Phase-sensitive deep reconstruction method for rapid multiparametric MR fingerprinting and quantitative susceptibility mapping in the brain

INTRODUCTION

This study explores the potential of Magnetic Resonance Fingerprinting (MRF) with a novel Phase-Sensitivity Deep Reconstruction Network (PS-DRONE) for simultaneous quantification of T1, T2, Proton Density, B1+, phase and quantitative susceptibility mapping (QSM).

METHODS

Data were acquired at 3 T in vitro and in vivo using an optimized EPI-based MRF sequence. Phantom experiments were conducted using a standardized phantom for T1 and T2 maps and a custom-made agar-based gadolinium phantom for B1 and QSM maps. In vivo experiments included five healthy volunteers and one patient diagnosed with brain metastasis. PSDRONE maps were compared to reference maps obtained through standard imaging sequences.

RESULTS

Total scan time was 2 min for 32 slices and a resolution of [1 mm, 1 mm, 4.5 mm]. The reconstruction of T1, T2, Proton Density, B1+ and phase maps were reconstructed within 1 s. In the phantoms, PS-DRONE analysis presented accurate and strongly correlated T1 and T2 maps (r = 0.99) compared to the reference maps. B1 maps from PS-DRONE showed slightly higher values, though still correlated (r = 0.6) with the reference. QSM values showed a small bias but were strongly correlated (r = 0.99) with reference data. In the in vivo analysis, PS-DRONE-derived T1 and T2 values for gray and white matter matched reference values in healthy volunteers. PS-DRONE B1 and QSM maps showed strong correlations with reference values.

CONCLUSION

The PS-DRONE network enables concurrent acquisition of T1, T2, PD, B1+, phase and QSM maps, within 2 min of acquisition time and 1 s of reconstruction time.

Quantitative longitudinal mapping of radiation-treated prostate cancer using MR fingerprinting with radial acquisition and subspace reconstruction

MR fingerprinting (MRF) enables fast multiparametric quantitative imaging with a single acquisition and has been shown to improve diagnosis of prostate cancer. However, most prostate MRF studies were performed with spiral acquisitions that are sensitive to B0 inhomogeneities and consequent blurring. In this work, a radial MRF acquisition with a novel subspace reconstruction technique was developed to enable fast T1/T2 mapping in the prostate in under 4 min. The subspace reconstruction exploits the extensive temporal correlations in the MRF dictionary to pre-compute a low dimensional space for the solution and thus reduce the number of radial spokes to accelerate the acquisition. Iterative reconstruction with the subspace model and additional regularization of the signal representation in the subspace is performed to minimize the number of spokes and maintain matching quality and SNR. Reconstruction accuracy was assessed using the ISMRM NIST phantom. In-vivo validation was performed on two healthy subjects and two prostate cancer patients undergoing radiation therapy. The longitudinal repeatability was quantified using the concordance correlation coefficient (CCC) in one of the healthy subjects by repeated scans over 1 year. One prostate cancer patient was scanned at three time points, before initiating therapy and following brachytherapy and external beam radiation. Changes in the T1/T2 maps obtained with the proposed method were quantified. The prostate, peripheral and transitional zones, and visible dominant lesion were delineated for each study, and the statistics and distribution of the quantitative mapping values were analyzed. Significant image quality improvements compared with standard reconstruction methods were obtained with the proposed subspace reconstruction method. A notable decrease in the spread of the T1/T2 values without biasing the estimated mean values was observed with the subspace reconstruction and agreed with reported literature values. The subspace reconstruction enabled visualization of small differences in T1/T2 values in the tumor region within the peripheral zone. Longitudinal imaging of a volunteer subject yielded CCC of 0.89 for MRF T1, and 0.81 for MRF T2 in the prostate gland. Longitudinal imaging of the prostate patient confirmed the feasibility of capturing radiation treatment related changes. This work is a proof-of-concept for a high resolution and fast quantitative mapping using golden-angle radial MRF combined with a subspace reconstruction technique for longitudinal treatment response assessment in subjects undergoing radiation treatment.

CEST MR fingerprinting (CEST-MRF) for brain tumor quantification using EPI readout and deep learning reconstruction

PURPOSE

To develop a clinical CEST MR fingerprinting (CEST-MRF) method for brain tumor quantification using EPI acquisition and deep learning reconstruction.

METHODS

A CEST-MRF pulse sequence originally designed for animal imaging was modified to conform to hardware limits on clinical scanners while keeping scan time under 2 min. Quantitative MRF reconstruction was performed using a deep reconstruction network (DRONE) to yield the water relaxation and chemical exchange parameters. The feasibility of the six parameter DRONE reconstruction was tested in simulations using a digital brain phantom. A healthy subject was scanned with the CEST-MRF sequence, conventional MRF and CEST sequences for comparison. Reproducibility was assessed via test-retest experiments and the concordance correlation coefficient calculated for white matter and gray matter. The clinical utility of CEST-MRF was demonstrated on four patients with brain metastases in comparison to standard clinical imaging sequences. Tumors were segmented into edema, solid core, and necrotic core regions and the CEST-MRF values compared to the contra-lateral side.

RESULTS

DRONE reconstruction of the digital phantom yielded a normalized RMS error of ≤7% for all parameters. The CEST-MRF parameters were in good agreement with those from conventional MRF and CEST sequences and previous studies. The mean concordance correlation coefficient for all six parameters was 0.98 ± 0.01 in white matter and 0.98 ± 0.02 in gray matter. The CEST-MRF values in nearly all tumor regions were significantly different (P = 0.05) from each other and the contra-lateral side.

CONCLUSION

Combination of EPI readout and deep learning reconstruction enabled fast, accurate and reproducible CEST-MRF in brain tumors.

A multi-institutional analysis of a general pelvis continuous Hounsfield unit synthetic CT software for radiotherapy

Purpose

To validate a synthetic computed tomography (sCT) software with continuous HUs and large field‐of‐view (FOV) coverage for magnetic resonance imaging (MRI)‐only workflow of general pelvis anatomy in radiotherapy (RT).

Methods

An sCT software for general pelvis anatomy (prostate, rectum, and female pelvis) has been developed by Philips Healthcare and includes continuous HUs assignment along with large FOV coverage. General pelvis sCTs were generated using a two‐stack T1‐weighted mDixon fast‐field echo (FFE) sequence with a superior‐inferior coverage of 36 cm. Seventy‐seven prostate, 43 rectum, and 27 gynecological cases were scanned by three different institutions. mDixon image quality and sCTs were evaluated for soft tissue contrast by using a confidence level scale from 1 to 5 for bladder, prostate/rectum interface, mesorectum, and fiducial maker visibility. Dosimetric comparison was performed by recalculating the RT plans on the sCT after rigid registration. For 12 randomly selected cases, the mean absolute error (MAE) between sCT and CT was calculated to evaluate HU similarity, and the Pearson correlation coefficients (PCC) between the CT‐ and sCT‐generated digitally reconstructed radiographs (DRRs) were obtained for quantitative comparison. To examine geometric accuracy of sCT as a reference for cone beam CT (CBCT), the difference between bone‐based alignment of CBCT to CT and CBCT to sCT was obtained for 19 online‐acquired CBCTs from three patients.

