SPECT-MPI for Coronary Artery Disease: A Deep Learning Approach.

Background: Worldwide, coronary artery disease (CAD) is a leading cause of mortality and morbidity and remains to be a top health priority in many countries. A non-invasive imaging modality for diagnosis of CAD such as single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) is usually requested by cardiologists as it displays radiotracer distribution in the heart reflecting myocardial perfusion. The interpretation of SPECT-MPI is done visually by a nuclear medicine physician and is largely dependent on his clinical experience and showing significant inter-observer variability. Objective: The aim of the study is to apply a deep learning approach in the classification of SPECT-MPI for perfusion abnormalities using convolutional neural networks (CNN). Methods: A publicly available anonymized SPECT-MPI from a machine learning repository (https://www.kaggle.com/selcankaplan/spect-mpi) was used in this study involving 192 patients who underwent stress-test-rest Tc99m MPI. An exploratory approach of CNN hyperparameter selection to search for optimum neural network model was utilized with particular focus on various dropouts (0.2, 0.5, 0.7), batch sizes (8, 16, 32, 64), and number of dense nodes (32, 64, 128, 256). The base CNN model was also compared with the commonly used pre-trained CNNs in medical images such as VGG16, InceptionV3, DenseNet121 and ResNet50. All simulations experiments were performed in Kaggle using TensorFlow 2.6.0., Keras 2.6.0, and Python language 3.7.10. Results: The best performing base CNN model with parameters consisting of 0.7 dropout, batch size 8, and 32 dense nodes generated the highest normalized Matthews Correlation Coefficient at 0.909 and obtained 93.75% accuracy, 96.00% sensitivity, 96.00% precision, and 96.00% F1-score. It also obtained higher classification performance as compared to the pre-trained architectures. Conclusions: The results suggest that deep learning approaches through the use of CNN models can be deployed by nuclear medicine physicians in their clinical practice to further augment their decision skills in the interpretation of SPECT-MPI tests. These CNN models can also be used as a dependable and valid second opinion that can aid physicians as a decision-support tool as well as serve as teaching or learning materials for the less-experienced physicians particularly those still in their training career. These highlights the clinical utility of deep learning approaches through CNN models in the practice of nuclear cardiology.

Worldwide Diagnostic Reference Levels for Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging: Findings From INCAPS.

OBJECTIVES: This study sought to establish worldwide and regional diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). BACKGROUND: Reference levels serve as radiation dose benchmarks to compare individual laboratories against aggregated data, helping to identify sites in greatest need of dose reduction interventions. DRLs for SPECT MPI have previously been derived from national or regional registries. To date there have been no multiregional reports of DRLs for SPECT MPI from a single standardized dataset. METHODS: Data were submitted voluntarily to the INCAPS (International Atomic Energy Agency Nuclear Cardiology Protocols Study), a cross-sectional, multinational registry of MPI protocols. A total of 7,103 studies were included. DRLs and AAAs were calculated by protocol for each world region and for aggregated worldwide data. RESULTS: The aggregated worldwide DRLs for rest-stress or stress-rest studies employing technetium Tc 99m-labeled radiopharmaceuticals were 11.2 mCi (first dose) and 32.0 mCi (second dose) for 1-day protocols, and 23.0 mCi (first dose) and 24.0 mCi (second dose) for multiday protocols. Corresponding AAAs were 10.1 mCi (first dose) and 28.0 mCi (second dose) for 1-day protocols, and 17.8 mCi (first dose) and 18.7 mCi (second dose) for multiday protocols. For stress-only technetium Tc 99m studies, the worldwide DRL and AAA were 18.0 mCi and 12.5 mCi, respectively. Stress-first imaging was used in 26% to 92% of regional studies except in North America where it was used in just 7% of cases. Significant differences in DRLs and AAAs were observed between regions. CONCLUSIONS: This study reports reference levels for SPECT MPI for each major world region from one of the largest international registries of clinical MPI studies. Regional DRLs may be useful in establishing or revising guidelines or simply comparing individual laboratory protocols to regional trends. Organizations should continue to focus on establishing standardized reporting methods to improve the validity and comparability of regional DRLs.

