MDCTA三维重建在穿支皮瓣可视化研究与设计中的应用

目的：评价MDCTA三维重建技术对穿支皮瓣血管可视化定位方法及设计的指导意义。方法：2011年6月至20i3年8月,对23例皮肤软组织缺损的病例行穿支皮瓣修复术,术前在拟设计皮瓣区域采用MDCTA扫描及三维重建,根据重建的皮瓣穿支血管的位置及供血范围设计皮瓣,比较术前穿支血管定位与术中实际位置的差异。并根据三维重建后的3D图象观察穿支分布及彼此吻合情况,以此结果指导术中皮瓣设计,旋转方式等。结果：本组23例,其中胫后动脉穿支皮瓣9例,腹壁下动脉穿支皮瓣4例,臀上动脉穿支皮瓣6,腓肠肌穿支皮瓣2例,背阔肌肌穿支皮瓣2例。所有皮瓣经MDCTA扫描,均能清楚分辨皮瓣穿支以及其二级血管的位置走向,三维重建能清楚分辨穿支血管与其周围血管的解剖关系。MDCTA术前定位与术中解剖相符率达100％。23个皮瓣除2例远端1／3发绀经处理后无好转,II期植皮修复外,其余均I期愈合。随访1～10个月,皮瓣色泽,质地良好。皮瓣两点感觉大于0．3cm。结论：MDCTA三维重建能三维直观精确定位穿支血管及显示皮瓣血流灌注范围,术前用于指导皮瓣设计,能明显提高手术安全性,降低手术风险。     

多层螺旋CT血管造影技术在穿支皮瓣修复下肢软组织缺损中的应用

目的 探讨应用多层螺旋CT血管造影(MDCTA)进行术前穿支血管特征评估、指导“freestyle”穿支皮瓣临床应用的效果.方法 2011年2月至2012年12月,对下肢软组织缺损40例术前均采用MDCTA行穿支评估,包括位置、口径、走行、与邻近结构的关系.选择优势穿支设计不同的穿支皮瓣进行软组织修复重建,并评估术前与术中穿支位置的吻合率. 结果 应用带蒂螺旋桨穿支皮瓣19例,游离穿支皮瓣21例.术后所有皮瓣均存活,仅1例膝降动脉穿支皮瓣远端出现2 cm×2 cm的坏死,经换药后治愈.供区37例直接关闭缝合,3例通过部分植皮.术前穿支定位与术中所见穿支位置吻合率为97.5％.结论 术前MDCTA可以提供准确的穿支解剖学特征信息,在下肢软组织修复重建时,皮瓣的设计更具随意和准确,手术更加简单、安全,从而减少了供区损伤并获得最佳的修复效果.     

吻合血管腓骨移植的数字化设计与初步临床应用

目的 探讨吻合血管腓骨移植数字化设计修复长段骨和(或)软组织缺损的临床应用价值.方法 选择四肢长段骨缺损患者9例,术前血管造影后行螺旋CT供区小腿扫描.将扫描数据输入计算机,应用Amira 3.1软件对腓骨及其营养血管行三维重建.术前根据患者骨缺损长度、形态及软组织缺损面积.利用三维重建图像进行精确测量和个性化没计,并模拟手术关键操作.术中仔细核对腓动脉与重建血管走行,并依术前设计切取腓骨(皮)瓣.移植于骨缺损受区进行固定.参照Enneking系统对患肢功能进行评价,以达到正常肢体功能的百分数表示,参照国际挽救肢体专题讨论会制定的"同种及带血管移植的放射学评价方法"对移植腓骨的转归进行影像学评价.结果 三维重建图像直观地体现了腓骨、营养血管及腓动脉穿支皮瓣的三维结构及空间毗邻关系.通过数字化设计和模拟手术操作,町避免术中因小腿血管损伤或血管变异致切取失败和供区意外损伤.9例移植的腓骨(皮)瓣全部成活.术后随访6～30个月,平均15.8个月.骨缺损均修复,骨性愈合时间平均为4.5个月,肢体功能恢复率90.4%.结论 数字化设计可为修复长段骨缺损手术方案的选择提供科学依据,方便术前模拟及术中指导,降低手术风险.     

