The Status of the Quality Control in Acupuncture-Neuroimaging Studies

Using neuroimaging techniques to explore the central mechanism of acupuncture gains increasing attention, but the quality control of acupuncture-neuroimaging study remains to be improved. We searched the PubMed Database during 1995 to 2014. The original English articles with neuroimaging scan performed on human beings were included. The data involved quality control including the author, sample size, characteristics of the participant, neuroimaging technology, and acupuncture intervention were extracted and analyzed. The rigorous inclusion and exclusion criteria are important guaranty for the participants' homogeneity. The standard operation process of acupuncture and the stricter requirement for acupuncturist play significant role in quality control. More attention should be paid to the quality control in future studies to improve the reproducibility and reliability of the acupuncture-neuroimaging studies.


Introduction
Acupuncture, a traditional therapy originated from China, has been gradually accepted as an alternative and complementary therapy by the Western medical community for its undeniable efficacy for pain and chronic diseases [1][2][3][4][5]. As acupuncture is widely used all over the world, its underlying mechanism attracts increasing attention. Since the 1970s, several studies of acupuncture on experimental animals have proven that the integration of central nervous system (CNS) plays an important role in acupuncture efficacy [6,7]. With the development of neuroimaging techniques such as functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET), Single-Photon Emission Computed Tomography (SPECT), electroencephalography (EEG), and magnetoencephalography (MEG), using these techniques to investigate the cerebral responses to acupuncture stimulations in vivo [8] has gradually become a spotlight in acupuncture mechanism research. Over the past two decades, there are around 200 original articles having been published in English, and a growing body of evidence demonstrates the involvement of CNS in acupuncture mechanism [9]. However, it was found that the results of acupuncture-neuroimaging studies were untenable. For example, some studies on acupoint specificity showed that the cerebral responses to acupoint stimulation significantly differed from acupoint to sham acupoint [10][11][12][13]. Some studies demonstrated that there was no significant difference in cerebral reaction between acupoint and sham acupoint [14][15][16]. Some investigators held that the significant difference in cerebral responses between acupoint and sham acupoint was only found during Deqi (needle sensation) state [17]. Methodology issues might contribute to the conflict results.
As we know, design and quality control are key points which may affect the result of a study, and strict quality 2 Evidence-Based Complementary and Alternative Medicine control plays an essential role in the guarantee of a high repeatability, especially in acupuncture-neuroimaging study for relative smaller sample size, complexity of cerebral function, and integrity of acupuncture effect. So this study aims to investigate the current status of the quality control in acupuncture-neuroimaging studies from sample size, subjects screening, manipulation procedure, and scanning mode by analyzing the original articles published in English in the latest two decades, so as to provide ideas for the development of quality control criteria in future acupunctureneuroimaging study. We screened the bibliographies of identified trials and reviewed articles for further potentially relevant publication. Subsequently, we screened the full texts and assessed whether these articles met the inclusion criteria.

Inclusion and Exclusion
Criteria. The articles would be included if they were (1) original articles; (2) acupunctureneuroimaging studies on human beings; (3) published in English; and (4) published during 1995 to 2014.
The articles would be excluded if they were (1) reviews or editorials or trial protocols; (2) acupuncture-neuroimaging studies on animals; or (3) duplicate articles.

Data Extraction and Analysis.
We extracted the data including the author (nationality, affiliation, and component), sample size, characteristics of the participant (patients or the health, age, gender, race, handedness, emotional state, acupuncture experience, and accompanying symptoms), neuroimaging technology, acupuncture intervention (method of intervention, manipulation procedure, Deqi/needle sensation, and acupuncturist), and ethical review. The data analysis was conducted after data extraction. 168 [7, 10-176] original articles were included in this study.

Discussion
Owning to the complexity of the brain function and the diversity of acupuncture manipulations, the different or even reversed results occurring in similar acupunctureneuroimaging studies become a common phenomenon. Seeking reasonable and practical methods is essential to improve the reproducibility and reliability of results in acupuncture-neuroimaging studies. Based on the open published literatures, this study analyzed the status of quality control in acupuncture-neuroimaging study for the first time and tried to provide some new ideas for future studies.

