Pre-Injection Doppler Mapping Versus Landmark Guidance for Lower Facial Hyaluronic Acid Injection in a Prospective Safety Study

Summary

This prospective study suggests that pre-injection Doppler mapping can improve vascular risk assessment and early outcomes in lower facial hyaluronic acid injection. Compared with landmark guidance alone, Doppler mapping identified individualized vascular risk signals, supported pre-injection plan modification, and was associated with lower post-injection ecchymosis and improved short-term aesthetic scores.

Abstract

This study evaluated whether pre-injection Doppler mapping improves vascular safety and early aesthetic outcomes in lower facial hyaluronic acid injection compared with landmark guidance alone. In this prospective parallel-controlled study, 120 participants were randomly assigned to a Doppler mapping group (n = 60) or a landmark-guided group (n = 60). Vascular risk signal detection, post-injection ecchymosis, procedural features, and early aesthetic outcomes were compared between groups. Detectable vascular signals were identified in 63.3% of Doppler-group participants, and injection-plan modification was performed in 53.3%. Ecchymosis incidence on day 3 was significantly lower in the Doppler mapping group than in the landmark-guided group (23.3% vs. 48.3%; P = 0.004). Needle passes, intra-procedural adjustments, and overall early adverse events were also reduced. Aesthetic improvement scores and patient satisfaction were higher in the Doppler mapping group. In multivariable analysis, pre-injection Doppler mapping was independently associated with a lower risk of ecchymosis (OR = 0.38; P = 0.014). These findings suggest that pre-injection Doppler mapping may reduce vascular risk and early local trauma while improving short-term aesthetic outcomes after lower facial hyaluronic acid injection.

Introduction

With the continuous updates of modern facial aesthetic concepts, the treatment concepts have also transitioned from single local wrinkle injection to overall facial shaping across the entire face^1,2. Consequently, comprehensive rejuvenation of the lower face has become an essential component of contemporary aesthetic practice. As the key area that determines the facial-neck boundary and vertical facial proportions, the aging process of the lower face is a multi-faceted pathophysiological change, including deep bone tissue atrophy, loss of soft tissue volume, and gravity-induced descent of fat pads³. The alterations that appear clinically are blurred mandibular border contours, weakened mandibular angle support, pre-jowl depression, deepened perioral folds, and chin retraction. These morphological shifts disrupt facial contour continuity and contribute to a disproportionately bottom-heavy appearance. As a highly biocompatible, reversible, and immediately formable material, hyaluronic acid is widely used in clinics to treat lower face volume deficiency and skin laxity. However, due to the dense anatomical structure and frequent functional movements of the lower face, achieving a good aesthetic effect under vascular safety is still a challenge for clinicians⁴.

Landmark-guided injection remains the most commonly used approach in routine aesthetic practice. This technique depends on the injector's knowledge of standard surface anatomy and prior clinical experience. However, the course of the facial artery, facial vein, and their branches is highly variable in the lower face, including differences in vessel diameter, depth, and branching pattern⁵. Reliance on surface landmarks alone may be insufficient for individualized vascular risk assessment⁶. In this setting, injections performed without patient-specific vascular mapping may inadvertently injure small vessels or place filler near a high-risk vascular pathway, increasing the likelihood of ecchymosis, edema, vascular compromise, or tissue ischemia.

High-frequency ultrasound combined with Doppler blood-flow assessment is increasingly used in aesthetic medicine to improve the accuracy and safety of filler injection planning. High-frequency ultrasound can display the relationships among the skin, subcutaneous fat, muscle layers, and deeper supporting structures. Color Doppler imaging adds information on the location, depth, and direction of blood-flow signals before injection⁷. By mapping individualized vascular depth and spatial relationships, injectors can select safer entry points, trajectories, and tissue planes. This image-informed planning supports careful filler placement without implying that ultrasound can eliminate all vascular risk⁸.

