201020542 六、發明說明： 【發明所屬之技術領域】 本發明係有關於一種超音波成像裝置及方法，尤指一 種可增加訊雜比以及改善成像深度者。 【先前技術】 • 超音波影像系統已廣泛地使用於生物醫學上的偵 測。目前超音波影像技術主要利用脈衝回波（pu 1 se-echo) 的方式來成像’其原理乃由發射端於每個陣列探頭元素 (array element)發射一短脈衝波（puise)，藉由發射波束 成型（beamf orm i ng)調整每個頻道（channe 1)脈衝波之時間 延遲以及增益大小’將整個陣列信號聚焦於一條掃瞄線 (scan line)上的一個固定深度位置，之後藉由數位轉類比 裝置’將仏號類比化’再藉由陣列探頭（Transducer array) ❹將電信號轉化為超音波信號傳遞出去。於接收端部分，所 欲觀察的組織藉由背散射（back-scattering)的方式回傳 信號’此時超音波系統藉由發射/接收切換裝置（T/R switch)，將接收信號導向接收端系統等候所回傳的信號， 首先陣列探頭先將機械波轉化成電信號，隨即每個頻道的 4s號經由放大、濾波以及類比轉數位裝置進行取樣，之後 每個頻道所取樣的數位信號進入動態聚焦（dynamic focusing)波束成型裝置，其原理乃根據此條掃瞄線上的每 個空間取樣點，動態地調整每個頻道信號的時間延遲以及 增益大小，並且將所有頻道的信號加總起來，之後藉由包 201020542 絡偵測器將聚焦後的信號強度取出。上述過程為一條掃瞄 線的成像步驟，之後發射波束指向下一條掃瞄線重複上述 成像過程’所有掃瞄線所組合成的影像再經由掃瞄轉換裝 置（scan conversion)，將影像格式轉換成格狀式（grid)， 之後於顯示裝置展示影像。 目前超音波影像系統主要的限制之一在於穿透深度 以及訊雜比（signal-to-noise ratio, SNR)的不足，這兩 者之成因乃超音波於組織有訊號衰減（attenuati〇n)的現 ❷ 象，考慮頻率相依（frequency dependent)之衰減現象，典 型的哀減係數值（attenuation coefficient)介於0.5〜1 dB/MHz/cm，此值會隨著操作頻率以及成像深度變大而增 加’以中心頻率8 MHz、衰減係數〇. 6為例，在1〇公分深 度之彳§號較探頭表面之信號減少約96 dB，換句話說，如 果系統欲增加5公分的成像深度，則訊號強度或是訊雜比 需提高48 dB才能維持原深度的成像品質。頻率相依之衰 減現象在高頻系統更為嚴重，相較於上述低頻系統，高頻 ❹ 超音波系統（頻率高於20MHz)擁有更佳的空間解析度，可 偵測更為細微的組織，由於訊號衰減程度隨頻率上升，因 此有限的穿透深度大大地限制了目前高頻系統的應用。 增加信號於人體内的穿透深度可藉由提高發射信號 強度來達成，而發射信號強度的提高可藉由調整脈衝波的 大小以及持續時間（duration)來完成，為了防止瞬間信號 功率過大造成人體不良的影響，脈衝波的大小必須限制: 無法毫無限制的增加，另一方面，增加脈衝波的持續時間 會造成訊號頻寬過小’影響影像的空間解析度，以上兩種 作法皆有其限制，無法有效地增加穿透深度以及訊雜比。 4 、 201020542 為了增加信號持續時間以及同時維持信號頻寬及保 有原本空間解析度的一個作法是發射展頻信號 (spread-spectrum)，稱為編碼激發（coded excitation) 系統，圖一 A及圖一 B分別為習知編碼激發系統架構示意 圖以及習知脈衝激發（pulsed excitation)系統架構示意 圖，一些展頻訊號如PN碼（pseudo random)、線性調頻碼 (linear FM or chirp)或是Barker碼，由於擁有較大的 時間頻寬乘積（time-bandwidth product)，可以藉由脈波 壓縮濾波器（pulse compression filter)將一長持續時間 的訊號壓縮成一短脈衝波，還原其空間解析度，脈波壓縮 遽波器主要分為匹配（matched f i 1 ter)以及非匹配滤波器 (mismatched filter)兩種’理論上’編碼激發系統所能達 到最大訊號強度或訊雜比增加的幅度約等於時間頻寬乘 積，以8MHz中心頻率、5MHz頻寬，展頻信號長度為2〇微 秒為例，訊雜比增加了 20 dB，以上述計算衰減值為例， 可等效增加穿透深度達2公分’因此，編碼激發系統能夠201020542 VI. Description of the Invention: [Technical Field] The present invention relates to an ultrasonic imaging apparatus and method, and more particularly to an apparatus for increasing the signal-to-noise ratio and improving the imaging depth. [Prior Art] • Ultrasonic imaging systems have been widely used in biomedical detection. At present, ultrasonic imaging technology mainly uses pulse echo (pu 1 se-echo) to image 'the principle is that the transmitting end emits a short pulse wave (puise) in each array element of the array, by transmitting Beamforming adjusts the time delay and gain size of each channel (channe 1) pulse wave to focus the entire array signal on a fixed depth position on a scan line, followed by a digital bit The analog analog device 'classifies the nickname' and transmits the electrical signal into an ultrasonic signal by means of a Transducer Array. At the receiving end, the tissue to be observed returns the signal by back-scattering. At this time, the ultrasonic system directs the receiving signal to the receiving end by means of a T/R switch. The system waits for the signal to be returned. First, the array probe first converts the mechanical wave into an electrical signal, and then the 4s of each channel is sampled by the amplification, filtering, and analog-to-digital device, and then the digital signal sampled by each channel enters the dynamic state. A dynamic focusing beamforming device that dynamically adjusts the time delay and gain of each channel signal based on each spatial sampling point on the scanning line, and sums up the signals of all channels, after which The focused signal strength is taken out by the packet 201020542 detector. The above process is an imaging step of a scan line, and then the transmit beam is directed to the next scan line to repeat the above-mentioned imaging process. The image combined by all the scan lines is converted into an image conversion format by a scan conversion. A grid is displayed, and then the image is displayed on the display device. One of the main limitations of the current ultrasound imaging system is the depth of penetration and the lack of signal-to-noise ratio (SNR), which are caused by ultrasonic attenuation of the signal in the tissue. Now, consider the frequency dependent attenuation phenomenon. The typical attenuation coefficient is 0.5~1 dB/MHz/cm. This value will increase with the operating frequency and imaging depth. 