Design of improved spectral-spatial pulses for routine clinical use

Zur, Yuval

doi:10.1002/(sici)1522-2594(200003)43:3<410::aid-mrm13>3.0.co;2-3

Cited by 63 publications

(82 citation statements)

References 14 publications

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“…WATS tekniği yağ sinyallerini baskılamak için alternatif bir yöntem olarak geliştirilmiştir [45]. WATS tekniği manyetik alan inhomojenitesine daha az duyarlı olmasından dolayı presaturasyon tekniğine göre yağ sinyallerini daha iyi baskılar (Resim 5A, B) [46]. Yağ baskılı SPGR ile karşılaştırıldığında WATS tekniğinin tarama süre-si daha kısadır [45].…”

Section: Spoiled Gradient Recalled Echo Imaging (Spgr)unclassified

Diz Eklemi: Kikirdak

Sabir¹,

Tanriverdi²

2017

Trd Sem

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Kıkırdak Yapısı ve FonksiyonuEklem kıkırdağı net ağırlığının %4'ü kondrositlerden, geri kalan büyük kısmı ekstraselü-ler matriksten oluşur. Ekstraselüler mesafenin %65-85'ini su, çok az bir kısmını proteoglikan ve tip II kollajen oluşturur [1,2]. Yüksek sı-kıştırma kuvvetine dayanmayı sağlayan proteoglikan kıkırdak net ağırlığının %3-10'unu oluştururken, gerilme kuvvetinden sorumlu kollajen %15-20'sini yapar [1]. Eklem kıkırda-ğının lenfatiklerden, kan damarı ve sinirlerden yoksun olması iyileşme ve onarım potansiyelini kısıtlar [2]. Eklem kıkırdağının makromoleküler matris yapısının korunması eklem sağ-lığı için hayatidir. Tip II kollajenin kompleks üç boyutlu oryantasyonu doku anizotropisinden sorumludur [3]. Kıkırdağın eklem yüzeyi lamina splendis ile korunur; yoğun kollajen demetlerinin yüzeyindeki lubrisin adı verilen proteoglikan ve sinovyal sıvı kayganlık sağlar [4]. Kıkırdağın yüzeyel zonu kollajen lifleri ve eklem yüzeyine paralel elonge kondrositlerden; orta zon yuvarlak kontrositler ile rastgele konumlanmış kollajen fiberlerinden; derin zon ise kemik yüzeye dik olarak yerleşmiş elonge kondrositlerden ve kalın kollajen demetlerinden oluşur. Derin zonda radyal uzanan kollajen fibrilleri subkondral kemiğe bağlanmak için kalsifiye zona uzanır [2].Ayak bileği kıkırdak kalınlığı ortalama 1,1 mm iken; patella kıkırdağı farklı olarak 5 mm ve üzeri olabilir [5,6]. Farklı eklemlerdeki farklı kıkırdak yapıları gelişen farklı tipte kı-kırdak lezyonlarını da açıklar; örneğin idyopatik osteoartrit diz eklemi kıkırdağında daha sık iken osteokondral lezyonlar daha sık ayak bileğinde görülür [7]. Kıkırdak Görüntüleme EndikasyonlarıOsteoartrit, kronik ve akut osteokondral zedelenme, kondromalazi patella, femur kondilinin spontan osteonekrozu (SONK veya Ahlbaeck's hastalığı), enflamatuar artropatiler, invaziv kıkırdak onarımı ve konzervatif terapiler

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Section: Spoiled Gradient Recalled Echo Imaging (Spgr)unclassified

Diz Eklemi: Kikirdak

Sabir¹,

Tanriverdi²

2017

Trd Sem

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“…Also, one of the bipolar ghosts can be suppressed by using oscillating polarity in the RF sub-lobes, as introduced in [12] and further explained in [13]. However, for the high degree of attenuation needed to suppress the signal from the injected hyperpolarized compound, enabling imaging of a single metabolic product, a more advanced strategy that takes into account the zig-zag trajectory through excitation k-space must be used.…”

