Clinical domain knowledge-derived template improves post hoc AI explanations in pneumothorax classification.

OBJECTIVE: Pneumothorax is an acute thoracic disease caused by abnormal air collection between the lungs and chest wall. Recently, artificial intelligence (AI), especially deep learning (DL), has been increasingly employed for automating the diagnostic process of pneumothorax. To address the opaqueness often associated with DL models, explainable artificial intelligence (XAI) methods have been introduced to outline regions related to pneumothorax. However, these explanations sometimes diverge from actual lesion areas, highlighting the need for further improvement. METHOD: We propose a template-guided approach to incorporate the clinical knowledge of pneumothorax into model explanations generated by XAI methods, thereby enhancing the quality of the explanations. Utilizing one lesion delineation created by radiologists, our approach first generates a template that represents potential areas of pneumothorax occurrence. This template is then superimposed on model explanations to filter out extraneous explanations that fall outside the template's boundaries. To validate its efficacy, we carried out a comparative analysis of three XAI methods (Saliency Map, Grad-CAM, and Integrated Gradients) with and without our template guidance when explaining two DL models (VGG-19 and ResNet-50) in two real-world datasets (SIIM-ACR and ChestX-Det). RESULTS: The proposed approach consistently improved baseline XAI methods across twelve benchmark scenarios built on three XAI methods, two DL models, and two datasets. The average incremental percentages, calculated by the performance improvements over the baseline performance, were 97.8% in Intersection over Union (IoU) and 94.1% in Dice Similarity Coefficient (DSC) when comparing model explanations and ground-truth lesion areas. We further visualized baseline and template-guided model explanations on radiographs to showcase the performance of our approach. CONCLUSIONS: In the context of pneumothorax diagnoses, we proposed a template-guided approach for improving model explanations. Our approach not only aligns model explanations more closely with clinical insights but also exhibits extensibility to other thoracic diseases. We anticipate that our template guidance will forge a novel approach to elucidating AI models by integrating clinical domain expertise.

Application of deep learning algorithms in classification and localization of implant cutout for the postoperative hip.

OBJECTIVE: This study aims to explore the feasibility of employing convolutional neural networks for detecting and localizing implant cutouts on anteroposterior pelvic radiographs. MATERIALS AND METHODS: The research involves the development of two Deep Learning models. Initially, a model was created for image-level classification of implant cutouts using 40191 pelvic radiographs obtained from a single institution. The radiographs were partitioned into training, validation, and hold-out test datasets in a 6/2/2 ratio. Performance metrics including the area under the receiver operator characteristics curve (AUROC), sensitivity, and specificity were calculated using the test dataset. Additionally, a second object detection model was trained to localize implant cutouts within the same dataset. Bounding box visualizations were generated on images predicted as cutout-positive by the classification model in the test dataset, serving as an adjunct for assessing algorithm validity. RESULTS: The classification model had an accuracy of 99.7%, sensitivity of 84.6%, specificity of 99.8%, AUROC of 0.998 (95% CI: 0.996, 0.999) and AUPRC of 0.774 (95% CI: 0.646, 0.880). From the pelvic radiographs predicted as cutout-positive, the object detection model could achieve 95.5% localization accuracy on true positive images, but falsely generated 14 results from the 15 false-positive predictions. CONCLUSION: The classification model showed fair accuracy for detection of implant cutouts, while the object detection model effectively localized cutout. This serves as proof of concept of using a deep learning-based approach for classification and localization of implant cutouts from pelvic radiographs.

Cementoplasty to cryoablation: review and current status.

Recent advances in percutaneous image-guided techniques have empowered interventional radiologists with diverse treatment options for the management of musculoskeletal lesions. Of note, there is growing utility for cementoplasty procedures, with indications ranging from stabilization of bone metastases to treatment of painful vertebral compression fractures. Likewise, cryoablation has emerged as a viable adjunct in the treatment of both primary and secondary bone and soft tissue neoplasms. These treatment options have been progressively incorporated into the multidisciplinary approach to holistic care of patients, alongside conventional radiotherapy, systemic therapy, surgery, and analgesia. This review article serves to outline the indications, technical considerations, latest developments, and evidence for the burgeoning role of cementoplasty and cryoablation in the musculoskeletal system, with an emphasis on pain palliation and tumour control.

Dual-energy CT applications in musculoskeletal disorders.