'With a center frequency of 8 MHz and an attenuation coefficient 〇. 6 as an example, the 彳 § at 1 〇 depth is about 96 dB less than the signal on the probe surface. In other words, if the system wants to increase the imaging depth by 5 cm, then The signal strength or signal-to-noise ratio needs to be increased by 48 dB to maintain the original depth of imaging quality. The frequency-dependent attenuation phenomenon is more serious in high-frequency systems. Compared with the above-mentioned low-frequency systems, the high-frequency ❹ ultrasonic system (frequency higher than 20MHz) has better spatial resolution and can detect finer structures due to The degree of signal attenuation increases with frequency, so the limited penetration depth greatly limits the application of current high frequency systems. Increasing the penetration depth of the signal in the human body can be achieved by increasing the intensity of the transmitted signal, and the improvement of the transmitted signal strength can be achieved by adjusting the magnitude and duration of the pulse wave, in order to prevent the transient signal power from being excessively large. Bad effects, the size of the pulse wave must be limited: can not increase without limit, on the other hand, increasing the duration of the pulse wave will cause the signal bandwidth to be too small 'influencing the spatial resolution of the image, both of which have their limitations It is not possible to effectively increase the penetration depth and the signal-to-noise ratio. 4 , 201020542 One way to increase the signal duration and maintain the signal bandwidth while maintaining the original spatial resolution is to transmit a spread-spectrum, called a coded excitation system, Figure 1A and Figure 1. B is a schematic diagram of a conventional coded excitation system architecture and a schematic diagram of a conventional pulsed excitation system architecture. Some spread spectrum signals such as PN code (pseudo random), linear FM code (linear FM or chirp) or Barker code, due to With a large time-bandwidth product, a long duration signal can be compressed into a short pulse wave by a pulse compression filter to restore its spatial resolution and pulse compression. The chopper is mainly divided into matched fi 1 ter and mismatched filter. The two theoretically encoded excitation systems can achieve the maximum signal strength or the increase of the signal-to-noise ratio is equal to the time-frequency product. Taking the 8MHz center frequency, 5MHz bandwidth, and the spread spectrum signal length as 2〇 microseconds as an example, the signal-to-noise ratio is increased by 20 dB. In the above-described calculated attenuation value, for example, may be equivalent to increasing the penetration depth of 2 cm 'Thus, the coding system can excite
有效的增進訊號強度，一方面亦能夠維持良好的空間解析 度0 圖一 A及圖二B均為習知編碼激發系統之架構示: 圖。其中圖二A之脈波壓縮滤波器係置於波束成型哭之) 而圖《-Β之脈賴誠波輯置於波束成—之後: 於傳統脈衝激發系統，編碼激發超m賊財效如 加穿透深度’提高系統訊雜比，其跟傳統㈣在架構上d 要的差異除了需要發射展頻彳士骑卜 縮，來回復其空間 動m皮束成型之前，每㈣職遵需自行先完成㈣ 5 201020542 壓縮（如圖一 A所示），如此才能正確壓縮成短脈衝信號， 如欲將脈波壓缩據波器置於波束成型器之後，如圖二B所 二丄f會1^成展頻信號的壓縮錯誤，無法正確還原成短脈 衝仏號”成因乃因為動態聚焦之波束成型所致，圖三A及 圖B刀别為動態聚焦以及固定聚焦之波束成型對於脈波 壓縮的效應不意圖，如圖三A及圖三B所示，假設單一散 射點位於發射聚焦位置，在接收端方面，由於動態聚焦之 波束成型裝置需對每個成像深度聚焦，因此所需要的延遲 ❿時間曲線（亦即，每個陣列頻道對應的延遲時間）會隨深度 變化如此將會造成信號加總（beamsum)之後的變形，造成 脈波，縮滤波器的壓縮錯誤，反之而言，當波束成型裝置 為固定聚焦的情泥下（亦即，對某深度聚焦），則每個成像 深度所對應延遲時間曲線一致’在此情況下，加總後的信 號會跟原發射波形一致，脈波壓縮濾波器能夠正確的還原 成短脈衝纟&合上述討論，在沒有補償的情況下，脈波 壓縮濾波器只能夠置於動態聚焦波表成型裝置之前，才能 〇 正確地壓縮展頻信號。 但在動態聚焦的架構τ ’由於每個陣列頻道需配備脈 縮濾波器，相較於傳統脈衝激發系統，編碼激發系統 ?，體複雜度將大幅提高。以256個陣列探頭元素、展頻 信號長度20微秒、接收端系統取樣頻率4〇 ΜΗζ、以及脈 波壓縮滤波器長度等於30微秒為例，則脈波 ⑽數目達測個，因此，所有頻道全狀總⑽ 達3G72G0個丨#此魔大數目將大幅度提升系統複 雜度。 因此，如何研發出一種超音波成像裝置及方法，其可 6 201020542 增加訊雜比以及改善成像深度並減少系統複雜度，將3木 發明所欲積極探討之處。 疋 【發明内容】 本發明提出一種超音波成像裝置及方法，其主要特性 為可增加訊雜比以及改善成像深度並減少系統複雜度。' 本發明之一樣態為一種超音波成像裝置，包含^— • 發射單元，其係用以產生一編碼信號，並將該編碣信號加 以濾波、放大及聚焦；一換能器探頭，其與該發射 接，以做為聲壓與電之間的轉換器，其係為陣列多頰=妹 構，並具有複數個發射及複數個接收頻道，以將該發 疋之編碼信號，傳送至一物體，並接收該物體之回波:單 一接收單元，其與該換能器探頭耦接，以接收該回波I號； 一波束成型單元，其與該接收單元耦接，以將該回； 加以放大、濾波並執行信號聚焦，以產生複數個_/铋逯 ❹波束；一脈波壓縮濾波單元，其與該波束成型單:綠或 以壓縮該些掃瞄線或波束；以及一空間濾波器，其接， 波壓縮濾波單元輕接，以將該些掃瞄線或波束錯存、讀脈 合該些掃瞄線或波束，對選定之一影像區域進行癔竣趂結 本發明之另一樣態為一種超音波成像方法，。 列步驟： 、巴含下 利用一發射單元傳送一編碼信號，以將該蝙螞作^ 定聚焦於-深度，並藉由一換能器探頭發射； 說固 利用一接收單元接收自該換能器探頭每個頰道樓 回波信號，並完成聚焦，以得到複數個掃瞄線或竣東.的 201020542 利用一脈波壓縮濾波單元壓縮該些掃瞄線或波束；以 及 利用一空間濾波器結合該些掃瞄線或波束，根據所選 定之影像區域進行滤波。 藉此可增加超音波成像的訊雜比以及改善成像深度並 減少系統複雜度。 【實施方式】 ❿ 為充分暸解本發明之特徵及功效，茲藉由下述具體之 實施例，並配合所附之圖式，對本發明做一詳細說明，說 明如後： 圖四為本發明之具體實施例的系統架構示意圖，請參 考圖四，本發明為一種超音波成像裝置1，包含有：一發 射單元2，其係用以產生一編碼信號，並將該編碼信號加 以濾波、放大及聚焦，其中該發射單元2包含波形產生器， 其可為雙極性（bipolar)以及單極性（unipolar)的波形產 瘳 生器，而該編碼信號的波形可為任一個具有高時間頻寬乘 積之展頻信號，例如PN碼、線性/非線性調頻以及Barker 碼等；.一換能器探頭3，其與該發射單元2耦接，以做為 聲壓與電之間的轉換器，其係為陣列多頻道結構，並具有 複數個發射頻道及複數個接收頻道，以將該發射單元2之 編碼信號，傳送至一物體4，並接收該物體4之回波信號， 其中該換能器探頭3係為一維或二維陣列結構；一接收單 元5，其與該換能器探頭3耦接，以接收該回波信號；一 波束成型單元6，其與該接收單元5耦接，以將該回波信 8 201020542 號加以放大、濾波並執行信號聚焦，以產生複數個掃瞄線 或波束，其中該接收單元5内的信號聚焦係可固定聚焦於 一深度以產生一聚焦點或是可固定聚焦於複數個深度以產 生複數個聚焦點，且該些聚焦點之間的距離需大於或等於 該編碼信號的長度，另外前述之聚焦點可以跟該發射單元 2所設定之聚焦點相同或相異；一脈波壓縮濾波單元7(例 如，匹配濾波器或非匹配濾波器），其與該波束成型單元6 耦接，以壓縮該些掃瞄線或波束；以及一空間濾波器8， φ 其與該脈波壓縮濾波單元7耦接，以將該些掃瞄線或波束 儲存，並結合該些掃瞄線或波束，對選定之一影像區域進 行濾波。