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.

The mean age of the Doppler mapping group and landmark-guided group was 36.8 ± 8.7 years and 37.4 ± 9.1 years, respectively, with no significant between-group difference. Most subjects were female (86.7% and 83.3%, respectively). Body mass index, previous facial aesthetic treatment, previous filler treatment in other facial areas, easy-ecchymosis history, and current smoking status were not significantly different between groups.

Treatment-related characteristics were also comparable. Bilateral treatment, total injection volume per case, number of treated lower facial regions, and distribution of mandibular border or angle, pre-jowl, labiomental fold or marionette line, chin, and lower-lip refinement treatments did not differ significantly between groups. Needle use was 45.0% in the Doppler mapping group and 48.3% in the landmark-guided group (P = 0.71), while cannula use was 55.0% and 51.7%, respectively (P = 0.71). The distribution of device types (needle-only, cannula-only, or combined) was likewise not significantly different between groups. Baseline lower facial volume-loss and aesthetic concern scores were similar.

Vascular risk signals identified by pre-injection Doppler mapping

In the Doppler mapping group, pre-injection high-frequency ultrasound with color Doppler assessment showed variable vascular risk exposure across lower facial regions. Among 60 subjects, 38 (63.3%) had a detectable blood-flow signal within or adjacent to the intended injection plane, 27 (45.0%) had superficial vascular signals requiring caution, and 29 (48.3%) had a vessel course crossing the originally planned entry pathway. Injection-plan modification based on Doppler findings was recorded in 32 subjects (53.3%). Details are shown in Table 2.

Regional analysis showed the highest vascular signal detection rate in the lower-lip refinement area (70.0%), with a mean vascular depth of 0.14 ± 0.03 cm from the skin surface. The pre-jowl region and labiomental fold or marionette line region also showed frequent vascular signals near the planned injection plane (45.2% and 46.4%, respectively). Planned entry pathways crossed visible vessels in 35.5% and 32.1% of these regions, respectively. The mandibular border or angle and chin regions had deeper mean vascular depths and lower risk-signal proportions, although selected cases still required entry-point or injection-plane modification based on imaging.

Figure 1 shows a representative pre-injection Doppler examination of the anterior mandibular region. Arterial and venous flow signals were visible within the mapped soft-tissue layers, and selected vascular signals were located close to the intended filler plane. The image illustrates how Doppler mapping was used to document patient-specific vascular distribution before injection.

Figure 2 illustrates the pre-jowl assessment workflow. Figure 2A shows surface marking of the treatment area, Figure 2B shows probe placement for pre-injection scanning, Figure 2C shows the adjusted entry site after Doppler assessment, and Figure 2D shows the gray-scale image with focal color Doppler signal adjacent to the target filler plane.

In the perioral region, Figure 3A shows superficial labial arterial signals and their measured depths relative to the skin surface. Figure 3B shows surface markings after vascular localization. These images were used to guide superficial lower-lip refinement planning and to avoid mapped vascular courses during injection.

Ultrasound-based identification of injection planes in key lower facial regions

In addition to vascular risk assessment, the Doppler mapping group underwent pre-injection gray-scale ultrasonography to identify layer-specific anatomy at different lower facial sites. Individual differences were observed in soft-tissue thickness, fat-layer distribution, and deeper supporting structures in the mandibular, anterior mandibular, and labiomental or marionette regions. Gray-scale imaging was used to select the intended filler plane before injection.

Figure 4 shows a representative baseline gray-scale ultrasound anatomy of the mandibular region. The epidermis, dermis, subcutaneous fat, deep fat compartment, and deeper supporting structures were visible. The image was used as a reference for selecting the tissue layer for contour-supportive injection.

Figure 5 shows layer-specific gray-scale ultrasound findings in the anterior mandibular region. The visible superficial fat pad, deep fat compartment, adjacent muscles, and vascular structures helped define the intended filler plane and the relationship between the target layer and nearby vessels.