Results

Two‐stack mDixon scans with large FOV did not show any image inhomogeneity or fat‐water swap artifact. Fiducials, Foley catheter, and even rectal spacer were visible as dark signal on the sCT. Average visibility confidence level (average ± standard deviation) on the sCT was 5.0 ± 0.0, 4.6 ± 0.5, 3.8 ± 0.4, and 4.0 ± 1.1 for bladder, prostate/rectum interface, mesorectum and fiducial markers. Dosimetric accuracy showed on average < 1% difference with the CT‐based plans for target and normal structures. The MAE of bone and soft tissue between the sCT and CT are 120.9 ± 15.4 HU, 33.4 ± 4.1 HU, respectively. Average PCC of all evaluated DRR pairs was 0.975. The average offset between CT and sCT as reference was (LR, AP, SI) = (0.19 ± 0.35, 0.14 ± 0.60, 0.44 ± 0.54) mm.

Conclusions

The continuous HU sCT software‐generated realistic sCTs and DRRs to enable MRI‐only planning for general pelvis anatomy.

Treating Glioblastoma Multiforme (GBM) with super hyperfractionated radiation therapy: Implication of temporal dose fractionation optimization including cancer stem cell dynamics

PURPOSE

A previously developed ordinary differential equation (ODE) that models the dynamic interaction and distinct radiosensitivity between cancer stem cells (CSC) and differentiated cancer cells (DCC) was used to explain the definitive treatment failure in Glioblastoma Multiforme (GBM) for conventionally and hypo-fractionated treatments. In this study, optimization of temporal dose modulation based on the ODE equation is performed to explore the feasibility of improving GBM treatment outcome.

METHODS

A non-convex optimization problem with the objective of minimizing the total cancer cell number while maintaining the normal tissue biological effective dose (BEDnormal) at 100 Gy, equivalent to the conventional 2 Gy × 30 dosing scheme was formulated. With specified total number of dose fractions and treatment duration, the optimization was performed using a paired simulated annealing algorithm with fractional doses delivered to the CSC and DCC compartments and time intervals between fractions as variables. The recurrence time, defined as the time point at which the total tumor cell number regrows to 2.8×109 cells, was used to evaluate optimization outcome. Optimization was performed for conventional treatment time frames equivalent to currently and historically utilized fractionation schemes, in which limited improvement in recurrence time delay was observed. The efficacy of a super hyperfractionated approach with a prolonged treatment duration of one year was therefore tested, with both fixed regular and optimized variable time intervals between dose fractions corresponding to total number of fractions equivalent to weekly, bi-weekly, and monthly deliveries (n = 53, 27, 13). Optimization corresponding to BEDnormal of 150 Gy was also obtained to evaluate the possibility in further recurrence delay with dose escalation.

RESULTS

For the super hyperfractionated schedules with dose fraction number equivalent to weekly, bi-weekly, and monthly deliveries, the recurrence time points were found to be 430.5, 423.9, and 413.3 days, respectively, significantly delayed compared with the recurrence time of 250.3 days from conventional fractionation. Results show that optimal outcome was achieved by first delivering infrequent fractions followed by dense once per day fractions in the middle and end of the treatment course, with sparse and low dose treatments in the between. The dose to the CSC compartment was held relatively constant throughout while larger dose fractions to the DCC compartment were observed in the beginning and final fractions that preceded large time intervals. Dose escalation to BEDnormal of 150 Gy was shown capable of further delaying recurrence time to 452 days.

CONCLUSION

The development and utilization of a temporal dose fractionation optimization framework in the context of CSC dynamics have demonstrated that substantial delay in GBM local tumor recurrence could be achieved with a super hyperfractionated treatment approach. Preclinical and clinical studies are needed to validate the efficacy of this novel treatment delivery method.

Analysis of Geometric Performance and Dosimetric Impact of Using Automatic Contour Segmentation for Radiotherapy Planning

Purpose: To analyze geometric discrepancy and dosimetric impact in using contours generated by auto-segmentation (AS) against manually segmented (MS) clinical contours. Methods: A 48-subject prostate atlas was created and another 15 patients were used for testing. Contours were generated using a commercial atlas-based segmentation tool and compared to their clinical MS counterparts. The geometric correlation was evaluated using the Dice similarity coefficient (DSC) and Hausdorff distance (HD). Dosimetric relevance was evaluated for a subset of patients by assessing the DVH differences derived by optimizing plan dose using the AS and MS contours, respectively, and evaluating with respect to each. A paired t-test was employed for statistical comparison. The discrepancy in plan quality with respect to clinical dosimetric endpoints was evaluated. The analysis was repeated for head/neck (HN) with a 31-subject atlas and 15 test cases. Results: Dice agreement between AS and MS differed significantly across structures: from (L:0.92/R: 0.91) for the femoral heads to seminal vesical of 0.38 in the prostate cohort, and from 0.98 for the brain, to 0.36 for the chiasm of the HN group. Despite the geometric disagreement, the paired t-tests showed the lack of statistical evidence for systematic differences in dosimetric plan quality yielded by the AS and MS approach for the prostate cohort. In HN cases, statistically significant differences in dosimetric endpoints were observed in structures with small volumes or elongated shapes such as cord (p = 0.01) and esophagus (p = 0.04). The largest absolute dose difference of 11 Gy was seen in the mean pharynx dose. Conclusion: Varying AS performance among structures suggests a differential approach of using AS on a subset of structures and focus MS on the rest. The discrepancy between geometric and dosimetric-end-point driven evaluation also indicates the clinical utility of AS contours in optimization and evaluating plan quality despite of suboptimal geometrical accuracy.