一般來說，為使能夠呈現特定影像區域之内容， 較佳係更包含一包絡偵測及掃描轉換單元9，其與該空間 濾波器8耦接，以對該影像區域進行包絡偵測及掃描轉 換，並且本發明可更包含一顯示裝置10，其與該包絡偵測-及掃描轉換單元9耦接，以顯示該影像區域之影像，其中 該影像區域之影像可為一維、二維或三維影像。 φ 圖五為本發明之具體實施例的方法步驟圖，請參考圖 五，本發明為一種超音波成像方法，首先利用一發射單元 傳送一編碼信號，以將該編碼信號固.定聚焦於一深度，並 藉由一換能器探頭發射；接著利用一接收單元接收自該換 能器探頭每個頻道接收的回波信號，並完成聚焦，以得到 複數個掃瞄線或波束，其中該接收單元内的信號聚焦係可 固定聚焦於一深度以產生一聚焦點或是可固定聚焦於複數 個深度以產生複數個聚焦點，且該些聚焦點之間的距離需 大於或等於該編碼信號的長度；之後利用一脈波壓縮濾波 單元壓縮該些掃瞄線或波束；之後利用一空間濾波器結合 201020542 該些制線缝束，根據所敎之f彡像區域進行 著利用該”m將該波束暫存；=拖接 加濾波之影像區域；以及最後根據相對 ^ 係數1中該係數可搭配該影像區域之訊雜比^為中之 圖/、為本發明之接收單元複數個 =;區域示意圖，其係將影像劃二;=個! 3=用單-固定聚焦點，為了方便呈現，圖中 點如圖六所示’每個子區域都配以單-個2 聚“、、點可於子區域之任意位置，不限於子區 〜 =聚=避免子區域過多’造成脈波壓縮的錯 ==對於脈波墨縮的效應)，因此，各個子區域聚(：同 以下：私應不以小於發射編碼信號的長度為基準:、、點 七為本發明之元:::圖步說明’圖 φ 器，每個第一延遲器 決疋之聚焦點與個別陣列夕 里則根據一預先 而每個第-乘法器12所乘上^相對置除以聲速決定， 重），或是傳統上置，可以一致（即不施予權 六所示之多區域聚焦。 “、、"可為早一聚焦，或如圖 而前述之脈波壓縮濾波單 回復其原有之空間解析度。一：：功能為壓縮編碼信號， 可，配滤波器以及非匹4、=波壓縮f皮單元 頻率響應乃為原編碼信號之兩種。匹配遽波器的 ^%的共軛複數，匹配濾波器 201020542 的優點是訊雜比的提升為理論上之最蚀 度跟僅需跟原編碼信號的長度—致即彳/滤波器的長 旁波瓣（sidelGbe)有其—定的準趨制=是壓縮後的 受影響“目較而言，非匹配遽波 =的對比度會 比’以及遽波器長度需要比原“此犧牲-些訊雜 圖八為本發明之空間濾波器架構圖， ❹ f ㈣t'波器8包含：—暫存器Η ’其與該脈波壓縮 ^單=7 以暫存該些掃崎或波束二訊雜比估 :::14 ’其與該暫存器13輕接，並根據該些掃瞒線或 估計該影像區域⑽訊雜比；—紐裝置15，其與該 暫^器13 _，並根據該些掃m皮束對該影像區域進 仃濾波，其中該濾波裝置15係為一維、二維或三維架構， =刀別對應所選定之-維、二維或三維影像區域；一記憶 體16,其儲存該空間濾波器8的係數；以及一查表裝置17, 其與該3fl雜比估計單兀14、該記憶體16及該濾波裝置15 耗接’以儲存該空間濾波器8的係數、該影像區域之訊雜 比以及該影像區域所在深度三者之間的對錢係，一般來 空間m 8的功能有；：—為補償接收單元因固定 聚焦所造成不佳的影像品質’二為改善脈波壓縮後信號可 能存在的旁波瓣’進而讓影像品質能逼近雙向動態聚焦的 影像品質。 圖九為本發明之訊雜比估計單元的訊雜比估計流程 圖，請參考圖九，由於濾波器係數的設計乃針對該影像區 域之所在深度，放置單-散射點，然後成像，此單一散射 之，ρ像稱為點擴散函數（p〇int spread functi〇n， 201020542 PSF)，PSF的求得可藉由兩種方式：藉由實驗方式以及電 腦模擬方式。一旦取得PSF，則可根據此PSF，設計最佳的 濾波器係數。文獻中已有關於利用空間濾波器來改善傳統 脈衝激發超音波系統的影像品質，但並無用於編碼激發超 音波系統。這裡，本發明採用最小平方法（least_sqau]res) 的原則來設計最佳空間濾波器係數，我們定義其價值函數 (cost function) E 為： E^fH(aQ+(l-a)I)f + ku(Cf-D)⑴ 籲 其中，f代表所欲求得之空間濾波器係數，其可為一維、 一維或二維架構；Q代表所欲最小化之旁波瓣區域所形成 之摺積矩陣（convolution matrix) ; I代表單仇陣列 (identitymatrix)，即除了矩陣之對角線為丨之外，其他 元素皆為0 ; α為一可調整之純量值，介於04之間了入 為一純量值丨C跟D定義為兩者之間關係Cf = D，為所設 定影像區域内固定的值。根據上式，則最佳濾波器係數化 為： ® f0 =(^Q+(l-a)I)-lCu(C(aQ+(l-a)I)~lCHylD ⑵ 式（2)顯示最佳濾波器係數可隨著α而變。為了了解不同 α值的選擇對於濾波後影像的影響，圖十為點擴散函數 (PSF)經過空間濾、波器後的♦值功率（peak power)與旁波 瓣的關係波形圖。圖中上、下曲線分別對應一維及二維空 間滤'波器’每條曲線上的值相對於式（2)中α值（介於ο」 之間）。此PSF位於Π公分的位置，系統發射、接收分別 固定聚焦於12、15公分。一維濾波器係數的個數為橫向 19個’二維濾波器在深度方向多了 5偭。由圖十可知，濾 12 201020542 波後的峰值與旁波瓣兩者之間存在妥協（trade-off)的關 係，而兩者之間的關係等效於訊雜比與影像對比度之間的 關係，而對於二維濾波器而言，此關係尤甚明顯，由圖可 知，訊雜比與影像對比度兩者之間最佳的妥協位置乃位於 轉折點處（即α =0. 2的位置）。因此，根據圖十，我們可以 分析在不同影像訊雜比（尚未經過空間濾、波器之前）的情況 下，每條曲線的轉折點，以便決定最佳α值以及式（2)最 佳濾波器。 • 圖十一為不同深度所求得的一維空間濾波器示意 圖，以空間濾波器採用一維架構，共25個濾波器係數為 例，因此圖八中之暫存器需預先儲存至少25條掃瞄線，由 於空間濾波器會隨著深度而變化，因此每隔5公釐的位置 我們重新設計一組新的濾波器，如此根據前述之方式，我 們便可求得不同深度之一維空間濾波器。· 為了驗證本案所提出的編碼激發超音波成像系統之 可行性，我們採用電腦模擬不同深度散射點之成像結果， φ 於深度10公分至17公分間，每0. 5公分放置一散射點。 模擬的參數如下所述：換能器探頭為256頻道之陣列架 構，中心頻率為5MHz .，頻寬為2MHz，探頭元素間的間距為 0. 75倍的波長，探頭長度約為5. 76 cm，聲速為1540 m/s， 發射以及接收為單一固定聚焦點，分別聚焦於12以及15 公分，接收端信號的取樣頻率為40MHz。所發射的編碼信 號為偽線性調頻信號（pseudo-chirp)，此信號乃將線性調 頻信號予以兩元化，亦即當原線性調頻信號大於0時，則 令為1 ;反之則令為0，所以此偽線性調頻信號為單極性信 號，此外，此偽線性調頻信號之掃瞄頻寬為3MHz，信號長 13 201020542 度為25微秒。脈波壓縮濾波器則採用非匹配濾波器，此類 濾波器能有效地將旁波瓣壓抑至預先設定的準位。空間濾 波器則採用二維架構：每個濾波器在橫向（即跟換能器探頭 平行的方向）有25個濾波器係數，縱向（即深度）方向有3 個係數，因此共75個濾波器係數。每隔5公釐的位置我 們重新設計一組新的濾波器，另外，為了驗證訊雜比估計 對於空間濾波器設計的重要性，我們於模擬中納入高斯白 色雜訊。 鲁 圖十二A及圖十二.B展示了不同編碼激發系統之成像 結果，其中圖十二A比較了散射點於深度上的變化，而圖 十二B比較了位於17公分處散射點的橫向波束場強分佈 (beam pattern)。圖中’標明” Dypost”的結果表發射固 定、接收動態聚焦後再加上單一脈波壓縮濾波器之架構； “Fxpost+filter”表雙向固定聚焦加上單一脈波壓縮遽 波器，並搭配空間濾波器之架構，所有空間濾波器係數的 決定乃基於前式中的 α 為 卜 ❷ “Fxpost+filter(adaptive)’’表雙向固定聚焦加上單— 脈波壓縮濾波器，並搭配空間濾波器之架構，然而空間濟 波器之係數根據訊雜比作動態的調整（即α非固定 值）；” GS”表發射、接收雙向動態聚焦之脈衝激發架構， 為理論上最佳的成像結果（實際上不可行’需假設物體不會 發生位移的理想狀態）。圖十二Α清楚證明了動態聚焦對於 脈波壓縮不良的效應，可發現壓縮後的結果造成準位的提 升（點線）’相較之下，固定聚焦的架構雖不會造成脈波壓 縮錯誤（準位低於動態聚焦結果至少達20dB)，然而空間濾 波器卻會對於訊號濾波後的大小有決定性的影響，特別的 201020542 是，濾波器係數隨訊雜比作動態調整之結果（實線），相較 於沒有動態調整的結果（斷線），其濾波後強度之增加可達 20dB。圖十二B則更進一步驗證了本發明所提出架構的有 效性，可以發現固定聚焦搭配動態調整之濾波器係數（實線) 擁有較低的旁波瓣，最為接近雙向動態聚焦之理想情況（點 線），總括而言，圖十二A及圖十二B可以證明本發明所提 出的系統及方法可補償脈波壓縮濾波器置於波束成型之 後，使得影像品質逼近雙向動態聚焦的影像品質。 ❿ 由以上所述可以清楚地明瞭，本發明係提供一種超音 波成像裝置及方法，其可增加訊雜比以及改善成像深度並 減少系統複雜度。 以上已將本發明專利申請案做一詳細說明，惟以上所 述者，僅為本發明專利申請案之較佳實施例而已，當不能 限定本發明專利申請案實施之範圍·。即凡依本發明專利申 請案申請範圍所作之均等變化與修飾等，皆應仍屬本發明 專利申請案之專利涵蓋範圍内。 【圖式簡單說明】 圖一 A為習知編碼激發系統之架構示意圖。 圖一 B為習知脈衝激發系統之架構示意圖。 圖二A為習知編碼激發系統之架構示意圖，其中脈波壓 縮濾波器係置於波束成型器之前。 圖二B為習知編碼激發系統之架構示意圖，其中脈波壓 縮濾波器係置於波束成型器之後。 圖三A為動態聚焦之波束成型對於脈波壓縮的效應示 15 201020542 意圖。 圖三B為固定聚焦之波束成型對於脈波壓縮的效應示 意圖。 圖四為本發明之具體實施例的系統架構示意圖。 圖五為本發明之具體實施例的方法步驟圖。 圖六為本發明之接收單元複數個固定聚焦深度與個別 接收聚焦區域示意圖。 圖七為本發明之波束成型單元架構圖。 ❿ 圖八為本發明之空間濾波器架構圖。 圖九為本發明之訊雜比估計單元的訊雜比估計流程圖。 圖十為點擴散函數經過空間濾波器後的峰值功率與旁 波瓣的關係波形圖。 圖十一為不同深度所求得的一維空間濾波器示意圖。 • 圖十二A為比較散射點於深度上的變化波形圖。 圖十二B為位於17公分處散射點的橫向波束場強分佈 圖。 