Three-Dimensional Printing and Medical Imaging: A Review of the Methods and Applications.

The purpose of this article is to review recent innovations on the process and application of 3-dimensional (3D) printed objects from medical imaging data. Data for 3D printed medical models can be obtained from computed tomography, magnetic resonance imaging, and ultrasound using the Data Imaging and Communications in Medicine (DICOM) software. The data images are processed using segmentation and mesh generation tools and converted to a standard tessellation language (STL) file for printing. 3D printing technologies include stereolithography, selective laser sintering, inkjet, and fused-deposition modeling . 3D printed models have been used for preoperative planning of complex surgeries, the creation of custom prosthesis, and in the education and training of physicians. The application of medical imaging and 3D printers has been successful in providing solutions to many complex medical problems. As technology advances, its applications continue to grow in the future.

Accuracy of magnetic resonance imaging to diagnose superior labrum anterior-posterior tears.

PURPOSE: The purpose of this study was to evaluate the accuracy of magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) in diagnosing superior labral anterior-posterior (SLAP) lesions. We hypothesized that the accuracy of MRI and MRA was lower than previously reported. METHODS: Between 2006 and 2008, 444 patients who had both shoulder arthroscopy and an MRI (non-contrast or MR arthrography) for shoulder pain at our institution prior to surgery were identified and included in the study. The radiologic diagnosis and surgical evaluation were compared to determine the accuracy of diagnosing a SLAP lesion by MRI. Using arthroscopy as the standard, sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated for all MRIs, as well as separately for the non-intra-articular contrast MRI group and the MR arthrography group. RESULTS: Of the 444 patients having an MRI and arthroscopy for shoulder pain, 121 had a SLAP diagnosis by MRI and 44 had a SLAP diagnosis by arthroscopy. Overall, MRI had an accuracy of 76 %, a PPV of 24 %, and a NPV of 95 %. Sensitivity was 66 %, and specificity was 77 %. MR arthrography had an accuracy of 69 %, sensitivity of 80 %, and a PPV of 29 %. Non-contrast MRI had an accuracy of 85 %, sensitivity of 36 %, and a PPV of 13 %. CONCLUSIONS: In our retrospective study of 444 patients, sensitivity, specificity, and accuracy were all lower than previously reported in the literature for diagnosing SLAP lesions. Our data indicated that while MRI could exclude a SLAP lesion (NPV = 95 %), MRI alone was not an accurate clinical tool. MR arthrography had a large number of false-positive readings in this study. We concluded that even with intra-articular contrast, MRI had limitations in the ability to diagnose surgically proven SLAP lesions.

A clinical and radiological study of peroneal tendon pathology.

BACKGROUND: The proportion of patients with clinical findings referable to peroneal pathology and magnetic resonance imaging (MRI)-diagnosed peroneal tendon pathology is unknown. Previous studies have correlated surgical findings with clinical data and preoperative MRI, but there are no published studies that reference clinical examination findings to imaging findings. PURPOSE: To determine the relationship between peroneal tendon pathology as diagnosed by MRI and clinical findings of peroneal tendon pathology. METHODS: Fifty-six patients who had both MRI evidence of peroneal tendon pathology and an associated clinical examination of the ankle were evaluated over a 3-year period at a tertiary care institution. Clinical examination criteria included lateral ankle tenderness, dislocation/snapping, and lateral ankle pain. A board-certified, fellowship-trained musculoskeletal radiologist confirmed the presence of MRI findings consistent with peroneal tendon pathology. RESULTS: Of the 56 patients with positive findings on MRI, 27 patients had an associated positive clinical exam and 29 patients had a negative clinical exam. The positive predictive value of MRI for peroneal tendon tears with positive clinical findings was 48% (95% confidence interval = 35% to 61%). CONCLUSION: Patients with MRI findings of peroneal tendon pathology should undergo careful clinical examination, as the positive predictive value of MRI for peroneal tendon pathology with actual clinical findings is low. This study demonstrates that peroneal tendon tears are often incidental findings on MRI.

What is normal femoral head/neck anatomy? An analysis of radial CT reconstructions in adolescents.