Practical Safety Considerations for Integration of Magnetic Resonance Imaging in Radiation Therapy

Interest in integrating magnetic resonance imaging (MRI) in radiation therapy (RT) practice has increased dramatically in recent years owing to its unique advantages such as excellent soft tissue contrast and capability of measuring biological properties. Continuous real-time imaging for intrafractional motion tracking without ionizing radiation serves as a particularly attractive feature for applications in RT. Despite its many advantages, the integration of MRI in RT workflows is not straightforward, with many unmet needs. MR safety remains one of the key challenges and concerns in the clinical implementation of MR simulators and MR-guided radiation therapy systems in radiation oncology. Most RT staff are not accustomed to working in an environment with a strong magnetic field. There are specific requirements in RT that are different from diagnostic applications. A large variety of implants and devices used in routine RT practice do not have clear MR safety labels. RT-specific imaging pulse sequences focusing on fast acquisition, high spatial integrity, and continuous, real-time acquisition require additional MR safety testing and evaluation. This article provides an overview of MR safety tailored toward RT staff, followed by discussions on specific requirements and challenges associated with MR safety in the RT environment. Strategies and techniques for developing an MR safety program specific to RT are presented and discussed.

Many-isocenter optimization for robotic radiotherapy

Despite significant dosimetric gains, clinical implementation of the 4π non-coplanar radiotherapy on the widely available C-arm gantry system is hindered by limited clearance, and the need to perform complex coordinated gantry and couch motion. A robotic radiotherapy platform would be conducive to such treatment but a new conflict between field size and MLC modulation resolution needs to be managed for versatile applications. This study investigates the dosimetry and delivery efficiency of purposefully creating many isocenters to achieve simultaneously high MLC modulation resolution and large tumor coverage. An integrated optimization framework was proposed for simultaneous beam orientation optimization (BOO), isocenter selection, and fluence map optimization (FMO). The framework includes a least-square dose fidelity objective, a total variation term for regularizing the fluence smoothness, and a group sparsity term for beam selection. A minimal number of isocenters were identified for efficient target coverage. Colliding beams excluded, high-resolution small-field 4π intensity-modulated radiotherapy (IMRT) treatment plans with 50 cm source-to-isocenter distance (SID-50) on 10 Head and Neck (H&N) cancer patients were compared with low-resolution large-field plans with 100 cm SID (SID-100). With the same or better target coverage, the average reduction of [Dmean, Dmax] of 20-beam SID-50 plans from 20-beam SID-100 plans were [2.09 Gy, 1.19 Gy] for organs at risk (OARs) overall, [3.05 Gy, 0.04 Gy] for parotid gland, [3.62 Gy, 5.19 Gy] for larynx, and [3.27 Gy, 1.10 Gy] for mandible. R50 and integral dose were reduced by 5.3% and 9.6%, respectively. Wilcoxon signed-rank test showed significant difference (p   <  0.05) in planning target volume (PTV) homogeneity, PTV Dmax, R50, Integral dose, and OAR Dmean and Dmax. The estimated delivery time of 20-beam [SID-50, SID-100] plans were [19, 18] min and [14, 9] min, assuming 5 fractions and 30 fractions, respectively. With clinically acceptable delivery efficiency, many-isocenter optimization is dosimetrically desirable for treating large targets with high modulation resolution on the robotic platform.

A novel optimization framework for VMAT with dynamic gantry couch rotation

Existing volumetric modulated arc therapy (VMAT) optimization using coplanar arcs is highly efficient but usually dosimetrically inferior to intensity modulated radiation therapy (IMRT) with optimized non-coplanar beams. To achieve both dosimetric quality and delivery efficiency, we proposed in this study, a novel integrated optimization method for non-coplanar VMAT (4πVMAT). 4πVMAT with direct aperture optimization (DAO) was achieved by utilizing a least square dose fidelity objective, along with an anisotropic total variation term for regularizing the fluence smoothness, a single segment term for imposing simple apertures, and a group sparsity term for selecting beam angles. Continuous gantry/couch angle trajectories were selected using the Dijkstra's algorithm, where the edge and node costs were determined based on the maximal gantry rotation speed and the estimated fluence map at the current iteration, respectively. The couch-gantry-patient collision space was calculated based on actual machine geometry and a human subject 3D surface. Beams leading to collision are excluded from the DAO and beam trajectory selection (BTS). An alternating optimization strategy was implemented to solve the integrated DAO and BTS problem. The feasibility of 4πVMAT using one full-arc or two full-arcs was tested on nine patients with brain, lung, or prostate cancer. The plan was compared against a coplanar VMAT (2πVMAT) plan using one additional arc and collimator rotation. Compared to 2πVMAT, 4πVMAT reduced the average maximum and mean organs-at-risk dose by 9.63% and 3.08% of the prescription dose with the same target coverage. R50 was reduced by 23.0%. Maximum doses to the dose limiting organs, such as the brainstem, the major vessels, and the proximal bronchus, were reduced by 8.1 Gy (64.8%), 16.3 Gy (41.5%), and 19.83 Gy (55.5%), respectively. The novel 4πVMAT approach affords efficient delivery of non-coplanar arc trajectories that lead to dosimetric improvements compared with coplanar VMAT using more arcs.

Magnetic Resonance Imaging Guidance Mitigates the Effects of Intrafraction Prostate Motion During Stereotactic Body Radiotherapy for Prostate Cancer

The accurate delivery of stereotactic body radiotherapy (SBRT) for definitive prostate cancer treatment is aided by intrafraction image guidance. The common methods for intrafraction imaging require the invasive placement of fiducial markers or electromagnetic transponders. Recently, a magnetic resonance imaging (MRI)-guided tri-cobalt-60 head radiotherapy system has become available for treatment, which can utilize real-time cine MRI to non-invasively track prostate motion. We report on a clinical vignette using this technique to deliver SBRT for the definitive treatment of intermediate-risk prostate cancer. The incorporation of an MRI-guided radiotherapy system and the implementation of real-time adaptive dose delivery accounting for intrafraction anatomic motion may improve outcomes using this technique.

Integrated beam orientation and scanning-spot optimization in intensity-modulated proton therapy for brain and unilateral head and neck tumors

PURPOSE

Intensity-Modulated Proton Therapy (IMPT) is the state-of-the-art method of delivering proton radiotherapy. Previous research has been mainly focused on optimization of scanning spots with manually selected beam angles. Due to the computational complexity, the potential benefit of simultaneously optimizing beam orientations and spot pattern could not be realized. In this study, we developed a novel integrated beam orientation optimization (BOO) and scanning-spot optimization algorithm for intensity-modulated proton therapy (IMPT).