三维重建技术在髂骨瓣临床手术中的初步应用

目的 探讨三维重建技术在髂骨瓣临床手术中的初步应用. 方法 2006年12月至2008年6月,采用旋髂深血管支髂骨瓣对1例股骨骨不连和5例胫骨骨缺损或骨不连的患者进行骨缺损修复.术前注射造影剂后采用CT扫描,应用Amira4.0软件对髂骨瓣结构进行三维重建,构建患者个性化骨瓣.根据患者骨缺损大小,进行个性化骨瓣三维构建,对患者进行髂骨瓣的点、线、面描记,用以指导手术切取. 结果三维重建患者个性化骨瓣6个,所重建个件化髂骨瓣能够清晰显示血管、骨骼及其毗邻结构的三维关系.6例患者所显示的骨瓣主要血供主干都与术中检查相符.术前测量旋髂深动脉起点距髂前上棘平均4.28 cm,旋髂深动脉主干血管外径平均为2.4 mm,穿支血管数平均为3条.术后6例患者获6个月～2年1个月(平均1年3个月)随访,髂骨瓣全部成活且Ⅰ期愈合,术后3～5个月均达到骨性愈合. 结论通过血管造影下肢CT扫描,采用数字化三维重建技术可以提供髂骨瓣的三维动态解剖,重建的组织瓣能够准确地标示术中切取范围,避免了术中血管的副损伤,保证了髂骨瓣良好的存活率.     

CT血管造影结合数字化技术在皮瓣移植术中的应用进展

近年来,穿支皮瓣移植术广泛应用于临床,术前明确各穿支血管走行以及可切取范围对进一步提高穿支皮瓣手术效果具有重要意义。随着数字化医学的发展,CT血管造影结合Mimics软件重建得到的图像结构清晰,三维可视化模型能真实反映动脉的分布、走行以及各穿支在体表皮肤的穿出位置,为临床设计动脉穿支皮瓣的游离移植和带蒂移植提供了精确的三维解剖学依据。该文就CT血管造影结合数字化技术在皮瓣移植术中的应用进展进行综述。     

CT血管成像技术在腹壁下动脉穿支皮瓣术前设计中的应用

目的 探讨CT血管成像(computed tomography angiography,CTA)技术在腹壁下动脉穿支(deep inferior epigastrie artery perforator,DIEAP)皮瓣术前设计中的应用. 方法 2007年1月至2008年3月,对13例拟行DIEAP皮瓣手术的患者术前应用CTA技术对腹壁下动脉进行检查,包括5例阴道先天性缺如、4例阴茎阴囊Paget's病、4例乳腺癌术后乳房缺损的患者,将获得的数据进行处理,包括多平面重组、最大密度投影以及容积显示.观察腹壁下动脉的走行、分支以及穿支位置,并将CTA图像结果与术中情况进行比较. 结果 CTA图像提供腹壁下动脉在肌肉内走行和穿支位置等有效信息,指导DIEAP皮瓣的术前设计,并在手术中得到验证. 结论 术前对腹壁下动脉进行CTA检查,可以有效地指导DIEAP皮瓣的术前设计.     

腹前外侧壁跨区穿支皮瓣设计的应用解剖学研究

目的 研究腹前外侧壁穿支的走行、起始外径及各穿支间吻合支的出现位置.探讨腹前外侧壁跨区穿支皮瓣的切取范围和组合方式.方法 对5具新鲜完整的成人尸体标本动脉造影后行CT扫描与三维重建,CT扫描后用交互式医学影像控制系统(Mimics)进行3D可视化研究,获取腹前外侧壁血管信息,观测穿支的数量以及彼此间的吻合情况、供血面积等.另对10具防腐的成人尸体标本行解剖学研究,观测腹前外侧壁区外径≥0.5 mm的穿支,测量其管径及走行、分支、吻合支等情况.结果 腹前外侧壁穿支间存在大量的吻合支,跨区穿支皮瓣组合后的营养面积:腹壁下动脉穿支+旋髂浅动脉穿支皮瓣(71.5±9.5) cm2,腹壁浅动脉穿支+旋髂浅动脉穿支皮瓣(140.6±10.4)cm2,腹壁下动脉穿支+腹壁浅动脉穿支皮瓣(122.2±15.2)cm2.结论 腹前外侧壁穿支数目、位置及走行较为恒定,穿支间存在大量吻合支,适合跨区穿支皮瓣的切取,且皮瓣的组合方式多样,为超大皮瓣的切取应用提供了一种新的术式选择.     

