臺灣博碩士論文加值系統

根據行政院衛生署86年的統計資料, 國人十大死因仍以惡性腫瘤(癌症)為首。因此，對於癌症的治療研究實為刻不容緩。根據實驗顯示，組織細胞在43℃以上的高溫環境中，存活率隨加熱時間增長而有明顯下降的趨勢。
對於深層腫瘤的加熱，本研究一改以往利用大型二維超音波換能器矩陣相位調變的方式，試圖利用一維超音波換能器矩陣加以旋轉，來達成對深層腫瘤細胞加熱的目標。這種方式，大量減少換能器的數目，同時減少控制的困難度，增加了系統的可實現性。
對於乳房腫瘤的治療，本研究發展出一掃描圓筒型超音波換能器，並對於在各種參數下的能量場及溫度場的分佈情形加以探討。經由控制參數調整，可以成功的將能量焦集在乳房的中心或表層。甚至可以控制加熱的方向性，對整個乳房或部份的乳房進行的加熱。
掃描型換能器所造成的變動波場難以計算，此外，暫態溫度場的計算也十分耗時。因此，本研究經由理論的推導及模擬，証明了生物熱傳模型是一個低通濾波器。所以，變動的能量場所造成的溫度效應與靜態的能量場所產生的溫度效應相當近似。這不但避免掉變動能量場計算的困難，也減少了計算暫態溫度場的時間。

The statistics from the Department of Health shows that cancer is the number one cause of death for residents in Taiwan in 1997. Hence, cancer treatment plays a very important role in health care. Current clinical experiences strongly suggest that hyperthermia will become an important modality as an adjuvant to radiotherapy in the treatment of locally advanced solid tumors.
The derivation of temperature distributions is usually difficult for scanned ultrasound transducers. It is shown in this thesis that a static transducer pattern can achieve very accurate approximation of the temperature distribution from a scanning transducer. The result can be further explained from the low-pass filtering effect from the tissue, which is described by the Bio Heat Transfer Equation. Theoretically derivations and simulations are given to provide an insight to this problem.
For deep-seated tumors, a one-dimensional phased array ultra-sound transducer is designed with proper scanning motion. The proposed system is equivalent to a two-dimensional phased array ultrasound transducer in terms of temperature distribution generated. This method can dramatically reduce the number of transducer element needed for ultrasound hyperthermia treatment.
This study is to examine the energy deposition and the temperature distributions for breast tissues with various sizes and locations when a scanned cylindrical ultrasound transducer is employed for hyperthermia treatments. Simulations show that power can be successfully deposited both in the central or the superficial portion of the breast. Combining low and high frequencies with scanning angle adjustments, successful treatment can be done from partial to whole breast.

Abstract ....................................................................................................................I
Content....................................................................................................................Ⅲ
Index ......................................................................................................................Ⅴ
CHAPTER 1
INTRODUCTION.............................................................................................1
1.1 INTRODUCTION TO HYPERTHERMIA......................................................2
1.2 ULTRASOUND HYPERTHERMIA................................................................2
1.3 SCANNED ULTRASOUND HYPERTHERMIA............................................5
1.4 THESIS ORGANIZATION...............................................................................7
CHAPTER 2
THEORETICAL ANALYSIS AND SIMULATION METHOD............................8
2.1 THEORETICAL ANALYSIS OF ACOUSTIC WAVES.................................9
2.2 NUMERICAL APPROXIMATION OF ACOUSTIC FIELD.........................18
2.3 BIOHEAT TRANSFER EQUATION AND TEMPERATURE DISTRIBUTION..................21
CHAPTER 3
TEMPERATURE DISTRIBUTION FOR SCANNED ULTRASOUND HYPERTHERMIA SYSTEMS....................23
3.1 PROBLEM FORMULATION..........................................................................24
3.2 THE TRANSFER FUNCTION OF BHTE.......................................................30
3.3 FREQUENCY RESPONSE..............................................................................32
3.4 THE EFFECTS OF SCANNING SPEED........................................................34
CHAPTER 4
DEEP-SEATED TUMOR TREATMENT STRATEGY........................................37
4.1 MOTIVATION.................................................................................................38
4.2 SYSTEM CONFIGURATION.........................................................................38
4.3 ULTRASOUND POWER DEPOSITION AND SAR RATIO.......................41
4.4 SIMULATION RESULTS................................................................................43
4.5 AN EXAMPLE OF SYSTEM DESIGN..........................................................55
4.6 CONCLUSION.................................................................................................56
CHAPTER 5
SCANNED CYLINDRICAL ULTRASOUND TRANSDUCERS FOR BREAST TUMOR...........57
5.1 REVIEW OF BREAST TUMOR TREATMENT SYSTEM...........................58
5.2 SYSTEM CONFIGURATION........................................................................59
5.3 SIMULATION PROCEDURES......................................................................60
5.4 DISTRIBUTIONS OF SAR RATIO...............................................................63
5.5 TEMPERATURE DISTRIBUTION................................................................77
CHAPTER 6
CONCLUSIONS........................................................................................................................80
6.1 POWER DISTRIBUTION FOR SCANNED ULTRASOUND HYPERTHERMIA........80
6.2 DEEP-SEATED TREATMENT STRATEGY.....................................................................81
6.3 SCANNED CYLINDRICAL ULTRASOUND TRANSDUCERS................................... 81
REFERENCE.....................................................83
APPENDIX A...................................................87
APPENDIX B...................................................90

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