Satoshi Yoshioka

1972年に登場したCTは,生体の中を観察する夢を現実のものとした.耳鼻咽喉科領域においてもその恩恵に預かっていることは論を待たないが,近年,さまざまな革新的な技術が開発され,単に断面を撮影するツールとしての位置づけを凌駕するようになった.新しいCT技術と,その耳鼻咽喉科領域における応用について概説する.1980年代後半,らせん状にスキャンするという現在のCTの基本概念が確立した.一方,2006年頃,ADCTといわれる圧倒的に広い多列検出器を持つ機器が登場した.寝台移動なしに検出器が高速1回転で撮影するため,画像のどの部分でも同じ時相となる.被曝が低減し,極めて短時間で撮影ができる.また,連続スキャンによる動的な撮影(4DCT)が可能である.嚥下動態,呼吸動態,耳管の挙動,発声,関節運動,血流などの機能の評価に使用できる.さらに,本機による超低被曝での撮影は小児において特に有用である.関心領域の近傍に金属がある場合に発生する金属アーチファクトは,従来回避不能であったがこれを低減する技術がMARである.歯科金属の影響を受ける口腔咽頭(中咽頭,舌),唾液腺領域の撮影で威力を発揮する.極めて高精細な描出能を持つCTが2017年に開発された.従来機の倍密度の画素を有し,また小焦点管球を具有することで画像が極めてシャープとなり,最高空間分解能は0.15mmとなった.耳科領域で特に有用であり,耳小骨形態の評価,耳硬化症の診断,真珠腫の進展の態様の評価などに利用できる.舌癌の深達度診断,鼻副鼻腔の微細骨構造などにも有用である.人工知能やDeep learningの活用,デュアルエナジー撮影による画質向上と低被曝化,立位CTによる全く新しい生理学的評価など,次世代のCT技術開発がさらに進行中である.(著者抄録)

Patulous Eustachian Tube (PET) is of increasing importance in otology. However, despite the abundance of diseases requiring a differential diagnosis from PET, such as superior semicircular canal dehiscence syndrome, perilymphatic fistula, acute low-tone sensorineural hearing loss, etc., there are currently no established diagnostic criteria for PET. In view of these circumstances, the Japan Otological Society (JOS) Eustachian Tube Committee proposed the diagnostic criteria for Patulous Eustachian Tube in 2012, in order to promote clinical research on PET. A revision was made in 2016, maintaining the original concept that the criteria should be very simple, avoid any contamination of “Definite PET” with uncertain cases. Moreover, it was also intended to minimize the number of cases that could be accidentally excluded even in the presence of some suspected findings (“Possible PET”). The criteria can be used by all otolaryngologists even without using the Eustachian tube function test apparatus. However, the use of such an apparatus may increase the chances of detecting “Definite PET”. The algorithm for the diagnosis of PET using the criteria has also been described. The JOS diagnostic criteria for Patulous Eustachian Tube will further promote international scientific communication on PET.

<p>Despite apparent ability of computed tomography (CT) in clinical practice, otology, which requires diagnosis and treatment of variaous diseases involve very small areas and sometimes entails a limitation on the performance of CT in depicting lesions located in such areas. Recently, ultra-high-resolution (UHR) CT, which can provide images at dramatically higher spatial resolution than ever before, has been developed and has become commercially available. UHRCT has a pixel size (0.25×0.25 mm) twice comparing dense in both vertical and horizontal directions as conventional high-resolution (CHR) CT and the maximum spatial resolution of 0.15mm or less in the axial direction. The maximum size image is 2048×2048 pixels. Here, we report our experience of the early stage development of UHRCT in the field of otology.</p><p>We performed UHRCT scan in otology patients and compared the images obtained from UHRCT with those obtained from CHRCT. Spatial resolution in UHRCT images was obviously improved. Tiny structures, such as the chorda tympani and ossicles, and small pathological changes caused by the progression of otitis media, etc. were clearly depicted. Due to an increase in the partial volume effect, improvements such as the performance of UHRCT in depicting soft-tissue lesions or lesions adjacent to the bone, were considered to be difficult to depict at CHRCT.</p><p>The tiny structures which had been indistinct before, became clearly visible due to UHRCT, indicating the possibility of providing important information for clinical practice. However, because the issues include the necessity of building infrastructure (including display) and a powerful computer system enough to save and handle huge volume of data, it is necessary to examine the further usage of UHRCT in the future.</p>