基于CT血管造影的胸背动脉三维可视化研究

目的探讨基于CT血管造影(CT angiography,CTA)的胸背动脉数字化解剖及应用价值。方法选取2012年9月-2014年6月行主动脉CTA并符合选择标准的10例患者(20侧)主动脉CTA图像,利用Mimics17.0三维重建软件进行图像后处理,观察并测量胸背动脉起源、穿支数量、分型、内径、蒂长,并行穿支血管的体表定位以及模拟胸背动脉穿支组织瓣切取。结果三维重建图像显示10例患者胸背动脉均起源于肩胛下动脉,共发现穿支血管76支,其中32支(42.1%)来自胸背动脉内侧支,44支(57.9%)来自胸背动脉外侧支。69支(90.8%)胸背动脉穿支属肌皮穿支型,7支(9.2%)为直接皮动脉型。胸背动脉内径(1.69±0.23)mm、蒂长(2.12±0.64)cm。胸背动脉外侧第1穿支位于肩胛下角水平线上方(1.65±0.42)cm、肩胛下角垂直线外侧(1.68±0.31)cm;内侧第1穿支位于肩胛下角水平线上方(1.43±0.28)cm,肩胛下角垂直线外侧(1.41±0.28)cm。成功模拟胸背动脉穿支组织瓣切取。结论 CTA是在体研究胸背动脉解剖较直观的方法,三维重建后可清晰显示皮瓣的主要供血动脉走行和分布等三维立体信息,能有效、准确指导皮瓣设计。     

高频彩超结合超声造影技术在穿支皮瓣术前设计及评估中的应用

目的 应用高频超声及超声造影增强技术(CEUS),定位并检查穿支血管,为皮瓣手术的方案设计和操作提供准确依据 方法 2011年12月至2012年7月对我科49例拟行穿支皮瓣手术患者,在高频彩超基础上运用CEUS行术前探测:皮瓣供区做穿支血管出肌点定位和血管三维重建,测量血管管径及峰值流速;皮瓣受区探测有无血管硬化,有无炎症、脓腔及液性坏死.根据穿支血管直径和峰值流速,结合血管三维图像,首选直径粗、峰值流速快、血管走行平直的穿支血管,设计并切取皮瓣. 结果 49例患者,43例在拟切取皮瓣的49个区域共找到117支穿支,平均每个区域找到2.39个穿支,除6例12个第四腰动脉穿支皮瓣术前探测的30个穿支血管因不需要显露、术中未证实外,其余87个穿支血管均在术中得到证实,所有皮瓣均成活.6例患者根据术前探测结果,认为不适合做穿支皮瓣,改行其他手术,疗效良好.结论 高频彩超能准确定位穿支血管并了解受区情况,结合CEUS可以获得更清晰连续的二维图像和三维立体图像,是提高穿支皮瓣手术准确性和成功率的有效手段.     

小腿穿支血管筋膜蒂皮瓣修复下肢软组织缺损

目的:探讨小腿穿支血管筋膜蒂皮瓣转移的手术方法和临床效果.方法:1998年5月至2009年1月临床应用带小腿内、后、前外、后外侧穿支血管的筋膜蒂皮瓣邻近转位,对下肢皮肤软组织缺损创面进行修复共62例,男50例,女12例;年龄7～78岁.其中应用带胫后动脉穿支的小腿内侧筋膜蒂皮瓣23例,带腓动脉终末穿支小腿前外侧筋膜蒂皮辩9例,带腓动脉穿支腓肠神经营养血管筋膜蒂皮瓣22例,带腘外侧动脉小腿后外侧筋膜蒂皮瓣8例.结果:除2例术后皮辩远端表皮坏死结痂,1例皮瓣远端部分皮肤坏死行Ⅱ期植皮,其余皮瓣均完全成活.随访1个月～3年,皮瓣外观满意,功能良好.结论:小腿部单个穿支血管供血面积有限,应用带穿支血管营养血管链的筋膜蒂度瓣可扩大小腿皮瓣的裁取面积,保证皮瓣的血供及回流.     