Comparison of bone scintigraphy with single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) in the detection of sphenoid bone extension from nasopharyngeal carcinoma (NPCA): A retrospective study

BACKGROUND/OBJECTIVE: Skeletal metastasis is one of the major clinical problems in managing cases of NPCA. Beginning osseous metastasis in the form of sphenoid bone extension is commonly seen in NPCA.Imaging modalities mainly used in detecting sphenoid bone extension are bone scintigraphy with SPECT and MRI. In this paper, the ability of bone scintigraphy with SPECT and MRI in detecting sphenoid bone extension was compared.MATERIALS AND METHODS: Twelve patients with nasopharyngeal carcinoma were studied by bone scintigraphy with SPECT and MRI. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of each modality against the gold standard, which is sphenoid bone biopsy, were computed. Statistical analysis was done using the McNemar's Test.RESULTS: The overall performances of bone scintigraphy with SPECT versus MRI were the following: sensitivity 89% vs 78%, specificity 33% vs 67%, positive predictive value 80% vs 88% and negative predictive value 50% vs 50%. There was no significant difference between the two modalities using McNemar's test (p>0.05).CONCLUSION: Bone scintigraphy with SPECT and MRI were both equally effective and were complementary with each other in detecting sphenoid bone extension in patients with NPCA.

The "Raven Sign": A case of apical left lung herniation into the superior right hemithorax detected on 99mTc-MAA lung perfusion scintigraphy in a pediatric patient with pulmonary tuberculosis

Lung hernia is a rare finding described as the protrusion of lung tissue outside the pleural cavity. Lung perfusion scintigraphy is used for pre-operative assessment of high-risk patients prior to pneumonectomy This case report presents a case of an apical left lung hernia detected in a lung perfusion scan prior to elective pneumonectomy in a seven-year-old girl with pulmonary tuberculosis destroyed right lung and compensatory left lung hyperinflation.

Pulmonary calcification detected by bone scintigraphy in a pediatric case of acute lymphoblastic leukemia

This is a case report of a pediatric patient with acute lymphoblastic leukemia and presenting with a rare finding of bilateral pulmonary calcification. The patient's pulmonary calcification was detected as an incidental finding during a routine bone scan performed to evaluate the patient's bone pains. Bone scintigraphy is one of the most sensitive and efficient modalities for detecting extra-osseous calcification.

Value of radiologic correlation and follow-up scintigraphy in detecting osseous metastasis in patients with non-specific bone scintigraphy lesions

Bone scintigraphy is highly sensitive in detecting bone metastasis but specificity is only about 50-60%. The aim of this study is to evaluate the value of radiologic correlation and followwup scintigraphy in detecting osseous metastasis in patients with equivocal bone scans. Bone scan results with non-specific interpretation of bone lesions from January to December 2007 were included. Results with no evidence of bone metastasis or metastatic bone disease were excluded from the study. Correlation with radiographs [X-ray, CT-scan, MRI] and follow-up bone scan within 6 months from the initial bone scan were reviewed. Of the 2322 bone scans, 435 have non-specific findings of bone lesions. From 435, only 228 patients have records of radiograph correlation and scintigraphic follow-up. Twenty two percent of the total population showed positive findings of bone metastasis in radiographs. The percentages of the non-specific findings determined to be negative from bone metastasis on correlation with X-ray, CT-scan, MRI and follow-up bone scan were 84%, 70%,73%, and 85%, respectively, whereas osseous metastasis revealed on radiologic correlation and follow-up scan were 76%, 30%,27%, and 75%, respectively. In conclusion, the finding of osseous metastasis in bone scan is increased when correlated with radiographs and scintigraphic follow-up.