Dual-energy CT (DECT) is an exciting application in CT technology conferring many advantages over conventional single-energy CT at no additional with comparable radiation dose to the patient. Various emerging and increasingly established clinical DECT applications in musculoskeletal (MSK) imaging such as bone marrow oedema detection, metal artefact reduction, monosodium urate analysis, and collagen analysis for ligamentous, meniscal, and disc injuries are made possible through its advanced DECT post-processing capabilities. These provide superior information on tissue composition, artefact reduction and image optimization. Newer DECT applications to evaluate fat fraction for sarcopenia, Rho/Z application for soft tissue calcification differentiation, 3D rendering, and AI integration are being assessed for future use. In this article, we will discuss the established and developing applications of DECT in the setting of MSK radiology as well as the basic principles of DECT which facilitate them.

Application of a deep learning algorithm in the detection of hip fractures.

This paper describes the development of a deep learning model for prediction of hip fractures on pelvic radiographs (X-rays). Developed using over 40,000 pelvic radiographs from a single institution, the model demonstrated high sensitivity and specificity when applied to a test set of emergency department radiographs. This study approximates the real-world application of a deep learning fracture detection model by including radiographs with sub-optimal image quality, other non-hip fractures, and metallic implants, which were excluded from prior published work. The study also explores the effect of ethnicity on model performance, as well as the accuracy of visualization algorithm for fracture localization.

Imaging Review of Hockey-Related Upper Extremity Injuries.

Ice hockey is a fast-paced contact sport with a high incidence of injuries. Upper extremity injury is one of the most common regions of the body to be injured in hockey. This imaging review will equip the radiologist with a knowledge of the more common and severe upper extremity injuries that occur in this sport.

Imaging Review of Hockey-related Lower Extremity Injuries.

Hockey is a fast-paced contact sport with a high incidence of injuries. Although injuries are more frequent among elite players, recreational hockey injuries are a common issue faced by primary care and emergency physicians. Lower extremity injuries in hockey are particularly important because they account for approximately a third of all injuries and > 60% of all overuse injuries. This pictorial review provides the general and specialty trained radiologist with a knowledge of the patterns of lower extremity injury that occur in ice hockey.

The Role of a Virtual Noncalcium Dual-Energy CT Application in the Detection of Bone Marrow Edema in Peripheral Osteomyelitis.

Purpose: To determine the sensitivity and specificity of dual-energy CT (DECT) virtual noncalcium images (VNCa) with bone and soft tissue reconstructions in the diagnosis of osteomyelitis. Materials & Methods: Between December 1, 2014 to December 1, 2020, 91 patients who had 99 DECT performed for a clinical indication of osteomyelitis with corresponding MRI, triphasic bone scan and/or white blood cell scintigraphy with CT/SPECT performed either 2 weeks before or 1 month after the DECT were retrospectively identified. The presence or absence of osteomyelitis was established using a second imaging test, bone biopsy or surgery. Two radiologists interpreted VNCa images alone and with bone and soft tissue reconstructions for osteomyelitis. Fleiss k statistics was used to assess inter-level agreement. Results: Osteomyelitis was present in 26 cases (26.2%), of which 4 cases (4%) had co-existing septic arthritis. DECT was performed at the following sites: ankle/foot (n = 59), calf (n = 12), knee (n = 3), thigh (n = 7), hip (n = 9), pelvis (n = 6), wrist/hand (n = 1), and shoulder (n = 2). Sensitivity with VNCa images alone was 53.8% and 73.1% and specificity was 84.9% and 71.2%. Sensitivity with VNCa images and bone and soft tissue reconstructions was 80.8% and 80.8% and specificity was 80.8% and 72.6%. Interobserver agreement was 76.7% (76 of 99 cases), for VNCa images alone (k = .487), and 66.7% (66 of 99 patients) for bone and soft tissue reconstructions with VNCa images together (k = .390). Conclusion: When VNCa images were combined with bone and soft tissue reconstructions, there is improved sensitivity in the diagnosis of osteomyelitis.

Cryotherapy in extra-abdominal desmoid tumors: A systematic review and meta-analysis.

INTRODUCTION: Desmoid tumor is a locally-invasive neoplasm that causes significant morbidity. There is recent interest in cryotherapy for treatment of extra-abdominal desmoid tumors. This systematic review assesses evidence on safety and efficacy of cryotherapy in the treatment of extra-abdominal desmoid tumors. MATERIALS AND METHODS: The systematic review was conducted with reference to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Literature search was performed using MEDLINE and the Cochrane Central Register of Controlled Trials. 9 full text papers were reviewed and meta-analysis was performed for measures of safety, efficacy and symptom relief. RESULTS: The estimated pooled proportion of major and minor complications was 4.2% (95% CI, 1.8-9.6; I 2 = 0%) and 10.2% (95% CI, 5.7-17.8; I 2 = 0%) respectively. The estimated pooled proportion of non-progressive disease rate of all studies was 85.8% (95% CI, 73.4-93.0; I 2 = 32.9%). The estimated progression free survival rate at 1 year was 84.5% (95% CI:74.6-95.8) and 78.0% at 3 years (95% CI: 63.8-95.3). As for pain control, the estimated pooled proportion of patients with decrease in visual analogue scale (VAS) > = 3 for those with VAS > = 3 before treatment for 2 studies was 87.5% (95% CI, 0.06-100; I 2 = 71.5%) while 37.5% to 96.9% of patients were reported to have experienced partial or complete symptom relief in the other studies. CONCLUSION: Cryotherapy is a safe and effective treatment modality for extra-abdominal desmoid tumors with efficacy similar to those treated with traditional strategies in the short to medium term.