应用彩色多普勒影像技术设计腹部轴型皮瓣修复手腕部深度创面

目的报道应用彩色多普勒影像技术设计腹部轴型皮瓣修复手腕部深度创面的方法和疗效，以克服既往设计轴型皮瓣时血管不能直观显像的缺陷。方法根据手腕部创面的特点，选用腹部不同部位的轴型皮瓣进行修复，其中应用腹股沟皮瓣41例，下腹壁皮瓣15例，脐旁皮瓣6例，共62块皮瓣。术前按传统方法设计皮瓣后，应用彩色多普勒显像仪，检测轴型皮瓣内供血动脉的起止点、外径、血管走行和长度；根据检测结果重新设计皮瓣，术中将皮瓣内所见血管情况与术前彩色多普勒显示的结果进行对比。结果彩色多普勒所检测皮瓣内血管的起止点、外径、血管走行和解剖学层次均能在屏幕上清晰显示，与术中所见一致。术后62例轴型皮瓣全部存活，术后随访6～30个月，所有皮瓣在外观、感觉及功能等方面均较满意。结论彩色多普勒显像对腹部轴型皮瓣内血管的判断具有简单、直观和无创的特点，为确定轴型皮瓣移植术提供了更为科学、准确的依据。     

The utility of multidetector-row computed tomography angiography for evaluating perforators of fibular osteocutaneous flaps

Multidetector-row computed tomography angiography (MDCTA) can be used to visualize small vessels and has been used to search for perforators in deep inferior epigastric artery perforator flaps and anterolateral thigh flaps. Fibula osteocutaneous flaps are often used for mandibular reconstruction, but questions remain about the reliability of these flaps and the variety of their perforators. Eight patients who were candidates for mandibular or pedal reconstruction with a fibula osteocutaneous flap were prospectively evaluated with MDCTA and Doppler sonography. We evaluated the number, position, and course of perforators with MDCTA. The perforators were classified, and intraoperative findings were compared with those of Doppler sonography and MDCTA. MDCTA accurately identified the perforators and showed a satisfactory concordance with intraoperative findings. The high spatial resolution of MDCTA allows the perforators' origin, course, and type to be precisely described. Eighteen vessels were identified with MDCTA, and on average, 2.3 vessels were identified in the leg of each patient. The rate of concordance with operative findings was 87.5% for MDCTA. With MDCTA, flap perforators can be accurately evaluated before surgery in a manner not possible with traditional angiography or Doppler sonography. Reliable perforators can be chosen, and detailed operative plans can be made.     

Preoperative Angio-CT preliminary study of the TRAM flap after selective vascular delay

BACKGROUND: The pedicled TRAM (pTRAM) flap is one of the best options for autologous breast reconstruction, but vascular complications reported in the standard versions are about 30%. To reduce complication rate, especially in high-risk patients, surgical delay has been suggested.Individual precise preoperative location and evaluation of perforating vessels and of variations of the diameter of the deep superior epigastric artery (DSEA) are highly desirable for improving surgical strategy. Previous reports using color duplex scanning, although generally confirming the validity of the delay maneuver, have showed several pitfalls. The aim of this report was to demonstrate the usefulness of multidetector computed tomography angiography (MDCTA) for preoperative planning in patients undergoing pTRAM flap breast reconstruction after selective vascular delay. METHODS: Three patients were considered for breast reconstruction with the pTRAM flap. An MDCTA was performed before and after selective delay to locate the muscle perforators and to show increase in DSEA diameter. Axial images, multiplanar reconstruction, and 3D volume images were analyzed. RESULTS: Accurate identification of the main perforators was achieved. Location, course, and anatomic variations of DSEA were reported. The average increase in diameter of the DSEA was 29.3%. CONCLUSION: Preoperative planning of pTRAM flap with MDCTA allows surgeons to visualize and locate the dominant perforators and to select the best DSEA. Consequently, the choice between the homolateral or contralateral rectus muscle is facilitated. The high sensitivity and specificity and the ease of interpreting data have made MDCTA a highly promising diagnostic tool for planning a pTRAM flap.     

