ROLE OF CONTINUOUS WAVE VS PULSE WAVE AND COLOR DOPPLER IN IDENTIFYING ARTERIAL PERFORATORS OF LOWER LIMB
Description
An arterial perforator is a vessel, which arises from a main (parent) artery and passes through the intermuscular/septocutaneous/myocutaneous plane to supply blood to the deeper structures. In the present day, arterial perforators have become the mainstay of perforator flap reconstructive surgeries after trophic or superficial soft tissue defects, secondary to insults like burns, trauma or gangrene secondary to peripheral vaso-occlusive pathology. Even though there is voluminous and ever-increasing knowledge of anatomy, there is no systematic approach to locate the perforating arteries in the lower limb. This is mainly due to high amount of anatomical variation amongst individuals and asymmetry being the general rule in every individual. There is asymmetry in anatomical spread of arterial perforators between two lower limbs of one individual as well. Therefore, it is natural that the pre-operative planning before surgical flap surgery cannot be based upon any previously laid down set of rules. Every individual must be evaluated independent Lee and anatomical variations in perforator a mapping must be taken into account. Continuous-Wave Doppler (CW Doppler) CW doppler is the one of the simpler configurations of Doppler imaging & consists of 2 different types of transducers: a receiving & a transmitting transducer. The main role of the transmitting transducer is to produce a continuous ultrasound beam output at a predetermined frequency. This transmitted signal is then received by receiving crystal. Addition of the received and transmitted signals is done, which leads to formation of a waveform which consists of a beat frequency. This beat frequency is equal to the doppler-shift frequency. There is no information or data provided the continuous wave doppler in terms of the depth of the point of analysis or at which the analyzed motion is occurring, that causes the doppler shift.1 Pulsed Wave Doppler (PW Doppler) The main aim of development of pulse wave doppler was to primary obtain information regarding depth perception of the region of interest which is leading to the doppler shift phenomenon. Also, PW doppler system comprises of only one transducer. This same transducer does the job of transmitting and receiving signals. There is substantial difference in the pulse used for pulse wave doppler as compared to pulse which is used in B mode imaging. Electronic gating is used which times interval between the transmitted and received pulse. This allows the operator to analyze a specific point along the long axis of the transmitted beam. Main output from a PW doppler is primarily an audible signal. When combined together, PW doppler and B mode imaging are called Duplex ultrasound imaging. This lets the operator to analyze both entities together and focus on a specific point in the B mode image for doppler analysis
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Machines used: Samsung HS-40 housed in Government Wenlock Hospital Huntleigh Doppler DMX continuous wave hand held Doppler Study design: Cross sectional study Study participants: Patients referred to Department of Radiodiagnosis for lower limb arterial perforator identification and assessment. Inclusion criteria: 1. Age between 18 to 60 years. 2. No history of any lower limb arterial disease. Exclusion criteria: 1. Smokers 2. Known case of peripheral vascular disease. 3. Hypertensive patients/ patients on anti-hypertensive therapy. 4. Diabetes with microvascular complications. 5. Recent orthopedic/surgical intervention in lower limb. 6. Any pathological data collected on Doppler study will lead to exclusion of the sample. Study duration: November 2018 to September 2020. Data collection began after due permission of ISEC & MS of hospital. Sample size: Calculated using prevalence and sensitivity. n=Zš¼^2Ćšš(1āšš) šæ^2Ćš Where Sn=94% The minimum number required for the study is 90.54 Sampling Method: Non-probability convenience sampling The study was conducted after obtaining the permission from the Institutional Ethics Committee. The study was conducted in the Government Wenlock Hospital and Government Lady Goschen Hospital, Mangalore. It was an observational study, with data collected prospectively for a period of 2 years. Sample size was estimated based on a study by N.S Bali et al..54 Considering 5% alpha error and 95% Confidence level, sample size of 90 was obtained. Total of 100 healthy volunteers underwent doppler evaluation. Continuous wave doppler was done using Huntleigh Doppler DMX handheld device and Pulse wave and color doppler evaluation was done using Samsung HS 40 machine. Outcome variables: 1. PW Doppler: Distance from nearest anatomical landmark, depth from skin, diameter and velocity of blood flow in arterial perforator. 2. CW Doppler: Identification and site of arterial perforator with respect to nearest anatomical landmark. In the study, we localized arterial perforators using pulse wave doppler and did anatomical mapping of these perforators for ATA & PTA. Later on, at the localized sites, we performed continuous wave doppler study and tried to record the spectral wave and sound from the continuous wave doppler. Data was also recorded from the pulse wave doppler data in the form of sound output using a 3.5 mm jack and an indigenous in house made amplifier. This amplifier removed background doppler noise and improved efficacy of the analysis of data. Tabular data was provided from the duplex ultrasound machine using grey scale display. The data provided was depth of the vessel from skin surface, maximum luminal caliber of the vessel, site of origin of the vessel from nearest anatomical landmark and the peak systolic velocity of the wave.