【主要元件符號說明】 1超音波成像裝置 2發射單元 3換能器探頭 4物體 5接收單元 6波束成型單元 7脈波壓縮濾波單元 201020542 8空間濾波器 9包絡偵測及掃描轉換單元 10顯示裝置 11第一延遲器 12第一乘法器 13暫存器 14訊雜比估計單元 15濾波裝置 16記憶體 17查表裝置 17Effectively enhance the signal strength, on the one hand, it can maintain a good spatial resolution. Figure 1A and Figure 2B are the architectures of the conventional coded excitation system: Figure. The pulse compression filter of Figure 2A is placed in the beamforming crying) and the picture "- Β Β 脉 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖 赖Through depth 'increased system signal-to-noise ratio, the difference between the traditional (4) and the architectural d is in addition to the need to launch the spread frequency gentleman to shrink, to restore the space before the m-beam formation, each (four) job required to complete first (4) 5 201020542 Compression (as shown in Figure 1A), so that it can be correctly compressed into a short pulse signal. If the pulse compression data is to be placed after the beamformer, as shown in Figure 2B, The compression error of the spread spectrum signal cannot be correctly restored to the short pulse nickname. The cause is due to the beam shaping of dynamic focus. Figure 3A and Figure B show the effect of dynamic focusing and fixed focus beamforming on pulse compression. Without intending, as shown in FIG. 3A and FIG. 3B, assuming that a single scattering point is located at the transmitting focus position, in terms of the receiving end, since the dynamic focusing beamforming device needs to focus on each imaging depth, the required delay time is required. The curve (ie, the delay time corresponding to each array channel) will vary with depth, which will cause distortion after signal summation, resulting in compression errors of the pulse wave and the convolution filter. Conversely, when beamforming When the device is in a fixed focus (that is, focusing on a certain depth), the delay time curve corresponding to each imaging depth is consistent. In this case, the summed signal will be consistent with the original emission waveform, and the pulse compression The filter can be correctly restored to a short pulse amp& In the above discussion, the pulse compression filter can only be placed in front of the dynamic focus wave table forming device without compensation, in order to correctly compress the spread spectrum signal. In the dynamic focus architecture τ 'Because each array channel needs to be equipped with a pulse reduction filter, compared to the traditional pulse excitation system, the coding excitation system?, the body complexity will be greatly improved. With 256 array probe elements, spread spectrum signal length 20 microseconds, the sampling frequency of the receiving system is 4 〇ΜΗζ, and the pulse compression filter length is equal to 30 microseconds. For example, the number of pulse waves (10) is up to one. Therefore, all channels have a total of 10 (10) up to 3G72G0 丨 # This number of magic will greatly increase the system complexity. Therefore, how to develop an ultrasonic imaging device and method, which can increase the signal-to-noise ratio and improve the imaging depth And reducing the complexity of the system, the 3 wood invention is to actively explore. 疋 [Summary] The present invention provides an ultrasonic imaging device and method, the main characteristics of which are to increase the signal-to-noise ratio and improve the imaging depth and reduce system complexity The same state of the present invention is an ultrasonic imaging apparatus comprising: - a transmitting unit for generating an encoded signal and filtering, amplifying and focusing the encoded signal; a transducer probe, It is connected to the transmitter as a converter between sound pressure and electricity, which is an array of cheeks = sister structure, and has a plurality of transmissions and a plurality of receiving channels to transmit the encoded signals of the hairpins. To an object and receiving an echo of the object: a single receiving unit coupled to the transducer probe to receive the echo I number; a beamforming unit, and The receiving unit is coupled to: amplify, filter, and perform signal focusing to generate a plurality of _/铋逯❹ beams; a pulse compression filtering unit that is combined with the beamforming unit: green or compressed a scan line or beam; and a spatial filter connected to the wave compression filter unit to store the scan lines or beams, read and scan the scan lines or beams, and select one of the images FIELD OF THE INVENTION Another aspect of the present invention is an ultrasonic imaging method. The column