METHODS

A brain chordoma and three unilateral head-and-neck patients with a maximal target size of 112.49 cm³ were included in this study. A total number of 1162 noncoplanar candidate beams evenly distributed across 4π steradians were included in the optimization. For each candidate beam, the pencil-beam doses of all scanning spots covering the PTV and a margin were calculated. The beam angle selection and spot intensity optimization problem was formulated to include three terms: a dose fidelity term to penalize the deviation of PTV and OAR doses from ideal dose distribution; an L1-norm sparsity term to reduce the number of active spots and improve delivery efficiency; a group sparsity term to control the number of active beams between 2 and 4. For the group sparsity term, convex L2,1-norm and nonconvex L2,1/2-norm were tested. For the dose fidelity term, both quadratic function and linearized equivalent uniform dose (LEUD) cost function were implemented. The optimization problem was solved using the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA). The IMPT BOO method was tested on three head-and-neck patients and one skull base chordoma patient. The results were compared with IMPT plans created using column generation selected beams or manually selected beams.

RESULTS

The L2,1-norm plan selected spatially aggregated beams, indicating potential degeneracy using this norm. L2,1/2-norm was able to select spatially separated beams and achieve smaller deviation from the ideal dose. In the L2,1/2-norm plans, the [mean dose, maximum dose] of OAR were reduced by an average of [2.38%, 4.24%] and[2.32%, 3.76%] of the prescription dose for the quadratic and LEUD cost function, respectively, compared with the IMPT plan using manual beam selection while maintaining the same PTV coverage. The L2,1/2 group sparsity plans were dosimetrically superior to the column generation plans as well. Besides beam orientation selection, spot sparsification was observed. Generally, with the quadratic cost function, 30%~60% spots in the selected beams remained active. With the LEUD cost function, the percentages of active spots were in the range of 35%~85%.The BOO-IMPT run time was approximately 20 min.

CONCLUSION

This work shows the first IMPT approach integrating noncoplanar BOO and scanning-spot optimization in a single mathematical framework. This method is computationally efficient, dosimetrically superior and produces delivery-friendly IMPT plans.

The development and verification of a highly accurate collision prediction model for automated noncoplanar plan delivery

PURPOSE

Significant dosimetric benefits had been previously demonstrated in highly noncoplanar treatment plans. In this study, the authors developed and verified an individualized collision model for the purpose of delivering highly noncoplanar radiotherapy and tested the feasibility of total delivery automation with Varian TrueBeam developer mode.

METHODS

A hand-held 3D scanner was used to capture the surfaces of an anthropomorphic phantom and a human subject, which were positioned with a computer-aided design model of a TrueBeam machine to create a detailed virtual geometrical collision model. The collision model included gantry, collimator, and couch motion degrees of freedom. The accuracy of the 3D scanner was validated by scanning a rigid cubical phantom with known dimensions. The collision model was then validated by generating 300 linear accelerator orientations corresponding to 300 gantry-to-couch and gantry-to-phantom distances, and comparing the corresponding distance measurements to their corresponding models. The linear accelerator orientations reflected uniformly sampled noncoplanar beam angles to the head, lung, and prostate. The distance discrepancies between measurements on the physical and virtual systems were used to estimate treatment-site-specific safety buffer distances with 0.1%, 0.01%, and 0.001% probability of collision between the gantry and couch or phantom. Plans containing 20 noncoplanar beams to the brain, lung, and prostate optimized via an in-house noncoplanar radiotherapy platform were converted into XML script for automated delivery and the entire delivery was recorded and timed to demonstrate the feasibility of automated delivery.

RESULTS

The 3D scanner measured the dimension of the 14 cm cubic phantom within 0.5 mm. The maximal absolute discrepancy between machine and model measurements for gantry-to-couch and gantry-to-phantom was 0.95 and 2.97 cm, respectively. The reduced accuracy of gantry-to-phantom measurements was attributed to phantom setup errors due to the slightly deformable and flexible phantom extremities. The estimated site-specific safety buffer distance with 0.001% probability of collision for (gantry-to-couch, gantry-to-phantom) was (1.23 cm, 3.35 cm), (1.01 cm, 3.99 cm), and (2.19 cm, 5.73 cm) for treatment to the head, lung, and prostate, respectively. Automated delivery to all three treatment sites was completed in 15 min and collision free using a digital Linac.

CONCLUSIONS

An individualized collision prediction model for the purpose of noncoplanar beam delivery was developed and verified. With the model, the study has demonstrated the feasibility of predicting deliverable beams for an individual patient and then guiding fully automated noncoplanar treatment delivery. This work motivates development of clinical workflows and quality assurance procedures to allow more extensive use and automation of noncoplanar beam geometries.

Viability of Non-Coplanar VMAT for Liver SBRT as Compared to Coplanar VMAT and Beam Orientation Optimized 4π IMRT

Purpose

The 4π static noncoplanar radiation therapy delivery technique has demonstrated better normal tissue sparing and dose conformity than the clinically used volumetric modulated arc therapy (VMAT). It is unclear whether this is a fundamental limitation of VMAT delivery or the coplanar nature of its typical clinical plans. The dosimetry and the limits of normal tissue toxicity constrained dose escalation of coplanar VMAT, noncoplanar VMAT and 4π radiation therapy are quantified in this study.

Methods and materials

Clinical stereotactic body radiation therapy plans for 20 liver patients receiving 30 to 60 Gy using coplanar VMAT (cVMAT) were replanned using 3 to 4 partial noncoplanar arcs (nVMAT) and 4π with 20 intensity modulated noncoplanar fields. The conformity number, homogeneity index, 50% dose spillage volume, normal liver volume receiving >15 Gy, dose to organs at risk (OARs), and tumor control probability were compared for all 3 treatment plans. The maximum tolerable dose yielding a normal liver normal tissue control probability <1%, 5%, and 10% was calculated with the Lyman-Kutcher-Burman model for each plan as well as the resulting survival fractions at 1, 2, 3, and 4 years.

Results

Compared with cVMAT, the nVMAT and 4π plans reduced liver volume receiving >15 Gy by an average of 5 cm³ and 80 cm³, respectively. 4π reduced the 50% dose spillage volume by ∼23% compared with both VMAT plans, and either significantly decreased or maintained OAR doses. The 4π maximum tolerable doses and survival fractions were significantly higher than both cVMAT and nVMAT (P < .05) for all normal liver normal tissue control probability limits used in this study.

Conclusions

The 4π technique provides significantly better OAR sparing than both cVMAT and nVMAT and enables more clinically relevant dose escalation for tumor local control. Therefore, despite the current accessibility of nVMAT, it is not a viable alternative to 4π for liver SBRT.

Dose domain regularization of MLC leaf patterns for highly complex IMRT plans

PURPOSE

The advent of automated beam orientation and fluence optimization enables more complex intensity modulated radiation therapy (IMRT) planning using an increasing number of fields to exploit the expanded solution space. This has created a challenge in converting complex fluences to robust multileaf collimator (MLC) segments for delivery. A novel method to regularize the fluence map and simplify MLC segments is introduced to maximize delivery efficiency, accuracy, and plan quality.