Figure 6 shows gray-scale ultrasound visualization of the labiomental region. The image demonstrates superficial skin layers, subcutaneous fat, depressor labii inferioris, depressor anguli oris, and deeper bony or foraminal landmarks near the intended filler plane.

Comparison of procedural characteristics between groups

Procedural characteristics are shown in Table 3. The Doppler mapping group required an additional pre-injection imaging step, but the actual injection pathway was more frequently completed as planned and required fewer intra-procedural modifications than the landmark-guided group.

Total procedural time was longer in the Doppler mapping group than in the landmark-guided group (18.6 ± 4.2 min vs. 14.9 ± 3.8 min; P < 0.001). This difference reflected the pre-injection assessment time (5.4 ± 1.6 min vs. 1.8 ± 0.7 min; P < 0.001). Actual injection time was not significantly different between groups (10.9 ± 2.8 min vs. 11.7 ± 2.9 min; P = 0.13).

Trauma-related procedural indicators were lower in the Doppler mapping group. Mean needle passes per patient were 4.1 ± 1.5 in the Doppler mapping group and 5.3 ± 1.8 in the landmark-guided group (P < 0.001). The number of skin entry points was 2.6 ± 1.0 and 3.2 ± 1.1, respectively (P = 0.003).

Intra-procedural modifications were less frequent in the Doppler mapping group. Entry-point changes occurred in 11.7% and 26.7% of cases, respectively; injection-plane changes occurred in 8.3% and 23.3%; and needle or cannula redirection occurred in 15.0% and 35.0%. The procedure was completed as initially planned in 85.0% of Doppler mapping cases and 65.0% of landmark-guided cases.

Comparison of ecchymosis and early local adverse events

Post-injection ecchymosis and early local adverse events are summarized in Table 4. The Doppler mapping group had lower ecchymosis incidence and severity than the landmark-guided group at the prespecified early follow-up points.

Ecchymosis within the first 24 h occurred in 18.3% of subjects in the Doppler mapping group and 40.0% in the landmark-guided group (P = 0.010). On day 3, ecchymosis remained significantly less frequent in the Doppler mapping group (23.3% vs. 48.3%; P = 0.004). Persistent ecchymosis on day 7 occurred in 6.7% and 20.0% of subjects, respectively (P = 0.031). The Doppler mapping group also had lower ecchymosis severity scores at 24 h and day 3 and a smaller largest ecchymosis diameter.

Other early local reactions showed similar directional trends. Local swelling, tenderness, and erythema within 24 h were numerically lower in the Doppler mapping group. Immediate puncture-site bleeding was significantly lower in the Doppler mapping group (10.0% vs. 23.3%; P = 0.047). Transient blanching and need for unscheduled post-procedure review were less frequent in the Doppler mapping group, although these differences did not reach statistical significance.

Comparison of early aesthetic outcomes and patient satisfaction

Early aesthetic outcomes and patient-reported satisfaction are shown in Table 5. At day 7, the Doppler mapping group had higher investigator-rated and patient-reported aesthetic improvement scores than the landmark-guided group.

The Doppler mapping group had higher investigator-rated aesthetic improvement scores (3.9 ± 0.7 vs. 3.5 ± 0.8; P = 0.006) and patient-reported improvement scores (4.0 ± 0.8 vs. 3.6 ± 0.9; P = 0.011). Global Aesthetic Improvement Scale scores were lower in the Doppler mapping group (2.1 ± 0.7 vs. 2.5 ± 0.8; P = 0.004), where lower GAIS scores indicate greater improvement. Naturalness, symmetry, contour smoothness, and lower facial line-continuity scores were also higher in the Doppler mapping group.

Patient-reported experience was more favorable in the Doppler mapping group. Overall satisfaction scores were higher (8.4 ± 1.1 vs. 7.6 ± 1.4; P = 0.001). A greater proportion of subjects in the Doppler mapping group were willing to undergo the same procedure again (90.0% vs. 76.7%; P = 0.047), were satisfied with the recovery process (83.3% vs. 65.0%; P = 0.022), and considered downtime acceptable (86.7% vs. 68.3%; P = 0.016).

