Interpretation Of Imaging Studies Research Articles

A morphometric study of the atlas occipitalization and coexisted congenital anomalies of the vertebrae and posterior cranial fossa with neurological importance.

Our study highlights the morphometry of the partial and complete atlas occipitalization (AOZ), its coexistence with fusions of the 2nd and 3rd cervical vertebrae and morphological and morphometric abnormalities of the posterior cranial fossa that are of paramount neurological importance. One hundred and eighty adult dry skulls, the atlas and axis vertebrae were examined. Four skulls (2.2%) showed AOZ. Two of them (1.1%) presented a partial AOZ, one male skull (0.6%) a complete AOZ and a female skull (0.6%) had a fused left hemiatlas with the occipital bone and a fusion of the 2nd and 3rd cervical vertebrae. The inner anteroposterior and transverse diameters of the foramen magnum (FM) in the control group were 34.6±3.46 and 29.3±3.47mm. Only the skull with the complete AOZ had a reduced outer anteroposterior diameter of the FM (29.8mm), while no specimen was found with a reduced transverse diameter. A wide total decrease (range 13.1-50.9%) in the surface area of the FM in skulls with AOZ was detected. Extracranial, the clivus length in two skulls with AOZ was smaller than the normal range. No skull was detected with a reduction in the intracranial length of the clivus. All skulls with the AOZ had a vermian fossa. The study adds important morphometric details about the partial and complete AOZ and correlates the phenomenon of synostosis with the narrowing of the FM, particularly in the case of complete AOZ. Awareness of the AOZ and other fusions of the upper cervical vertebrae and their topographical relations and attendant problems are of paramount importance to surgeons, when operate to the craniocervical junction, or interpret imaging studies to plan a safe surgery for nerve or spinal tissue decompression.

Imaging of Head Trauma

Head trauma is a common cause of emergency room visits, and traumatic brain injury (TBI) accounts for approximately 1.4million emergency department visits per year in the United States. The scope of head trauma also includes calvarial, facial, and skull base trauma. The role of the emergency radiologist is to help identify who might benefit from imaging, to determine which imaging protocols to use, and to provide efficient and accurate interpretation of imaging studies. This article reviews these topics, focusing on practical applications. Computed tomography (CT) is the primary imaging modality used in the emergency department for the evaluation of head trauma. Although some centers use radiography for the evaluation of maxillofacial fractures, in most cases CT is the imaging study of choice to evaluate facial trauma, and CT is superior to radiography for the evaluation of skull base trauma, detecting previously unsuspected fractures. Contrast is used to evaluate for vascular injury, as discussed in the next chapter, but does not play a role in the diagnosis of traumatic brain lesions or fractures. Magnetic resonance imaging (MRI) may play a role in problem solving in the emergency department, but generally is not used for primary diagnosis in head trauma as it is more costly, more time consuming, and less well-tolerated by critically ill patients who may be undergoing intensive monitoring. Whereas conventional MRI is more sensitive than CT for detecting traumatic lesions in patients sustaining mild TBI, these findings were not correlated with neurocognitive outcome, and the utility of obtaining early MRI in this setting has not been validated. Advanced MRI techniques such as diffusion tensor imaging may play a role in predicting outcome, and functional MRI may also play a role in demonstrating sequela of mild TBI but much active research is still ongoing in this area.

Demystifying the persistent pneumothorax: role of imaging.