METHODS

In this work, we implemented a novel approach to regularize optimized fluences in the dose domain. The treatment planning problem was formulated in an optimization framework to minimize the segmentation-induced dose distribution degradation subject to a total variation regularization to encourage piecewise smoothness in fluence maps. The optimization problem was solved using a first-order primal-dual algorithm known as the Chambolle-Pock algorithm. Plans for 2 GBM, 2 head and neck, and 2 lung patients were created using 20 automatically selected and optimized noncoplanar beams. The fluence was first regularized using Chambolle-Pock and then stratified into equal steps, and the MLC segments were calculated using a previously described level reducing method. Isolated apertures with sizes smaller than preset thresholds of 1-3 bixels, which are square units of an IMRT fluence map from MLC discretization, were removed from the MLC segments. Performance of the dose domain regularized (DDR) fluences was compared to direct stratification and direct MLC segmentation (DMS) of the fluences using level reduction without dose domain fluence regularization.

RESULTS

For all six cases, the DDR method increased the average planning target volume dose homogeneity (D95/D5) from 0.814 to 0.878 while maintaining equivalent dose to organs at risk (OARs). Regularized fluences were more robust to MLC sequencing, particularly to the stratification and small aperture removal. The maximum and mean aperture sizes using the DDR were consistently larger than those from DMS for all tested number of segments.

CONCLUSIONS

The fluence map to MLC segmentation conversion problem was formulated as a secondary optimization problem in the dose domain to minimize the smoothness-regularized dose discrepancy. The large scale optimization problem was solved using a primal-dual algorithm that transformed complicated fluences into maps that were more robust to the MLC segmentation and sequencing, affording fewer and larger segments with minimal degradation to dose distribution.

Incorporating cancer stem cells in radiation therapy treatment response modeling and the implication in glioblastoma multiforme treatment resistance

PURPOSE

To perform a preliminary exploration with a simplistic mathematical cancer stem cell (CSC) interaction model to determine whether the tumor-intrinsic heterogeneity and dynamic equilibrium between CSCs and differentiated cancer cells (DCCs) can better explain radiation therapy treatment response with a dual-compartment linear-quadratic (DLQ) model.

METHODS AND MATERIALS

The radiosensitivity parameters of CSCs and DCCs for cancer cell lines including glioblastoma multiforme (GBM), non-small cell lung cancer, melanoma, osteosarcoma, and prostate, cervical, and breast cancer were determined by performing robust least-square fitting using the DLQ model on published clonogenic survival data. Fitting performance was compared with the single-compartment LQ (SLQ) and universal survival curve models. The fitting results were then used in an ordinary differential equation describing the kinetics of DCCs and CSCs in response to 2- to 14.3-Gy fractionated treatments. The total dose to achieve tumor control and the fraction size that achieved the least normal biological equivalent dose were calculated.

RESULTS

Smaller cell survival fitting errors were observed using DLQ, with the exception of melanoma, which had a low α/β = 0.16 in SLQ. Ordinary differential equation simulation indicated lower normal tissue biological equivalent dose to achieve the same tumor control with a hypofractionated approach for 4 cell lines for the DLQ model, in contrast to SLQ, which favored 2 Gy per fraction for all cells except melanoma. The DLQ model indicated greater tumor radioresistance than SLQ, but the radioresistance was overcome by hypofractionation, other than the GBM cells, which responded poorly to all fractionations.

CONCLUSION

The distinct radiosensitivity and dynamics between CSCs and DCCs in radiation therapy response could perhaps be one possible explanation for the heterogeneous intertumor response to hypofractionation and in some cases superior outcome from stereotactic ablative radiation therapy. The DLQ model also predicted the remarkable GBM radioresistance, a result that is highly consistent with clinical observations. The radioresistance putatively stemmed from accelerated DCC regrowth that rapidly restored compartmental equilibrium between CSCs and DCCs.

Feasibility of extreme dose escalation for glioblastoma multiforme using 4π radiotherapy

Background

Glioblastoma multiforme (GBM) frequently recurs at the same location after radiotherapy. Further dose escalation using conventional methods is limited by normal tissue tolerance. 4π non-coplanar radiotherapy has recently emerged as a new potential method to deliver highly conformal radiation dose using the C-arm linacs. We aim to study the feasibility of very substantial GBM dose escalation while maintaining normal tissue tolerance using 4π.

Methods

11 GBM patients previously treated with volumetric modulated arc therapy (VMAT/RapidArc) on the NovalisTx™ platform to a prescription dose of either 59.4 Gy or 60 Gy were included. All patients were replanned with 30 non-coplanar beams using a 4π radiotherapy platform, which inverse optimizes both beam angles and fluence maps. Four different prescriptions were used including original prescription dose and PTV (4πPTV_PD), 100 Gy to the PTV and GTV (4πPTV_100Gy), 100 Gy to the GTV only while maintaining prescription dose to the rest of the PTV (4πGTV_100Gy), and a 5 mm margin expansion plan (4πPTV_PD+5mm). OARs included in the study are the normal brain (brain – PTV), brainstem, chiasm, spinal cord, eyes, lenses, optical nerves, and cochleae.

Results

The 4π plans resulted in superior dose gradient indices, as indicated by >20% reduction in the R50, compared to the clinical plans. Among all of the 4π cases, when compared to the clinical plans, the maximum and mean doses were significantly reduced (p < 0.05) by a range of 47.01-98.82% and 51.87-99.47%, respectively, or unchanged (p > 0.05) for all of the non-brain OARs. Both the 4πPTV_PD and 4π GTV_100GYplans reduced the mean normal brain mean doses.

Conclusions

4π non-coplanar radiotherapy substantially increases the dose gradient outside of the PTV and better spares critical organs. Dose escalation to 100 Gy to the GTV or additional margin expansion while meeting clinical critical organ dose constraints is feasible. 100 Gy to the PTV result in higher normal brain doses but may be tolerated when delivered in proportionally increased treatment fractions. Therefore, 4π non-coplanar radiotherapy on C-arm gantry may provide an accessible tool to improve the outcome of GBM radiotherapy through extreme dose escalation.

Relationships of urinary phyto-oestrogen excretion to BMD in postmenopausal women

OBJECTIVE

Phyto-oestrogens are plant compounds with both oestrogenic and anti-oestrogenic properties. However, it is not known whether natural phyto-oestrogens are beneficial or harmful in human osteoporosis. This study was performed to investigate the relationships between urinary phyto-oestrogens and bone mineral density (BMD) in Korean postmenopausal women.

DESIGN

The subjects were classified into osteoporotic, osteopenic and normal groups according to their BMD as defined by WHO criteria. We compared the urinary phyto-oestrogens of each group and studied whether urinary phyto-oestrogens correlate with BMD.