Multivariable analysis of factors associated with ecchymosis and suboptimal early outcomes

Multivariable logistic regression analysis is shown in Table 6. After adjustment for age, sex, body mass index (BMI), easy-ecchymosis history, smoking status, injection dose, device type, number of needle passes, and treatment area, assignment to the Doppler mapping group was independently associated with lower odds of post-injection ecchymosis (OR = 0.38; 95% CI: 0.17–0.82; P = 0.014). Doppler mapping was also associated with lower odds of suboptimal early aesthetic outcomes (OR = 0.44; 95% CI: 0.20–0.96; P = 0.039).

Easy-ecchymosis history, needle use rather than cannula-only use, and a greater number of needle passes were associated with increased odds of post-injection ecchymosis. Lower-lip refinement was also associated with increased ecchymosis risk. Age, sex, BMI, and smoking status were not independently associated with post-injection ecchymosis in this model.

In the model for suboptimal early aesthetic outcomes, ecchymosis severity at 24 h was independently associated with worse early aesthetic outcomes. Higher total injection volume and treatment involving the labiomental fold or marionette lines showed a trend toward increased risk but did not reach statistical significance.

In summary, the principal findings demonstrate that pre-injection Doppler mapping effectively identified individualized vascular risk signals, leading to a higher rate of pre-planned procedural modifications. Compared with landmark guidance alone, this imaging-informed strategy significantly reduced procedure-related trauma and the incidence of early post-injection ecchymosis, while being independently associated with enhanced short-term aesthetic outcomes and overall patient satisfaction.

DATA AVAILABILITY:

The de-identified dataset supporting the tables and numerical source data for the figures has been deposited in Zenodo and is publicly available at https://doi.org/10.5281/zenodo.20677606. The deposited record is titled Pre-Injection Doppler Mapping Versus Landmark Guidance for Lower Facial Hyaluronic Acid Injection: A Prospective Safety Study and includes the file data.xlsx. The public dataset includes de-identified participant-level demographic, treatment, Doppler-mapping, follow-up, adverse-event, and outcome variables used for the analyses.

Figure 1: Pre-injection Doppler mapping of vascular signals in the anterior mandibular region. Color Doppler demonstrates arterial and venous flow signals in relation to the mapped lower facial soft-tissue layers and intended filler plane. Please click here to view a larger version of this figure.

Figure 2: Pre-injection Doppler assessment workflow for the pre-jowl area. (A) Surface marking of the pre-jowl treatment area. (B) Placement of the high-frequency ultrasound probe for pre-injection scanning. (C) Needle entry site selected after Doppler vascular assessment. (D) Gray-scale ultrasound with a focal color Doppler signal adjacent to the target filler plane. Please click here to view a larger version of this figure.

Figure 3: Pre-injection Doppler identification of superficial labial arterial signals for lower facial hyaluronic acid injection planning. (A) Color Doppler image showing superficial labial arterial signals and measured depth from the skin surface. (B) Surface marking after vascular localization. Please click here to view a larger version of this figure.

Figure 4: Baseline ultrasound anatomy of the mandibular region in the Doppler mapping group. The image demonstrates skin layers, subcutaneous fat, deep fat compartment, and deeper supporting structures relevant to filler-plane selection. Please click here to view a larger version of this figure.

Figure 5: Layer-specific gray-scale ultrasound of the anterior mandibular region. The intended filler plane is shown in relation to superficial and deep fat compartments, adjacent muscles, and nearby vascular structures. Please click here to view a larger version of this figure.

Figure 6: Gray-scale ultrasound visualization of the labiomental region for lower facial injection planning. The image shows superficial layers, subcutaneous fat, perioral depressor muscles, deeper bony or foraminal landmarks, and the intended filler plane. Please click here to view a larger version of this figure.

