and evaluated on phantom and humans. Image texture analysis was performed to test quantitatively improvements. Compared to other ASL-MRI methods, the newly designed sequence provided improved signal to noise ratio improved signal uniformity across slices, and thus, increased measurement reliability. This new ASL-MRI sequence should therefore provide improved measurements of regional changes of brain perfusion in normal aging and neurodegenerative disorders.

• Korean Journal of Radiology
• /
• 제2권4호
• /
• pp.192-196
• /
• 2001

Objective: To compare conventional and diffusion-weighted MR imaging in terms of their depiction of the abnormalities occurring in Creutzfeldt-Jakob disease. Materials and Methods: We retrospectively analyzed the findings of conventional (T2-weighted and fluid-attenuated inversion recovery) and diffusion-weighted MR imaging in four patients with biopsy-proven Creutzfeldt-Jakob disease. The signal intensity of the lesion was classified by visual assessment as markedly high, slightly high, or isointense, relative to normal brain parenchyma. Results: Both conventional and diffusion-weighted MR images demonstrated bilateral high signal intensity in the basal ganglia in all four patients. Cortical lesions were observed on diffusion-weighted MR images in all four, and on fluid-attenuated inversion recovery MR images in one, but in no patient on T2-weighted images. Conventional MR images showed slightly high signal intensity in all lesions, while diffusion-weighted images showed markedly high signal intensity in most. Conclusion: Diffusion-weighted MR imaging is more sensitive than its conventional counterpart in the depiction of Creutzfeldt-Jakob disease, and permits better detection of the lesion in both the cerebral cortices and basal ganglia.

• 전자공학회논문지
• /
• 제53권3호
• /
• pp.151-159
• /
• 2016

본 연구의 목적은 가돌리늄 조영제를 사용한 Head & Neck MR Angio검사에 있어서 매개변수인 FA(Flip Angle)이 MR신호에 미치는 영향에 대해서 알아보고자 하였으며, 이에 따른 FA의 적정 값을 제시하는 것이다. 실험은 FA증가에 따른 MR팬텀실험과 임상실험으로 진행하였고, 이에 대한 정량적 분석이 이루어졌다. 실험결과 팬텀실험에서의 조영증강 반응시작 지점인 RSP(Reaction Starting Point)는 FA증가에 따라 300~400 mmol 사이에서 반응하였고, 최대 신호강도인 MPSI(Max Peak Signal Intensity)는 2,086, 3,705, 5,109, 6,194, 7.096, 7,192 [a.u]를 기록하였다. MPSI가 형성되는 몰농도 지점인 MPP(Max Peak Point)는 FA에 증가에 따라 40, 50, 50, 40, 50, 40 mmol에서 보였으며, MPSI의 증가율인 IRMPSI(Increase Rate of MPSI)는 77.6%, 37.9%, 21.2%, 14.6%, 1.4%임을 확인하였다. 임상실험에서의 평가기준인 SICB(Signal Intensity of Carotid artery Bifurcation)는 FA증가에 따라 각 평균값 2392.5, 4165.2, 4270, 3502.2, 3263.7, 3119.6 [a.u]를 기록하였고, 아티팩트 발생율인 ORA(Occurence Rate of Artifact)는 0, 0, 20, 40, 50, 70%로 점차 증가하였다. 본 연구를 통하여 FA의 증가는 혈관 내 가돌리늄과 결합한 H1스핀의 신호강도와 아티팩트에 영향을 미친다는 사실을 확인하였고, 이는 실제 임상에서의 CE(Contrast Enhanced)-Head&Neck MR Angio검사에 있어서 본 연구의 데이터를 활용한다면 진단학적으로 효율적인 MR Angiography 영상을 구현할 수 있을 것으로 사료된다.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1995년도 춘계학술대회
• /
• pp.42-44
• /
• 1995

The original DANTE sequence and its variations have limitation in excitation profile (a sinc function-like excitation) due to the finite duration of the DANTE pulsetrain. This sinc function-like selection profile excites only a small fraction of the spins in the pixel thereby results in poor signal to noise ratio (only about ${\sim}1%$ of normal MR imaging sequence). Therefore, this poor signal to noise ratio (SNR) has been the main drawback of the original DANTE sequence. To improve the signal to noise ratio, phases of individual RF pulses in the DANTE pulse train were modulated so that more spins in the object were excited ($1{\sim}3$). We have introduced a new FM (Frequency Modulation) DANTE sequence and analyzed the signal intensity and excitation profiles.