step: transmitting a coded signal by using a transmitting unit to focus the bat to focus on the depth and transmitting by a transducer probe; said using a receiving unit to receive the transducing The probe echoes the signal of each cheek floor and completes the focus to obtain a plurality of scan lines or 201020542. The pulse line compression filter unit compresses the scan lines or beams; and utilizes a spatial filter. In combination with the scan lines or beams, filtering is performed according to the selected image area. This increases the signal-to-noise ratio of ultrasound imaging and improves imaging depth and system complexity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to fully understand the features and functions of the present invention, the present invention will be described in detail by the following specific embodiments and the accompanying drawings. For a schematic diagram of a system architecture of a specific embodiment, referring to FIG. 4, the present invention is an ultrasonic imaging apparatus 1 including: a transmitting unit 2 for generating an encoded signal, and filtering and amplifying the encoded signal. Focusing, wherein the transmitting unit 2 comprises a waveform generator, which may be a bipolar and unipolar waveform generator, and the waveform of the encoded signal may be any product having a high time bandwidth. Spread spectrum signals, such as PN code, linear/non-linear frequency modulation, and Barker code; etc.; a transducer probe 3 coupled to the transmitting unit 2 as a converter between sound pressure and electricity, Is an array multi-channel structure, and has a plurality of transmission channels and a plurality of receiving channels, to transmit the encoded signal of the transmitting unit 2 to an object 4, and receive an echo signal of the object 4, wherein The transducer probe 3 is a one-dimensional or two-dimensional array structure; a receiving unit 5 coupled to the transducer probe 3 to receive the echo signal; a beamforming unit 6, and the receiving unit 5 is coupled to amplify, filter, and perform signal focusing on the echo signal 8 201020542 to generate a plurality of scan lines or beams, wherein the signal focus in the receiving unit 5 can be fixedly focused on a depth to generate a focus point may be fixedly focused on the plurality of depths to generate a plurality of focus points, and the distance between the focus points needs to be greater than or equal to the length of the coded signal, and the aforementioned focus point may be associated with the transmitting unit 2 Setting the focus points to be the same or different; a pulse compression filtering unit 7 (eg, a matched filter or a non-matching filter) coupled to the beamforming unit 6 to compress the scan lines or beams; A spatial filter 8, φ is coupled to the pulse compression filtering unit 7 to store the scan lines or beams and combine the scan lines or beams to filter a selected image region. In general, in order to enable the content of a specific image area, an envelope detection and scan conversion unit 9 is further included, which is coupled to the spatial filter 8 to perform envelope detection and scanning on the image area. The present invention may further include a display device 10 coupled to the envelope detection and scan conversion unit 9 for displaying an image of the image region, wherein the image of the image region may be one-dimensional, two-dimensional or 3D imagery. φ Figure 5 is a method step diagram of a specific embodiment of the present invention. Referring to Figure 5, the present invention is an ultrasonic imaging method. First, a transmitting unit is used to transmit an encoded signal to focus the encoded signal on a Depth, and transmitted by a transducer probe; then receiving, by a receiving unit, an echo signal received from each channel of the transducer probe and performing focusing to obtain a plurality of scan lines or beams, wherein the receiving The signal focus in the unit can be fixedly focused on a depth to generate a focus point or can be fixedly focused on a plurality of depths to generate a plurality of focus points, and the distance between the focus points needs to be greater than or equal to the coded signal. Length; then compressing the scan lines or beams by using a pulse compression filter unit; then using a spatial filter in combination with the 201020542 line stitches, and using the "m" image area Beam temporary storage; = drag and filter image area; and finally according to the relative coefficient 1 in the coefficient can be matched with the image area of the signal