Quantitative measurement of post-irradiation neck fibrosis based on the young modulus: description of a new method and clinical results

Quantitative measurements of radiation-induced fibrosis for head and neck cancer: A narrative review

Objectives

To provide a comprehensive summary of the different modalities available to measure soft tissue fibrosis after radiotherapy in head and neck cancer patients.

Data Sources

PubMed, Scopus, and Web of Sciences.

Review Methods

A search was conducted using a list of medical subject headings and terms related to head and neck oncology, radiation fibrosis, and quantitative measurements, including bioimpedance, MRI, and ultrasound. Original research related to quantitative measurement of neck fibrosis post-radiotherapy was included without time constraints, while reviews, case reports, non-English texts, and inaccessible studies were excluded. Discrepancies during the review were resolved by discussing with the senior author until consensus was reached.

Results

A total of 284 articles were identified and underwent title and abstract screening. Seventeen articles had met our criteria for full-text review based on relevance, of which nine had met our inclusion criteria. Young's modulus (YM) and viscoelasticity measures have demonstrated efficacy in quantifying neck fibrosis, with fibrotic tissues displaying significantly higher YM values and altered viscoelastic properties such as increased stiffness rate-sensitivity and prolonged stress-relaxation post-radiation. Intravoxel incoherent motion offers detailed insights into tissue changes by assessing the diffusion of water molecules and blood perfusion, thereby differentiating fibrosed from healthy tissues. Shear wave elastography has proven to be an effective technique for quantifying radiation-induced fibrosis in the head and neck region by measuring shear wave velocity.

Conclusion

There are various modalities to measure radiation-induced fibrosis, each with its unique strengths and limitations. Providers should be aware of these implications and decide on methodologies based on their specific clinical workflow.

Level of Evidence

Step 5.

Bioactive skin-mimicking hydrogel band-aids for diabetic wound healing and infectious skin incision treatment

The treatment of diabetic chronic wounds remains a global challenge due to the up-regulated inflammation response, oxidant stress, and persistent infection during healing process. Developing wound dressing materials with ideal biocompatibility, adequate mechanical strength, considerable under-water adhesion, sufficient anti-inflammation, antioxidant, and antibacterial properties is on-demand for clinical applications. In this study, we developed a bioactive skin-mimicking hydrogel band-aid through the combination of tannic acid (TA) and imidazolidinyl urea reinforced polyurethane (PMI) (TAP hydrogel) and explored its potentials in various medical applications, including hemostasis, normal skin incision, full-thickness skin wounds, and bacterial-infection skin incision on diabetic mice. TA was loaded into PMI hydrogel network to enhance the mechanical properties of TAP hydrogels through multiple non-covalent interactions (break strength: 0.28–0.64 MPa; elongation at break: 650–930%), which could resist the local stress and maintain the structural integrity of wound dressings during applications. Moreover, owing to the promising moisture-resistant adhesiveness and organ hemostasis, outstanding anti-inflammation, antibacterial, and antioxidant properties, TAP hydrogels could efficiently promote the recovery of skin incision and defects on diabetic mice. To further simulate the practical situation and explore the potential in clinical application, we also verified the treatment efficiency of TAP hydrogel in S. aureus-infected skin incision model on diabetic mice.

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Bioactive skin-mimicking hydrogels were developed through the combination of tannic acid and polyurethane.

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The wound healing and infected skin incision closure by the bioactive skin-mimicking hydrogels were studied on diabetic mice.

Fat Grafting in Radiation-Induced Soft-Tissue Injury: A Narrative Review of the Clinical Evidence and Implications for Future Studies

SUMMARY

Radiation-induced changes in skin and soft tissue result in significant cosmetic and functional impairment with subsequent decrease in quality of life. Fat grafting has emerged as a therapy for radiation-induced soft-tissue injury, and this narrative review aims to evaluate the current clinical evidence regarding its efficacy. A review was conducted to examine the current clinical evidence of fat grafting as a therapy for radiation-induced injury to the skin and soft tissue and to outline the clinical outcomes that can be used to more consistently quantify chronic radiation-induced injury in future clinical studies. The current clinical evidence regarding the efficacy of fat grafting to treat radiation-induced injury of the skin and soft tissue suggests that fat grafting increases skin softness and pliability, induces volume restoration, improves hair growth in areas of alopecia, reduces pain, and improves cosmetic and functional outcomes. However, literature in this field is far from robust and mired by the retrospective nature of the studies, lack of adequate controls, and inherent limitations of small case series and cohorts. A series of actions have been identified to strengthen future clinical data, including the need for physical examination using a validated scale, appropriate imaging, skin biomechanics and microcirculation testing, and histologic analysis. In conclusion, radiation-induced soft-tissue injury is a significant health burden that can lead to severe functional and aesthetic sequelae. Although still in a preliminary research phase, there is promising clinical evidence demonstrating the benefits of fat grafting to treat chronic changes after radiation therapy. Future clinical studies will require larger cohorts, adequate controls, and consistent use of objective measurements.

A portable pen-sized instrumentation to measure stiffness of soft tissues in vivo

Quantitative assessment of soft tissue elasticity is crucial to a broad range of applications, such as biomechanical modeling, physiological monitoring, and tissue diseases diagnosing. However, the modulus measurement of soft tissues, particularly in vivo, has proved challenging since the instrument has to reach the site of soft tissue and be able to measure in a very short time. Here, we present a simple method to measure the elastic modulus of soft tissues on site by exploiting buckling of a long slender bar to quantify the applied force and a spherical indentation to extract the elastic modulus. The method is realized by developing a portable pen-sized instrument (EPen: Elastic modulus pen). The measurement accuracies are verified by independent modulus measures using commercial nanoindenter. Quantitative measurements of the elastic modulus of mouse pancreas, healthy and cancerous, surgically exposed but attached to the body further confirm the potential clinical utility of the EPen.

Cervical Fibrosis as a Predictor of Dysphagia

OBJECTIVE

Radiotherapy of head and neck cancer (HNCA) causes dysfunction through radiation-induced fibrosis (RIF). We hypothesize that the degree of cervical fibrosis is associated with swallowing dysfunction. This study evaluated the association between cervical fibrosis and swallowing dysfunction in patients after radiation therapy for HNCA.

STUDY DESIGN

Cross sectional study.