Although Doppler ultrasound has a strong theoretical role in lower facial filler safety, prospective controlled evidence in high-risk lower facial regions remains limited. Many reports are case-based or retrospective and do not quantify how pre-injection mapping affects ecchymosis, procedural efficiency, and early aesthetic outcomes. The objective of this study was to compare pre-injection Doppler mapping with landmark guidance alone for lower facial hyaluronic acid injection, focusing on vascular risk-signal detection, injection-plan modification, post-injection ecchymosis, procedural characteristics, and short-term aesthetic outcomes assessed by blinded reviewers⁹.

Protocol

The study protocol was reviewed and approved by the institutional ethics committee of Chengdu YiXing Plastic Surgery Hospital (Approval Number: ETUAA80928). All participants provided written informed consent before enrollment and before standardized facial photography. Written consent was also obtained for the publication of identifiable or potentially identifiable facial photographs included in the manuscript. The study was conducted in accordance with the Declaration of Helsinki and local clinical research requirements.

Study design

This study was a single-center, prospective, parallel-control clinical trial. Consecutive patients scheduled for lower facial hyaluronic acid injections were screened, and 120 eligible participants were enrolled. Participants were assigned in a 1:1 ratio to the Doppler mapping group (n = 60) or the landmark-guided group (n = 60) using a pre-generated random allocation sequence before treatment. The Doppler mapping group received pre-injection ultrasound and Doppler assessment, whereas the landmark-guided group received standard anatomical landmark-guided injections without pre-injection imaging. Vascular risk-signal identification, post-injection ecchymosis, procedural characteristics, and early aesthetic outcomes were compared between groups¹⁰.

The random allocation sequence was generated before enrollment using a computerized random-number list and was implemented sequentially after eligibility screening and baseline documentation. Group assignment was completed before treatment, and the same allocation process was applied to both study arms.

The study was conducted in a conventional outpatient aesthetic medicine setting. Before intervention, all participants completed baseline assessment, standardized facial photography, and treatment-area documentation. Injections in both groups were performed by the same experienced injector team after unified training in the study protocol, lower facial anatomy, hyaluronic acid injection principles, and the Doppler mapping workflow. The two groups were kept consistent with respect to filler material, treatment areas, postoperative care instructions, and follow-up schedule to support between-group comparison.

To reduce performance bias, injections in both groups were performed by the same designated injector team rather than by group-specific injectors. The team had routine experience in lower facial hyaluronic acid filler procedures and completed unified training in the study protocol, Doppler mapping workflow, injection safety precautions, standardized photography, and follow-up documentation before study initiation.

The study's follow-up time points were pre-treatment, immediately after treatment, 24 h after treatment, day 3, and day 7. The main observation indicators were whether there was early ecchymosis and the identification results of vascular risk-related signals, and the secondary indicators were local adverse reactions, early aesthetic improvement scores, and patients' own satisfaction levels. This study design focuses on early complications and immediate aesthetic outcomes¹¹.

Patient selection

The study subjects were selected continuously from patients visiting the cosmetic medicine outpatient clinic at the study institution. The inclusion criteria were individuals aged 18–60 years who intended to undergo lower facial hyaluronic acid injection, with the treatment area covering at least one of the following regions: mandibular border, mandibular angle, pre-jowl area, labiomental fold or marionette line region, or chin. All subjects were required to complete pre-injection assessment, standardized photographic documentation, and post-injection follow-up. To reduce interference from prior treatments, subjects were required to have no history of hyaluronic acid or other filler injections in the same area within 6 months prior to enrollment.

The exclusion criteria were patients who were currently taking anticoagulant or antiplatelet drugs that could not be stopped, those with confirmed coagulation disorders, those with active infections, significant inflammation, or open wounds in the treatment area, those who have received non-degradable filler injections or complex repair procedures in the same area before, pregnant or nursing women, and subjects considered unsuitable by the investigators for this research plan. Patients with severe keloid predisposition, significant facial anatomical abnormalities, or who cannot be followed up completely were also excluded.

Before enrollment, all subjects signed an informed consent form, and standardized baseline data were collected. The baseline parameters included age, gender, body mass index (BMI), history of previous aesthetic medical treatment, target injection area, initial facial contour defect, and treatment objective. To ensure data consistency, standardized facial photographs were taken under uniform lighting, positioning, and angles to facilitate the evaluation of early aesthetic results and intergroup comparisons.