• Annals of Clinical Neurophysiology
• /
• 제4권2호
• /
• pp.114-118
• /
• 2002

Backgrounds : Carpal tunnel syndrome (CTS) is a common condition that is usually diagnosed by electrophysiologic studies. However, CTS provide limited information to determine the causes of CTS and to choose the treatment method. We evaluated diagnostic sensitivity of MR imaging and treatment decisions by MR imaging in electrodiagnosed CTS. Methods : 14 patients (26 wrists) with electrodiagnosed CTS were studied using MR imaging. In 26 wrists for which axial T1 & T2 weighted images were obtained at 1.5T with a decided wrist coil. Previously described MR imaging of CTS such as increased median nerve signal, flattening of median nerve, reticular bowing, tenosynovitis and space occupying lesions were retrospectively evaluated. Degree of improvement was evaluated by global symptom score (GSS). The GSS rated symptoms from 0 (no symptoms) to 10 (severe) in each of five categories: pain, numbness, paresthesia, weakness/clumsiness, and nocturnal awakening. Subjects' GSS was recorded at baseline, 2 weeks, 1 month, 6 months after treatment. We decided to medical treatment that showed mainly inflammatory sign such as increased median nerve signal, tenosinovitis and to surgical treatment such as space occupying lesion, high canal pressure sign. Results : MR imaging showed that increased median nerve signal were in 20 wrists (77%), flattening of median nerve were in 6 wrists (23%), reticular bowing were in 3 wrists (12%), tenosynovitis were in 8 wrists (32%), decreased canal size in 2 wrists (7.6%), space occupying lesion were in 1 wrist (4%). A good outcome was revealed in 21 wrists by medical treatment that showed mainly increased median nerve signal, tenosynovitis. The mean GSS were 27.7 at baseline, 11.2 at 2 weeks, 11.0 at 6 months in medical treatment group. Another 5 wrist had surgical treatment shown by ganglion and high canal pressure sign such as median nerve flattening, reticular bowing, decreased canal size: 3 wrists had good prognosis, but 2 wrists (one patient) had no significant improvement due to small carpal tunnel size. Conclusions : Our results are in agreement with most previously described MR imaging signs of CTS. MR imaging plays an important role in several cases and especially in the assessment of failure of surgical treatment. Knowledge of MR findings may permit more rational choice of treatment.

• Investigative Magnetic Resonance Imaging
• /
• 제6권2호
• /
• pp.158-165
• /
• 2002

목적: 체내에 주입된 Gd-DTPA가 뇌의 확산강조 자기공명영상 신호강도 및 현성확산계수에 미치는 영향을 알아보았다. 대상 및 방법 : 성숙한 잡견 5마리에 대하여 동맥내 도관삽입에 의한 좌측 내경동맥 색전방법을 이용하여 초급성 뇌경색 동물모델을 만들었다. 색전 후 1시간째 확산강조영상을 시행하고, Gd-DTPA를 주입한 다음 다시 90분까지 11회의 추가 확산강조영상을 얻었다. 관심영역을 설정하여 측정한 초급성 뇌경색부위와 반대측 정상부위의 확산강조영상 신호강도 및 현성확산계수를 분석하였다. 결과: 뇌경색은 색전 후 1시간에 시행한 확산강조 자기공명영상에서 잡견 5마리 모두에서 발견되었다. 확산강조영상에서 초급성 뇌경색부위의 신호강도는 Gd-DTPA 주입 여부와 관계없이 시간이 경과함에 따라 증가하였으나, 관류가 유지된 정상부위의 신호강 도는 Gd-DTPA 주입 후 2분에 시행한 첫 검사에서 오히려 저하된 후, 시간경과에 따라 다시 증가하였다. 현성확산계수는 초급성 뇌경색부위에서 Gd-DTPA주입여부에 관계없이 시간 이 경과함에 따라 지속적으로 감소되었으나, 관류가 유지된 반대측 정상부위에서는 변화하지 않았다. 결론: 체내에 주입된 Gd-DTPA는 초급성 뇌경색부위 및 정상부위의 현성확산계수에 영향을 미치지 않으나, 정상부위에서는 조영제 주입 직후 초기의 자화율효과에 의해 확산강조영상의 신호 강도를 저하시켰다. 조영제 주입 후 시행한 확산강조영상 신호 강도의 정량적인 측정이 필요한 연구 혹은 임상 증례에 대하여는 현성확산계수를 측정함으로써 Gd-DTPA의 자화율효과에 의한 영향을 배제하여야 할 것이다.