Variable		Doppler mapping group	Landmark-guided group	P value
		(n = 60)	(n = 60)
Age, years		36.8 ± 8.7	37.4 ± 9.1	0.71
Female, n (%)		52 (86.7)	50 (83.3)	0.6
BMI, kg/m²		22.4 ± 2.8	22.7 ± 3.0	0.58
Previous facial aesthetic treatment, n (%)		19 (31.7)	21 (35.0)	0.7
Previous filler treatment in other facial areas, n (%)		11 (18.3)	13 (21.7)	0.64
Easy bruising history, n (%)		8 (13.3)	10 (16.7)	0.6
Current smoker, n (%)		6 (10.0)	7 (11.7)	0.77
Bilateral treatment, n (%)		48 (80.0)	46 (76.7)	0.66
Total injection volume per patient, mL		2.3 ± 0.7	2.4 ± 0.8	0.49
Needle use, n (%)		27 (45.0)	29 (48.3)	0.71
Cannula use, n (%)		33 (55.0)	31 (51.7)	0.71
Number of treated lower facial regions		2.1 ± 0.8	2.2 ± 0.7	0.56
Jawline/mandibular angle treatment, n (%)		39 (65.0)	41 (68.3)	0.7
Pre-jowl treatment, n (%)		31 (51.7)	29 (48.3)	0.71
Labiomental fold/marionette line treatment, n (%)		28 (46.7)	30 (50.0)	0.71
Chin treatment, n (%)		24 (40.0)	26 (43.3)	0.71
Lower lip refinement, n (%)		10 (16.7)	9 (15.0)	0.8
Baseline lower facial volume loss score		2.6 ± 0.7	2.5 ± 0.8	0.52
Baseline aesthetic concern score (0–10)		6.9 ± 1.4	7.1 ± 1.5	0.47

Table 1: Baseline demographic and treatment characteristics of participants in the Doppler mapping and landmark-guided groups. Data are presented as mean ± standard deviation or n (%). BMI: Body Mass Index. Baseline aesthetic concern score was evaluated on a scale from 0 (no concern) to 10 (severe concern).

Variable		Jawline / mandibular angle	Pre-jowl region	Labiomental fold / marionette line (n = 28)	Chin	Lower lip refinement	Overall
		(n = 39)	(n = 31)		(n = 24)	(n = 10)	(n = 60)
Detectable vascular signal within or adjacent to intended injection plane, n (%)		11 (28.2)	14 (45.2)	13 (46.4)	5 (20.8)	7 (70.0)	38 (63.3)
Superficial vascular signal requiring caution, n (%)		6 (15.4)	9 (29.0)	10 (35.7)	3 (12.5)	7 (70.0)	27 (45.0)
Course of vessel crossing the planned entry pathway, n (%)		8 (20.5)	11 (35.5)	9 (32.1)	4 (16.7)	5 (50.0)	29 (48.3)
Mean vessel depth from skin surface, cm		0.84 ± 0.18	0.63 ± 0.15	0.58 ± 0.14	0.91 ± 0.21	0.14 ± 0.03	0.64 ± 0.29
Modification of entry point after Doppler assessment, n (%)		7 (17.9)	10 (32.3)	8 (28.6)	3 (12.5)	5 (50.0)	24 (40.0)
Modification of injection plane, n (%)		6 (15.4)	9 (29.0)	8 (28.6)	2 (8.3)	4 (40.0)	21 (35.0)
Modification of injection direction, n (%)		5 (12.8)	8 (25.8)	7 (25.0)	2 (8.3)	4 (40.0)	19 (31.7)
Change in device choice between needle and cannula, n (%)		3 (7.7)	5 (16.1)	4 (14.3)	1 (4.2)	2 (20.0)	11 (18.3)
Any injection-plan modification based on Doppler findings, n (%)		10 (25.6)	13 (41.9)	11 (39.3)	4 (16.7)	6 (60.0)	32 (53.3)
Cases judged to have relatively high vascular risk, n (%)		5 (12.8)	8 (25.8)	8 (28.6)	2 (8.3)	5 (50.0)	20 (33.3)

Table 2: Pre-injection vascular risk signals and injection-plan modifications identified in the Doppler mapping group. Cases with "relatively high vascular risk" were defined as those exhibiting a detectable vascular signal adjacent to the intended plane, a superficial vessel requiring caution, or a vessel crossing the planned pathway.