Evaluation for pneumothorax is an important indication for obtaining chest radiographs in patients who have had trauma, recent cardiothoracic surgery or are on ventilator support. By definition, a persistent pneumothorax constitutes ongoing bubbling of air from an in situ chest drain, 48 h after its insertion. Persistent pneumothorax remains a diagnostic dilemma and identification of potentially treatable aetiologies is important. These may be chest tube related (kinks or malposition), lung parenchymal disease, bronchopleural fistula, or rarely, oesophageal-pleural fistula. Although radiographs remain the mainstay for diagnosis and follow up of pneumothorax, computed tomography (CT) is increasingly being used for problem solving. Aetiology of persistent air leak determines the optimal treatment. For some, a simple repositioning of the chest tube/drain may suffice; others may require surgery. In this pictorial review, we will briefly describe the physiology of pneumothorax, discuss imaging features of identifiable causes for persistent pneumothorax and provide a brief overview of treatment options. Specific aetiology of a persistent air leak may often not be immediately discernible, and will need to be carefully sought. Accurate interpretation of imaging studies can expedite diagnosis and facilitate prompt treatment.Key points• Persistent pneumothorax is defined as a leak persisting for more than 2 days.• Radiographs can identify chest-tube-related causes of pneumothorax.• CT is the most useful test to identify other causes.• Penetrating thoracic injury can cause fistulous communication resulting in a persistent pneumothorax.• Discontinuity of visceral pleura identified by CT may indicate a bronchopleural fistula.

Abnormal Injury Response in Spontaneous Mild Ventriculomegaly Wistar Rat Brains: A Pathological Correlation Study of Diffusion Tensor and Magnetization Transfer Imaging in Mild Traumatic Brain Injury.

Spontaneous mild ventriculomegaly (MVM) was previously reported in ∼43% of Wistar rats in association with vascular anomalies without phenotypic manifestation. This mild traumatic brain injury (TBI) weight drop model study investigates whether MVM rats (n = 15) have different injury responses that could inadvertently complicate the interpretation of imaging studies compared with normal rats (n = 15). Quantitative MRI, including diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI), and immunohistochemistry (IHC) analysis were used to examine the injury pattern up to 8 days post-injury in MVM and normal rats. Prior to injury, the MVM brain showed significant higher mean diffusivity, axial diffusivity, and radial diffusivity, and lower fractional anisotropy (FA) and magnetization transfer ratio (MTR) in the corpus callosum than normal brain (p < 0.05). Following TBI, normal brains exhibited significant decreases of FA in the corpus callosum, whereas MVM brains demonstrated insignificant changes in FA, suggesting less axonal injury. At day 8 after mild TBI, MTR of the normal brains significantly decreased whereas the MTR of the MVM brains significantly increased. IHC staining substantiated the MRI findings, demonstrating limited axonal injury with significant increase of microgliosis and astrogliosis in MVM brain compared with normal animals. The radiological-pathological correlation data showed that both DTI and MTI were sensitive in detecting mild diffuse brain injury, although DTI metrics were more specific in correlating with histologically identified pathologies. Compared with the higher correlation levels reflecting axonal injury pathology in the normal rat mild TBI, the DTI and MTR metrics were more affected by the increased inflammation in the MVM rat mild TBI. Because MVM Wistar rats appear normal, there was a need to screen rats prior to TBI research to rule out the presence of ventriculomegaly, which may complicate the interpretation of imaging and IHC observations.

Extranodal natural killer T-cell lymphoma—new profiling, old tricks

Extranodal natural killer T-cell lymphomas (ENKTL) are aggressive lymphoid malignancies that present in two distinct forms: nasal and extra-nasal. 1 Au WY Weisenburger DD Intragumtornchai T et al. Clinical differences between nasal and extranasal natural killer/T-cell lymphoma: a study of 136 cases from the International Peripheral T-Cell Lymphoma Project. Blood. 2009; 113: 3931-3937 Crossref PubMed Scopus (564) Google Scholar Several features separate it from all other non-Hodgkin lymphomas. For example, that all cases are associated with Epstein-Barr virus 2 Chan JK Yip TT Tsang WY et al. Detection of Epstein-Barr viral RNA in malignant lymphomas of the upper aerodigestive tract. Am J Surg Pathol. 1994; 18: 938-946 Crossref PubMed Scopus (171) Google Scholar suggests a unique carcinogenesis and creates an opportunity for both accurate diagnosis and sensitive molecular monitoring. Second, extranodal presentation in the upper aerodigestive tract or other sites (such as the intestine, lungs, skin, testes) and rare isolated involvement of lymph nodes 1 Au WY Weisenburger DD Intragumtornchai T et al. Clinical differences between nasal and extranasal natural killer/T-cell lymphoma: a study of 136 cases from the International Peripheral T-Cell Lymphoma Project. Blood. 2009; 113: 3931-3937 Crossref PubMed Scopus (564) Google Scholar poses specific challenges to the staging with the traditional Ann-Arbor classification system and accurate risk stratification with the International Prognostic Index. Third, chemotherapy resistance results in limited long-term disease control, and radiotherapy seems to produce durable remissions in a substantial proportion of patients with early-stage disease. 3 Li YX Yao B Jin J et al. Radiotherapy as primary treatment for stage IE and IIE nasal natural killer/T-cell lymphoma. J Clin Oncol. 2006; 24: 181-189 Crossref PubMed Scopus (302) Google Scholar Finally, extensive tissue necrosis and remodelling (and the associated inflammation and chronic infections) make interpretation of imaging studies at both diagnosis and response assessment very difficult. A prognostic index for natural killer cell lymphoma after non-anthracycline-based treatment: a multicentre, retrospective analysisPINK and PINK-E are new prognostic models that can be used to develop risk-adapted treatment approaches for patients with ENKTL being treated in the contemporary era of non-anthracycline-based therapy. Full-Text PDF