ratio ^ is in the map /, The receiving unit of the invention has a plurality of = area schematic diagrams, which divides the image into two; = one! 3 = uses a single-fixed focus point, for the convenience of presentation, the point in the figure is as shown in Fig. 6 'Each sub-area is matched with a single - 2 聚 ", , the point can be anywhere in the sub-area, not limited to the sub-area ~ = poly = avoid too many sub-areas 'cause the pulse compression error = = effect on the pulse wave ink), therefore, each sub- Regional convergence (: Same as the following: Private should not be based on the length of the signal that is less than the transmission code:,, point seven is the element of the invention::: The step description shows the figure φ, the focus of each first delay The point and the individual arrays are arbitrarily divided according to a pre-multiple-multiplier 12, and the relative speed is determined by the sound speed, or the conventionally set, and can be consistent (ie, the multi-region focus is not applied as shown in the sixth). ",," can be used for early focus, or as shown in the above pulse compression filter to restore its original spatial resolution. One:: function is compression coded signal, can, with filter and non-pile 4 , = wave compression f-cell frequency response is two of the original coded signal. Matching the conjugate complex number of the ^% of the chopper, the advantage of the matched filter 201020542 is that the signal-to-noise ratio is increased to the theoretical maximum degree of erosion and only needs to be the length of the original coded signal - that is, the long side of the filter / filter The lobe (sidelGbe) has its own quasi-convergence = it is the affected after compression. "Comparatively, the contrast of non-matching chopping = will be compared with the length of the chopper and the original "this sacrifice - some news The hybrid diagram is the spatial filter architecture diagram of the present invention, and the ❹ f (four) t' waver 8 includes: - a temporary register Η 'which is compressed with the pulse wave = 7 to temporarily store the smear or beam Comparing:::14' is lightly connected to the register 13, and based on the broom lines or estimating the image area (10) signal ratio; the button device 15, which is associated with the device 13_, and The scanning m-beams filter the image region, wherein the filtering device 15 is a one-dimensional, two-dimensional or three-dimensional structure, and the corresponding tool corresponds to the selected dimensional, two-dimensional or three-dimensional image region; 16. The coefficient of the spatial filter 8 is stored; and a look-up device 17, which is compared with the 3fl ratio estimation unit 14, the memory 16 and The filter device 15 consumes the function of storing the coefficient of the spatial filter 8, the signal-to-noise ratio of the image region, and the depth of the image region. Generally, the function of the space m 8 is: The compensated receiving unit has poor image quality due to fixed focus. The second is to improve the side lobes of the signal after the pulse compression, and the image quality can be approximated to the image quality of the two-way dynamic focus. FIG. 9 is a flow chart of estimating the signal-to-noise ratio of the signal-to-noise ratio estimating unit according to the present invention. Referring to FIG. 9 , since the filter coefficient is designed for the depth of the image region, a single-scattering point is placed, and then imaging is performed. For scattering, the ρ image is called the point spread function (p〇int spread functi〇n, 201020542 PSF), and the PSF can be obtained in two ways: by experimental method and computer simulation. Once the PSF is obtained, the best filter coefficients can be designed based on this PSF. The use of spatial filters to improve the image quality of conventional pulse-excited ultrasound systems has not been used in the literature, but is not used to encode excitation-ultrasonic systems. Here, the present invention uses the principle of the least squares method (least_sqau)res to design the optimal spatial filter coefficients. We define the cost function E as: E^fH(aQ+(la)I)f + ku( Cf-D) (1) where f represents the spatial filter coefficient to be obtained, which may be a one-dimensional, one-dimensional or two-dimensional structure; Q represents the convolution matrix formed by the sidelobe region to be minimized ( Convolution matrix) ; I stands for identitymatrix, that is, except that the diagonal of the matrix is 丨, all other elements are 0; α is an adjustable scalar