中耳から補聴器のイヤモールド印象材を手術的に除去した2症例を報告した。症例1は持続的な耳漏を主訴とする78歳男性。当初は慢性中耳炎と診断され保存的療法を受けていたが耳漏の改善は見られなかった。その後の検査で鼓室に異物を認め、その異物の素材分析により印象材であることが判明した。その後の問診で患者は約15年前に補聴器のイヤモールドを調製したことを思い出し、鼓室形成術を受けて異物除去に成功した。症例2はcanal wall down型鼓室形成術を受けた84歳女性で、左耳に印象材を注入されたが、その除去を受けていなかった。検査で乳突腔に埋入した印象材を認め、耳介後部の切開による異物を摘出した。いずれの症例でも、患者の病歴の問診、鼓膜の十分な検査、術後の補聴器フィッティング関連のリスクへの注意、ならびに不注意による補聴器フィッティング時の印象材押し込みの回避が重要になると考えられた。

小児の耳管の成人との相違を形態面・機能面から概説した。形態的には、小児の耳管は短く、耳管咽頭口が小さく、耳管軟骨部が平坦である。機能的には、過度なコンプライアンスをもち、圧負荷による通過は良好であるのにフレーム構造は脆弱なため、陰圧や炎症で容易に閉塞し、能動的に開大しにくい。小児では中耳疾患が高頻度に発生するが、これらの特徴にその要因がある可能性がある。胃食道逆流現象の関与や特殊症例についても触れる。(著者抄録)

OBJECTIVE: The Eustachian tube is difficult to evaluate because it is located deep in the head. However, the introduction of 320-row area detector CT has made it possible to evaluate this region. In the present study, movement of the Eustachian tube during sniffing was visualized using area detector CT in patients with patulous Eustachian tube. METHODS: Four patients with patulous Eustachian tube were examined using an area detector CT scanner (Aquilion ONE, Toshiba). This scanner supports 320-row scanning of 0.5-mm slices at up to 0.275 s/rot., eliminating temporal mismatch between various parts of the acquired images and permitting 4-dimensional CT (4DCT) images to be obtained by continuous scanning. The scan conditions were 120 kV, 120 to 150 mA, 0.5 mm × 280 to 320 slices, and 0.35 seconds per rotation × 9 rotations. The patient was seated on a reclining chair tilted to 45 degrees and was instructed to sniff during continuous scanning. Images of the Eustachian tube were generated at 0.1-second intervals. CONCLUSION: At the start of sniffing, the cartilaginous portion of the Eustachian tube closed from the isthmus toward the pharynx. The starting point differed from patient to patient. In patients with patulous Eustachian tube, sniffing (an unconscious habit that helps to relieve ear discomfort) is an important factor in the development of middle ear diseases. We have successfully depicted this event for the first time, demonstrating various patterns of Eustachian tube closure during sniffing in patients with patulous Eustachian tube. This method may be useful for evaluating Eustachian tube dysfunction. Copyright © 2013 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