Esophagectomy and Gastric Pull-through Procedures: Surgical Techniques, Imaging Features, and Potential Complications.

Esophagectomy takes the center stage in the curative treatment of local and local-regional esophageal cancer. It is a complex procedure with a high postoperative complication rate. When interpreting imaging studies, radiologists must understand the surgical techniques used and their potential complications. The most common surgical techniques are transthoracic esophagectomies, such as the Ivor Lewis and McKeown techniques, and transhiatal esophagectomy. Variations of these techniques include different choices of conduit (ie, stomach, colon, or jejunum) to serve in lieu of the resected esophagus. Postoperative imaging and accurate interpretation is vital in the aftercare of these patients. Chest radiographs, esophagrams, and computed tomographic images play an essential role in early identification of complications. Pulmonary complications and anastomotic leaks are the leading causes of postoperative morbidity and mortality secondary to esophagectomy. Other complications include technical and functional problems and delayed complications such as anastomotic strictures and disease recurrence. An esophagographic technique is described that is performed by using hand injection of contrast material into an indwelling nasogastric tube. Familiarity with the various types of esophagectomy and an understanding of possible complications are of utmost importance for radiologists and allow them to be key participants in the treatment of patients undergoing these complicated procedures.

The University of Michigan Imaging Assessment Tool (UM-IAT)

Abstract Introduction Evidence in the literature is mixed regarding the competence of health professional trainees when interpreting imaging studies independently, as there are no widely accepted a...

Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors.

Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

Needs assessment for a focused radiology curriculum in surgical residency: a multicenter study

BackgroundPatient instability and limited radiology staffing may compel surgeons to make clinical decisions based on their independent interpretations of imaging studies. Despite potential implications for patients, no research to date has assessed the need for a diagnostic radiology curriculum in general surgery residency. MethodsWe performed a cross-sectional study of surgery faculty and residents at 13 teaching hospitals across the United States. Survey responses were summarized using frequency and percentage, and analyzed by chi-square, Mantel-Haenszel chi-square, and McNemar tests. ResultsSurveys were distributed to 465 faculty and 520 residents, with response rates of 26% and 30%, respectively. Most respondents reported making decisions based on their independent imaging interpretation at least sometimes, with higher frequency in acute scenarios. The majority voiced a need for a dedicated radiology curriculum, with teaching in chest x-rays, abdominal x-rays, abdominal computed tomography, chest computed tomography, and focused assessment with sonography in trauma examinations. ConclusionsSurgeons and surgical residents enact treatment plans based on their independent interpretation of imaging studies, especially during acute patient scenarios. Further curricular development efforts are warranted to ensure trainee accuracy in radiologic interpretation.

Feasibility of Using Electronic Medical Record Data for Tracking Quality Indicators in Adults with Congenital Heart Disease.