PATIENTS

The subjects were 75 Korean postmenopausal women with ages ranging from 52 to 65 years (mean 58 +/- 1.1 years). Mean number of years after menopause was 7.3 +/- 1.3.

MEASUREMENTS

Twenty-four-hour urinary phyto-oestrogens were measured by gas chromatography-mass spectrometry (GCMS) and BMD by dual-energy X-ray absorptiometry (DXA, Lunar Expert-XL, Lunar Co., WI, USA).

RESULTS

In Korean postmenopausal women, urinary enterolactone (1.46 +/- 1.11 micromol/day) was lower and daidzein (2.59 +/- 3.25 micromol/day) was higher than in western women, and both levels were comparable to those in Japanese women. Daily urinary excretion of genistein and apigenin were 1.09 +/- 0.912 and 0.48 +/- 0.40 micromol/day, respectively. In subjects with osteoporosis, urinary enterolactone was lower (P < 0.05) but apigenin was significantly higher (P < 0.05) than in the controls. BMD of L2-L4 correlated positively with urinary enterolactone (r = 0.388, P < 0.01), and BMD of the femoral neck and Ward's triangle correlated positively with urinary enterolactone (r = 0.271, P < 0.05 and r = 0.322, P < 0.05) but negatively with apigenin (r = -0.412, P < 0.01 and r = -0.395, P < 0.01). By multiple stepwise regression, the variables associated with spinal BMD were age, the amount of urinary apigenin and body mass index (BMI). The variables associated with femoral neck BMD were age and urinary apigenin.

CONCLUSIONS

From these results, we conclude that urinary phyto-oestrogens, especially enterolactone and apigenin, are related to BMD in Korean postmenopausal women. Our results also suggest the possibility that phyto-oestrogens have differential effects on bone density. Further studies are needed to clarify the exact biological roles of phyto-oestrogenic components on bone metabolism.

Antenatal counselling, resuscitation practices and attitudes among Australian neonatologists towards life support in extreme prematurity

A questionnaire survey of Australian neonatologists was conducted to ascertain their antenatal counselling and resuscitation practices, and attitudes towards life support in the extremely preterm infant. This study showed that in antenatal parental counselling, whether a paediatrician was given the opportunity to participate depends on the gestation at the time of the threatened preterm delivery The counselling employed almost invariably covered mortality and morbidity. The obstetrician's opinion was considered to be of utmost importance. Both financial and moral obligations were found to be of little importance in counselling and resuscitation. Only one-third of institutions had guidelines for limiting resuscitation. The onus remained on the neonatologists concerning which infant to resuscitate, and the level of the resuscitation to be conducted. In Australia, resuscitation at birth was restricted to infants of 23 weeks' gestation or above, and neonatologists did not believe the legal system has a role to play in limiting or mandating resuscitation of extremely preterm infants. Neither were they concerned with the threat of litigation when they decide to limit resuscitation. The majority of neonatologists agreed with their institution's approach to life support in extremely preterm infants. One grey area was the question of withholding assisted feeding in an infant for which the decision to withdraw life support has been made. Australia lacked a current consensus policy on selective non-treatment. The establishment of national guidelines would be helpful to aid Australian obstetricians and neonatologists in their clinical practice.

The management of extremely premature infants and the perceptions of viability and parental counselling practices of Australian obstetricians

The attitudes of Australian obstetricians to the resuscitation of extremely premature infants are reported. A structured questionnaire including questions regarding antenatal parent counselling, resuscitation practices, survival rates and personal attitudes about life support was distributed to obstetricians working in Australian hospitals with a Level 3 nursery Eighty-nine (48% response rate) replies were received from 12 units located in seven major cities. Obstetricians are more likely to discuss resuscitation with prospective parents with increasing gestation with a major shift occurring at 23-24 weeks' gestation. They strive for consensus with parents regarding resuscitation options and they act upon the opinion of both the prospective parents and their paediatric colleagues. Threat of litigation rarely influences the decision to limit resuscitation of an extremely preterm infant. Obstetricians may underestimate the prognosis for extremely preterm infants. The data presented offer useful insights into current attitudes and practice of tertiary hospital obstetricians.

Developmental outcome of extremely preterm infants

Institution-based studies from perinatal centers are reporting encouraging survival and developmental outcome in extremely preterm infants, but population-based studies of all such births within a geographical-defined region are necessary to examine the impact of perinatal-neonatal care on the entire community. We have reported that their perinatal mortality and severe disability rate were significantly lower in those born within perinatal centers compared with those born elsewhere. Promotion of "in utero transfer" is associated with a significant improvement in their survival and developmental outcome. Postnatal surfactant therapy, which began a decade ago, saw a doubling of the survival rate for infants born as early as 24-26 weeks, while their severe disability rate remains below 10%. Although surfactant and mechanical ventilation are expensive therapies, the resulting improvement in outcome was responsible for a reduction in the cost per additional quality-adjusted life-year gained.

Fetal acalvaria with amniotic band syndrome

A case of amniotic band syndrome (ABS) presenting with acalvaria is reported. ABS includes a spectrum of non-genetic anomalies, varying from simple digital band constriction to major craniofacial and visceral defects, and even fetal death. Acalvaria is a rare congenital malformation characterised by the absence of the dome-like superior portion of the cranium comprising the frontal, parietal, and occipital bones and dura mater, in the presence of a normal skull base and facial bones with complete cranial contents. No two cases are the same. Acrania or absence of the flat skull bones with disorganised cerebral hemispheres have been reported in the presence of amniotic bands. ABS is an aetiological factor in acalvaria. Appropriate counselling for affected families needs to be given after prenatal diagnosis.

Enteral feeding in the preterm infant

In planning enteral feeding in the preterm infant, decisions need to be made regarding the feeding schedule, choice of milk, and the route of administration. Feeds should be commenced within a week after birth beginning with subnutritional quantities. Preterm human milk from the infant's own mother is the milk of choice. When full enteral feeding is established, supplementation with human milk fortifier is recommended. Donor human milk and preterm formula are alternatives. Early establishment of enteral nutrition and maintenance of optimal nutrition during infancy are important as dietary manipulations in preterm infants have potential long-term influences on their health, growth and neurodevelopment.

Mechanisms of blood pressure increase induced by dopamine in hypotensive preterm neonates

AIMS

To compare changes in global haemodynamics as well as anterior cerebral and superior mesenteric artery perfusion after dopamine treatment.

METHODS

Anterior cerebal and superior mesenteric artery perfusion was measured using Doppler ultrasonography in hypotensive preterm neonates in whom cardiac output increased (group 1, n=10) or decreased (group 2, n=40) after dopamine treatment.