BACKGROUND: Cam morphology in femoroacetabular impingement has been implicated in the development of osteoarthritis. The alpha angle and femoral head/neck offset are widely used to determine femoral head asphericity. To our knowledge, no study has evaluated the alpha angle circumferentially using three-dimensional imaging in a population of healthy individuals of adolescent age. QUESTIONS/PURPOSES: We sought to (1) determine normal values for the alpha angle in adolescents, (2) define the location along the neck with the highest alpha angle, and (3) determine normal femoral head and neck radii and femoral head/neck offset. METHODS: Fifty CT scans from a database of scans obtained for reasons not related to hip pain were studied. The average age of the subjects was 15 years (range, 14-16 years). Alpha angle and femoral head/neck offset were measured circumferentially. RESULTS: The alpha angle averaged 40.66 ± 4.46 mm for males and 37.77 ± 5.65 mm for females. The alpha angle generally was highest between the 11:40 and 12:40 o'clock and between the 6:00 and 7:40 o'clock positions. The femoral head radius was 24.53 ± 1.74 mm for males and 21.94 ± 1.13 mm for females, and the femoral neck radius was 16.14 ± 2.32 mm for males and 13.82 ± 2.38 mm for females. The mean femoral head/neck offset was 8.39 ± 1.97 mm for males and 8.13 ± 2.27 mm for females. CONCLUSIONS: In this healthy population of 14- to 16-year-old subjects, the highest alpha angle was at the superior and inferior aspects of the heads rather than at the anterosuperior aspect. This information will provide benchmark values for distinction between normal and abnormal morphologic features of the femoral head.

An analysis of the use of the Kellgren and Lawrence grading system to evaluate peritalar arthritis following total ankle arthroplasty.

BACKGROUND: The Kellgren and Lawrence grading system (KLGS) has been used throughout the literature for the radiographic staging of osteoarthritis (OA) of the peritalar joints. Despite its widespread use, the KLGS has never been validated for use in this clinical circumstance. The purpose of this study was to determine the inter- and intrarater reliability of the KLGS in the assessment of radiographic progression of OA in the peritalar joints following total ankle replacement (TAR). METHODS: One hundred twenty pre- and minimum 5-year postoperative weight-bearing lateral radiographs following 60 consecutive cases of TAR were utilized. Each individual film was considered separately for the purposes of this study. Of those films, 93 and 98 were found to have adequate visualization of the subtalar (STJ) and talonavicular (TNJ) joints, respectively. Three qualified reviewers graded the films according to the KLGS on 2 separate occasions, with 1 month separating the 2 readings. The results were analyzed for intra- and interobserver reliability. The degree of agreement was analyzed using the weighted kappa (κ(w)) statistic, Fleiss's kappa (Fleiss's κ), and percentage agreement RESULTS: Interrater agreements were moderate (κ(w) = 0.37 ± 0.06; Fleiss's κ = 0.21 ± 0.03) for the STJ to fair (κ(w) = 0.43 ± 0.06; Fleiss's κ = 0.25 ± 0.03) for the TNJ. Intrarater agreements for the STJ were moderate (mean κ(w) = 0.43 ± 0.07) and moderate for the TNJ as well (mean κ(w) = 0.46 ± 0.07). The reliability of the KLGS, although not originally designed for use in the setting of inflammatory arthropathy, was not notably affected when being used to grade inflammatory versus noninflammatory arthropathy. CONCLUSIONS: The KLGS is likely not a reliable tool for grading the degree of OA present in the peritalar joints prior to treatment and following TAR for research purposes. Using the KLGS in the setting of inflammatory arthritis versus OA did not produce any notable differences in the observed reliability. It is important to remember this has not been assessed in the clinical environment. Further work is required to determine the optimal method for assessment of peritalar OA. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Development of a standardized method for contouring the lumbosacral plexus: a preliminary dosimetric analysis of this organ at risk among 15 patients treated with intensity-modulated radiotherapy for lower gastrointestinal cancers and the incidence of radiation-induced lumbosacral plexopathy.

PURPOSE: To generate a reproducible step-wise guideline for the delineation of the lumbosacral plexus (LSP) on axial computed tomography (CT) planning images and to provide a preliminary dosimetric analysis on 15 representative patients with rectal or anal cancers treated with an intensity-modulated radiotherapy (IMRT) technique. METHODS AND MATERIALS: A standardized method for contouring the LSP on axial CT images was devised. The LSP was referenced to identifiable anatomic structures from the L4-5 interspace to the level of the sciatic nerve. It was then contoured retrospectively on 15 patients treated with IMRT for rectal or anal cancer. No dose limitations were placed on this organ at risk during initial treatment planning. Dosimetric parameters were evaluated. The incidence of radiation-induced lumbosacral plexopathy (RILSP) was calculated. RESULTS: Total prescribed dose to 95% of the planned target volume ranged from 50.4 to 59.4 Gy (median 54 Gy). The mean (± standard deviation [SD]) LSP volume for the 15 patients was 100 ± 22 cm(3) (range, 71-138 cm(3)). The mean maximal dose to the LSP was 52.6 ± 3.9 Gy (range, 44.5-58.6 Gy). The mean irradiated volumes of the LSP were V40Gy = 58% ± 19%, V50Gy = 22% ± 23%, and V55Gy = 0.5% ± 0.9%. One patient (7%) was found to have developed RILSP at 13 months after treatment. CONCLUSIONS: The true incidence of RILSP in the literature is likely underreported and is not a toxicity commonly assessed by radiation oncologists. In our analysis the LSP commonly received doses approaching the prescribed target dose, and 1 patient developed RILSP. Identification of the LSP during IMRT planning may reduce RILSP. We have provided a reproducible method for delineation of the LSP on CT images and a preliminary dosimetric analysis for potential future dose constraints.