METHODOLOGY

A convenience sample of patients with dysphagia who were at least 1 year post radiation therapy for HNCA underwent simultaneous cervical ultrasound (US) and video-fluroscopic swallow study (VFSS). US determinants of fibrosis were measurements of sternocleidomastoid fascia (SCMF) thickness bilaterally at the level of the cricoid. Primary and secondary outcome variables on VFSS were pharyngeal constriction ratio, a validated measure of pharyngeal contractility, and penetration aspiration scale (PAS). A qualitative assessment of lateral neck rotation was performed as a functional measure of neck fibrosis.

RESULTS

Simultaneous cervical US and VFSS examinations were performed on 18 patients with a history of radiotherapy for HNCA and on eight controls. The mean (±SD) age of the entire cohort (N = 26) was 66 (±10) years. Individuals with a history of radiation had significantly thinner mean SCMF (0.26 [±0.04 mm]) compared to controls (0.48 [±0.06 mm]; P < .05). Individuals with thinner SCMF were more likely to have moderate to severe restriction in lateral neck rotation, a higher PCR, and a higher PAS (P < .05).

CONCLUSION

Thinner sternocleidomastoid fascia on ultrasound in patients having undergone radiotherapy for head and neck cancer was associated with reduced lateral neck movement, poorer pharyngeal constriction and greater penetration/aspiration scale. The data suggest that cervical fibrosis is associated with swallowing dysfunction in head and neck cancer survivors and support the notion that, "As the neck goes, so does the swallow."

LEVEL OF EVIDENCE

3. Laryngoscope, 131:548-552, 2021.

Can knee flexion contracture affect cervical alignment and neck tension? A prospective self-controlled pilot study

BACKGROUND CONTEXT

The coordination of the alignment between the lower extremities and cervical spine helps to achieve balance and horizontal gaze during standing and walking. Malalignment in any segment can disturb the global balance, causing compensation in another segment. Knee flexion contracture (KFC) can cause spine inclination with increased C7 tilt or C7 SVA (sagittal vertical axis). Cervical alignment and the posterior muscles are essential for maintaining the horizontal gaze which is closely related to neck tension (NT).

PURPOSE

This study aimed to determine whether KFC can affect cervical alignment and its potential effects on the posterior muscles and NT.

DESIGN

A prospective pilot study was carried out in preoperative (pre-op) and postoperative (post-op) phases.

PATIENT SAMPLE

This study included 22 consecutive patients with KFC and 12 control subjects in our department who agreed to participate from between August 1, 2018 and February 28, 2019 in our department.

OUTCOME MEASURES

Visual analog scale (VAS) and neck disability index (NDI) were used. The sagittal alignment parameters and cervical range of motion (ROM) were measured on radiographic images, and included the C0-C2 lordosis (C0-2L), C2-C7 lordosis (C2-7L), C2 SVA, C7 SVA, T1 slope, thoracic kyphosis, lumbar lordosis (LL), pelvic tilt, sacral slope, and knee flexion angle (KA). Surface electromyography-based flexion-relaxation ratio (FRR) and ultrasound-based shear wave elastography (SWE) were performed.

METHODS

The control group was matched for age, sex, and body mass index with the KFC group. Patients in the KFC group underwent arthroscopic surgery to correct knee alignment. Comparisons between pre-op and post-op phases were performed using paired sample t tests, comparisons between KFC and control groups were performed using independent samples t tests. The correlation analysis between the parameters was performed using Spearman analysis. Funding for this study was provided by the National Natural Science Foundation of China (60,000 USD), Beijing Municipal Administration of Hospitals Incubating Program (50,000 USD), and Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support (20,000 USD). There were no conflicts of interest associated with this study.

RESULTS

The average follow-up time for this pilot study was 11.4±1.5 days. Pre-op, the KFC group had higher KA, T1S, C7 SVA, C2 SVA, C0-2L, SWE, VAS, and NDI compared with the control group, but all of these parameters were decreased significantly post-op. The LL, FRR of splenius capitis (FRRsc), and ROM of the KFC group pre-op were lower than the control group, and all of these were increased significantly post-op. There were no differences in pelvic tilt, sacral slope, C2-7 L, or TK between the KFC and control groups, or in FRR of splenius capitis (FRRutr) between pre-op and post-op phases. KA had strong correlations with LL (r=-0.83), which correlated well with C7 SVA (r=-0.75). C7 SVA correlated strongly with C2 SVA (r=0.79), which also correlated strongly with C0-2 L (r=0.76). C0-2 L correlated well with FRRsc (r=-0.65) and SWEsc (r=0.72), and both of them correlated well with VAS (r=-0.54, r=0.71) and NDI (r=-0.57, r=0.76). ROM correlated well with FRRsc (r=0.71), SWEsc (r=-0.74), VAS (r=-0.66), and NDI (r=-0.66).

CONCLUSIONS

KFC may cause spine inclination and craniocervical malalignment, leading to NT and ROM reduction. The results of this pilot study may be helpful in guiding further studies concerning KFC and NT.

Quantitative Evaluation of Shear Wave Elastography on Radiation-Induced Neck Fibrosis in Patients With Nasopharyngeal Carcinoma

ABSTRACT

The value of shear wave elastography (SWE) for quantitatively assessing neck fibrosis induced by radiotherapy (RT) in patients with nasopharyngeal carcinoma was evaluated over time. We prospectively observed 56 patients with nasopharyngeal carcinoma before and after therapeutic neck irradiation. The elasticity parameters including Emax and Emean were used to measure the stiffness of the bilateral sternocleidomastoid muscles. Twenty-seven patients completed a 1.5-year follow-up, with examinations beginning at 3, 6, 12, and 18 months after RT. Forty controls were recruited for reliability tests (along with the patients) and measurement comparisons. The consistency of SWE measurements with the Late Effects Normal Tissue Task Force-Subjective, Objective, Management and Analytic (LENT-SOMA) scale was tested. The intraclass correlation coefficients of elasticity indices for both patients and controls were higher than 0.75. The Emax and Emean of bilateral sternocleidomastoid muscles in the pre-RT patient group were comparable with those of the controls, and increased with increasing postirradiation duration (r = 0.514-0.555; P < 0.01). Significant increases in the Emax and Emean were observed 18 months after RT. The SWE correlated well with the LENT-SOMA score when assessing radiation-induced neck fibrosis 1.5 years after RT (r = 0.557-0.649; P < 0.01). Furthermore, both the Emax and Emean in the LENT-SOMA grade 0 subtype were higher 18 months after RT than before RT (P < 0.01). Because of its high reliability and good consistency with the LENT-SOMA score and better stiffness reflection at grade 0, SWE may be used to objectively and quantitatively evaluate the variation trend of radiation-induced neck fibrosis.

