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Ultrasonography versus fluoroscopy in modern pain management

2016; Medknow; Volume: 30; Issue: 2 Linguagem: Inglês

10.4103/0970-5333.186459

2321-7820

Kailash Kothari, DineshK Sahu,

Vascular Procedures and Complications

Introduction Pain management as a science is progressing rapidly. The technology has advanced and newer technologies are making inroads with a rapid pace. Modern pain management interventions use image-guided procedures. The various types of imaging used are fluoroscopy, ultrasonography (ultrasound), and computerized tomography. The gold standard till today is thought to be fluoroscopy. However, ultrasound is posing a real challenge to its supremacy. More doctors are using ultrasound technology than ever before. In this era of evidence-based medicine, clinicians must analyze and choose the best modality to be used for interventional pain management procedures.[1] Fluoroscopy In the past two decades, fluoroscopy has revolutionized the pain management interventions. The specialty of pain management has grown to new heights and fluoroscopy is the cornerstone of it. With improvement in the understanding of radiological imaging, anatomy, and pathophysiology of pain, physicians in pain management are much better placed to accurately diagnose and treat the pain generators.[123] Professor Wilhelm Roentgen discovered X-rays in 1895, the first X-ray image was created in 1896, and he won the Nobel Prize for this great discovery in 1901.[1] Fluoroscopy consists of X-ray tube comprising cathode and anode, an image intensifier, and a fluorescent phosphor screen to capture the image created. Fluoroscope converts electrical energy to X-rays. Use of collimation in modern machine helps in reducing the glare, overall radiation exposure (both direct and scatter radiation) for patients as well as for the operator. Modern fluoroscopes (C-arms) incorporate optical coupling chains. Optical coupling chains optimize the viewing capabilities and sharpen the images. These images are usually taken through video camera, and live images can be seen on the television monitor during live continuous fluoroscopy. The images captured can be saved and viewed on a second monitor for the reference and to keep the record. In latest C-arms, the images can be stored and transferred to pen drives, CDs, and to other computers for future references.[1] Radiation Hazards and Safety It was evident soon after the discoveries of X-ray (1885) and radium (1897) that radiation is hazardous. It causes cell injury and cell death. It has various side effects but not limited to skin injury including burns, alteration of DNA-causing somatic mutations (future generations are affected), and radiation-induced leukemia. These side effects can be caused by high radiation exposure.[12345] In 1994, the US Food and Drug Administration issued an advisory, warning health-care facilities of the potential for radiation-induced burns to patients from prolonged fluoroscopic procedures.[6] In the list of the procedures, no pain management procedure was listed.[7] However, the risk to exposed physicians and staff could be same. To prevent these side effects, radiation protection guidelines are recommended, which include intermittent fluoroscopy, removal of grid, collimation, dose spreading, adjust exposure to required level at the start of the procedure, dose level setting, and appropriately trained operators. We need to take the following measures to reduce the risk - minimize tube current, keep kV high and mA as low as possible, keep tube as much away and image intensifier as close to the patient as possible, collimate the area of interest, wear protective aprons, eye shields, thyroid shields, radiation-protective curtains over the side of the operating table, stand as far as possible from the tube to avoid scattered and direct radiation, and keep dosimeter for the operators and OT staff.[6] How fluoroscopy helps during interventions is described as follows: These technical errors can be avoided in most cases by the use of fluoroscopy. Any technique which is replacing the fluoroscope as an imaging technique must be able to prevent such technical errors [Figures 1234]. Correct needle placement Prevent untoward effects - use of contrast under fluoroscopy to confirm the absence of vascular and cerebrospinal fluid spread. There is a number of instances of recognizing vascular spread while injecting contrast under live fluoroscopy Laterality - to confirm if the drug is being delivered on the side of the pain (e.g., in caudal or interlaminar injection), the needle tip can be placed on the side of the pain To confirm if the drug is reaching the site of problem (e.g., in herniated disc - transforaminal approach is considered gold standard to deliver the drug very close to the site of disco-radicular conflict). While performing transforaminal injection, it is important to note that the drug is spreading from lateral to medial. If needle placement looks satisfactory, but contrast is only flowing laterally outside the foramen, it may not be beneficial as the drug is not reaching the site of inflammation. Fluoroscopy images help in detecting these smaller but important issues, and needle placement has to be rectified to get better drug placement In spine pain - most patients are referred to the