Changes in the peroneal flap and its use in reconstructive surgery of the lower limb. Apropos of an experience of 10 cases]

A peroneal fasciocutaneous flap supplied by the peroneal septocutaneous vessels and raised from the lateral side of the lower leg was reported by Yoshimura in 1983. This flap which can be used as a proximally or distally pedicled or free flap is very useful for leg skin coverage. This flap has a great potential for skin cover and composite reconstruction of the lower limb due to its multiple structural facets (cutaneo-aponevrotic or composite flap), its possible extensions to other vascular territories and the variable geometry of its mode of transfer. 8 reconstructions have been performed. Their indications are described: 4 proximally pedicled flaps (3 with the fibula), 4 reverse-flow island flaps (1 with Soleus and Peroneus longus muscles). The authors stress the importance of preoperative assessment of the feasibility of a given flap which may be limited by post-traumatic, surgical or anatomic modifications. In particular, the uppermost septocutaneous artery which corresponds inconstantly to the "circumflex peroneal artery" can only be visualized by preoperative arteriography. This artery supplies a proximal peroneal flap which can be used as an island or a free flap. We have used this new variety as a free flap in 2 cases and were satisfied with the results. These various clinical applications without any significant complication or flap failure confirm the biological performance and the safe procedure of peroneal flaps.     

The efficacy of preoperative vascular mapping by MDCTA in selecting flap in abdominal flap breast reconstruction

Current methods of breast reconstruction using abdominal tissue include the transverse abdominal myocutaneous (TRAM) flap, deep inferior epigastric arterial perforator (DIEP) flap, superficial inferior epigastric arterial (SIEA) flap, and some other composite flaps. Because of the variant vascular anatomy in abdominal region, it is hard to choose an appropriate flap for a specific patient without accurate preoperative vascular mapping. This study was drawn to address the efficacy of preoperative vascular mapping by multidetector-row computed tomographic angiography (MDCTA) in selecting flap in abdominal flap breast reconstruction. A total of 34 breast reconstructions using abdominal flap from December 2006 to July 2009 were included. In all the patients included, MDCTA was performed preoperatively. Three indexes were obtained including choice of flaps, operation time, and flap complication rate. Then, these data were compared with the former data stored in the databank of our hospital from January 2004 to December 2006, before MDCTA was introduced in our center. Among the 34 patients, the flap selection was: SIEA flaps 11.8%, DIEP flaps 61.8%, TRAM flaps 11.8%, and bilateral flaps 14.7%. The correlate indexes from the data bank were as follows: SIEA flap 0; DIEP flaps 51.7%; TRAM flaps 32.8%; bilateral flaps 15.5%. p < 0.05 occurred between the comparison of SIEA, DIEP, and TRAM flap choice in the two groups. The operation time in the study group was as follows: SIEA flap (4.02 ± 0.46) hours, DIEP flap (6.23 ± 1.42) hours, TRAM flap (4.72 ± 1.53) hours, Bilateral flap (7.86 ± 1.16) hours; while the former correlate data were: DIEP (9.67 ± 1.74) hours, TRAM flap (6.64 ± 1.83) hours, bilateral flap (11.83 ± 1.35) (all the three comparison p < 0.05). The total flap complication rate was about 5.9% in the test group; while in the databank, it was 12.1% (p < 0.05). With the accurate mapping of vascular territory in abdomen by MDCTA, we could easily select a suitable abdominal flap for breast reconstruction, and we can also simplify the procedure to save operation time and make the process more safely.     

超声血流成像在乳腺癌手术放疗后乳房再造肌皮瓣选择中的应用

目的分析应用彩色多普勒血流成像（CDFI）技术辅助设计轴型肌皮瓣再造乳房的方法和疗效。方法根据乳腺癌手术放疗后局部病灶的特点,选择不同部位的轴型肌皮瓣对26例乳腺癌手术放疗后患者再造乳房,包括同侧背阔肌肌皮瓣、对侧横形腹直肌肌皮瓣和双侧横形腹直肌肌皮瓣,术前传统方法设计肌皮瓣后,应用具有高分辨率的多功能彩色多普勒血流成像仪检测轴型肌皮瓣供血动脉的起止点、外径、血管走向和长度等,根据检测结果再次设计肌皮瓣并转移至胸壁重建乳房,并将术中所见血管情况与CDFI的显示结果进行对照和比较。结果在CDFI探测肌皮瓣轴型血管中,发现有1例胸背动脉血流缓慢,管壁粗糙,动脉硬化较明显;其余血管探测结果均显示血流顺畅,管壁光滑,无栓塞、硬化现象,亦无血管缺如现象。CDFI所检测供血动脉的起止点、外径、血管走向和解剖学层次均可清晰显示,与术中所见完全一致,术后26例轴型肌皮瓣全部成活,伤口愈合良好;再造的乳房在形态及感觉等方面均满意。结论CDFI对轴型肌皮瓣供血血管判断具有简单、直观和无创的特点,为确定轴型肌皮瓣移植术提供更为科学、准确的依据。     