Pravastatin Reverses Established Radiation-Induced Cutaneous and Subcutaneous Fibrosis in Patients With Head and Neck Cancer: Results of the Biology-Driven Phase 2 Clinical Trial Pravacur

PURPOSE

The "PRAVACUR" phase 2 trial (NCT01268202) assessed the efficacy of pravastatin as an antifibrotic agent in patients with established cutaneous and subcutaneous radiation-induced fibrosis (RIF) after head and neck squamous cell carcinoma (HNSCC) radiation therapy and/or radiochemotherapy.

METHODS AND MATERIALS

The main inclusion criteria were: NSCC in remission, grade ≥2 cutaneous and subcutaneous neck RIF (National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0), and no current treatment with statins or fibrates. Patients received pravastatin 40 mg/d for 12 months. The primary endpoint was reduction of RIF thickness by more than 30% at 12 months, as measured by cutaneous high-frequency ultrasonography. Secondary endpoints included RIF severity reduction, pravastatin tolerance, and quality of life.

RESULTS

Sixty patients with grade 2 (n = 37), grade 3 (n = 22), or grade 4 (n = 1) RIF were enrolled from February 2011 to April 2016. The mean interval between RIF diagnosis and pravastatin initiation was 17.1 months. Pravastatin was stopped before 11 months of treatment in 18 patients (because of grade ≥2 adverse events related to pravastatin in 8 patients [13%]). In the 40 patients in whom pravastatin efficacy was assessed by high-frequency ultrasonography at baseline and at 12 months of treatment, a reduction of RIF thickness ≥30% was observed in 15 of 42 patients (35.7%; 95% confidence interval, 21.6%-52.0%). At the 12-month clinical evaluation, RIF severity was decreased in 50% of patients (n = 21; 95% confidence interval, 34.2%-65.8%), and the patients' self-perception, mood state, and social functioning were significantly improved. Pravastatin was well tolerated, with a very low occurrence of grade 3 toxicities (myalgia, n = 1) and grade 2 toxicities (myalgia/arthralgia or esophagitis, n = 3).

CONCLUSIONS

This phase 2 prospective study supports the notion of radioinduced fibrosis reversibility. It showed that pravastatin (40 mg/d for 12 months) is an efficient antifibrotic agent in patients with grade ≥2 cutaneous and subcutaneous fibrosis after HNSCC radiation therapy.

Endoscope-assisted conservative resection and reconstruction in recurrent subglottic carcinoma

BACKGROUND

Very few cases of conservative laryngectomy in recurrent carcinoma of subglottis postradiotherapy have been reported. Technical aspects of conservative resection and reconstruction in subglottic carcinoma have not been well described.

METHODS

Herein, we present a case of recurrent carcinoma of subglottis for which conservative resection with adequate margins was done with endoscope assistance and defect reconstructed by buccal mucosa, conchal cartilage, and temporoparietal free flap. The technique of resection, reconstruction, complications, postoperative outcome, and our suggestions are described.

RESULTS

The lesion could be removed with wide margins. Reconstruction could preserve the voice, and deglutition was unaffected. There was no donor site-related complication. Complications were a result of the choice of the stent, which included infection and difficulty in removal.

CONCLUSION

Selected cases of recurrent carcinoma of the subglottis can be managed by conservative resection with adequate margins and appropriate reconstruction with good functional outcomes.

Essential Role of Lyn in Fibrosis

Fibrotic disorders involve replacement of normal parenchyma with myofibroblasts, which deposit connective tissue, leading to obliteration of the function of the underlying organ. The treatment options are inadequate and reflect the fact that signaling targets in myofibroblasts are unknown. Here we identify the hyperactive Lyn signaling in myofibroblasts of patients with chronic pancreatitis-induced fibrosis. Lyn activation coexpress with markers of activated myofibroblasts, and is increased ~11-fold in chronic pancreatitis compared to normal tissue. Inhibition of Lyn with siRNA or INNO-406 leads to the substantial decrease of migration and proliferation of human chronic pancreatitis myofibroblasts in vitro, while leaving migration and proliferation of normal myofibroblasts only slightly affected. Furthermore, inhibition of Lyn prevents synthesis of procollagen and collagen in myofibroblasts in a mouse model of chronic pancreatitis-induced fibrosis. We conclude that Lyn, as a positive regulator of myofibroblast migration, proliferation, and collagen production, is a key target for preventing fibrosis.

Lipotransfer for radiation-induced skin fibrosis

BACKGROUND

Radiation-induced fibrosis (RIF) is a late complication of radiotherapy that results in progressive functional and cosmetic impairment. Autologous fat has emerged as an option for soft tissue reconstruction. There are also sporadic reports suggesting regression of fibrosis following regional lipotransfer. This systematic review aimed to identify cellular mechanisms driving RIF, and the potential role of lipotransfer in attenuating these processes.

METHODS

PubMed, OVID and Google Scholar databases were searched to identify all original articles regarding lipotransfer for RIF. All articles describing irradiated fibroblast or myofibroblast behaviour were included. Data elucidating the mechanisms of RIF, role of lipotransfer in RIF and methods to quantify fibrosis were extracted.

RESULTS

Ninety-eight studies met the inclusion criteria. A single, definitive model of RIF is yet to be established, but four cellular mechanisms were identified through in vitro studies. Twenty-one studies identified connective tissue growth factor and transforming growth factor β1 cytokines as drivers of fibrotic cascades. Hypoxia was demonstrated to propagate fibrogenesis in three studies. Oxidative stress from the release of reactive oxygen species and free radicals was also linked to RIF in 11 studies. Purified autologous fat grafts contain cellular and non-cellular properties that potentially interact with these processes. Six methods for quantifying fibrotic changes were evaluated including durometry, ultrasound shear wave elastography, thermography, dark field imaging, and laser Doppler and laser speckle flowmetry.

CONCLUSION

Understanding how lipotransfer causes regression of RIF remains unclear; there are a number of new hypotheses for future research.