Sample
Size. The appropriate sample size is important for designing an acupuncture-neuroimaging study. Bigger sample size increases statistical power because the standard error of the mean decreases by the square root of number ( ). Due to the potential radioactivity (PET/SPECT) and the costs of imaging, the sample size in most of the neuroimaging studies was small. Some investigators suggested that 12 to 15 subjects per group could get statistical power in fMRI studies [177,178]. Others held that the method should ensure large sample size to use rigorous corrections for multiple tests [179]. In this study, we found that the average sample size was 15 participants per group, and the average sample size for patients was slightly bigger than that for healthy subjects (16 versus 14 per group). Nowadays, most investigators agreed that, to achieve the stable statistical power, bigger sample size (at least 20 participants per group) was needed in the future acupuncture-neuroimaging study [180]. In this study, we found that there was a preponderance of nervous system disorders such as stroke among the diseases involved in acupuncture-neuroimaging studies. The result indicated that acupuncture stimulation promoted the action of neural rehabilitation and its mechanism is a focus of acupuncture study. Furthermore, we noticed that some studies were performed on functional disorders such as functional dyspepsia and irritable bowel syndrome [65, 101]. As we know, regulating functional disorder is the advantage of acupuncture, so functional disorder might be a new approach in future studies.

The Selection of
Moreover, the subtypes of a disease should be taken into consideration when you choose patients as the participants in neuroimaging study for the patients with different subtypes might have functional or/and structural differences in brain. For example, schizophrenic subjects with predominantly negative symptoms have greater metabolic abnormalities than subjects with predominantly positive symptoms [181]. So, in acupuncture-neuroimaging study, it is better to choose the same subtype of a disease to ensure the homogeneity of participants.

Demographic Characteristics of Participants.
Some demographic characteristics of participants including age, gender, race, and handedness should be defined in the inclusion criteria.
The changes of cerebral function and structure come with age. Some studies indicated that the cerebral glucose metabolism decreased unevenly and brain tissues began aging after 40 years old [182,183]. Older age directly correlated with reduced gray matter volume in bilateral rostral and right dorsal ACC [184]. So the age range of participants should not be ignored in neuroimaging studies. However we found that most of these studies (101 studies) described the age range of participants, that the average age range of healthy subjects was 18.3 years old, and that the average age range of patients was 29 years old. Even in some studies, the age range was more than 50 years old. It is better to keep the age range within 20 years to reduce the effect of outlier.
The functional and structural differences in human brain induced by handedness have long been investigated [185][186][187][188], although the mechanism remains unclear. So the majority of the current studies (137 studies) choose right-hand participants.
Furthermore, gender differences of the human brain are an important issue in neuroimaging studies. It has been identified that gender has significant influence on the regional neuronal activity [189,190] and brain structure [191]. Race differences may lead to differences of brain function and structure. For example, it is reported that brain size varies by race [192]. In this study, we found that 14 studies (8.33%) described and restricted the race of the participants. Taking gender and race as covariates is needed when designing acupuncture-neuroimaging experiments.

Emotional State.
The psychological factors have significant influence on the function and structure of human brain. For example, Drevets et al. have found an area of abnormally decreased activity in the prefrontal cortex ventral to the genu of the corpus callosum in both unipolar depressives and bipolar depressives [193]. Our study shows that only 4 articles described the psychological assessment performed on the participants; more attention should be paid to the emotional state of subjects during the inclusion and data analysis in future studies, except for the study which focuses on the mechanism of acupuncture treating for psychological disorders.
Furthermore, our study demonstrated that participants with claustrophobia have been excluded in 9 studies. Claustrophobia is a phobic disorder which will cause panic, fear, or anxiety in the confined space. Scanning cannot be accomplished when it is performed on a participant with claustrophobia. So the participants with claustrophobia should be excluded in acupuncture-neuroimaging studies.

Menstrual Period.
In this study, we found that female participants were involved in 145 studies. Recently, some studies performed on healthy subjects indicated the cerebral functional and structural changes in menstrual period. For example, Veldhuijzen et al. [194] found that the pain-related cerebral activation varied significantly across the menstrual cycle. Hagemann et al. [195] found a significant gray matter volume peak and cerebral spinal fluid loss at the time of ovulation in females. So, for female participants, scanning should be performed during the same physiological period to avoid the possible changes in brain size and activity in menstrual cycles.