Section: Theorymentioning

confidence: 99%

Pulse sequence for dynamic volumetric imaging of hyperpolarized metabolic products

Cunningham

Chen

Lustig

et al. 2008

Journal of Magnetic Resonance

119

152

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Dynamic nuclear polarization and dissolution of a (13)C-labeled substrate enables the dynamic imaging of cellular metabolism. Spectroscopic information is typically acquired, making the acquisition of dynamic volumetric data a challenge. To enable rapid volumetric imaging, a spectral-spatial excitation pulse was designed to excite a single line of the carbon spectrum. With only a single resonance present in the signal, an echo-planar readout trajectory could be used to resolve spatial information, giving full volume coverage of 32 x 32 x 16 voxels every 3.5s. This high frame rate was used to measure the different lactate dynamics in different tissues in a normal rat model and a mouse model of prostate cancer.

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“…Several techniques have been presented to selectively excite or suppress water or fat with or without spatial selection [7]. Conventional fat suppression techniques are often based on spectrally selective radio-frequency (RF) pulses (so-called FATSAT pulses) to presaturate the signal from the lipids.…”

Section: Introductionmentioning

confidence: 99%

“…Water (or fat) selective spectral-spatial (spsp) excitation pulses [12] can be implemented for clinical use into any kind of SSFP sequence in conjunction with slice-(2D) or volume-(3D)selective magnetic field gradients [7]. At low-to-high fields, spsp pulses are increasingly used because they offer shorter TRs and are less sensitive to magnetic field inhomogeneities than FATSAT preparations [7].…”

Section: Introductionmentioning

confidence: 99%

“…At low-to-high fields, spsp pulses are increasingly used because they offer shorter TRs and are less sensitive to magnetic field inhomogeneities than FATSAT preparations [7]. While susceptibilityrelated field inhomogeneities can be confined to 100-200 Hz even at 7 T the chemical fat-water shift amounts to ∼1,040 Hz as compared to ∼440 Hz at 3 T and ∼220 Hz at 1.5 T. As a result, especially at ultra-high fields, alternative selective water excitation schemes may become applicable that are too time-consuming at low fields.…”

Section: Introductionmentioning

confidence: 99%

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Optimized spectrally selective steady-state free precession sequences for cartilage imaging at ultra-high fields

Bieri

Mamisch

Trattnig

et al. 2007

Magn Reson Mater Phy

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Object Fat suppressed 3D steady-state free precession (SSFP) sequences are of special interest in cartilage imaging due to their short repetition time in combination with high signal-to-noise ratio. At low-to-high fields (1.5-3.0 T), spectral spatial (spsp) radio frequency (RF) pulses perform superiorly over conventional saturation of the fat signal (FATSAT pulses). However, ultra-high fields (7.0 T and more) may offer alternative fat suppression techniques as a result of the increased chemical shift. Materials and methodsApplication of a single, frequency selective, RF pulse is compared to spsp excitation for water (or fat) selective imaging at 7.0 T. Results For SSFP, application of a single frequency selective RF pulse for selective water or fat excitation performs beneficially over the commonly applied spsp RF pulses. In addition to the overall improved fat suppression, the application of single RF pulses leads to decreased power depositions, still representing one of the major restrictions in the Conclusion The ease of applicability and implementation of single frequency selective RF pulses at ultra-high-fields might be of great benefit for a vast number of applications where fat suppression is desirable or fat-water separation is needed for quantification purposes.

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Design of improved spectral-spatial pulses for routine clinical use

Cited by 63 publications

References 14 publications

Diz Eklemi: Kikirdak

Diz Eklemi: Kikirdak

Pulse sequence for dynamic volumetric imaging of hyperpolarized metabolic products

Optimized spectrally selective steady-state free precession sequences for cartilage imaging at ultra-high fields

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