In order to determine the feasibility of tracking quality of care in adults with congenital heart disease (ACHD), we aimed to estimate the availability of relevant data in electronic medical records (EMR) used in North American ACHD centers. Previously proposed quality indicators (QIs) were reviewed to consider what types of data would be required for each. ACHD program directors were surveyed about the nature of electronic data in existing EMRs. From the survey, the availability of data types needed for the denominator and numerator of each QI were estimated, and an overall estimate of data availability was calculated for each QI. These estimates were adjusted by the sensitivity of identifying the patients through administrative codes. Analysis was repeated for scenarios in which various data type estimates were hypothetically dropped by half to determine the overall impact of each data type. A total of 64 ACHD program directors responded to the survey. Of 55 QIs, average estimated data availability was 67%. QIs for tetralogy of Fallot had the highest estimated data availability (mean 88%), whereas those for atrial septal defect were lowest (mean 23%), reflecting both the need for interpretation of imaging studies and the lower reliability of billing codes for identification of ACHD patients. QIs with highest estimates were based largely on administrative data, which had the biggest impact on overall estimates. QIs needing interpretation of imaging findings had the lowest estimates, as well as certain overuse measures. For a wide range of ACHD programs, data for proposed QIs based on administrative data are most likely to be obtainable through EMR. Data related to imaging interpretation or overuse measures are least likely. Our findings can inform future efforts to establish registry efforts or data reporting tools to track these indicators.

Cancer Imaging Training in the 21st Century: An Overview of Where We Are, and Where We Need To Be

Advances in cancer care over the past decade have significantly changed treatment algorithms and life expectancies. Time from cancer diagnosis to death is rapidly increasing, as new, targeted therapies are developed, many prolonging life even in advanced disease. Tumors are now genotyped at diagnosis, allowing personalization of treatment. The FDA is continually approving new drugs that quickly become the standard of care for common tumors; the impact of these drugs and their side effects is monitored with imaging, and accurate interpretation of imaging studies has become essential as these patients live longer. Oncologists rely on radiologists to understand new patterns of treatment response and novel drug side effects that are associated with new drug classes, increasing the knowledge required for accurate image interpretation. These factors have led to the demand for dedicated cancer imaging training for radiologists, who can integrate findings throughout the body on various imaging modalities. In addition, we need to expand radiology’s focus beyond diagnosis, staging, and restaging of tumors, and include education about the influence of genomics on tumor characterization and guidance for cancer care, the spectrum of treatment response, and the imaging characteristics of adverse events associated with various therapies. The time has come, therefore, to formally incorporate, as part of radiology residency, a distinct cancer imaging curriculum that is standardized, tested, and will allow the new generation of radiologists to effectively communicate with and assist their oncologic colleagues and optimally contribute to the care of patients with cancer.

Cam-type deformities: Concepts, criteria, and multidetector CT features

Interpreting imaging studies of a painful hip requires detailed knowledge of the regional anatomy. Some variants of the proximal femur, such as cam-type deformities, can course asymptomatically or cause femoroacetabular impingement. The principal numerical criterion for defining cam-type deformities, the alpha angle, has some limitations. In this article, we review the anatomic variants of the anterior aspect of the proximal femur, focusing on cam-type deformities. Using diagrams and multidetector CT images, we describe the parameters that are useful for characterizing these deformities in different imaging techniques. We also discuss the potential correspondence of imaging findings of cam-type deformities with the terms coined by anatomists and anthropologists to describe these phenomena.

Deformidades tipo cam: conceptos, criterios y apariencia en TC multidetector

Interpreting imaging studies of a painful hip requires detailed knowledge of the regional anatomy. Some variants of the proximal femur, such as cam-type deformities, can course asymptomatically or cause femoroacetabular impingement. The principal numerical criterion for defining cam-type deformities, the alpha angle, has some limitations. In this article, we review the anatomic variants of the anterior aspect of the proximal femur, focusing on cam-type deformities. Using diagrams and multidetector CT images, we describe the parameters that are useful for characterizing these deformities in different imaging techniques. We also discuss the potential correspondence of imaging findings of cam-type deformities with the terms coined by anatomists and anthropologists to describe these phenomena.