Right-to-left shunting secondary to microvascular pulmonary arteriovenous malformation demonstrated by lung perfusion scintigraphy

Right-to-left shunting is usually associated with congenital conditions involving the heart, lungs, and the blood vessels that connect both organs. It is demonstrated by echocardiography, transesophageal ultrasound, CT scan, MRI and more definitively by conventional angiography. In this paper, we present a 16-year old female who manifested with progressive dyspnea, persistent cyanosis and decreased arterial oxygen saturation. Clinical assessment and arterial blood gas parameters suggested the presence of significant shunting. However, cardiac evaluation showed no intracardiac defects. High resolution CT scan of the chest with CT angiography of the pulmonary artery also showed no evidence of pulmonary vascular malformation or shunt anomaly. Lung perfusion scintigraphy performed after intravenous administration Tc99m-MAA showed tracer uptake in the brain, spleen and kidneys signifying the presence of a right-to-left shunt in the lungs. Cardiac catheterization later demonstrated the presence of primary pulmonary telangiectasia.

The usefulness of dual phase 99mTC sestamibi parathyroid scintigraphy in pre-operative localization of parathyroid adenomas

Pre-operative localization of abnormal parathyroid tissue helps in deciding whether surgery begins with a neck or mediastinal exploration. In this study we aimed to evaluate the usefulness of parathyroid scintigraphy in pre-operative localization of parathyroid adenomas and treatment. From February 2006 to October 2008, patients with signs and symptoms of hyperparathyroidism were recruited to join the study. The study group consisted of 3 males and 8 females. All subjects had a pre-operative parathyroid scintigraphy with Tc99m Sestamibi followed by parathyroidectomy. Ten patients had a positive scintigraphic finding which correlated to the actual location of the adenoma determined during the operation. Almost all patients (10 out of 11) underwent minimally invasive parathyroidectomy (MIP) while only one patient underwent bilateral neck dissection. The average incision length was 3.73 + 0.65 cm. Only one patient had an adverse event (transient hypocalcemia and bleeding necessitating a drain) which resolved later. The average hospital stay was 2.5 + 0.7 days. Parathyroid Tc99m-sestamibi scan is a reliable, non-invasive, and cost effective imaging modality in pre-operative localization of parathyroid adenomas for first time parathyroidectomy. This can help and guide surgeons to perform focused parathyroid surgery with minimal incision, successful localization, less complications, and shorter hospital stays.

Clinical utility of dacryoscintigraphy in the assessment of nasolacrimal duct obstruction

Epiphora, or pathological overflow of tear due to obstruction in the nasolacrimal drainage system, is a common problem encountered in ophthalmology. The ophthalmologist relies mainly on symptoms to guide further diagnosis and therapy. However, there appears to be a discrepancy between the degree of discomfort experienced by the patient and the severity of pathological finding. The purpose of this study was to determine the clinical utility of dacryoscintigraphy in the assessment of nasolacrimal duct (NLD) obstruction. We retrospectively reviewed the records of 27 patients who underwent dacryoscintigraphy between July-January 2007. Thirty-six eyes in these patients had epiphora. Three eyes (8%) showed partial obstruction. On the other hand, 33/36 eyes (92%) had complete obstruction in different areas of the NLD system. Patients with complete obstruction were treated by dacryocystorhinostomy and silicon tube insertion. Patients with partial nasolacrimal duct obstruction were treated medically. Dacryoscintigraphy is a simple, non-invasive, safe and non-traumatic procedure in assessing NLD obstruction. It demonstrates anatomical pathway of tear by physiological drainage. This can aid the surgeon in localizing the site of obstruction and guide him in choosing the appropriate treatment.