Assessment of volar radiocarpal ligaments: MR arthrographic and arthroscopic correlation.

OBJECTIVE: The purpose of this study, with wrist arthroscopy as the reference standard, was to assess the usefulness of MRI in the detection of tears of the radioscaphocapitate and long radiolunate extrinsic carpal ligaments. MATERIALS AND METHODS: The cases of 26 patients consecutively registered from 2003 to 2009 who underwent wrist arthroscopy and wrist MR arthrography at our institution were identified. MR images were read by a musculoskeletal radiologist blinded to the arthroscopic findings. Operative reports and arthroscopic photographs were examined for descriptions of the radioscaphocapitate and long radiolunate ligaments. Ligaments were classified as intact or torn in all studies. With arthroscopy as the reference standard, sensitivity and specificity were calculated for both the radioscaphocapitate and the long radiolunate ligaments. RESULTS: Radioscaphocapitate and long radiolunate tears were diagnosed with MR arthrography in 50% and 31% of the 26 cases and arthroscopy in 31% and 31% of cases. With arthroscopy as the reference standard, the sensitivity of MR arthrography in the detection of radioscaphocapitate and long radiolunate tears was 63% and 25%; the specificity was 56% and 67%. CONCLUSION: With currently established imaging criteria, correlation between MR arthrographic and wrist arthroscopic findings in the assessment of tears of the radioscaphocapitate and long radiolunate ligaments is inconsistent. Because of the increasing clinical importance ascribed to the extrinsic carpal ligaments, further work aimed at refining both imaging techniques and diagnostic criteria in the MRI evaluation of these structures is warranted to improve correlation with results obtained at arthroscopy.

Pelvic osteoid osteoma in a skeletally mature female.

Osteoid osteoma is the most common bone-producing tumor that typically presents with "throbbing night pain" and that improves dramatically with use of low-dose salicylates. Few cases of pelvic osteoid osteoma have been reported, and most have involved patients younger than age 30. Surgical excision classically has been the treatment of choice, but, recently, less invasive modalities, including radiofrequency ablation, have begun to supplant surgical management of osteoid osteoma, resulting in a decrease in the need for definitive surgical diagnosis and treatment. We present a rare case of osteoid osteoma in the pelvis of a woman older than age 30.

Radiographic and histologic response to neoadjuvant radiotherapy in patients with soft tissue sarcoma.

BACKGROUND: Limited data exist regarding the radiographic and histologic response of soft tissue sarcoma (STS) to neoadjuvant radiotherapy (RT). METHODS: Between February 2000 and January 2009, a total of 25 patients aged >16 years with intermediate- or high-grade primary STS of all sites were treated with neoadjuvant RT followed by definitive resection. Patients receiving chemoradiotherapy were excluded. Cross-sectional images obtained before and after RT as well as pathologic specimens were reviewed for maximal change in tumor diameter and percentage tumor necrosis, respectively. Clinicopathologic variables were analyzed for their association with pathologic and radiographic response. RESULTS: There were 18 extremity (72%) and 7 retroperitoneal (28%) tumors. Median maximal tumor size was 9 cm (range, 3.3-35 cm), and 88% were of high grade. There were 21 R0 resections (84%) and 4 R1 resections (16%). Radiographically, the median percentage change in tumor diameter was 0% (range, -25 to +86%). By Response Evaluation Criteria in Solid Tumors (RECIST), 5 patients demonstrated progressive disease, 20 demonstrated stable disease, and 0 demonstrated partial/complete response. The median pathologic percentage tumor necrosis was 30% (range, 5-100%). Two tumors (8%) demonstrated near-complete pathologic response (≥95% necrosis). Near-complete pathologic response was associated with favorable oncologic outcomes, although these associations were not statistically significant. CONCLUSIONS: Radiologic and near-complete pathologic responses are rare events after preoperative RT for STS. Near-complete pathologic response may be a potentially meaningful surrogate marker for disease outcome and is not predicted by RECIST response. Knowledge of these historical response rates is important for the evaluation of novel neoadjuvant therapies for patients with STS.

Hoffa Fracture of the Femoral Condyle.

In this report, we present a case of an uncommon coronal fracture of the femoral condyle, known as a Hoffa fracture. Classification of these injuries and commonly associated injuries are discussed. We describe previously proposed mechanisms of injury and review the current literature. The difficulty in establishing radiologic diagnosis on the basis of radiography exclusively is emphasized. Finally, current approaches to operative fixation are outlined.