以旋股外侧动脉降支为蒂的穿支嵌合皮瓣修复口腔颌面部缺损

目的 设计以旋股外侧动脉降支为蒂的股部皮肤穿支血管的嵌合皮瓣,为修复口腔颌面部的大面积、复杂的洞穿性缺损提供一种新的方法.方法 根据旋股外侧动脉降支的走行及分支、其在股部正面及两侧可能存在的皮肤穿支血管,设计以旋股外侧动脉降支为蒂的穿支嵌合皮瓣修复口腔颌面部软组织缺损8例.此种皮瓣可分为3种类型:股前外侧皮瓣+股前内侧皮瓣、股前外侧皮瓣+股直肌穿支皮瓣、股前外侧皮瓣+股前外侧皮瓣.结果 术后8例16块皮瓣均成活,无并发症,且供区均直接拉拢缝合,未行皮片移植.术后随访1～9个月,患者面部外形和功能均良好,供区畸形和功能障碍均不明显.结论 以旋股外侧动脉降支为血管蒂的穿支嵌合皮瓣吻合血管数量少,较切取2个皮瓣供区损伤小,组织量大,适合口腔颌面部大型复杂的组织缺损的修复.     

An anatomic study and clinical application of medial pedis flap in Asians

Several investigators have reported their clinical experience with medial pedis flaps for reconstruction of soft tissue defects of the hand and digits. In a cadaveric study in 1997, Jayme and Hamilton described the anatomy of the medial branch of the deep division of the medial plantar artery, which is used in the medial pedis flap. However, they had only a few cases where this flap was used. There have been no such anatomic studies in Korea to date. We found the medial pedis flap to be a reliable option for reconstruction of soft tissue defects of the hand and digits, based on an anatomic study with 10 dissected fresh cadavers (20 cases) and analyzing the clinical outcomes in 17 patients. An anatomic study revealed that there were some racial differences in the diameter and length of the vessels. The diameter of vessels in the Korean population is larger than that in whites. Using a thin, flexible medial pedis flap, which has skin and subcutaneous tissue similar to that of the volar aspect of the hand and digits, we harvested and performed the reconstruction on 17 patients with soft tissue defects of the hands and digits. The vessels used for this flap were the medial branch of the deep division of the medial plantar artery and vena comitantes, or subcutaneous veins. The mean size of the flap was 2.82 cm x 4.15 cm. All flaps were successful without any significant complications. The medial pedis flap possesses several advantages: (1) it is very thin in comparison to other standard free flaps; (2) it has 2 draining venous pathways; (3) it provides a good color and texture match for the hand and fingers; (4) it has a satisfactory recovery of protective sensation.     

股前外侧组织瓣临床应用112例分析

目的 总结分析股前外侧组织瓣解剖规律及其在组织缺损修复重建中的适应证和应用价值。方法1985年3月-2004年8月，对112例股前外侧组织瓣移植进行临床总结。其中男67例，女45例。年龄5～65岁，平均38．5岁。针对受区不同情况，将股前外侧组织瓣切取分为4类：吻合血管的游离皮瓣移植78例；吻合血管的游离脂肪筋膜瓣移植22例；带蒂顺行岛状皮瓣移位5例；远端为蒂逆行岛状皮瓣移位7例。对面、颈、肢体、躯干等部位的软组织缺损所致功能障碍或外观缺陷进行修复，并对术后效果和供区恢复情况进行评价。结果营养股前外侧组织瓣的动脉皮支出现率100％，具有肌间隙皮穿支（33％）和肌皮穿支（67％）两种基本解剖类型。组织瓣源血管均为旋股外侧动脉降支或横支。皮瓣移植成活107例，成活率达95．6％。术后33例获随访6个月～11年，远期随访效果满意率91％，供区无功能受限。结论股前外侧组织瓣解剖恒定，具有多种突出优点，是修复软组织缺损的理想材料。尤其是穿支皮瓣形式，可保持受区形态，降低供区损伤，成为应用趋势。