pain clinic for establishing the source of pain, to give a "trial" of pain management injections (as commonly termed by surgical colleagues), and if this fails, the next step is surgery. If the procedure is failed due to any one of the following reasons, it will have a huge impact on patient's life: Wrong technique, which includes wrong placement of needle Vascular uptake is not recognized (i.e., no drug remains at the site of action) Wrong side spread of the drug (especially in caudal and interlaminar injection). Figure 1: Fluoroscopic image eedle directed towards the inferior border of pedicle (Infrapedicular approach for Transforaminal epidural injection at L5 nerve root on right sideFigure 2: Fluoroscopic image n AP view Needle is at 6 O'clock position of the pedicle for Transforaminal epidural injection at L5 nerve root on right sideFigure 3: Live fluoroscopic image after injection of contrast for Transforaminal epidural injection at L5 nerve root on right side (No vascular/Intrathecal spread noted)Figure 4: Fluoroscopic image after injection of drug (Steroid) for Transforaminal epidural injection at L5 nerve root on right sideUltrasonography Use of ultrasound has gained a lot of ground in the last decade in the field of anesthesia. The use is very common in today's regional anesthesia practice. This rapid growth in the use of ultrasound is due to many factors, to mention few are technology advancement, compact ultrasound machines, high resolution, better tissue penetration, and improved availability.[8] Anesthesiologists were performing regional nerve blocks using standard landmark techniques. The success rate was variable as per the skill of the individual practitioner and also as per the anatomical variation of the patient. With the use of ultrasound in anesthesia, critical care, and pain management, the placement of needle in the blood vessel, epidural space, and near the nerve has become more targeted. The success rate has improved a lot. The successful use of ultrasound in these settings needs not only good quality machine but also intense training of the operator to make use of this technology.[8] Ultrasound is studied in living systems since 1920. History suggests that the use of ultrasound in clinical practice was accepted in 1960s.[8] The mechanical energy traveling through the matter produces sound waves due to alternate compression and rarefaction of the matter. Scattering of sound waves by interface produced by different types of matter and the amplitudes of this reflected energy is captured as ultrasound image.[8] The components of ultrasound machine includes transducer (sends electrical energy, converts it into acoustic pulses, sends it to patients, and receives reflected echoes from patients to convert it into ultrasound images), receiver and processor (collects, processes, and refines the reflected signals for display), image display (A-Mode, M-Mode, and B-Mode displays). The transducers work on the principle of piezoelectricity. Different types of matter absorb sound waves at different rates[9] [Table 1]. They reflect the sound wave at different rates. The rate of absorption is least by fluids and most by solids. The distance of the reflecting tissue is calculated by time taken for the sound wave from and to the transducer. As the bones and air reflect maximum, we cannot see beyond such interfaces, and this is one of the limitations of ultrasound.[810]Table 1: Acoustic impedance of different materials[Table 1] Use of Doppler in ultrasound has further enhanced its use, especially near vascular structures. In Doppler, the sound transmitted from a moving object is perceived by a stationary observer to be of a different frequency depending on the velocity and direction of travel. Using the frequency changes, velocity of the movement of blood is calculated.[9] Ideal imaging technique should include good resolution, no radiation, real-time imaging, should be portable, and requires minimal personnel. Ultrasound is very near to fulfill all these criteria. Use of Ultrasound in the Clinical Practice of Anesthesia, Critical Care, and Pain Management In short, compared to other imaging techniques, advantages of ultrasound includes real-time imaging, portable (bedside and office-based procedures can be done), lower cost, and no harmful ionizing radiation. Vascular access: Improved success rate, reduced number of attempts, and reduced complications compared to landmark techniques[8111213] Regional nerve blocks: Large nerves can be visualized easily, direct visualization of the nearby structures such as blood vessels helps in identifying smaller nerves, real-time needle guidance, and drug is visualized while injection and redirection of needle are possible in-between the procedure. High-resolution probe is used for superficial and low-resolution probe is used for deeper nerves. Nerve stimulator can be combined with ultrasound, but has not shown any added advantage[141516] Central neuraxial blocks in children and in patients with difficult anatomy: Due to the presence of bony structures, the deeper planes cannot be visualized properly. It has to be used with the loss of resistance (LOR) technique. However, the use of ultrasound has shown to reduce dural puncture episodes and overall better block quality. This has been a boon, especially for pediatric patients. Drawbacks of ultrasonography