Improving Complex Brachytherapy Efficiency in the Current Financial Climate

PURPOSE/OBJECTIVE(S)

To optimize multidisciplinary collaboration in the setting of limited resources to increase the efficiency of complex brachytherapy workflow for patients with locally advanced cervical cancer.

MATERIALS/METHODS

High Dose Rate (HDR) brachytherapy is a critical component in the treatment of women with locally advanced cervical cancer. The completion of HDR brachytherapy to provide a complete treatment of concurrent chemoradiation and brachytherapy of <56 days has been well established. A quality improvement (QI) initiative was born out of the need to accommodate an increasing volume of patients with locally advanced cervical cancer. The challenges addressed were: different location of the operating room (OR), HDR brachytherapy suite, MR scanner; Inconsistent OR days; Post-Anesthesia Care Unit (PACU)/transportation delays; Anesthesiology staffing constraints. The QI initiative required multidisciplinary collaboration. A new protocol was finalized which provided protected OR time, and changed analgesia from general anesthesia requiring prolonged monitoring in PACU, to a pre-procedural epidural with moderate sedation. Additionally, a dedicated anesthesiologist was assigned to discuss process improvement, and the medical history for these complex patients as it relates to anesthesia safety. The streamlined process allows the patients' physical time in PACU to be bypassed; a dedicated brachytherapy nurse competent in moderate sedation recovery accompanies the patient to CT simulation. An MR protocol was established with tentative slots secured. The primary metric was the change in the number of interstitial cases performed. Additional metrics included: total case time, anesthesiology delay, MR delay, and number of OR days where 2 complex cases are performed.

RESULTS

Prior to initiation of QI initiative, from 01/2022-09/2022 there were 27 cases, average 3.0/month. After implementation of QI project, from 10/2022-02/2023 there were 32 cases, average 6.4/month, a 113.3% increase. Total case time decreased from baseline 9.3 hours to average 6 hours (Range: 3.8-10.6). Anesthesiology related delays were on average 18.5 minutes (Range: -15-35). MR related delays were on average 87.6 minutes (Range: 35-275). These changes now permit the flexibility of performing 2 complex interstitial cases per day, instead of one. The average days per month where two interstitial cases are performed increased from 0.4 to 1.4.

CONCLUSION

As hospital systems continue to face economic constraints, it is critical that we leverage our existing resources in order to provide timely care to our patients. This QI initiative shows that despite the limitation in brachytherapy operations, systems can be changed through multidisciplinary collaboration to improve efficiencies and increase capacities while working within financial workforce constraints to provide optimal patient care.

Detection and characterization of intermittent complexity variations in cardiac arrhythmia

OBJECTIVE

A frequent observation during cardiac fibrillation is a fluctuation in complexity where the irregular pattern of the fibrillation is interrupted by more regular phases of varying length.

APPROACH

We apply different measures to sliding windows of raw ECG signals for quantifying the temporal complexity. The methods include permutation entropy, power spectral entropy, a measure for the extent of the set of reconstructed states and several wavelet measures.

MAIN RESULTS

Using these methods, variations of fibrillation patterns over time are detected and visualized.

SIGNIFICANCE

These quantifications can be used to characterize different phases of the ECG during fibrillation and might improve diagnosis and treatment methods for heart diseases.

Mechanisms of vortices termination in the cardiac muscle

We propose a solution to a long-standing problem: how to terminate multiple vortices in the heart, when the locations of their cores and their critical time windows are unknown. We scan the phases of all pinned vortices in parallel with electric field pulses (E-pulses). We specify a condition on pacing parameters that guarantees termination of one vortex. For more than one vortex with significantly different frequencies, the success of scanning depends on chance, and all vortices are terminated with a success rate of less than one. We found that a similar mechanism terminates also a free (not pinned) vortex. A series of about 500 experiments with termination of ventricular fibrillation by E-pulses in pig isolated hearts is evidence that pinned vortices, hidden from direct observation, are significant in fibrillation. These results form a physical basis needed for the creation of new effective low energy defibrillation methods based on the termination of vortices underlying fibrillation.

Incidence of lower limb motor weakness in patients receiving postoperative epidural analgesia and factors associated with it: An observational study

Introduction and Aim:

Epidural analgesia is an effective technique for postoperative pain relief following thoracoabdominal surgeries. Lower limb motor weakness is a well-known complication of epidural analgesia with local anesthetics and delays postoperative rehabilitation. Our aim in conducting this observational study was to assess the frequency of lower limb motor weakness in patients receiving epidural analgesia following upper abdominal surgery and the factors associated with it.

Materials and Methods:

All adult patients, aged 20-70 years, who underwent upper abdominal surgery and received postoperative analgesia with an epidural infusion of bupivacaine with fentanyl, were included. Data were collected over 4 months from notes entered by acute pain service after each round. Data collected included level of epidural placement, drug solution and volume, degree of lower limb motor weakness and measures taken to relieve it. Bromage scale was used to assess motor weakness.

Results:

Data were collected on 123 patients. Bupivacaine 0.1% with fentanyl 2 μg/mL was used in 113 (92%) patients. Lower limb motor weakness developed in 45 patients (36.5%). The highest frequency was seen in patients with epidural at L2-L3 level. The common management steps were a change of patient's position or decrease in concentration of local anesthetic. These measures produced improvement in 39 (87%) patients whereas the local anesthetic was stopped temporarily in the remaining six patients.

Conclusion:

Lower limb motor weakness occurred in 36.5% patients. It was more common with a lumbar epidural. It was successfully managed in all patients. Lower thoracic epidurals are recommended for abdominal surgeries.

Parallel transmit excitation at 1.5 T based on the minimization of a driving function for device heating

PURPOSE

To provide a rapid method to reduce the radiofrequency (RF) E-field coupling and consequent heating in long conductors in an interventional MRI (iMRI) setup.

METHODS

A driving function for device heating (W) was defined as the integration of the E-field along the direction of the wire and calculated through a quasistatic approximation. Based on this function, the phases of four independently controlled transmit channels were dynamically changed in a 1.5 T MRI scanner. During the different excitation configurations, the RF induced heating in a nitinol wire immersed in a saline phantom was measured by fiber-optic temperature sensing. Additionally, a minimization of W as a function of phase and amplitude values of the different channels and constrained by the homogeneity of the RF excitation field (B1) over a region of interest was proposed and its results tested on the benchtop. To analyze the validity of the proposed method, using a model of the array and phantom setup tested in the scanner, RF fields and SAR maps were calculated through finite-difference time-domain (FDTD) simulations. In addition to phantom experiments, RF induced heating of an active guidewire inserted in a swine was also evaluated.

RESULTS

In the phantom experiment, heating at the tip of the device was reduced by 92% when replacing the body coil by an optimized parallel transmit excitation with same nominal flip angle. In the benchtop, up to 90% heating reduction was measured when implementing the constrained minimization algorithm with the additional degree of freedom given by independent amplitude control. The computation of the optimum phase and amplitude values was executed in just 12 s using a standard CPU. The results of the FDTD simulations showed similar trend of the local SAR at the tip of the wire and measured temperature as well as to a quadratic function of W, confirming the validity of the quasistatic approach for the presented problem at 64 MHz. Imaging and heating reduction of the guidewire were successfully performed in vivo with the proposed hardware and phase control.

CONCLUSIONS

Phantom and in vivo data demonstrated that additional degrees of freedom in a parallel transmission system can be used to control RF induced heating in long conductors. A novel constrained optimization approach to reduce device heating was also presented that can be run in just few seconds and therefore could be added to an iMRI protocol to improve RF safety.