Review of ultrasound image guidance in external beam radiotherapy part II: intra-fraction motion management and novel applications

Imaging has become an essential tool in modern radiotherapy (RT), being used to plan dose delivery prior to treatment and verify target position before and during treatment. Ultrasound (US) imaging is cost-effective in providing excellent contrast at high resolution for depicting soft tissue targets apart from those shielded by the lungs or cranium. As a result, it is increasingly used in RT setup verification for the measurement of inter-fraction motion, the subject of Part I of this review (Fontanarosa et al 2015 Phys. Med. Biol. 60 R77-114). The combination of rapid imaging and zero ionising radiation dose makes US highly suitable for estimating intra-fraction motion. The current paper (Part II of the review) covers this topic. The basic technology for US motion estimation, and its current clinical application to the prostate, is described here, along with recent developments in robust motion-estimation algorithms, and three dimensional (3D) imaging. Together, these are likely to drive an increase in the number of future clinical studies and the range of cancer sites in which US motion management is applied. Also reviewed are selections of existing and proposed novel applications of US imaging to RT. These are driven by exciting developments in structural, functional and molecular US imaging and analytical techniques such as backscatter tissue analysis, elastography, photoacoustography, contrast-specific imaging, dynamic contrast analysis, microvascular and super-resolution imaging, and targeted microbubbles. Such techniques show promise for predicting and measuring the outcome of RT, quantifying normal tissue toxicity, improving tumour definition and defining a biological target volume that describes radiation sensitive regions of the tumour. US offers easy, low cost and efficient integration of these techniques into the RT workflow. US contrast technology also has potential to be used actively to assist RT by manipulating the tumour cell environment and by improving the delivery of radiosensitising agents. Finally, US imaging offers various ways to measure dose in 3D. If technical problems can be overcome, these hold potential for wide-dissemination of cost-effective pre-treatment dose verification and in vivo dose monitoring methods. It is concluded that US imaging could eventually contribute to all aspects of the RT workflow.

Quantitative Ultrasonic Nakagami Imaging of Neck Fibrosis After Head and Neck Radiation Therapy

PURPOSE

To investigate the feasibility of ultrasound Nakagami imaging to quantitatively assess radiation-induced neck fibrosis, a common sequela of radiation therapy (RT) to the head and neck.

METHODS AND MATERIALS

In a pilot study, 40 study participants were enrolled and classified into 3 subgroups: (1) a control group of 12 healthy volunteers; (2) an asymptomatic group of 11 patients who had received intensity modulated RT for head and neck cancer and had experienced no neck fibrosis; and (3) a symptomatic group of 17 post-RT patients with neck fibrosis. Each study participant underwent 1 ultrasound study in which scans were performed in the longitudinal orientation of the bilateral neck. Three Nakagami parameters were calculated to quantify radiation-induced tissue injury: Nakagami probability distribution function, shape, and scaling parameters. Physician-based assessments of the neck fibrosis were performed according to the Radiation Therapy Oncology Group late morbidity scoring scheme, and patient-based fibrosis assessments were rated based on symptoms such as pain and stiffness.

RESULTS

Major discrepancies existed between physician-based and patient-based assessments of radiation-induced fibrosis. Significant differences in all Nakagami parameters were observed between the control group and 2 post-RT groups. Moreover, significant differences in Nakagami shape and scaling parameters were observed among asymptomatic and symptomatic groups. Compared with the control group, the average Nakagami shape parameter value increased by 32.1% (P<.001), and the average Nakagami scaling parameter increased by 55.7% (P<.001) for the asymptomatic group, whereas the Nakagami shape parameter increased by 74.1% (P<.001) and the Nakagami scaling parameter increased by 83.5% (P<.001) for the symptomatic group.

CONCLUSIONS

Ultrasonic Nakagami imaging is a potential quantitative tool to characterize radiation-induced asymptomatic and symptomatic neck fibrosis.

Radiation-induced fibrosis: mechanisms and implications for therapy

PURPOSE

Radiation-induced fibrosis (RIF) is a long-term side effect of external beam radiation therapy for the treatment of cancer. It results in a multitude of symptoms that significantly impact quality of life. Understanding the mechanisms of RIF-induced changes is essential to developing effective strategies to prevent long-term disability and discomfort following radiation therapy. In this review, we describe the current understanding of the etiology, clinical presentation, pathogenesis, treatment, and directions of future therapy for this condition.

METHODS

A literature review of publications describing mechanisms or treatments of RIF was performed. Specific databases utilized included PubMed and clinicaltrials.gov, using keywords "Radiation-Induced Fibrosis," "Radiotherapy Complications," "Fibrosis Therapy," and other closely related terms.

RESULTS

RIF is the result of a misguided wound healing response. In addition to causing direct DNA damage, ionizing radiation generates reactive oxygen and nitrogen species that lead to localized inflammation. This inflammatory process ultimately evolves into a fibrotic one characterized by increased collagen deposition, poor vascularity, and scarring. Tumor growth factor beta serves as the primary mediator in this response along with a host of other cytokines and growth factors. Current therapies have largely been directed toward these molecular targets and their associated signaling pathways.

CONCLUSION

Although RIF is widely prevalent among patients undergoing radiation therapy and significantly impacts quality of life, there is still much to learn about its pathogenesis and mechanisms. Current treatments have stemmed from this understanding, and it is anticipated that further elucidation will be essential for the development of more effective therapies.

Quantifying fibrosis in head and neck cancer treatment: An overview

BACKGROUND

Fibrosis is a common late complication of radiotherapy and/or surgical treatment for head and neck cancers. Fibrosis is difficult to quantify and formal methods of measure are not well recognized. The purpose of this review was to summarize the methods available to quantify neck fibrosis.

METHODS

A PubMed search of articles was carried out using key words "neck" and "fibrosis."

RESULTS

Many methods have been used to assess fibrosis, however, there is no preferred methodology. Specific to neck fibrosis, most studies have relied upon hand palpation rating scales. Indentation and suction techniques have been used to mechanically quantify neck fibrosis. There is scope to develop applications of ultrasound, dielectric, bioimpedance, and MRI techniques for use in the neck region.

CONCLUSION

Quantitative assessment of neck fibrosis is sought after in order to compare treatment regimens and improve quality of life outcomes in patients with head and neck cancer.

Oncologic results of the surgical salvage of recurrent laryngeal squamous cell carcinoma in a multicentric retrospective series: emerging role of supracricoid partial laryngectomy

BACKGROUND

Several studies in the last decade evaluated conservative surgical procedures and, in particular, supracricoid operations as an alternative to total laryngectomy for the salvage of recurrences of laryngeal squamous cell carcinoma (SCC) after a first attempt of organ preservation.

METHODS

The clinical records of 68 consecutive patients primarily treated by irradiation or endoscopic surgery and surgically salvaged by total laryngectomy or supracricoid partial laryngectomy in 2 large university hospitals in Italy from 2004 to 2010 were reviewed.