SingHealth Radiology Archives pictorial essay Part 2: gastroenterology, musculoskeletal, and obstetrics and gynaecology cases.

The Singapore Health Services cluster (SingHealth) radiology film archives are a valuable repository of local radiological cases dating back to the 1950s. Some of the cases in the archives are of historical medical interest, i.e. cerebral angiography in the workup of patients with hemiplegia. Other cases are of historical social interest, being conditions seen during earlier stages of Singapore's development, i.e. bound feet. The archives form a unique portal into the development of local radiology as well as the national development of Singapore. A selection from the archives is published in commemoration of the International Day of Radiology in 2020, as well as the 200th anniversary of the Singapore General Hospital in 2021. This pictorial essay comprises gastroenterology, musculoskeletal and obstetrics and gynaecology cases from the archives.

SingHealth Radiology Archives pictorial essay Part 1: cardiovascular, respiratory and neurological cases.

The Singapore Health Services cluster (SingHealth) radiology film archives are a valuable repository of local radiological cases dating back to the 1950s. Some of the cases in the archives are of historical medical interest, i.e. cerebral angiography in the workup of patients with hemiplegia. Other cases are of historical social interest, being conditions seen during earlier stages of Singapore's development, i.e. bound feet. The archives form a unique portal into the development of local radiology as well as the national development of Singapore. A selection from the archives is published in 2020 in commemoration of the 20th anniversary of the formation of SingHealth, the 55th National Day of Singapore, and the 125th anniversary of the International Day of Radiology. This pictorial essay comprises cardiovascular, respiratory and neurological cases from the archives.

Spontaneous partial regression of a microcystic jejunal mesenteric lymphangioma and a proposed management algorithm.

Mesenteric lymphangiomas are relatively rare, with clinical symptoms ranging from an asymptomatic presentation to an acute abdomen. The natural history and biological behaviour of this entity can range from slow indolent lesions to aggressive tumours with a risk of malignant transformation. Spontaneous regression of a mesenteric lymphangioma is rare. We herein report a case of a jejunal mesenteric lymphangioma that was initially detected incidentally in an asymptomatic patient with a subsequent sudden increase in size with resulting surrounding mass effect after 9 months and a spontaneous partial regression at surgical resection. Our case is the first reported case which outlines a period in the natural history and evolution of microcystic mesenteric lymphangioma, illustrating the sudden enlargement likely attributable to spontaneous and self-limiting haemorrhage and subsequent partial regression at surgical resection. We thenceforth propose a possible management algorithm for adult patients with mesenteric lymphangiomas.

Fracture of a Bipartite Medial Hallux Sesamoid Masquerading as a Tripartite Variant: A Case Report and Review of the Literature.

We report a case of a competitive athlete who complained of chronic pain over the first metatarsal head in the absence of preceding trauma that was exacerbated with forced plantar flexion of the big toe. Initial radiographic findings suggested a tripartite appearance of the medial hallux sesamoid, and the patient was treated as for sesamoiditis. However, persistent symptoms over a period of 12 months necessitated further imaging with magnetic resonance, which confirmed a fracture of the bipartite medial hallux sesamoid. Considering that it is clinically important to differentiate between a tripartite/multipartite hallux sesamoid variant and a fracture of a bipartite hallux sesamoid, an expedient diagnosis is vital to avoiding complications of stress fractures. This can be a diagnostic challenge for the radiologist, emergency physician, and orthopedic surgeon, requiring a high index of suspicion. Accurate and timely diagnosis can be achieved with a clear history, detailed physical examination, and appropriate radiological evaluation.

Accessory ossicles of the foot-an imaging conundrum.

Various anatomical variations can be found in the foot and ankle, including sesamoid bones and accessory ossicles. These are usually incidental findings and remain asymptomatic; however, they may cause complications resulting in painful syndromes or degenerative changes secondary to overuse or trauma. They can also lead to fractures or simulate fractures. These complications are challenging to diagnose on radiographs. Advanced imaging with US, CT, MRI, or Tc-99m bone scan is useful for definitive diagnosis. This study aims to illustrate how imaging modalities can be used to diagnose complications of common sesamoids and accessory ossicles of the ankle and foot (hallux sesamoids, os trigonum, accessory navicular, os supranaviculare, os peroneum, os intermetatarseum, and os calcaneus secundarius) and demonstrate the imaging differences between fractures and their mimics.