Variable		Doppler mapping group	Landmark-guided group	P value
		(n = 60)	(n = 60)
Total procedural time per patient, min		18.6 ± 4.2	14.9 ± 3.8	<0.001
Pre-injection assessment time, min		5.4 ± 1.6	1.8 ± 0.7	<0.001
Injection time, min		10.9 ± 2.8	11.7 ± 2.9	0.13
Needle passes per patient		4.1 ± 1.5	5.3 ± 1.8	<0.001
Number of skin entry points		2.6 ± 1.0	3.2 ± 1.1	0.003
Total injection volume per patient, mL		2.3 ± 0.7	2.4 ± 0.8	0.49
Change of entry point during procedure, n (%)		7 (11.7)	16 (26.7)	0.038
Change of injection plane during procedure, n (%)		5 (8.3)	14 (23.3)	0.024
Intra-procedural redirection of needle or cannula, n (%)		9 (15.0)	21 (35.0)	0.011
Use of needle only, n (%)		21 (35.0)	24 (40.0)	0.57
Use of cannula only, n (%)		18 (30.0)	17 (28.3)	0.84
Combined needle and cannula use, n (%)		21 (35.0)	19 (31.7)	0.7
Immediate blanching or suspected vascular compression requiring pause, n (%)		1 (1.7)	5 (8.3)	0.09
Immediate visible puncture-site bleeding, n (%)		6 (10.0)	14 (23.3)	0.047
Procedure completed as initially planned, n (%)		51 (85.0)	39 (65.0)	0.012

Table 3: Comparison of procedural features between the Doppler mapping and landmark-guided groups. Data are presented as mean ± standard deviation or n (%).

Variable	Doppler mapping group	Landmark-guided group	P value
	(n = 60)	(n = 60)
Any ecchymosis within 24 h, n (%)	11 (18.3)	24 (40.0)	0.01
Any ecchymosis on day 3, n (%)	14 (23.3)	29 (48.3)	0.004
Persistent ecchymosis on day 7, n (%)	4 (6.7)	12 (20.0)	0.031
Ecchymosis severity score at 24 h	0.7 ± 0.9	1.4 ± 1.1	<0.001
Ecchymosis severity score on day 3	0.9 ± 1.0	1.7 ± 1.2	<0.001
Largest ecchymosis diameter, cm	0.8 ± 0.5	1.5 ± 0.8	<0.001
Local swelling within 24 h, n (%)	19 (31.7)	27 (45.0)	0.13
Local swelling on day 3, n (%)	10 (16.7)	19 (31.7)	0.055
Tenderness within 24 h, n (%)	16 (26.7)	23 (38.3)	0.17
Tenderness on day 3, n (%)	7 (11.7)	15 (25.0)	0.058
Erythema within 24 h, n (%)	9 (15.0)	16 (26.7)	0.12
Palpable irregularity or lump sensation on day 7, n (%)	3 (5.0)	6 (10.0)	0.3
Immediate puncture-site bleeding, n (%)	6 (10.0)	14 (23.3)	0.047
Transient blanching, n (%)	1 (1.7)	5 (8.3)	0.09
Need for unscheduled post-procedure review, n (%)	2 (3.3)	7 (11.7)	0.08
Any early local adverse event, n (%)	24 (40.0)	37 (61.7)	0.018

Table 4: Comparison of post-injection ecchymosis and early local adverse events between groups. Ecchymosis severity was graded on a 0–3 scale (0 = no visible ecchymosis, 1 = mild punctate/limited, 2 = moderate localized, 3 = extensive/severe).