RESULTS

The survival was not affected by the primary treatment or by salvage modality. The only parameter always keeping a prognostic value is the involvement of resection margins of salvage surgery. Patients with early relapse seem to have a worse prognosis than patients with a delayed relapse (p = .05 at Cox multivariate analysis and p = .048 at Wilcoxon test for overall survival [OS] from the primary treatment).

CONCLUSION

Supracricoid operations, if the indications are careful, can prove reliable salvage procedures.

Skin elasticity as a measure of radiation fibrosis: is it reproducible and does it correlate with patient and physician-reported measures?

Current means of measuring RT-induced fibrosis are subjective. We evaluated the DermaLab suction cup system to measure objectively skin deflection as a surrogate for fibrosis. Sixty-nine patients with E-STS were treated with limb-sparing surgery and 50-66 Grays (Gy) of RT. Using a “scleroderma” DermaLab Suction Cup, the skin stiffness was measured by two clinicians. The National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) scale, the Musculoskeletal Tumor Rating Scale (MSTS) and Toronto Extremity Salvage Score (TESS) questionnaires were completed for each patient. Levels of agreement between measurers were estimated using the Kappa (κ) coefficient and the concordance correlation coefficient (CCC). All sixty-nine patients were included. The level of agreement between measurers for NCI-CTCAE grading was moderate (range κ = 0.41-0.59). The CCC for the elasticity measurements were higher, with CCC = 0.82 for fibrotic skin and CCC = 0.84 for normal skin. The elasticity measurements were significantly higher when MSTS scores were <30 and or TESS scores were <90. Suction Cup measurement of skin elasticity is more reproducible than CTCAE grading and shows promise in generating reproducible measurements for radiation-induced skin fibrosis. Furthermore, it correlates well with the MSTS and TESS.

Quantification of stiffness change in degenerated articular cartilage using optical coherence tomography-based air-jet indentation

Articular cartilage is a thin complex tissue that covers the bony ends of joints. Changes in the composition and structure of articular cartilage will cause degeneration, which may further lead to osteoarthritis. Decreased stiffness is one of the earliest symptoms of cartilage degeneration and also represents the imperfect quality of repaired cartilage. An optical coherence tomography (OCT)-based air-jet indentation system was recently developed in our group to measure the mechanical properties of soft tissues. In this study, this system was applied to quantify the change of mechanical properties of articular cartilage after degeneration induced by enzymatic digestions. Forty osteochondral disks (n = 20 × 2) were prepared from bovine patellae and treated with collagenase and trypsin digestions, respectively. The apparent stiffness of the cartilage was measured by the OCT-based air-jet indentation system before and after the degeneration. The results were also compared with those from a rigid contact mechanical indentation and an ultrasound water-jet indentation. Through the air-jet indentation, it was found that the articular cartilage stiffness dropped significantly by 84% (p < 0.001) and 63% (p < 0.001) on average after collagenase and trypsin digestions, respectively. The stiffness measured by the air-jet indentation system was highly correlated (R > 0.8, p < 0.001) with that from the other two indentation methods. This study demonstrated that the OCT-based air-jet indentation can be a useful tool to quantitatively assess the mechanical properties of articular cartilage, and this encourages us to further develop a miniaturized probe suitable for arthroscopic applications.

Indentation versus tensile measurements of Young's modulus for soft biological tissues

In this review, we compare the reported values of Young's modulus (YM) obtained from indentation and tensile deformations of soft biological tissues. When the method of deformation is ignored, YM values for any given tissue typically span several orders of magnitude. If the method of deformation is considered, then a consistent and less ambiguous result emerges. On average, YM values for soft tissues are consistently lower when obtained by indentation deformations. We discuss the implications and potential impact of this finding.

Immediate effects of 2 different whole-body vibration frequencies on muscle peak torque and stiffness

OBJECTIVE

To examine the immediate effects of 2 vibration protocols with different vibration frequencies that yielded the same maximum acceleration (106.75ms(-2)) on muscle peak torque and stiffness of knee extensor and flexor.

DESIGN

Randomized crossover study with repeated measures.

SETTING

Laboratory setting.

PARTICIPANTS

Recreationally active male adults (N=10).

INTERVENTION

Participants performed 10 bouts of 60-second static half squats intermitted with a 60-second rest period between bouts on a platform with no vibration (control) and a vibration frequency of 26Hz or 40Hz.

MAIN OUTCOME MEASURES

Concentric and eccentric peak torques of knee extensor and flexor were examined within 5 minutes before and after vibration by isokinetic test. Young's modulus as an index of tissue stiffness was determined at quadriceps and hamstring pre- and postvibration by using an ultrasound indentation method.

RESULTS

The 2-way repeated-measures analysis of variance indicated a significant interaction effect between vibration and vibration frequency for knee extensor concentric peak torque (P=.003). The vibration-induced changes of knee extensor concentric peak torque in vibration frequency of 26Hz (14.5Nm) and 40Hz (12.0Nm) were found to be significantly greater than that in controls (-29.4Nm) (P<.05). The change in eccentric peak torque of knee flexor after vibration tended to be greater in 26Hz of vibration frequency when compared with controls (26Hz of vibration frequency vs controls: 13.9±7.1 vs -11.4±5.3Nm, P=.08). No statistically significant differences were obtained in tissue stiffness in the quadriceps and hamstring with any of the conditions.

CONCLUSIONS

Our data suggest that whole-body vibration at a frequency of 26Hz and 40Hz preclude the decline in concentric peak torque of knee extensor observed after 10 bouts of 60 seconds of static half squats. A change in muscle mechanical stiffness property as induced by whole-body vibration is not supported by our data.

Current management strategy of nasopharyngeal carcinoma

Nasopharyngeal carcinoma is an unique head and neck cancer. It is common among the southern Chinese and is closely associated with the Epstein Barr virus (EBV). To diagnose the disease in its early stage is infrequent as the symptoms are usually trivial and patients only present in late stages. Testing the blood for elevated EBV DNA has now become a screening test for the high risk group of patients, aiming to diagnose the disease in its early stages. Imaging studies, positron emission tomography scans in addition to clinical examination provide information on the extent of the disease. The confirmation of the disease still depends on endoscopic examination and biopsy. Radiotherapy with or without chemotherapy has been the primary treatment modality. The application of intensity modulated radiotherapy and the use of concomitant chemoradiation have improved the control of nasopharyngeal carcinoma together with the reduction of long term side effects. The early detection of residual or recurrence tumor in the neck or at the primary site has allowed delivery of salvage treatment. The choice of the optimal surgical salvage, either for neck disease or primary tumor depends on the extent of the residual or recurrent disease. The outcome of these patients have improved with the application of the appropriate surgical salvage.