Accompanying Symptoms/Disorders. The accompany-
ing symptoms/disorders such as head trauma, pain (including headache and dysmenorrhea), and insomnia should be excluded as possible as we could considering their influence on the neuroimaging data. Tu et al. [196,197] found that abnormal gray matter volume changes are presented in primary dysmenorrhea patients even in the absence of pain.
Furthermore, some investigators held that blood coagulation disorders should be excluded in acupuncture studies [6].

Acupuncture Experience.
Some studies have reported the significant differences in cerebral response between the participant with acupuncture experience and the participant without acupuncture experience [198]. In our study, we found that participants in 44.04% of the studies were acupuncture naive. To ensure the consistency of the baseline of the participants and the comparability of consequence, the acupuncture experience of participants should be taken into consideration.

Image Technology.
Among the neuroimaging technologies, fMRI (82.14%) was most commonly used in the acupuncture-neuroimaging studies. But we also found that multimodel imaging techniques became a new trend in acupuncture-neuroimaging studies for their significant advantages in improving spatial/temporal resolutions and lowing noise. Among the manual acupuncture studies, 79.21% studies have described the needle manipulation. The results indicated that (1) although the stimulation of manual acupuncture is hard to be quantified for the individual differences of manipulation induced by different practitioners, manual acupuncture, as the traditional acupuncture intervention, is easier to be accepted by investigators and (2) the majority of these studies with manual acupuncture treatment describe the acupuncture manipulation including sterilization, the angle and depth of needle insertion, and the duration of retaining needle to ensure consistency of acupuncture treatment. Considering the influence of different manipulation results, we should not allocate too many acupuncturists in one neuroimaging study. In order to ensure the accuracy of the results, it is better to perform acupuncture manipulation with one acupuncturist.

Acupuncture
Meanwhile, transcutaneous electric acupoint stimulation, magnetic stimulation, heat stimulation, and laser acupuncture were used in some neuroimaging studies. The results indicated that not only manual acupuncture and electroacupuncture, but also other acupuncture-related interventions attract increasing interests of investigators. In the future, more attention should be paid to those acupuncture methods which have not or seldom been touched such as ear acupuncture, abdominal acupuncture, and wrist and ankle acupuncture.

Qualification of Acupuncturist and Operation Procedure.
The qualification of acupuncturist and operation procedure Evidence-Based Complementary and Alternative Medicine 7 is important in quality control of acupuncture trial. In our study, 59.5% of the studies have mentioned the qualification of acupuncturists and 79.88% of the studies have described the manipulation procedure of acupuncture. For the defined influence of the qualification of acupuncturist and manipulation procedure on clinical efficacy, the needling details including numbers of needle, depth of insertion, elicited response, and needle retention time and the background of practitioners including the duration of relevant training, length of clinical experience, and details of expertise in treating the specific condition being evaluated as well as any other experience that may be relevant to the trial should be reported according to the standards for reporting interventions in controlled trials of acupuncture (The STRICTA Recommendations) [199].

Deqi (Needle Sensation) and Evaluation of Sensation.
Deqi (needle sensation) plays an important role in acupuncture efficacy. Clinical trials have demonstrated that acupuncture with needle sensation was superior to acupuncture without needle sensation for analgesia [200] and paralysis [201]. A neuroimaging study [54] also showed the significant differences of cerebral responses under the Deqi and non-Deqi condition. So it is important to record the Deqi sensation in acupuncture studies.
In this study, we found that the questionnaire-based forms such as 10-point VAS, MASS, SASS, Park questionnaire, Psychophysical Rating of Needling Sensation, and NSQ were used to assess the needle sensation in acupunctureneuroimaging studies. Among them, 10-point VAS was the most commonly used (68.3%). However, the liabilities and validities of some specific or nonspecific questionnaires/scales for needle sensation need further investigation.

The Author Nationality and Ethical Review.
In this study, we found that 63.7% of the studies were accomplished by the cooperation of more than two countries. The international cooperation improved the study level and quality control in some degree. To get more international recognition and perfecting research, the acupuncture-neuroimaging studies need more international cooperation. Furthermore, ethics has got growing attention by the researchers. The interests of the participants should be taken in the first place. The ethics was an essential component which should be considered during the whole acupuncture-neuroimaging studies.
In conclusion, to improve the reproducibility and reliability of the acupuncture-neuroimaging studies, more attention should be paid to the quality control including sample size, participants screening, and acupuncture manipulations in future studies. A practical and standard quality control criterion should be developed to improve the acupunctureneuroimaging studies.