Variable	Doppler mapping group	Landmark-guided group	P value
	(n = 60)	(n = 60)
Investigator-rated aesthetic improvement score at day 7	3.9 ± 0.7	3.5 ± 0.8	0.006
Patient-reported aesthetic improvement score at day 7	4.0 ± 0.8	3.6 ± 0.9	0.011
Global Aesthetic Improvement Scale at day 7	2.1 ± 0.7	2.5 ± 0.8	0.004
Overall patient satisfaction score at day 7	8.4 ± 1.1	7.6 ± 1.4	0.001
Naturalness score at day 7	4.1 ± 0.7	3.7 ± 0.8	0.008
Symmetry score at day 7	4.0 ± 0.8	3.6 ± 0.9	0.014
Willingness to undergo the same procedure again, n (%)	54 (90.0)	46 (76.7)	0.047
Satisfaction with recovery process, n (%)	50 (83.3)	39 (65.0)	0.022
Perceived downtime as acceptable, n (%)	52 (86.7)	41 (68.3)	0.016
Need for minor touch-up or correction by day 7, n (%)	4 (6.7)	10 (16.7)	0.08
Investigator-rated contour smoothness score at day 7	4.0 ± 0.6	3.6 ± 0.8	0.003
Investigator-rated lower facial line continuity score at day 7	3.9 ± 0.7	3.5 ± 0.8	0.005

Table 5: Comparison of early aesthetic effects and patient-reported satisfaction between the two groups. Investigator-rated aesthetic scores (improvement, naturalness, symmetry, smoothness, continuity) and patient-reported improvement scores were assessed on a 5-point scale (1 = poor, 5 = excellent). The Global Aesthetic Improvement Scale (GAIS) was evaluated from 1 (exceptional improvement) to 5 (worse). Overall patient satisfaction was scored on a scale of 0–10.

Variable		Post-injection ecchymosis OR (95% CI)	P value	Suboptimal early aesthetic outcomes OR (95% CI)	P value
Doppler mapping group (vs landmark-guided group)		0.38 (0.17–0.82)	0.014	0.44 (0.20–0.96)	0.039
Age, per year increase		1.02 (0.98–1.07)	0.29	1.03 (0.99–1.07)	0.11
Female sex		0.91 (0.28–2.95)	0.88	0.84 (0.25–2.81)	0.78
BMI, per kg/m² increase		1.06 (0.94–1.20)	0.34	1.04 (0.92–1.18)	0.53
Easy ecchymosis history		2.61 (1.01–6.74)	0.048	1.39 (0.49–3.96)	0.54
Current smoker		1.48 (0.47–4.61)	0.5	1.72 (0.54–5.46)	0.36
Total injection volume, per 1 mL increase		1.31 (0.82–2.08)	0.25	1.56 (0.97–2.52)	0.067
Needle use (vs cannula only)		1.94 (1.01–3.75)	0.047	1.42 (0.72–2.81)	0.31
Combined needle and cannula use (vs cannula only)		1.28 (0.61–2.68)	0.52	1.19 (0.56–2.51)	0.65
Number of needle passes, per additional pass		1.22 (1.01–1.49)	0.043	1.16 (0.95–1.40)	0.14
Pre-jowl treatment		1.63 (0.80–3.33)	0.18	1.49 (0.72–3.08)	0.28
Labiomental fold / marionette line treatment		1.71 (0.84–3.47)	0.14	1.88 (0.91–3.89)	0.09
Lower lip refinement		2.84 (1.01–8.01)	0.048	1.67 (0.56–4.97)	0.36
Presence of detectable vascular risk signal near intended plane		1.89 (0.92–3.88)	0.083	1.41 (0.68–2.95)	0.35
Ecchymosis severity score at 24 h		—	—	1.92 (1.28–2.89)	0.002

Table 6: Multivariable analyses of factors related to post-treatment ecchymosis and suboptimal early aesthetic results. OR: Odds Ratio; CI: Confidence Interval. “Suboptimal early aesthetic outcomes” were defined as an investigator-rated aesthetic improvement score of ≤3 or a score of ≤3 in any individual aesthetic domain (naturalness, symmetry, contour smoothness, or line continuity) at day 7.