Meconium in Perinatal Imaging: Associations and Clinical Significance

An abnormal location, distribution, volume, or appearance of meconium is associated with a spectrum of bowel abnormalities, including atresia, obstruction, perforation, fistula, aganglionosis, immaturity, and absorptive dysfunction. This review discusses the fetal and perinatal imaging of these entities, their differential diagnoses, clinical significance, and appropriate imaging workup. Understanding the spectrum of normal and abnormal, specific and nonspecific appearances of meconium and its associated abnormalities on imaging will provide a practical, useful framework for performing and interpreting imaging studies and guiding clinical management.

Neuroimaging of Cerebral Venous Thrombosis (CVT) - Old Dilemma and the New Diagnostic Methods.

SummaryBackgroundCerebral venous thrombosis is a relatively uncommon neurologic disorder that is potentially reversible with prompt diagnosis and appropriate medical care. The pathogenesis is multifactorial and the disease may occur at any age. CVT is often associated with nonspecific symptoms. Radiologists play a crucial role in patient care by providing early diagnosis through interpretation of imaging studies.Underdiagnosis or misdiagnosis can increase the risk of severe complications, including hemorrhagic stroke or death. The purpose of this study is to investigate radiological and clinical characteristics of cerebral venous thrombosis (CVT) based on material from 34 patients under care of our hospital.Material/MethodsA total of 34 patients were diagnosed with CVT from August 2009 until March 2015. A clinical and radiological database of patients with final diagnosis of CVT was analyzed.ResultsPatient group included 22 women and 12 men at a mean age of 48.7 years (ranging from 27 to 77 years). In the study group 8 patients (23.5%) suffered from hemorrhagic infarction, whereas 16 patients (47%) were diagnosed with venous infarction without hemorrhage. Thirty patients (88%) had transverse sinus thrombosis.ConclusionsAccording to our study, CVT was more prevalent in women. Transverse sinus was the most common location. Among all age groups, the highest prevalence was seen in the fifth decade (n=14). Contrast-enhanced CT and MR venography were the most sensitive imaging modalities.

Imaging features of thoracic metastases from gynecologic neoplasms.

Gynecologic malignancies are a heterogeneous group of common neoplasms and represent the fourth most common malignancy in women. Thoracic metastases exhibit various imaging patterns and are usually associated with locally invasive primary neoplasms with intra-abdominal spread. However, thoracic involvement may also occur many months to years after initial diagnosis or as an isolated finding in patients without evidence of intra-abdominal neoplastic involvement. Thoracic metastases from endometrial carcinoma typically manifest as pulmonary nodules and lymphadenopathy. Thoracic metastases from ovarian cancer often manifest with small pleural effusions and subtle pleural nodules. Thoracic metastases to the lungs, lymph nodes, and pleura may also exhibit calcification and mimic granulomatous disease. Metastases from fallopian tube carcinomas exhibit imaging features identical to those of ovarian cancers. Most cervical cancers are of squamous histology, and while solid pulmonary metastases are more common, cavitary metastases occur with some frequency. Metastatic choriocarcinoma to the lung characteristically manifests with solid pulmonary nodules. Some pulmonary metastases from gynecologic malignancies exhibit characteristic features such as cavitation (in squamous cell cervical cancer) and the "halo" sign (in hemorrhagic metastatic choriocarcinoma) at computed tomography (CT). However, metastases from common gynecologic malignancies may be subtle and indolent and may mimic benign conditions such as intrapulmonary lymph nodes and remote granulomatous disease. Therefore, radiologists should consider the presence of locoregional disease as well as elevated tumor marker levels when interpreting imaging studies because subtle imaging findings may represent metastatic disease. Positron emission tomography/CT may be helpful in identifying early locoregional and distant tumor spread.