value, which is between 04 and The scalar value 丨C and D are defined as the relationship between the two, Cf = D, which is a fixed value in the set image area. According to the above formula, the optimal filter coefficient is: ® f0 = (^Q + (la) I) - lCu (C (aQ + (la) I) ~ lCHylD (2) Equation (2) shows that the optimal filter coefficient can be In order to understand the influence of the choice of different α values on the filtered image, Figure 10 shows the relationship between the peak power and the side lobes of the point spread function (PSF) after spatial filtering and wave filter. In the figure, the upper and lower curves correspond to the values on each curve of the one-dimensional and two-dimensional spatial filters, respectively, relative to the alpha value (between ο) in equation (2). This PSF is located in the Π cm The position of the system is fixed and focused on 12 and 15 cm respectively. The number of one-dimensional filter coefficients is 19 in the lateral direction. The 2D filter is 5 在 in the depth direction. As shown in Figure 10, the filter 12 201020542 wave There is a trade-off relationship between the latter peak and the side lobes, and the relationship between the two is equivalent to the relationship between the signal-to-noise ratio and the image contrast, and for the two-dimensional filter. This relationship is particularly obvious. As can be seen from the figure, the best compromise between the signal-to-noise ratio and the image contrast is at the turn. At the point (ie, the position of α = 0.2). Therefore, according to Figure 10, we can analyze the turning point of each curve in the case of different image signal-to-noise ratios (before passing through the spatial filter and the wave filter), in order to decide The best alpha value and the best filter of equation (2). • Figure 11 is a schematic diagram of the one-dimensional spatial filter obtained at different depths. The spatial filter adopts a one-dimensional architecture, and a total of 25 filter coefficients are taken as an example. Therefore, the register in Figure 8 needs to store at least 25 scan lines in advance. Since the spatial filter will vary with depth, we redesign a new set of filters every 5 mm, so according to the above In this way, we can find one-dimensional spatial filter with different depths. · In order to verify the feasibility of the coded excitation ultrasonic imaging system proposed in this case, we use computer to simulate the imaging results of different depth scattering points, φ at depth 10 A scattering point is placed every 0.5 cm between centimeters and 17 cm. The parameters of the simulation are as follows: The transducer probe is a 256-channel array architecture with a center frequency of 5 MHz and a bandwidth of 2 MHz. The distance between the head elements is 0.75 times the wavelength, the probe length is about 5.76 cm, the sound speed is 1540 m/s, the transmission and reception are a single fixed focus point, respectively focusing on 12 and 15 cm, the receiving end signal The sampling frequency is 40 MHz. The transmitted coded signal is a pseudo-chirp signal, which is used to binarize the chirp signal, that is, when the original chirp signal is greater than 0, it is 1; The order is 0, so the pseudo-chirp signal is a unipolar signal. In addition, the pseudo-chirp signal has a scan bandwidth of 3 MHz and a signal length of 13 201020542 degrees of 25 microseconds. The pulse compression filter uses a non-matching filter that effectively suppresses the sidelobe to a predetermined level. The spatial filter uses a two-dimensional architecture: each filter has 25 filter coefficients in the lateral direction (ie, parallel to the transducer probe) and 3 coefficients in the longitudinal (ie depth) direction, so a total of 75 filters coefficient. We redesigned a new set of filters every 5 mm. In addition, to verify the importance of the signal-to-noise ratio estimation for spatial filter design, we included Gaussian white noise in the simulation. Lutu 12A and Fig. 12.B show the imaging results of different coding excitation systems, in which Figure 12A compares the variation of the scattering point in depth, while Figure 12B compares the scattering point at 17 cm. Lateral beam field strength (beam pattern). In the figure, the result table of 'Dypost' is transmitted, fixed dynamic, and then combined with a single pulse compression filter; "Fxpost+filter" table bidirectional fixed focus plus a single pulse compression chopper, and with The structure of the spatial filter, the decision of all spatial filter coefficients is based on the α in