Pre-injection ultrasound assessment and lower facial anatomical planning

Pre-injection ultrasound assessment was performed only in the Doppler mapping group. A high-frequency linear-array probe operating at 18 MHz was used. Participants were examined in the supine or semi-supine position with the head slightly extended to expose the target lower facial region. Gray-scale ultrasonography was used to identify the skin, subcutaneous fat, muscle layers, deep supporting structures, and intended filler plane. Color Doppler mode was then used to identify superficial or deep blood-flow signals and to assess their spatial relationship to the planned injection plane. Based on these findings, cases were classified as having a “relatively high vascular risk” if they presented with a detectable vascular signal within or adjacent to the intended injection plane, a superficial vascular pathway requiring caution, or a vessel crossing the planned entry pathway.

Color Doppler was used as the prespecified vascular-screening mode for this protocol. Power Doppler was not incorporated as a separate primary screening mode because the study was designed to evaluate a standardized, time-limited pre-injection mapping workflow suitable for routine outpatient aesthetic practice. Therefore, absence of a color Doppler signal was recorded only as absence of a detectable signal under the prespecified color Doppler protocol and was not interpreted as proof that no vessel was present.

The pre-injection scanning range included the mandibular border and angle, anterior mandibular region, pre-jowl area, labiomental fold or marionette line region, chin, and superficial lower-lip refinement area. In the mandibular border and angle regions, assessment focused on tissue layers relevant to periosteal or subcutaneous placement. In the pre-jowl, labiomental fold, and marionette line regions, scanning emphasized the distance between visible vascular signals and the intended filler plane. In the perilabial and superficial lower-lip regions, the location and depth of labial arterial signals were recorded to reduce the risk of superficial vascular injury. These scanning targets are consistent with published recommendations on high-frequency ultrasound-assisted lower-face filler procedures^1,5.

Individualized injection strategies were formulated from pre-injection imaging data. The injector used these data to select entry sites, choose target tissue planes, and adjust trajectories away from visible high-risk vascular zones. If a blood-flow signal was detected adjacent to the planned injection plane, the filling layer, entry route, or device choice was reassessed before injection. Because this study used pre-injection mapping rather than continuous real-time ultrasound guidance, negative Doppler findings were interpreted cautiously and did not replace careful aspiration, slow injection, small aliquots, and continuous tissue monitoring during the procedure.

Injection protocol and group-specific procedural strategy

All subjects received the same cross-linked hyaluronic acid filler. The routine procedure included face washing, skin disinfection, and treatment-area marking. Sharp needles or blunt cannulas were selected according to the anatomical requirements of each lower facial region, local vascular findings, and the intended filler plane. Injection dosages were adjusted according to baseline contour deficiency and clinical objectives, using conservative dosing, multilayer placement, and microaliquot techniques to limit tissue tension and support even filler distribution.

Device selection was based on the intended anatomical plane, treatment area, contour objective, and vascular-risk assessment. Blunt cannulas were preferentially considered for broader subcutaneous contouring, linear threading, or trajectories requiring passage across a relatively wide lower-facial area, whereas sharp needles were used for focal, small-aliquot correction or deeper support when precise placement was required. Device type was recorded for each procedure, compared between groups, and included in the multivariable models because needle/cannula selection may influence ecchymosis, hematoma, edema, and early recovery.

Subjects in the Doppler mapping group underwent pre-injection ultrasound and Doppler assessment. The injector determined the entry point, direction, injection plane, and device choice (needle or blunt cannula) based on the scan data and adjacent anatomical structures. In the mandibular border and mandibular angle regions, contour-supportive filling was performed in the pre-injection confirmed safer anatomical layer. In the pre-jowl, labiomental fold, and marionette line regions, the injection depth and trajectory were modified according to tissue layering and visible vascular distribution. For superficial treatment near the labial arterial pathway, injections were performed at the pre-injection planned safe depth while avoiding the mapped vascular course.