Total Artificial Heart Implantation: Clinical Indications, Expected Postoperative Imaging Findings, and Recognition of Complications

The purposes of this article are to review the treatment options for late-stage biventricular heart failure, discuss the clinical indications for total artificial heart (TAH) implantation, illustrate the expected imaging findings after uncomplicated TAH implantation, and highlight the radiologic findings of common and uncommon complications associated with TAH implantation through case examples. TAH implantation is an effective therapeutic option for the treatment of patients with end-stage biventricular heart failure. The duration of implantation varies depending on a particular patient's medical condition and the eventual availability of a human heart for orthotopic transplantation. TAH recipients often undergo imaging with conventional radiography, CT, or both for the assessment of device-related issues, many of which are life-threatening and require emergency management. As the clinical use of the TAH increases and becomes more commonplace, it is imperative that radiologists interpreting imaging studies recognize both the expected and the unexpected imaging findings that affect patient care.

Cross-sectional Anatomy, Computed Tomography and Magnetic Resonance Imaging of the Head of Common Dolphin (Delphinus delphis) and Striped Dolphin (Stenella coeruleoalba)

Computed tomography (CT) and low-field magnetic resonance imaging (MRI) were used to scan seven by-caught dolphin cadavers, belonging to two species: four common dolphins (Delphinus delphis) and three striped dolphins (Stenella coeruleoalba). CT and MRI were obtained with the animals in ventral recumbency. After the imaging procedures, six dolphins were frozen at -20°C and sliced in the same position they were examined. Not only CT and MRI scans, but also cross sections of the heads were obtained in three body planes: transverse (slices of 1cm thickness) in three dolphins, sagittal (5cm thickness) in two dolphins and dorsal (5cm thickness) in two dolphins. Relevant anatomical structures were identified and labelled on each cross section, obtaining a comprehensive bi-dimensional topographical anatomy guide of the main features of the common and the striped dolphin head. Furthermore, the anatomical cross sections were compared with their corresponding CT and MRI images, allowing an imaging identification of most of the anatomical features. CT scans produced an excellent definition of the bony and air-filled structures, while MRI allowed us to successfully identify most of the soft tissue structures in the dolphin's head. This paper provides a detailed anatomical description of the head structures of common and striped dolphins and compares anatomical cross sections with CT and MRI scans, becoming a reference guide for the interpretation of imaging studies.

Molar tooth sign − looking beyond the obvious

The molar tooth sign was initially identified in Joubert syndrome, named after Marie Joubert who first described it in 1968 as a rare autosomal recessive disorder characterised by the neuroradiological hallmark of the molar tooth sign caused by cerebellar vermian hypoplasia. Subsequently, it emerged that the molar tooth sign encompasses many syndromes that are now grouped together and termed Joubert syndrome and related disorders (JSRDs). Knowledge of the newer classification system and the subtypes is important and helps to direct and interpret imaging studies based on clinical signs so as to avoid delay in diagnosis of the hepatic oculorenal and renal subtypes of JSRDs in patients in whom the molar tooth sign is identified on brain MRI.

Cross-Sectional Anatomy, Computed Tomography and Magnetic Resonance Imaging of the Thoracic Region of Common Dolphin (Delphinus delphis) and Striped Dolphin (Stenella coeruleoalba)

The aim of this study was to provide a detailed anatomical description of the thoracic region features in normal common (Delphinus delphis) and striped dolphins (Stenella coeruleoalba) and to compare anatomical cross-sections with computed tomography (CT) and magnetic resonance imaging (MRI) scans. CT and MRI were used to scan 7 very fresh by-caught dolphin cadavers: four common and three striped dolphins. Diagnostic images were obtained from dolphins in ventral recumbency, and after the examinations, six dolphins were frozen (-20°C) and sliced in the same position. As well as CT and MRI scans, cross-sections were obtained in the three body planes: transverse (slices of 1 cm thickness), sagittal (5 cm thickness) and dorsal (5 cm thickness). Relevant anatomical features of the thoracic region were identified and labelled on each section, obtaining a complete bi-dimensional atlas. Furthermore, we compared CT and MRI scans with anatomical cross-sections, and results provided a complete reference guide for the interpretation of imaging studies of common and striped dolphin's thoracic structures.