Evaluation of bone-tendon junction healing using water jet ultrasound indentation method

The re-establishment of bone-tendon junction (BTJ) tissues with the junction, characterized as a unique transitional fibrocartilage zone, is involved in many trauma and reconstructive surgeries. Experimental and clinical findings have shown that a direct BTJ repair requires a long period of immobilization, which may be associated with a postoperative weak knee. Therefore, it is necessary to evaluate the morphologic and mechanical properties of BTJ tissues in situ to better understand the healing process for the purpose of reducing the adverse effects of immobilization. We previously reported a noncontact ultrasound water jet indentation system for measuring and mapping tissue mechanical properties. The key idea was to utilize a water jet as an indenter as well as the coupling medium for high-frequency ultrasound. In this article, we used ultrasound water jet indentation to evaluate the BTJ healing process. The system's capability of measuring the material elastic modulus was first validated using tissue-mimicking phantoms. Then it was employed to assess the healing of the BTJ tissues after partial patellectomy over time on twelve 18-week-old female New Zealand White rabbits. It was found that in comparison with the normal control samples, the elastic modulus of the fibrocartilage of the postoperative samples was significantly smaller, while its thickness increased significantly. Among the postoperative sample groups, the elastic modulus of the fibrocartilage of the samples harvested at week 18 was significantly higher than those harvested at week 6 and week 12, which was even comparable with the value of the control samples at the same sacrifice time. The results suggested that the noncontact ultrasound water jet indentation system provided a nondestructive way to evaluate the material properties of small animal tissues in situ and thus had the ability to evaluate the healing process of BTJ.

Implementation and validation of an ultrasonic tissue characterization technique for quantitative assessment of normal-tissue toxicity in radiation therapy

The goal of this study was to implement and validate a noninvasive, quantitative ultrasonic technique for accurate and reproducible measurement of normal-tissue toxicity in radiation therapy. The authors adapted an existing ultrasonic tissue characterization (UTC) technique that used a calibrated 1D spectrum based on region-of-interest analysis. They modified the calibration procedure by using a reference phantom instead of a planar reflector. This UTC method utilized ultrasonic radiofrequency echo signals to generate spectral parameters related to the physical properties (e.g., size, shape, and relative acoustic impedance) of tissue microstructures. Three spectral parameters were investigated for quantification of normal-tissue injury: Spectral slope, intercept, and midband fit. They conducted a tissue-mimicking phantom study to verify the reproducibility of UTC measurements and initiated a clinical study of radiation-induced breast-tissue toxicity. Spectral parameter values from measurements on two phantoms were reproducible within 1% of each other. Eleven postradiation breast-cancer patients were studied and significant differences between the irradiated and untreated (contralateral) breasts were observed for spectral intercept (p = 0.003) and midband fit (p < 0.001) but not for slope (p = 0.14). In comparison to the untreated breast, the average difference in the spectral intercept was 2.99 +/- 0.75 dB and the average difference in the midband fit was 3.99 +/- 0.65 dB. The preliminary clinical study demonstrated the feasibility of using the quantitative ultrasonic method to evaluate normal-tissue toxicity in radiation therapy.

An optical coherence tomography (OCT)-based air jet indentation system for measuring the mechanical properties of soft tissues

A novel noncontact indentation system with the combination of an air jet and optical coherence tomography (OCT) was presented in this paper for the quantitative measurement of the mechanical properties of soft tissues. The key idea of this method is to use a pressure-controlled air jet as an indenter to compress the soft tissue in a noncontact way and utilize the OCT signals to extract the deformation induced. This indentation system provides measurement and mapping of tissue elasticity for small specimens with high scanning speed. Experiments were performed on 27 silicone tissue-mimicking phantoms with different Young's moduli, which were also measured by uniaxial compression tests. The regression coefficient of the indentation force to the indentation depth (N mm(-1)) was used as an indicator of the stiffness of tissue under air jet indentation. Results showed that the stiffness coefficients measured by the current system correlated well with the corresponding Young's moduli obtained by conventional mechanical testing (r = 0.89, p < 0.001). Preliminary in vivo tests also showed that the change of soft tissue stiffness with and without the contraction of the underlying muscles in the hand could be differentiated by the current measurement. This system may have broad applications in tissue assessment and characterization where alterations of mechanical properties are involved, in particular with the potential of noncontact micro-indentation for tissues.

Extraction of mechanical properties of foot plantar tissues using ultrasound indentation associated with genetic algorithm

This paper demonstrates the use of ultrasound indentation technique for estimating the mechanical properties of foot plantar tissues in virtue of the reconstruction of the force response using genetic algorithm (GA) from an indentation test based on a quasi-linear viscoelastic (QLV) model. The indentation test on the plantar tissues covering the right first metatarsal head of a normal subject was carried out to verify the feasibility of the GA for the extraction of the tissue properties. The QLV properties of the plantar tissues were determined by the GA with a fixed Poisson's ratio. Such results were then compared with those obtained using a classical optimization method. Moreover, the GA was further employed to simultaneously determine the QLV properties as well as the Poisson's ratio of the plantar tissues. The correlations between the QLV properties and the Poisson's ratio are discussed.

High frequency ultrasound assessment of skin fibrosis: clinical results

Fibrosis is a common late effect of radiotherapy treatment for cancer patients. Current clinical assessment of radiation-induced fibrosis is generally limited to clinician-based rating scales, which are usually not sufficient for quantitative and objective evaluations. Ultrasonic propagation properties of tissues are widely reported to be sensitive to the alterations of tissue compositions and structures. Based on our previous feasibility study, we used four parameters including skin thickness and three ultrasonic parameters of dermal tissues (attenuation slope [beta], integrated attenuation [IA] and integrated backscatter [IBS]) in the frequency range of 10 to 25 MHz for the assessment of skin fibrosis. Experiments were conducted on the forearm and neck skin in patients with postirradiation fibrosis in the neck region. The palpation score and stiffness of the neck soft tissue were also measured as an indication of fibrotic severity. Comparisons of the results between 38 patients and 20 control subjects showed a significantly smaller beta (p = 0.005) and a significantly larger skin thickness (p < 0.004) and IA (p = 0.04) in the neck skins of the patients. However, age-matched comparisons showed there were neither significant differences among patient subgroups with different fibrotic levels assessed using manual palpation or significant correlations between the four parameters and the overall stiffness of the neck soft tissues (p > 0.05). In conclusion, ultrasound tissue characterization may provide additional information for the assessment of postirradiation skin fibrosis in the neck region. Further studies are necessary to investigate the feasibility of applying the current measurement for differentiating the severity of skin fibrosis.