RESULTS

Despite a lower dopamine infusion rate, the blood pressure increase (mm Hg) in group 2 [Delta=13(1); mean(SE)] exceeded that in group 1 [Delta=8(1)], while systemic vascular resistance (mm Hg/l/min/kg) rose in group 2 [Delta=106 (37)], but was unchanged in group 1 [Delta=9 (6)]. Anterior cerebral artery blood velocity and resistance were unaffected by dopamine. However, compared with unchanged values in group 1, superior mesenteric artery blood velocity fell by 14.7(4.8) cm/s and resistance increased by 4.1(0.7) mm Hg/cm in group 2.

CONCLUSIONS

These results suggest that, in a portion of hypotensive preterm neonates, the increase in blood pressure induced by dopamine is related to a predominant vasoconstrictor action and is associated with a fall in bowel perfusion.

Cerebral blood volume measured using near-infrared spectroscopy and radiolabels in the immature lamb brain

Near-infrared spectroscopy (NIRS) is a technique that is increasingly being used for the noninvasive measurement of cerebral blood volume (CBV) in newborn infants, but it has not been fully validated against established methods. These experiments in immature lambs (gestation 92+/-1 d, mean+/-SEM) compared CBV measured using NIRS-derived estimates of oxygenated Hb (n = 5) with CBV estimated with radiolabeled indicators (125I-labeled serum albumin and 51Cr-labeled red blood cells, n = 10). Total brain CBV (mL/100 g tissue) measured using NIRS was 2.5+/-0.2 compared with 2.5+/-0.2 using radiolabels (NS). Regional tissue plasma, red blood cells, and whole blood volumes from radiolabels varied significantly (p < or = 0.05) throughout the brain. Whole blood volume (mL/100 g tissue) was largest in choroid plexus (16.2+/-2.1) and least in white matter (0.7+/-0.1) with a significant hierarchy evident among regions: choroid plexus > cerebellum > cortex > brain stem = midbrain > white matter. Regional plasma and red blood cell distributions were similar to whole blood, being highest in choroid plexus (13.0+/-1.6 and 3.2+/-0.9, respectively), and least in white matter (0.8+/-0.1 and 0, respectively). These data from the immature lamb brain indicate that total CBV measured with NIRS is essentially identical with the volumes obtained using intravascular radiolabels. Among cerebral regions, white matter contributes little to the global blood volume measured with NIRS because its red blood cell content is very low.

Major vasodilator role for nitric oxide in the gastrointestinal circulation of the mid-gestation fetal lamb

As nitric oxide (NO) may be a particularly important vasodilator in early life, we investigated its role in the regulation of the gastrointestinal (GI) circulation at mid-gestation. Cardiac output and GI blood flow were measured by the radioactive microsphere technique in eight chronically instrumented and unanesthetized mid-gestation fetal sheep. Mean arterial pressure (MAP), heart rate, blood flow, oxygen delivery, and vascular resistance were determined before and after infusion of the specific NO synthase inhibitor, Nomega-nitro-L-arginine (L-NNA) at doses of 10 and 25 mg/kg. In response to L-NNA infusion, MAP increased (p < 0.01) and combined ventricular output decreased (p < 0.001). GI blood flow and oxygen delivery decreased and vascular resistance increased in the stomach and all segments of the small and large intestine (all p < 0.001). The greatest reduction in blood flow was in the small intestine (p < 0.01) and the basal differential pattern of small intestinal blood flow exceeding large intestinal flow was completely abolished. These changes were much greater than those previously described in late-gestation fetuses. Our results suggest that, at mid-gestation, NO plays a major role in the regulation of blood flow and vascular tone across all segments of the fetal GI tract, with its effects being more pronounced than later in development.

Assisted reproduction technology, multiple births, and adverse perinatal outcome

The increase in the rate of multiple pregnancies in Australia in recent years is primarily due to the use of assisted reproduction technology. Compared to singleton births, fetal, neonatal, and perinatal mortality rates are 3-6 times higher in twins and 5-15 times higher in multiple births of a higher order. Cerebral palsy rates among survivors are six times higher in twins and twenty times higher in triplets. The increased risks in multiple pregnancies are not entirely explained by their higher prematurity and low birthweight rates. In Australia, the practice of transferring more than three embryos in any one assisted reproduction technology cycle has declined in recent years and, as a result, the number of multiple pregnancies from assisted reproduction technology has also declined. Nevertheless, assisted reproduction technology pregnancies remain to have poorer than normal outcome with regards to spontaneous abortion, ectopic pregnancy, preterm birth, low birthweight, and perinatal mortality. Infants born after assisted reproduction technology have a higher neonatal morbidity rate, including a greater requirement for assisted ventilation, and a higher long-term neurodevelopmental disability rate. These adverse outcomes following assisted reproduction technology are partly due to the increased risk of multiple pregnancy and partly due to preterm and low birthweight. This fact and the lack of evidence that the transfer of more than two embryos improves pregnancy rates, make it advisable to limit the number of embryos transferred to no more than one or two per cycle.

The role of dietary nucleotides in neonatal and infant nutrition

Human milk has a higher concentration of nucleotides than bovine milk which is the source of most infant formulas. As the composition of human milk is considered the 'gold standard,' an increasing number of infant formulas are supplemented with nucleotides. This review summarises the biology of human milk nucleotides and evaluates the studies which investigated the clinical benefits of feeding infants with nucleotide-supplemented formulas. Although dietary nucleotides have been suggested to have beneficial gastrointestinal and immunological effects, nucleotide-supplemented formula feeding has not been shown to confer the same benefits as breast feeding, and randomised controlled trials have yet to prove that healthy term infants fed nucleotide-supplemented formulas compared to those fed nonsupplemented formulas, have accelerated physical growth and neurological development, better growth and development of their gastrointestinal tract resulting in improved digestive and absorptive functions, enhanced development of their immune system resulting in increased resistance to infection and lower bacterial and viral infection rates during infancy, and a more favourable intestinal microflora associated with a lower rate of infectious diarrhoea. However, a randomised controlled trial has reported that term infants with severe intrauterine growth retardation do have better catch-up growth with nucleotide supplementation. The hypothesis that nucleotides are semi-essential nutrients needs to be further studied, in particular in the presence of prematurity, fetal growth retardation, intestinal injury and limited nutrient intake. As no deleterious effects have been reported with the use of nucleotide-supplemented formulas, the first of which was introduced over 30 years ago, such products are considered safe when nucleotides are supplemented to an amount equivalent to the free nucleotide concentration of human milk. More basic and clinical research studies are awaited to further define the biology and role of human milk nucleotides, and to critically assess the potential benefits and appropriate level of nucleotide supplementation of infant formula.