the former formula, “Fxpost+filter(adaptive)”' table bidirectional fixed focus plus single-pulse compression filter, combined with spatial filtering The architecture of the device, however, the coefficient of the space encoder is dynamically adjusted according to the signal-to-noise ratio (ie, α is not fixed); the GS" table transmits and receives the bidirectional dynamic focus pulse excitation architecture, which is the theoretically optimal imaging result. (In fact, it is not feasible to 'predict the ideal state of the object without displacement.' Figure 12 shows the effect of dynamic focusing on poor pulse compression. It can be found that the result of compression causes the level to rise (dotted line). 'In contrast, the fixed-focus architecture does not cause pulse compression errors (the level is lower than the dynamic focus result by at least 20 dB), but the spatial filter will The size of the signal after filtering has a decisive influence. In particular, 201020542 is the result of the dynamic adjustment of the filter coefficient with the signal-to-noise ratio (solid line), compared to the result without dynamic adjustment (broken line), the filtered intensity. The increase can reach 20dB. Figure 12B further verifies the effectiveness of the proposed architecture of the present invention. It can be found that the fixed focus with the dynamic adjustment of the filter coefficient (solid line) has a lower side lobes, the closest to the two-way The ideal situation of dynamic focus (dotted line), in summary, Figure 12A and Figure 12B can prove that the system and method proposed by the present invention can compensate the pulse compression filter after beamforming, so that the image quality is approached Image quality of bidirectional dynamic focusing. ❿ It is clear from the above that the present invention provides an ultrasonic imaging apparatus and method which can increase the signal to noise ratio and improve the imaging depth and reduce the system complexity. The patent application is described in detail, but the above is only the preferred embodiment of the patent application of the present invention. The scope of implementation of the patent application of the present invention is that the equivalent changes and modifications of the scope of application of the patent application of the present invention should remain within the scope of the patent application of the patent application of the present invention. A is a schematic diagram of a conventional coded excitation system. Figure 1B is a schematic diagram of a conventional pulse excitation system. Figure 2A is a schematic diagram of a conventional coded excitation system in which a pulse compression filter is placed in a beamformer. Figure 2B is a schematic diagram of a conventional coded excitation system in which a pulse compression filter is placed behind a beamformer. Figure 3A shows the effect of beamforming for dynamic focusing on pulse compression 15 201020542 Intention. Three B is a schematic diagram of the effect of beamforming with fixed focus on pulse compression. FIG. 4 is a schematic diagram of a system architecture of a specific embodiment of the present invention. Figure 5 is a process step diagram of a specific embodiment of the present invention. Figure 6 is a schematic diagram of a plurality of fixed focus depths and individual received focus areas of the receiving unit of the present invention. Figure 7 is a diagram of the beam forming unit architecture of the present invention. ❿ Figure 8 is a diagram of the spatial filter architecture of the present invention. FIG. 9 is a flowchart of the signal-to-noise ratio estimation of the signal-to-noise ratio estimating unit of the present invention. Figure 10 is a waveform diagram showing the relationship between the peak power and the sidelobe of the point spread function after passing through the spatial filter. Figure 11 is a schematic diagram of a one-dimensional spatial filter obtained at different depths. • Figure 12A is a waveform diagram showing the variation of the scattering point in depth. Figure 12B shows the transverse beam field strength distribution at the scattering point at 17 cm. [Description of main component symbols] 1 Ultrasonic imaging device 2 Transmitting unit 3 Transducer probe 4 Object 5 Receiving unit 6 Beam forming unit 7 Pulse compression filtering unit 201020542 8 Spatial filter 9 Envelope detection and scanning conversion unit 10 Display device 11 first retarder 12 first multiplier 13 register 14 signal ratio estimation unit 15 filter device 16 memory 17 table lookup device 17