A novel method to obtain modulus image of soft tissues using ultrasound water jet indentation: a phantom study

The alteration of tissue stiffness is generally known to be associated with pathological changes. Ultrasound indentation is one of the methods that can be used to assess the mechanical properties of the soft tissues. It uses a flat-ended ultrasound transducer to directly contact the tissue to sense tissue deformation under an applied load. This paper introduced a novel noncontact ultrasound indentation system using water jet compression. The key idea was to utilize a water jet as the indenter as well as the coupling medium for propagation of the ultrasound beam. High frequency focused ultrasound (20 MHz) was used to measure the indentation deformation at a microscopic level. It has been demonstrated that the system could effectively assess the tissue-mimic phantoms with different stiffness. Water jet coupling allows the system to conduct C-scan on soft tissues rapidly and conveniently. By applying different pressures while taking C-scan sequences, the modulus images of the phantoms could be obtained based on the applied pressure and the phantom deformation and thickness. This paper presented the preliminary results on gel phantoms. The spatial resolution, the contrast resolution of the measurements and the reproducibility of the results were also discussed.

Reliability of measurement of skin ultrasonic properties in vivo: a potential technique for assessing irradiated skin

BACKGROUND/AIMS

Quantitative and objective technique to assess radiation-induced tissue fibrosis is important for clinicians to estimate the efficiency of radiotherapeutic schemes. It has been widely reported that ultrasonic properties are sensitive to changes of acoustic scatterers in biological tissues. Therefore, measurement of ultrasonic properties may serve as a potential assessment technique for irradiated skins. The aim of the present study is to investigate the reliability of such measurement so as to evaluate its potentials for future clinical applications.

METHODS

Ultrasonic parameters including attenuation slope (beta), integrated attenuation (IA) and integrated backscatter (IBS) were measured for the frequency range of 10-25 MHz from echographic signals of the forearm and neck dermis of 20 normal subjects in vivo. The intra- and inter-rater reliability of measurement was assessed in 10 normal subjects using intra-class correlation coefficients (ICC) and Bland-Altman test.

RESULTS

The intra- and inter-rater measurement was demonstrated to be reliable as indicated by high ICC values generally larger than 0.80. In addition, the ultrasonic parameters could successfully differentiate the skins in the neck and forearm regions.

CONCLUSION

The measurement provided reliable information on the ultrasonic properties of the skins and could be potentially applied to comparative clinical trials to assess the late effects of radiotherapy on skins.

Nasopharyngeal carcinoma

Incidence of nasopharyngeal carcinoma has remained high in endemic regions. Diagnosing the disease in the early stages requires a high index of clinical acumen and, although most cross-sectional imaging investigations show the tumour with precision, confirmation is dependent on histology. Epstein-Barr virus (EBV)-encoded RNA signal is present in all nasopharyngeal carcinoma cells, and early diagnosis of the disease is possible through the detection of raised antibodies against EBV. The quantity of EBV DNA detected in blood indicates the stage and prognosis of the disease. Radiotherapy with concomitant chemotherapy has increased survival, and improved techniques (such as intensity-modulated radiotherapy), early detection of recurrence, and application of appropriate surgical salvage procedures have contributed to improved therapeutic results. Screening of high-risk individuals in endemic regions together with developments in gene therapy and immunotherapy might further improve outcome.

Application of tissue ultrasound palpation system (TUPS) in objective scar evaluation

One of the characteristics of hypertrophic scarring is its raised appearance. Its maturation often results in increased thickness. Therapists usually rely on subjective observation and palpation to document scar thickness. The result of these subjective assessments may reflect only the superficial scar thickness but is unable to measure the whole scar volume and thickness under the skin surface. Measurement of scar thickness using ultrasound imaging has been previously reported, but has not been commonly used in clinics due to its complex operation method and high cost. In this study, we have adopted a newly developed and user-friendly Tissue ultrasound palpation system (TUPS) for the assessment of scar thickness. It consists of a finger size palpation probe, connected to an ultrasound transducer and an in-series load cell to measure the thickness of the soft tissue over the human body. The method of operation is easy and it can be used to measure skin thickness on various parts of the body, thus reflecting the skin thickness. The reliability of the TUPS in clinical application was tested on 30 subjects with a hypertrophic scar at a local hospital. Three raters implemented two assessments on each subject to study its test-retest and inter-rater reliabilities. It was then used to assess 100 subjects with various severity of hypertrophic scar caused by trauma, scald, burn or surgery. They were assessed using TUPS as well as the Vancouver Scar Scale (VSS) for rating scar thickness, pliability, pigmentation and vascularity. Two-way mixed intra-class correlation showed a high test-retest reliability with Intraclass Correlation Coefficient (ICC)=0.98 and inter-rater reliability ICC=0.84. Fair positive correlations with VSS thickness score and VSS total score r=0.34 (p<0.05) and 0.42 (p<0.05), respectively. A significant difference between two scar type groups (50 burn scald scars and 50 surgical scars) was demonstrated (d.f.=52.94, t=3.99, p<0.01). TUPS was proved to have high inter-rater, test-retest reliability and it had a moderate correlation with the VSS that clinicians used for assessment of the scar. This system is recommended for clinical assessment of scar thickness.

A novel noncontact ultrasound indentation system for measurement of tissue material properties using water jet compression

This study is aimed to develop a novel noncontact ultrasonic indentation system for measuring quantitative mechanical properties of soft tissues, which are increasingly important for tissue assessment and characterization. The key idea of this method is to use a water jet as an indenter to compress the soft tissue while at the same time as a medium for an ultrasound beam to propagate through. The use of water jet indentation does not require a rigid compressor in front of the focused high frequency ultrasound transducer to compress the tissue, so that the additional attenuation caused by the rigid compressor and the strong echoes reflected from its surfaces can be avoided. The indentation deformation was estimated from the ultrasound echoes using a cross-correlation algorithm and the indentation force was calculated from the water pressure measured inside the water pipe. Experiments were performed on uniform tissue-mimicking phantoms with different stiffness. The Young's moduli and Poisson's ratios of these phantoms were measured using a uniaxial ultrasound compression system. The ratio of the indentation pressure to the tissue relative deformation was obtained from the water indentation. This ratio was well correlated with the Young's modulus (r = 0.87). The results also demonstrated that the water indentation approach could differentiate materials with different stiffness in a combined phantom (288 kPa and 433 kPa). This novel noncontact water indentation approach could be potentially used for the measurement of the elasticity of small samples and with a fast scanning speed.