Parathyroid scintigraphy and gamma probe-guided surgery in the management of parathyroid carcinoma

This paper aims to present one of the rarest types of malignancies, parathyroid carcinoma. Parathyroid carcinoma is an important cause of primary hyper par athyroidism. Diagnostic evaluation of patients presenting with signs and symptoms of hyperparathyroidism consists of serum calcium and parathyroid hormone determination, parathyroid imaging using ultrasound, computed tomography, magnetic resonance imaging, or Tc-99m sestamibi scintigraphy, and histopathologic evaluation of tissues after surgical intervention. Therapeutic management of an identified parathyroid tumor is by parathyroidectomy during neck exploration or radioisotope-guided with the use of a gamma probe. The histology of a resected tumor determines if the initial surgery completes the management, or, in cases of parathyroid carcinoma, if another completion surgical intervention is to be made. This paper will present a patient who has been initially diagnosed with primary hyperparathyroidism and was referred to our nuclear medicine department for parathyroid scintigraphy. The patient underwent MIRP and rapid intraoperative PTH determination. Histopathologic report on the tissues revealed parathyroid carcinoma. The patient underwent a second surgery for definitive treatment. This paper will discuss the clinical role of nuclear medicine in the diagnosis and surgical management of parathyroid carcinoma.

Clinical utility of SPECT-CT co-registration imaging

The interpretation of nuclear medicine studies is largely based on function. However, this interpretation becomes more accurate and reliable when there is a corresponding precise anatomical localization. Hybrid systems are opening up a new era in SPECT imaging. A tertiary hospital in the Philippines has acquired the country's first hybrid imaging device combining a dual-detector, variable angle gamma camera with a low dose X-ray tube attached to the same gantry. This study evaluates the clinical utility of a hybrid imaging system, SPECT/CT for functional mapping with selected radiotracers. SPECT data were first interpreted alone and then re-assessed with the addition of SPECT/CT co-registered images. Patients referred for various nuclear medicine procedures with SPECT components in the first six months of operation studied for various clinical situations were evaluated in the study. Our study included sixty-four (64) patients in the first year of operation of SPECT/CT co-registered imaging systems. This included 23 with I-131, six with sulfur colloid, four with Gallium 67, five with Tc99m Sestamibi and 26 with Tc99m HOP. The pathologic sites in 28 out of 64 (44 percent) patients were noted in both SPECT and SPECT/CT co-registered images. Additionally, SPECT/CT co-registered images provided the precise anatomical localization in 12 (19 percent) patients not clearly evident in SPECT images alone and enabled the exclusion of disease in sites of physiologic tracer deposition in 16 (25 percent) patients found suspicious in SPECT alone leading to a change in the therapeutic approach. SPECT/CT allows a more precise interpretation of scintigraphic studies using selected radiotracers for various clinical situations. It provides additional information that improves diagnostic accuracy of SPECT and impacts on patient management indicating that SPECT/CT co-registered systems are suited for routine use in clinical practice.

The value of three-phase bone scintigraphy in the assessment of stress fractures

Stress fractures are overuse injuries of the bones resulting from repetitive stresses. Since symptoms are non-specific, an imaging modality is mandatory for accurate diagnosis. Bone scintigraphy used to be the gold standard in evaluating stress fracture, but the advent of MRI led to its underutilization. This study aims to determine the role of three-phase bone scintigraphy in the assessment of stress fracture, and to determine the sensitivity, specificity, positive and negative predictive values and the accuracy rate of bone scan. In a tertiary hospital in Metro Manila, 15 patients referred for three-phase bone scintigraphy to assess for stress fracture from 2004 to 2006 were included in the study. Of these 15 patients, 12 also underwent MRI. Sensitivity, specificity, positive and negative predictive values, and the accuracy rate were computed with MRI as the gold standard. The sensitivity of bone scans approach 100 percent. However, its specificity is low due to other conditions that can produce a positive scan. Because of the limitations inherent to scintigraphy, MRI could be a valid first-line imaging technique in diagnosing stress fracture. MRI provides a greater anatomic detail of the area in question. It may secure an accurate diagnosis if the fracture line is demonstrated. However, extensive marrow edema precludes the visualization of the fracture line in some cases. Bone scintigraphy together with an accurate history is still a very useful tool in diagnosing stress fracture. MRI should be reserved for cases where the radiographic and scintigraphic findings are indeterminate.