Ambrose J. Huang

Performance of an automated segmentation algorithm for 3D MR renography

The accuracy and precision of an automated graph‐cuts (GC) segmentation technique for dynamic contrast‐enhanced (DCE) 3D MR renography (MRR) was analyzed using 18 simulated and 22 clinical datasets. For clinical data, the error was 7.2 ± 6.1 cm3 for the cortex and 6.5 ± 4.6 cm3 for the medulla. The precision of segmentation was 7.1 ± 4.2 cm3 for the cortex and 7.2 ± 2.4 cm3 for the medulla. Compartmental modeling of kidney function in 22 kidneys yielded a renal plasma flow (RPF) error of 7.5% ± 4.5% and single‐kidney GFR error of 13.5% ± 8.8%. The precision was 9.7% ± 6.4% for RPF and 14.8% ± 11.9% for GFR. It took 21 min to segment one kidney using GC, compared to 2.5 hr for manual segmentation. The accuracy and precision in RPF and GFR appear acceptable for clinical use. With expedited image processing, DCE 3D MRR has the potential to expand our knowledge of renal function in individual kidneys and to help diagnose renal insufficiency in a safe and noninvasive manner. Magn Reson Med 57:1159–1167, 2007.

RAR agonists stimulate SOX9 gene expression in breast cancer cell lines: evidence for a role in retinoid-mediated growth inhibition

Retinoic acid receptors (RARs) are ligand-dependent transcription factors which are members of the steroid/thyroid hormone receptor gene family. RAR-agonists inhibit the proliferation of many human breast cancer cell lines, particularly those whose growth is stimulated by estradiol (E2) or growth factors. PCR-amplified subtractive hybridization was used to identify candidate retinoid-regulated genes that may be involved in growth inhibition. One candidate gene identified was SOX9, a member of the high mobility group (HMG) box gene family of transcription factors. SOX9 gene expression is rapidly stimulated by RAR-agonists in T-47D cells and other retinoid-inhibited breast cancer cell lines. In support of this finding, a database search indicates that SOX9 is expressed as an EST in breast tumor cells. SOX9 is known to be expressed in chondrocytes where it regulates the transcription of type II collagen and in testes where it plays a role in male sexual differentiation. RAR pan-agonists and the RARα-selective agonist Am580, but not RXR agonists, stimulate the expression of SOX9 in a wide variety of retinoid-inhibited breast cancer cell lines. RAR-agonists did not stimulate SOX9 in breast cancer cell lines which were not growth inhibited by retinoids. Expression of SOX9 in T-47D cells leads to cycle changes similar to those found with RAR-agonists while expression of a dominant negative form of SOX9 blocks RA-mediated cell cycle changes, suggesting a role for SOX9 in retinoid-mediated growth inhibition.

Musculoskeletal Neoplasms: Biopsy and Intervention

Percutaneous core needle biopsy and fine-needle aspiration are safe and cost-effective methods and can be important steps in the workup of a bone or soft tissue lesion. These procedures should be performed in collaboration with the orthopedic oncologist who performs the definitive surgery. In the extremities, attention to compartmental anatomy is paramount. With frozen section evaluation at the time of biopsy, the chances of a nondiagnostic specimen necessitating rebiopsy are minimized. The principles underlying the percutaneous approach to various lesions are valuable and can be applied to minimally invasive percutaneous therapy for bone and soft tissue lesions.

Single breath-hold T1 measurement using low flip angle TrueFISP.

A method for estimating T1 using a single breath‐hold, segmented, inversion recovery prepared, true fast imaging with steady‐state precession (sIR‐TrueFISP) acquisition at low flip angle (FA) was implemented in this study. T1 values measured by sIR‐TrueFISP technique in a Gd‐DTPA‐doped water phantom and the human brain and abdomen of healthy volunteers were compared with the results of the standard IR fast spin echo (FSE) technique. A good correlation between the two methods was observed (R2 = 0.999 in the phantom, and R2 = 0.943 in the brain and abdominal tissues). The T1 values of the tissues agreed well with published results. sIR‐TrueFISP enables fast measurements of T1 to be obtained within a single breath‐hold with good accuracy, which is particularly important for chest and abdominal imaging. Magn Reson Med, 2006.