Although modern multislice CT systems can quickly scan a wide range in fine detail, the high exposure dose and long examination time of CT studies are still important issues. CT is therefore generally considered to be unsuitable for screening. This is particularly true for pediatric patients, who are especially sensitive to radiation, and plain radiography is therefore frequently selected for examination of the temporal bone. We have developed an ultra-low-dose CT imaging method using a 320-row area detector CT (ADCT) scanner that may be suitable for screening for diseases of the ear even in pediatric patients.<BR>Temporal bone specimens were scanned with an ADCT scanner (Aquilion ONE^<TM>, Toshiba Medical Systems, Otawara, Japan) using various scan conditions. Image quality was evaluated, and the optimal scan conditions providing clinically acceptable images at the lowest possible exposure dose were identified. A human-body phantom was then scanned with ADCT using these scan conditions. Plain radiography using the Schu..ller method was also performed for the same phantom to acquire images of the temporal bones bilaterally. The CT and radiographic exposure doses were compared to assess the suitability of our ADCT method for screening.<BR>The gantry of the ADCT scanner includes an X-ray source unit and a detector (area detector) which is several times larger than that used in a conventional CT system. Three-dimensional data can be acquired over a wide range in a single high-speed rotation, making it possible to quickly obtain images in the same temporal phase.<BR>As the results, the optimal scan conditions were found to be tube voltage 100 kV, tube current 10 mA, and exposure time 1.5 s/rot. by 1 rotation. The CTDIVOL (standard dose) was 1.7 mGy, which is 0.7% of the usual value of 243.4 mGy. The maximum skin dose to the head in plain radiography of the temporal bones bilaterally was 2.12 mGy on average. The maximum skin dose to the external ear in CT scanning with the above conditions was 1.59 mGy on average, which was lower than that for the Sch&uuml;ller method. However, the dose in CT scanning was slightly higher at the front and rear.<BR>With our proposed CT imaging method, images are acquired in a very short time, three-dimensional image data is obtained, and the exposure dose is equal to or lower than that of plain radiography. This method is therefore expected to be a useful new tool for morphological screening examinations.

Since impairment of functions of the Eustachian tube can lead to various diseases of the middle ear, it is considered that morphological and functional evaluation of the Eustachian tube is of clinical importance. However, it has been difficult to evaluate the Eustachian tube because it is located deep in the head, and most of the morphological studies conducted in the past have been based on the examination of specimens obtained from cadavers. One limitation of such studies is that dynamic processes in the living body cannot be evaluated. Multislice CT permits the Eustachian tube to be evaluate greater detail in living subjects and has provided new findings in morphological studies. Furthermore, the latest Area Detector CT systems allow dynamic studies to be performed. This report describes the basic principles of this examination technique and presents the latest findings obtained by analysis of the morphological and functional characteristics of the Eustachian tube using Multislice CT and Area Detector CT.

A 320-detector-row multislice computed tomography (320-MSCT) scanner can acquire a volume data set covering a maximum range of 16 cm and can generate axial images 0.5-mm thick at 0.5-mm intervals. Three-dimensional (3D) images reconstructed from the thin axial slices include multiplanar reconstruction and 3D-CT. Single-phase 3D images are reconstructed from 0.175-s data, and multiphase 3D images are created in 29 phases at intervals of 0.1 s. Continuous replay of these 3D images produces four-dimensional moving images. In order to determine the feasibility of the morphologic and kinematic analyses of swallowing using 320-MSCT, single- phase volume scanning was performed on three patients and multiphase volume scanning was performed on one healthy volunteer. The single-phase 3D images clearly and accurately showed the structures involved in swallowing, and the multiphase 3D images were able to show the oral stage to the early esophageal stage of swallowing, allowing a kinematic analysis of swallowing. We developed a reclining chair that allows scanning to be performed with the subject in a semisitting position, which makes swallowing evaluation by 320-MSCT applicable not only to research on healthy swallowing but also to the clinical examination of dysphagia patients. © 2010 Springer Science+Business Media, LLC.