Reporting of CT cervical spine after office hours by radiology trainees-analysis of discrepancy rates and RADPEER scores.

PURPOSE: To review the errors made by radiology trainees in the reporting of cervical spine CTs (CCT) and to compare the discrepancy rates between the stages of training. METHODS: All CCTs reported by trainees after office hours between January 2015 and December 2015 were retrospectively reviewed by a team of five musculoskeletal consultants with experience ranging between 7 and 15 years. Discrepancies between the provisional report by the trainee and the findings by the musculoskeletal consultants were graded according to the RADPEER scoring system. Sensitivity and specificity of the trainees were assessed. RESULTS: Of 254 CCT provisional reports, there were 12 (4.7%) discrepancies, of which 5 (2.0%) discrepancies were likely to be clinically significant. We found a clinically significant difference between the stage of training of the trainee and RADPEER score (P = 0.023). The sensitivity and specificity of the senior radiology trainees were 97.0 and 98.1%, respectively, and that of the junior radiology trainees were 80 and 98.0% respectively (P = 0.039). Conditions misinterpreted as fractures include degenerative changes (n = 2) and nutrient vessel (n = 1). Other missed abnormalities include ossification of the posterior longitudinal ligament (n = 1), fracture of the foramen transversarium (n = 2), vertebral body fractures (n = 2), articular facet fractures (n = 2), and transverse process fractures (n = 2). CONCLUSION: Cervical spine CTs performed after office hours can be safely interpreted by senior radiology trainees to a reasonable degree, although a targeted intervention to improve diagnostic performance of junior radiology trainees may be of clinical benefit.

Utility of Magnetic Resonance Imaging in the Surgical Management of Drug Extravasation: A Case Report.

We report a case of phenytoin extravasation complicated by eschar formation. Pre-operative MRI study showed a large non-enhancing area over the dorsum of the imaged right wrist and hand corresponding with the site of phenytoin extravasation and raising the suspicion of subcutaneous tissue necrosis. The MRI findings correlated well with the intra-operative findings. We believe that pre-operative MRI in drug extravasation cases can characterise the type of soft tissue injury and define the extent of injury. This helps the surgeon in the surgical approach and treatment options.

Fracture of the os trigonum: A report of two cases and review of the literature.

We report two cases of acute fractures of the os trigonum. The os trigonum fracture related to the first case was sustained following a hyper-plantar flexion injury during a game of soccer. The second case involved a patient who fell from height and also sustained open fractures of the left distal tibia and lateral malleolus as well as the right calcaneus. In both cases, a preliminary diagnosis of a posterior talar process fracture was made from the initial radiographs of the ankle. The correct diagnosis of an os trigonum fracture rather than a fracture of the posterior talar process was only made following further assessment with CT imaging. Given that the course of treatment is largely determined by imaging findings, CT for further imaging evaluation should be performed in cases of suspected acute bony injuries of the posterior ankle, particularly when the limitations of using radiographs for the assessment of such injuries are expected to be encountered.

Intravoxel incoherent imaging of renal fibrosis induced in a murine model of unilateral ureteral obstruction.

PURPOSE: To evaluate non-invasive imaging biomarkers for assessing renal fibrosis. DWI is used to assess renal function; intravoxel incoherent motion (IVIM) provides additional measures of perfusion-related diffusion (D*, blood flow; f, perfusion fraction). We aim to determine if reduced ADC seen in renal fibrosis is attributable to perfusion-related diffusion changes or to known reduction in tissue diffusivity (D). MATERIALS AND METHODS: Unilateral ureteral obstruction (UUO) was created in six mice to induce renal fibrosis. DWI was performed the day before and 7 days post-UUO. A range of b-values from 0 to 1200 s/mm(2) were used. IVIM parameters were obtained using region of interests drawn over the renal parenchyma. Histopathological analysis of both kidneys was performed in all mice. Results were analyzed using the paired t-test with P<0.05 considered statistically significant. RESULTS: D and f were significantly lower in the ligated kidneys at Day 7 compared to before ligation and no significant difference was found for D*. Comparing non-ligated and ligated kidneys within the same mouse at Day 7, significantly lower D values were observed in the ligated kidneys, while no significant difference was found for f and D*, although the values of f were generally lower. Histopathological analysis confirmed development of fibrosis and reduction in glomeruli in all the ligated kidneys at Day 7. CONCLUSION: Our study shows that the reduction in ADC seen in renal fibrosis is attributable not only to reduced D as previously encountered but also a decrease in vascularity as assessed by f. Reduction in f is possibly related to a reduction in glomeruli.