Subjects in the landmark-guided group received injections guided by standard anatomical landmarks. The injector selected injection sites, trajectories, tissue planes, and device choice according to empirical anatomical knowledge and facial depression morphology, without pre-injection ultrasound or Doppler mapping. Apart from the absence of pre-injection imaging, other treatment conditions were kept as similar as possible between groups, including filler type, treatment areas, injection principles, and postoperative care.

Approximate injection-volume ranges were individualized by region and baseline contour deficiency, and are summarized alongside the treatment characteristics. During each procedure, the total injected volume, number of needle passes, number of skin entry points, use of needle and/or cannula, procedural duration, and any intra-procedural route modifications were recorded. All subjects received standardized post-injection instructions for local compression, cold application, activity restriction, and warning signs requiring unscheduled review.

Outcome measures and follow-up schedule

The outcome measures in this study were categorized into three domains: pre-injection vascular risk identification, early post-injection safety, and short-term aesthetic improvement. The primary outcomes were vascular risk-related signals detected during pre-injection Doppler mapping and post-injection ecchymosis. In the Doppler mapping group, the pre-injection assessment recorded whether clear blood-flow signals were present in the target region, the relationship between the signal and the planned injection plane, whether superficial vascular pathways required avoidance, and whether the entry point, direction, depth, or device choice was modified. Ecchymosis was recorded by occurrence, timing, involved area, maximum diameter, and severity. Severity was graded using a standardized 0–3 scale based on standardized photographs and clinical assessment, where 0 indicated no visible ecchymosis, 1 mild punctate or limited ecchymosis, 2 moderate localized ecchymosis, and 3 extensive or severe ecchymosis.

Secondary endpoints included localized adverse events, short-term aesthetic improvement, and patient-reported satisfaction. Aesthetic parameters (naturalness, symmetry, contour smoothness, and lower facial line-continuity) were each evaluated using a 5-point scale (1 = poor, 5 = excellent). The Global Aesthetic Improvement Scale (GAIS) was also utilized, where lower scores indicate greater improvement (1 = exceptional improvement, 5 = worse). For the multivariable analysis, a “suboptimal early aesthetic outcome” was defined as a composite indicator: achieving an investigator-rated overall aesthetic improvement score of ≤ 3, or scoring ≤ 3 in any of the individual aesthetic domains (naturalness, symmetry, smoothness, or continuity) at day 7. Local swelling, tenderness, erythema, sensory change, palpable irregularity, transient pallor, and the need for additional review were recorded from 24 h to day 7. Aesthetic outcomes were assessed using standardized pre- and post-treatment photographs. Investigator assessments were performed by blinded reviewers who were not involved in the injection procedure and were masked to group allocation, Doppler findings, and treatment details. Image files were anonymized and coded before review to reduce assessor bias. Participants separately reported perceived improvement, satisfaction with recovery, downtime acceptability, and willingness to undergo the same procedure again.

Follow-up time points were pre-treatment, immediately post-treatment, 24 h post-treatment, day 3, and day 7. Baseline facial photographs, treatment-area documentation, and pre-injection facial condition were recorded before treatment. Immediate post-treatment records focused on procedural findings, temporary bleeding, skin color change, early ecchymosis, and immediate aesthetic effect. The 24 h visit captured early swelling, tenderness, and ecchymosis. Day 3 was selected because minor hematoma and local tissue reactions are typically more stable at this stage, and day 7 was selected to assess recovery of mild-to-moderate early reactions and patient acceptance of short-term aesthetic outcomes. Follow-up was preferentially performed in person. When a scheduled in-person visit could not be completed, standardized facial photographs and symptom records were submitted for unified interpretation, and photograph-only assessments were flagged in the dataset for review during analysis.

For photograph-only follow-up records, participants received standardized instructions regarding lighting, distance, facial position, and viewing angles. Images were reviewed for quality before inclusion. Photograph-only records that did not meet the prespecified quality standard were excluded from image-based aesthetic scoring, and all included photograph-only records were flagged so that sensitivity review could be performed.

Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics. Continuous variables were tested for normality. Normally distributed data are presented as mean ± standard deviation and compared using independent-samples t tests; non-normally distributed data were compared using Mann-Whitney U tests. Categorical variables are presented as n (%) and were compared using chi-square tests or Fisher's exact tests. Needle-only, cannula-only, and combined needle/cannula use were compared between groups because device selection may influence ecchymosis. Binary logistic regression models were constructed to identify variables associated with post-injection ecchymosis and suboptimal early aesthetic outcomes; associations are expressed as odds ratios (ORs) and 95% confidence intervals (CIs). Photograph-only follow-up records were included if image quality met the prespecified standard and were flagged for sensitivity review. All tests were two-sided, and P < 0.05 was considered statistically significant.

Results

Baseline characteristics of the study population

A total of 120 subjects were recruited from patients receiving lower facial hyaluronic acid injection; 60 were assigned to the Doppler mapping group and 60 to the landmark-guided group. All subjects completed baseline assessment and were included in the analysis. The two groups were demographically comparable and had similar treatment-related baseline characteristics, as shown in Table 1.

Discussion

This prospective controlled study compared pre-injection Doppler mapping with landmark guidance alone for lower facial hyaluronic acid injection^12,13,14. The main finding was that Doppler mapping was associated with more frequent pre-injection identification of vascular risk signals, more planned route modifications before injection, fewer trauma-related procedural events, lower early ecchymosis, and better short-term aesthetic ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Blunt-tip cannulas	TSK Laboratory International	https://shopeu.tsklab.com/product/steriglide-cannula-30g-x-25mm/	Sterile blunt-tip cannulas, 25–30 G. Used for broader subcutaneous filler distribution and for reducing local tissue trauma when avoidance of superficial vascular pathways was required.
Color Doppler imaging mode	Mindray Bio-Medical Electronics Co.	/	Superficial facial vascular mapping preset, used to identify superficial and deep blood-flow signals and to evaluate their spatial relationship to the planned hyaluronic acid injection plane.
Cross-linked hyaluronic acid filler	Allergan	/	Juvéderm Voluma XC, used for lower facial contour correction and soft-tissue augmentation in the mandibular border, mandibular angle, pre-jowl area, labiomental fold/marionette line region, chin, and superficial lower-lip refinement area.
Digital facial photography system	Chengdu YiXing Plastic Surgery Hospital	/	Standardized lighting, positioning, and facial-angle protocol; used to obtain standardized pre-treatment and post-treatment facial photographs for blinded assessment of ecchymosis and early aesthetic outcomes.
High-frequency linear-array ultrasound probe	Mindray Bio-Medical Electronics Co.	/	L20-5s linear-array probe, used to visualize skin, subcutaneous fat, muscle layers, deeper supporting structures, intended filler plane, and adjacent vascular signals before injection.
High-frequency ultrasound system	Mindray Bio-Medical Electronics Co.	/	Resona 7 Diagnostic Ultrasound System, used for pre-injection gray-scale ultrasonography and Doppler vascular mapping of lower facial soft-tissue layers and vascular risk signals.
IBM SPSS Statistics	IBM Corp.	Version 26.0	Used for statistical analysis, including normality testing, independent-samples t tests, Mann-Whitney U tests, chi-square tests, Fisher exact tests, and binary logistic regression models.
Povidone-iodine skin disinfectant	Shandong Lircon Medical Technology Co., Ltd.	/	Standard clinical skin disinfectant, used for routine treatment-area disinfection before lower facial hyaluronic acid injection.
Sharp injection needles	TSK Laboratory International	/	Sterile sharp needles, 30–32 G, used for precise focal filler placement when periosteal, deep-plane, or region-specific structural support was clinically appropriate.
Sterile marking pen	Viscot Medical, LLC	/	Used to mark lower facial treatment areas, surface landmarks, planned entry points, and Doppler-adjusted injection routes.
Sterile ultrasound gel	Parker Laboratories, Inc.	https://www.parkerlabs.com/product/sterile-aquasonic-ultrasound-transmission-gel/	Used to improve acoustic coupling during pre-injection gray-scale ultrasound and color Doppler assessment.