A 320-row area detector CT scanner was used to assess foreign bodies in the bronchi of pediatric patients. This system, which employs a detector of 0.5 mm &times; 320 rows, permits a range of up to 160 mm to be scanned in a single rotation at a maximum scan speed of 0.35 s/rot. This makes it possible to perform imaging with no temporal mismatch between any parts of the acquired images and to acquire consecutive three-dimensional dynamic image data over time by continuous rotation (4DCT).<br>The subjects were 4 pediatric patients in whom the presence of a foreign body in the bronchi was suspected. The system used was a 320-row CT scanner (Aquilion ONE, Toshiba). Multiplanar reconstruction (MPR) images and three-dimensional CT (3DCT) images were generated. In addition, consecutive four-dimensional dynamic CT (4DCT) images were obtained over time.<br>With this system, scanning can be completed instantly, permitting examinations to be performed without sedation. In stationary images, artifacts due to respiration and cardiac contraction (which are unavoidable with conventional scanning methods) can be completely eliminated, and the continuity of images as well as the visualization of peripheral bronchi are significantly improved.<br>This leads to greater diagnostic confidence when evaluating small or multiple foreign bodies. 4DCT permits dynamic observation to be performed easily, which is useful, for example, for detecting the presence of a foreign body in the peripheral bronchi or evaluating incomplete ventilation of a part of the lung. In other words, the CT system can also be used to assess lung function. In addition, the exposure dose can be reduced to within permissible limits. It is therefore concluded that 320-row area detector CT is very useful as a new imaging tool for the evaluation of the bronchi and lungs.

We clarified the disease pathophysiology caused by Eustachian tube disfunction by examining the difference in each age of the Eustachian tube form. We measured the living human Eustachian tube using multislice CT (MSCT). Comparing without skew or contraction in case of cadaveric spesimens the length of each part of the Eustachian tube, the diameter, and the angle based on the image data obtained by MSCT for all age groups in our study, which involved 48 samples from adults and 31 from chidren (23 ears under 7 years old). We classified specimens from those less than 6 years old as the infant-youngchildren group, and from those 7 years or older as the schoolchildren-adult group. Mean total length, cartilage part length, and bony part length was, as expected, longer in schoolchildren-adult group than infant-youngchildren group, as was the pharyngeal orifice diameter. The mean angle between the bony part and cartilage part was more acute in schoolchildren-adult group, as was the cartilage part steepness. We proved a characteristic of three-dimensional anatomy of a child Eustachian tube in living human organism.

Morphological aberration of the Eustachian tube is a significant factor of various middle ear diseases.<BR>Traditionally, cadaveric specimens have been used for studies on the morphology of Eustachian tubes.However, this approach was not too efficient, as samples were limited in number as they were difficult to obtain, and biological conditions were not reflected due to rigor mortis and atrophy during specimen preparation.<BR>We thus decided to use Multi-Slice CT (MSCT) to perform 3-D anatomic measurements of the Eustachiantube. MSCT has benefits of isotropy and high resolution, and it is useful in preparing images of any plane.<BR>Forty-eight adults were studied. For the purpose of measurement, various anatomic indices were carefullyand precisely defined to identify each area on the image. Calculations based on each coordinate value enabledthe measurement of length, diameter and angle of the Eustachian tube of normal adults.<BR>Therefore, measurements of the Eustachian tube, which were traditionally difficult as it is located in the deeppart of the cranium, were simplified in many specimens.<BR>Mean value of total length was 39. 2&plusmn;3. 2 mm, cartilage part length of the tube 30.0&plusmn;2.7mm and bony part9.2&plusmn;1.6mm. Mean values of diameter of tympanic orifice were 5.2&times;3.2mm, and pharyngeal orifice 9.7&times;4.4mm. Mean value of angle between bony part and cartilage part was 160.9-13.6 degrees.<BR>This approach to anatomic measurement is expected to contribute greatly to investigation on various middleear diseases.

We demonstrated high-resolution multiplanner reformation (MPR) and 3-dimentional CT (3D-CT) imaging of Eustachian tube (ET) using a 1-mm, 8-row multislice CT scanner.<BR>CT scans were performed in 5 normal adult volunteers during quiet breathing and the Valsalva maneuver.<BR>Bony portion of ET was clearly detected on MPR, however cartilaginous portion of the ET was still elusive during quiet breathing scan.<BR>MPR and 3D-CT images during Valsalva maneuver improved visualization of cartilaginous portion of the ET and surrounding soft tissues including cartilage, muscle and fat.<BR>Imaging of the ET obtained by multislice CT during the Valsalva maneuver can propose further investigation for various middle ear disorders.