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 and patient-reported outcomes. These findings extend prior reports describing ultrasound-assisted filler practice by providing controlled prospective data in the lower face¹⁵.

Previous ultrasound-focused aesthetic reports have mainly emphasized anatomical visualization, vessel localization, and complication management, whereas fewer studies have prospectively compared a pre-injection mapping workflow with landmark guidance alone in lower facial filler procedures. The present results are therefore best interpreted as pragmatic evidence that patient-specific vascular mapping may improve early procedural planning and recovery metrics, while remaining consistent with prior recommendations that ultrasound should complement, not replace, conservative injection technique and continuous clinical monitoring.

The observed rate of pre-injection plan modification supports the clinical relevance of individualized vascular anatomy. Previous anatomical and ultrasound studies have described variability in the facial artery, inferior labial artery, and related branches around the mandibular border and perioral region¹⁶. In the present study, lower-lip refinement had the highest frequency of detectable vascular signals and the shallowest mean vessel depth. This depth should be interpreted as a study-specific imaging observation rather than a universal anatomical value, because vessel plane and detectability may vary with probe pressure, patient position, and Doppler settings.

The reduction in ecchymosis should be interpreted in relation to procedural planning rather than as proof that Doppler mapping alone prevents vascular injury. Needle/cannula distribution was comparable between groups, and multivariable analysis adjusted for device type and needle passes. Therefore, the lower ecchymosis rate was less likely to be explained solely by different device selection. A plausible explanation is that pre-injection visualization helped the injector avoid visible vascular pathways, reduce repeated entry attempts, and complete more procedures as initially planned¹⁷.

Compared with real-time ultrasound-guided injection, the workflow used in this study was a pre-injection mapping strategy. This approach may be easier to incorporate into routine aesthetic practice because it adds a short planning step without requiring continuous probe handling during injection. It may also support training by encouraging injectors to link surface landmarks with patient-specific layer anatomy. However, future studies should compare landmark guidance, pre-injection mapping, and real-time ultrasound-guided injection directly to define the relative advantages of each strategy^18,19.

Several limitations should be noted. First, this was a single-center study with a limited sample size, so multicenter validation is needed. Second, follow-up was limited to 7 days, and long-term filler stability or delayed adverse events were not assessed. Third, pre-injection mapping does not completely exclude vascular complications because vessels may have tortuous, branching, or plane-changing courses that cannot be fully captured in a single scan. Low-flow vessels may also be difficult to visualize with color Doppler alone; therefore, the absence of a detectable signal should not be interpreted as the absence of risk. Strict injection precautions, including slow injection, small aliquots, appropriate plane selection, and continuous clinical monitoring, remain essential²⁰.

Image acquisition may also influence interpretation. Excessive probe pressure can compress superficial tissues and low-flow vessels, and image labels must be anatomically precise to avoid misunderstanding. Future work should standardize scanning pressure, Doppler settings, photograph-only follow-up handling, and assessor blinding across centers.

Pre-injection Doppler mapping was associated with individualized vascular risk identification and safer injection-route planning for lower facial hyaluronic acid injection. Compared with landmark guidance alone, it was associated with lower early ecchymosis, fewer trauma-related procedural indicators, improved early aesthetic outcomes, and higher patient satisfaction. Because the study was prospective but single-center and not designed as real-time ultrasound guidance, the findings should be interpreted as supporting Doppler mapping as a useful adjunct rather than as a method that eliminates vascular risk.

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.