MR Imaging of Normal Hip Anatomy

Understanding normal anatomy of the hip is important for diagnosing its pathology. MR arthrography is more sensitive for the detection of intra-articular pathology than noncontrast MR imaging. Important elements of the osseous structures on MR imaging include the alignment and the marrow. Acetabular ossicles may be present. Normal variations involving the cartilage include the supra-acetabular fossa and the stellate lesion. Important muscles of the hip are the sartorius, rectus femoris, iliopsoas, gluteus minimus and medius, adductors, and hamstrings. The iliofemoral, ischiofemoral, and pubofemoral ligaments represent thickenings of the joint capsule that reinforce and stabilize the hip joint. Normal variations in the labrum include labral sulcus and absent labrum. The largest nerves in the hip and thigh are the sciatic nerve, the femoral nerve, and the obturator nerve.

Association between distal ulnar morphology and extensor carpi ulnaris tendon pathology

ObjectiveThe purpose of this study was to evaluate the association between distal ulnar morphology and extensor carpi ulnaris (ECU) tendon pathology.Materials and methodsWe retrospectively reviewed 71 adult wrist MRI studies with ECU tendon pathology (tenosynovitis, tendinopathy, or tear), and/or ECU subluxation. Subjects did not have a history of trauma, surgery, infection, or inflammatory arthritis. MRI studies from 46 subjects without ECU tendon pathology or subluxation were used as controls. The following morphological parameters of the distal ulna were measured independently by two readers: ulnar variance relative to radius, ulnar styloid process length, ECU groove depth and length. Subjects and controls were compared using Student’s t test. Inter-observer agreement (ICC) was calculated.ResultsThere was a significant correlation between negative ulnar variance and ECU tendon pathology (reader 1 [R1], P = 0.01; reader 2 [R2], P < 0.0001; R1 and R2 averaged data, P < 0.0001) and ECU tendon subluxation (P = 0.001; P = 0.0001; P < 0.0001). In subjects with ECU tendon subluxation there was also a trend toward a shorter length (P = 0.3; P <0.0001; P = 0.001) and a shallower ECU groove (P = 0.01; P = 0.03; P = 0.01; R1 and R2 averaged data with Bonferroni correction, P = 0.08). ECU groove depth (P = 0.6; P = 0.8; P = 0.9) and groove length (P = 0.1; P = 0.4; P = 0.7) showed no significant correlation with ECU tendon pathology, and length of the ulnar styloid process showed no significant correlation with ECU tendon pathology (P = 0.2; P = 0.3; P = 0.2) or subluxation (P = 0.4; P = 0.5; P = 0.5). Inter-observer agreement (ICC) was >0.64 for all parameters.ConclusionDistal ulnar morphology may be associated with ECU tendon abnormalities.

Is Biopsying the Paravertebral Soft Tissue as Effective as Biopsying the Disk or Vertebral Endplate? 10-Year Retrospective Review of CT-Guided Biopsy of Diskitis-Osteomyelitis