include imaging depends on patient cooperation and physique, difficulty in imaging structures behind bone and air, and its dependence on a skilled operator. In India, prenatal diagnostic test also acts as a major deterrent to use ultrasonography in clinical practice, especially in smaller hospitals and by private practitioners [Figures 5 and 6].Figure 5: Ultrasonography image - Transverse view at S1 level with right S1 foramenFigure 6: Ultrasound image at L4-5 level (Paramedian sagital view)Ultrasound versus Fluoroscopy With the introduction of ultrasound for peripheral nerve blocks, there has been a dramatic change in the way regional anesthesia has been practiced all over the world. However, this imaging modality is still not been accepted as an ideal imaging modality by pain practitioners. Pain practitioners are still not convinced about its usefulness due to the following reasons:[17] There are many published papers which suggest that the use of ultrasound makes the procedure very simple and safe, especially in superficially placed neural structures such as stellate ganglion block[1618] and cervical medial branch block.[17] With the use of ultrasound-guided paramedian approach to stellate ganglion block (at C6 Chassaignac tubercle), we can prevent damage to important structures such as thyroid and carotid arteries. Under fluoroscopy, this cannot be ascertained. The success rate is almost 82% for blocking 3rd occipital nerve under ultrasound.[19] The biggest advantage of ultrasound is no radiation. Most pain practitioners are trained to perform procedures under fluoroscopy Long learning curve Resistance to change (comfort zone) Pain clinics are established with fluoroscopy as an integral part, so its availability is widespread Almost all fluoroscopy-guided procedures are well established, having a lot of supporting evidence Difficulty in performing neuraxial techniques using ultrasound The inability of recognizing intravascular spread by ultrasound as seen under fluoroscope. However, there are some serious issues such as using ultrasound in obese patients, procedures below C6, miscalculation of the number of vertebra, questionable ability of ultrasound to detect vascular uptake, and poor accuracy of needle tip placement at lumbar level. In most studies, the procedures are operated by experienced sonographers,[16] and we do not know if the same results can be achieved by new physicians practicing chronic pain management.[1617192021] Considering all these, there is a very big concern while using ultrasound-guided procedures - if the procedure fails due to these avoidable errors (false-negative results), we will be doing injustice by denying patients an effective treatment. The prospective randomized controlled trial by Jee et al.[22] shows that ultrasound facilitates the identification and avoidance of the critical vessels around or within the sacroiliac joint (SIJ), the results of therapeutic injections are comparable in fluoroscopic and ultrasound-guided injections in noninflammatory SIJ dysfunction. However, the diagnostic application of ultrasound in the SIJ may be limited because of the significantly lower accuracy rate (87.3%) versus fluoroscopy (98.2%). The needle missed to enter the joint in 12.7% of the patients in ultrasound group. Few studies[2324] suggest that ultrasound guidance may be very helpful in avoiding complications in transforaminal cervical epidural steroid injections, which are considered very risky under fluoroscopic guidance. This was a prospective randomized trial, in which eighty patients with lumbar radiculopathy were treated with fluoroscopy versus ultrasound + fluoroscopy-guided transforaminal epidural injection of steroid. Ultrasound-guided injections were performed with an US device with a linear probe, and they were verified by fluoroscopy. Fluoroscopy-guided injection was given using a standard protocol. The needle tip reached the lateral side of the lamina in the axis view and the middle of the adjacent facet joints in the parasagittal view. Afterward, the needle was advanced slightly deeper until the LOR test was positive. The success ratio of the ultrasound-guided interventions was 85%. Interestingly, the time taken by the ultrasound group was much shorter, and the radiation dosage in the ultrasound group was almost one-third than in the fluoroscopy group[25] [Table 2].Table 2: Fluoroscopy versus ultrasonographyConclusion Ultrasound is well established, and beyond doubts, it is one of the best diagnostic modalities. It has a lot of proven advantages and it is promising in improving the results of peripheral nerve blocks. On the other hand, fluoroscopy is a well-established imaging tool in pain clinics. Physicians are very comfortable and confident using fluoroscopy as an imaging modality. Radiation safety is the biggest issue with the use of fluoroscope. The role of ultrasound is gaining importance in certain chronic pain management procedures, especially stellate ganglion and cervical medial branch blocks. With the progress in research and improvement of ultrasound technology, there is a good chance that the ultrasound can gain more popularity as the imaging technique of choice for many chronic pain management procedures in future. More well-controlled studies are the need of the time before we recommend its use in routine clinical practice.