Impact of dysphagia on quality of life after treatment of head-and-neck cancer

PURPOSE

To evaluate the quality of life (QOL) associated with dysphagia after head-and-neck cancer treatment.

METHODS AND MATERIALS

Of a total population of 104, a retrospective analysis of 73 patients who complained of dysphagia after primary radiotherapy (RT), chemoradiotherapy, and postoperative RT for head-and-neck malignancies were evaluated. All patients underwent a modified barium swallow examination to assess the severity of dysphagia, graded on a scale of 1-7. QOL was evaluated by the University of Washington (UW) and Hospital Anxiety and Depression questionnaires. The QOL scores obtained were compared with those from the 31 patients who were free of dysphagia after treatment. The QOL scores were also graded according to the dysphagia severity.

RESULTS

The UW and Hospital Anxiety and Depression scores were reduced and elevated, respectively, in the dysphagia group compared with the no dysphagia group (p = 0.0005). The UW scores were also substantially lower among patients with moderate-to-severe (Grade 4-7) compared with no or mild (Grade 2-3) dysphagia (p = 0.0005). The corresponding Hospital Anxiety (p = 0.005) and Depression (p = 0.0001) scores were also greater for the moderate-to-severe group. The UW QOL subscale scores showed a statistically significant decrease for swallowing (p = 0.00005), speech (p = 0.0005), recreation/entertainment (p = 0.0005), disfigurement (p = 0.0006), activity (p = 0.005), eating (p = 0.002), shoulder disability (p = 0.006), and pain (p = 0.004).

CONCLUSION

Dysphagia is a significant morbidity of head-and-neck cancer treatment, and the severity of dysphagia correlated with a compromised QOL, anxiety, and depression. Patients with moderate-to-severe dysphagia require a team approach involving nutritional support, physical therapy, speech rehabilitation, pain management, and psychological counseling.

Quasi-linear viscoelastic properties of fibrotic neck tissues obtained from ultrasound indentation tests in vivo

BACKGROUND

Hand palpation is a conventional way to assess and document soft tissue fibrosis. But it is semi-quantitative and subjective, so there is a need to develop quantitative and objective methods for this purpose.

METHODS

105 patients with different degrees of radiation-induced fibrosis of soft tissue of the neck were assessed using an ultrasound indentation method. The force response was reconstructed from the indentation history using a quasi-linear viscoelastic model with four material parameters. The parameters which best curve-fitted the force response with respect to the experimentally measured one, were selected as the viscoelastic properties of the tested soft tissue. These parameters were compared among patient subgroups with different degrees of fibrosis as scored by hand palpation, and also compared with those of a control group of healthy, non-irradiated subjects. Their relation to the rotation range of the neck and the effective Young's modulus, were also assessed.

FINDINGS

Soft tissue with a more severe degree of fibrosis was associated with a larger initial stiffness and a more rapid increase in stiffness under loading. Viscoelasticity parameters could discriminate soft tissue with different degrees of clinical fibrosis and had significant correlation with clinical parameters of fibrosis.

INTERPRETATION

Change of viscoelastic properties is reflection of pathological modifications of components in fibrotic soft tissues. Measurement of viscoelasticity parameters of soft tissue provides a quantitative and objective approach for the researcher and clinician to quantify soft tissue fibrosis.

RELEVANCE

Measurement of the change of viscoelastic properties of soft tissue provides a quantitative and objective approach for researchers and clinicians to quantify soft tissue fibrosis which is one of the most common late effects of radiotherapy.

Evaluation of clinical utility of BTC-2000 for measuring soft tissue fibrosis

PURPOSE

To evaluate whether mechanical tissue parameters, specifically laxity (in millimeters) and energy absorption (millimeters of mercury multiplied by millimeters) as measured by the BTC-2000, could discriminate levels of fibrosis severity among patients treated for extremity soft tissue sarcoma by surgery alone; preoperative radiotherapy (RT) and surgery; and surgery followed by postoperative RT.

METHODS AND MATERIALS

A total of 41 patients were treated for extremity soft tissue sarcoma by surgery alone (n = 11); preoperative RT (50 Gy in 2-Gy daily fractions) and surgery (n = 15); and surgery followed by postoperative RT (66 Gy in 2-Gy daily fractions; n = 15). Serial fibrosis measurements were evaluated at equal intervals from the midpoint of the surgical incision along the length of the incision. On the basis of the average of these measurements, differences among the three groups were analyzed using analysis of variance.

RESULTS

Pair-wise statistically significant differences were found among the three treatment groups for both laxity and energy absorption as determined by the average of all measurements. The treatment difference remained statistically significant even after adjusting for differences based on the untreated contralateral limb and anatomic site (p <0.001 and p = 0.002 for laxity and energy absorption, respectively).

CONCLUSION

The biomechanical tissue parameters of laxity and energy absorption discriminated fibrosis severity in patients treated with different RT doses. The BTC-2000 may provide a useful quantitative measure of soft tissue fibrosis.

Indentation test of soft tissues with curved substrates: A finite element study

Indentation is a commonly used approach to measure the mechanical properties of soft tissues, such as articular cartilage and limb tissues. The Young's modulus of tissue can be calculated from the indentation test using a mechanical model, where the soft tissue is normally assumed to have a flat substrate. In this study, a series of 2D finite element models were established to investigate the effects of bones with various curvatures embedded in the soft tissues during an indentation test. For each curvature of the hard substrate, the errors in the calculation of the Young's modulus were estimated for different indentation depths (0-10%) and aspect ratios a/h of the indentor diameter and the tissue thickness (0.2-2 in seven steps). The radius ratio a/R of the indentor and the curved substrate ranged from 0 to 0.38 in nine steps. Results showed that the error in calculation of the Young's modulus increased by 21.2% when the curvature a/R of the bone increased from 0 to 0.38 (under the condition of a/h=1.0, Poisson's ratio v=0.45). The error increased from 6.0 to 18.2% when the tissue thickness increased from 0.2 to 2 (a/R=0.18, v=0.45). It was found that the error in the Young's modulus calculation caused by the curved hard substrates could be corrected by a single factor for different indentation depths. This factor depends on the Poisson's ratio, the aspect ratio a/h and the radius ratio a/R.