OBJECTIVE The purpose of this study was to determine whether there is a difference in biopsying bone (endplate), disk, or paravertebral soft tissue to culture the pathogenic organism causing diskitis-osteomyelitis. MATERIALS AND METHODS A retrospective review was conducted of 111 spinal biopsies performed between 2002 and 2011. Pathologic examination was used as the reference standard for detecting diskitis-osteomyelitis. Microbiologic yield, sensitivity, and specificity were calculated. The yields for different groups were compared by use of Fisher exact test. The analysis was repeated with biopsy samples from patients not being treated with antibiotics at the time of biopsy. RESULTS A total of 122 biopsy specimens were obtained from 111 spinal biopsy procedures on 102 patients. Overall, 27 (22%) biopsies were performed on the endplate-disk, 61 (50%) on the disk only, and 34 (28%) on paravertebral soft tissue only. The microbiologic yield was 36% for all biopsies, 19% for endplate-disk biopsies, 39% for disk-only biopsies, and 44% for soft-tissue biopsies. The sensitivity and specificity of the microbiologic results for all specimens were 57% and 89%; endplate-disk, 38% and 86%; disk only, 57% and 89%; and paravertebral soft tissue, 68% and 92%. There was no statistically significant difference between the yields of the endplate-disk, disk-only, and paravertebral soft-tissue biopsies. CONCLUSION Paravertebral soft-tissue changes, when present, may be considered a viable target for biopsy in cases of diskitis-osteomyelitis, even in the absence of a paravertebral abscess.

Spine Injectables: What Is the Safest Cocktail?

OBJECTIVE Spinal injections are common pain management procedures using corticosteroids and local anesthetics. Most corticosteroid preparations are particulate suspensions, such as methylprednisolone acetate and triamcinolone acetonide. In the cervical spine, particulate corticosteroids have been linked to catastrophic complications, including blindness, paralysis, and death. Serious neurologic injuries have also been reported at the thoracic, lumbar, and sacral levels. CONCLUSION Nonparticulate preparations, such as dexamethasone, are safer but have shorter-lived antiinflammatory effects. Local anesthetics are often mixed with corticosteroids in pain management procedures. Although everyday risks are minimal, injection techniques should take into account neural and cardiac toxicities. In this article, we discuss the potential for serious adverse events associated with injected medications. We review the current literature to make conclusions on medication combinations that balance safety and efficacy.

Comparison of the diagnostic accuracy of 99 m-Tc-MDP bone scintigraphy and 18 F-FDG PET/CT for the detection of skeletal metastases

Background Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is commonly performed for cancer staging, as it can detect metastatic disease in multiple organ systems. However, there has been some controversy in the scientific literature when comparing FDG PET/CT and technetium-99 m-bone scintigraphy (bone scan) for the detection of skeletal metastases. Purpose To compare the accuracy of FDG PET/CT with bone scan for the detection of skeletal metastases. Material and Methods The study group comprised 202 adult cancer patients who underwent both FDG PET/CT and bone scan within 31 days for staging. Bone scans and FDG PET/CT were evaluated by two musculoskeletal radiologists for the presence and location of skeletal metastatic disease. Confirmation of the final diagnosis was based on the CT or magnetic resonance imaging (MRI) appearance, follow-up imaging, or histology. Results The sensitivity, specificity, and accuracy for detecting skeletal metastatic disease of FDG PET/CT were 97%, 98%, and 98%, respectively, and of bone scan were 83%, 98%, and 93%, respectively. The lesions that bone scan most commonly missed were located in the pelvis, spine, and sacrum. FDG PET/CT missed mostly lesions that were outside of the field of view, but in all of these cases the patient had additional sites of skeletal metastatic disease. Bone scan falsely identified six metastatic lesions and FDG PET/CT falsely identified three metastatic lesions. Conclusion FDG PET/CT is an accurate technique for detection of skeletal metastases, and is superior to bone scan, especially in the spine and pelvis.

Radiographic evaluation of hip implants.

Serial radiographs are the mainstay in the longitudinal assessment of hip implants. The prosthesis, periprosthetic bone, and juxta-articular soft tissues are inspected for fracture, periosteal reaction, stress shielding, calcar resorption, osteolysis, bony remodeling, metallic debris, and heterotopic ossification. Comparison radiographs best confirm implant migration, subsidence, and aseptic loosening. Infection, particle disease, reaction to metal, and mechanical impingement are important causes of postsurgical pain, but in their earliest stages they may be difficult to diagnose using radiographs. This article addresses the role of radiography following hip arthroplasty.