The use of digital magnification to reduce radiation dose in the cardiac catheter laboratory

Objectives: To audit whether using magnification of images by use of a large viewing screen using digital matrix magnification which enlarges the image by 33% without using the X-ray machine zoom magnification protocols on a Siemens Artis Zee X-ray machine in a cardiac catheter laboratory results in a reduction of kerma–area product (KAP) for both diagnostic and interventional procedures. This reduction was predicted in an in vitro study in our laboratory, which has previously shown a 20.4% reduction in KAP. Methods: A retrospective analysis was conducted of the radiation exposure to compare the measured KAP recorded during the period when conventional magnification with automatic brightness and dose control was used on a Siemens Artis Zee X-ray machine with a flat panel detector and when magnification settings were avoided by using a large screen to enlarge and project a non-magnified image by digital magnification. The analysis was carried out for patients having a diagnostic coronary angiogram and those having an interventional coronary procedure. Results: For diagnostic coronary angiograms the median KAP per procedure in the period using conventional magnification was 2124.5 µGy.m2 compared to 1401 µGy.m2 when image matrix magnification was used, a 34% reduction (p < 0.0001). For interventional coronary procedures, the median KAP per procedure in the period using conventional magnification was 3791 µGy.m2 compared to 2568.5 µGy.m2 when image matrix magnification was used, a 32% reduction (p < 0.0001). Conclusion: Avoiding using conventional magnification in the cardiac catheter laboratory and using a large screen to magnify images was associated with a statistically significant greater than 30% reduction in KAP. Advances in knowledge: This paper is the proof in clinical practice of a theoretical conclusion that radiation dose (KAP) is reduced by use of Image matrix magnification using a large viewing screen without the need to use X-ray tube magnification without significant loss of image resolution in interventional cardiology. The same approach will be useful in interventional radiology.

Outcomes of Complete Surgical Repair Versus Palliative Intervention in Neonates with Tetralogy of Fallot

Background: Surgical management of symptomatic neonates with Tetralogy of Fallot (TOF) is controversial. Either primary surgical repair (EPSR) in neonates with TOF or a staged palliation with initial palliative intervention (PI). Aim: Compare outcomes of neonates with TOF who had EPSR and those who had PI. Materials and Methods: The study utilized the US National Inpatient Sample dataset for the years 2000 to 2018. Patients with EPSR and those with PI (aortic to pulmonary shunt or cardiac catheter palliative intervention) identified. Results: A total of 29,292 neonates with TOF were identified; of them 1726 neonates had EPSR, 4363 had PI. Hospital mortality was similar in both groups (PI 7.4% vs EPSR 8.0%, p = 0.41). Patient in the PI group had more comorbidities; chromosomal anomalies (PI 13.2% vs. ESPR 7.8%, p < 0.001), prematurity (PI 15.1% vs. EPSR 10.4%, p < 0.001), and low birth weight < 2500 grams (PI 15.4% vs. EPSR 10.3%, p < 0.001). Median length of stay and median cost of hospitalization were significantly higher in the EPSR (25 days vs. 19 days, and $312,405 vs. $191,863, respectively, p < 0.001). Conclusion: EPSR had similar mortality to PI but comes with a higher resource utilization and complications. If we include the cumulative morbidity and resource utilization associated with a two staged repair, EPSR could be proven as a better strategy in symptomatic neonates with TOF. A prospective superiority study on symptomatic neonates with TOF randomized to either ESPR or PI is needed to further answer this question.

Frequency of hypothyroidism after cardiac catheter in infants with congenital heart diseases: A single center prospective study

This study aims to determine the incidence, potential onset and clinical course of hypothyroidism following cardiac catheter (CC) in infants with congenital heart diseases (CHD) and to evaluate the predictors for hypothyroidism in this vulnerable group. This prospective study included 102 patients with CHD, aged ≤ 3 years who underwent CC. Thyroid function tests were assessed before CC, one day, one week, two weeks and four weeks after the procedure. 12% of the studied group showed hypothyroidism four weeks after CC. Univariate analysis revealed that the significant predictors of hypothyroidism following CC are aortic stenosis (RR=10.0 (1.49-66.99), P=0.018), duration of fluoroscopy (RR=1.12 (0.99-1.26), P=0.05), and total cumulative dose of iodinated contrast media (iCM) (RR=1.01 (1.003 -1.01), P=0.019). Multivariate analysis revealed that iCM cumulative dose was the only significant predictor of developing hypothyroidism (RR=1.00 (1.00-1.01), P=0.04). ROC curve analysis showed that the cut-off point of iCM dose for prediction of hypothyroidism evolution is 8.7 gm/kg (26.1 ml/kg), (sensitivity: 83.3%, specificity: 65.1%), while the cut-off point of fluoroscopy duration which predicts development of hypothyroidism is 24 minutes, (sensitivity: 83.3%, specificity: 65.9%). In a median follow-up duration of 20 months, acquired hypothyroidism after CC persists in 5% of this cohort. Conclusion: Exposure to higher dose of iCM and longer duration of fluoroscopy during CC are risk factors for evolution of hypothyroidism. We recommend assessment of thyroid profile 4 weeks after CC particularly in patients who received a dose of iCM higher than 8.7 gm/kg and/or exposed to fluoroscopy for more than 24 minutes.

A Soft Resistive Sensor with a Semicircular Cross-Sectional Channel for Soft Cardiac Catheter Ablation

The field of soft robotics has attracted the interest of the medical community due to the ability of soft elastic materials to traverse the abnormal environment of the human body. However, sensing in soft robotics has been challenging due to the sensitivity of soft sensors to various loading conditions and the nonlinear signal responses that can arise under extreme loads. Ideally, soft sensors should provide a linear response under a specific loading condition and provide a different response for other loading directions. With these specifications in mind, our team created a soft elastomeric sensor designed to provide force feedback during cardiac catheter ablation surgery. Analytical and computational methods were explored to define a relationship between resistance and applied force for a semicircular, liquid metal filled channel in the soft elastomeric sensor. Pouillet’s Law is utilized to calculate the resistance based on the change in cross-sectional area resulting from various applied pressures. FEA simulations were created to simulate the deformation of the sensor under various loads. To confirm the validity of these simulations, the elastomer was modeled as a neo-Hookean material and the liquid metal was modeled as an incompressible fluid with negligible shear modulus under uniaxial compression. Results show a linearly proportional relationship between the resistance of the sensor and the application of a uniaxial force. Altering the direction of applied force results in a quadratic relationship between total resistance and the magnitude of force.

In-Vivo Microsystems: A Review

In-vivo sensors yield valuable medical information by measuring directly on the living tissue of a patient. These devices can be surface or implant devices. Electrical activity in the body, from organs or muscles can be measured using surface electrodes. For short term internal devices, catheters are used. These include cardiac catheter (in blood vessels) and bladder catheters. Due to the size and shape of the catheters, silicon devices provided an excellent solution for sensors. Since many cardiac catheters are disposable, the high volume has led to lower prices of the silicon sensors. Many catheters use a single sensor, but silicon offers the opportunity to have multi sensors in a single catheter, while maintaining small size. The cardiac catheter is usually inserted for a maximum of 72 h. Some devices may be used for a short-to-medium period to monitor parameters after an operation or injury (1–4 weeks). Increasingly, sensing, and actuating, devices are being applied to longer term implants for monitoring a range of parameters for chronic conditions. Devices for longer term implantation presented additional challenges due to the harshness of the environment and the stricter regulations for biocompatibility and safety. This paper will examine the three main areas of application for in-vivo devices: surface devices and short/medium-term and long-term implants. The issues of biocompatibility and safety will be discussed.