Spectrum of clinical and cardiac dysfunction in bronchopulmonary dysplasia: early prediction of long-term morbidity

OBJECTIVES

The objective of this study was to correlate the severity of bronchopulmonary dysplasia (BPD) in infants < or = 28 weeks' gestation with clinical and radiologic scoring and cardiac function as measured by echocardiography.

STUDY DESIGN

Twenty-five infants with a mean birth weight of 909 gm and gestational age 26 weeks were studied. All infants were categorized with a clinical and radiologic scoring system at 1 and 3 months. All infants were studied with two-dimensional, M-mode, and Doppler echocardiography.

RESULTS

A significant correlation was found between clinical and radiologic scores at 1 month (r = 0.42) and between radiologic scorings at 1 and 3 months (r = 0.67). Severe BPD is directly related with mean airway pressure on day 7 of life (p < 0.05), use of intralipids (p < 0.05), and average oxygen exposure (p < 0.05). Left ventricular posterior wall thickness is directly correlated to severity of BPD (p < 0.05), and transmitral flow velocities and early diastolic/atrial contraction flow velocity ratio are inversely related to severity of BPD (p < 0.05).

CONCLUSIONS

Severe BPD can be predicted at an early age, and certain subtle cardiac dysfunctions can be used as early markers of BPD.

Prolonged low-dose indomethacin therapy for patent ductus arteriosus in very low birthweight infants

OBJECTIVE

To determine the efficacy and side-effects of prolonged low-dose indomethacin therapy in very low birthweight (VLBW; < 1500 g) infants with a haemodynamically significant patent ductus arteriosus (hsPDA).

METHODOLOGY

Very low birthweight infants admitted over a 16 month period were studied (8 months, retrospectively and 10 months, prospectively). Cross-sectional and M-Mode echocardiograms with pulsed-wave and colour Doppler were performed to assess the significance of ductal patency.

RESULTS

Forty-one (28%) of 148 VLBW infants were diagnosed to have hsPDA. Indomethacin therapy was successful in 90% after the first course, increasing to 95% after the second course. The recurrence rate after the first course was 3%. Minor and transient complications included oliguria, urea retention, hyponatraemia and thrombocytopenia. Although three infants had focal bowel perforation and the fourth had bowel perforation associated with necrotizing enterocolitis, the incidence of gastrointenstinal pathology was not significantly different from infants without hsPDA and not given indomethacin.

CONCLUSIONS

Very low birthweight infants with hsPDA have a high response rate and low recurrence rate to prolonged low-dose indomethacin therapy. Side-effects were mild and transient. However, it is prudent to be cautious when administering indomethacin in critically ill infants < 1000 g with hsPDA who manifest clinical features of bowel ischaemia.

Principles and practice of parenteral nutrition in the neonatal period

In extremely preterm or critically ill infants, the parenteral route for maintaining nutritional integrity has to be relied upon before successful transition to the enteral route of feeding is achieved. Parenteral nutrition is now a fundamental part of neonatal intensive care. Fluid intake volumes vary from 60-150 ml/kg/d, depending on maturity of the infant and environmental conditions influencing insensible water loss from the skin. Parenteral nitrogen requirements are 30-35 mmol/kg/d, equivalent to 3.0-3.5 mg/kg/d of amino acids. Hyperglycaemia during parenteral nutrition can be minimised by starting glucose infusion at a rate of 6-8 g/kg/d with progressive increase to 18-20 g/kg/d by 2-3 weeks after birth. Parenteral fat is introduced at 1 g/kg/d, gradually increasing to 3 g/kg/d, given as a continuous infusion. An energy intake of 50 kcal/kg/d is adequate to match ongoing expenditure but an additional energy intake of 70 kcal/kg/d is required to achieve optimal growth. Minerals and trace elements delivered with parenteral nutrition are calculated to meet in-utero accretion rates. Multivitamins available for parenteral use should also be included. Improved techniques for the preparation, administration and monitoring of parenteral nutrition have helped minimise catheter-related and metabolic complications. In neonatal intensive care units where appropriate medical, nursing, pharmacy and laboratory expertise are available, the potential benefits of parenteral nutrition outweigh its hazards. Nevertheless, early initiation of enteral feeding in small subnutritional quantities to supplement parenteral nutrition is of major importance to enhance the growth and development of the gastrointestinal tract.

Ethical decision-making in newborn infants

One ethical dilemma which neonatologists are faced with on a regular basis is selective non-treatment, that is, clinical decisions made after the birth of a liveborn infant to withhold or to withdraw treatment in certain circumstances. Although the outcome of extremely preterm of critically ill infants has significantly improved over the last decade, many are often left to die at birth by withholding resuscitation or neonatal intensive care. Criteria for initiating life-sustaining treatment must be developed with proper ethical considerations. There are other infants whose clinical course after initiation of intensive care will suggest that further curative efforts are futile or lack compensating benefit. Criteria for withdrawing life-sustaining treatment must also be developed, and palliative care measures defined. Clinical situations in which selective non-treatment is taking place in neonatal medicine are: (1) when death is considered to be inevitable whatever treatment is provided, (2) even when death is not inevitable, there is a significantly high risk of severe physical and mental disability should the infant survive, and (3) when survival with moderate disability is possible, but the infant is likely to experience ongoing pain and suffering, repeated hospitalisation and invasive treatment, and early death in childhood. The decision-making process of selective non-treatment should involve less medical paternalism and more informed parental involvement. The process is built on trust between the neonatal staff and parents, and requires time, information, honesty and empathy. Ethical issues must be approached with extreme responsibility, extraordinary sensitivity and heroic compassion.

Nitric oxide modulates regional blood flow differences in the fetal gastrointestinal tract

We studied the role of endogenous nitric oxide (NO) in the regulation of gastrointestinal (GI) circulation in 11 chronically instrumented and unanesthetized late-gestation fetal sheep. Systemic and GI blood flows were measured by the radiolabeled microsphere technique. Mean arterial pressure (MAP), heart rate, blood flows, oxygen delivery, and vascular resistance were determined before and after infusion of the specific NO synthase inhibitor, N omega-nitro-L-arginine (L-NNA), to cumulative doses of 10 and 25 mg/kg. At both L-NNA doses, MAP increased, and combined ventricular output and heart rate decreased. GI blood flow and oxygen delivery decreased and vascular resistance increased for the stomach, all segments of the small intestine, and proximal colon and cecum but were unchanged in the middle and distal colon and rectum. Because blood flow reduction in the small intestine was pronounced (from 176 to 107 ml.min-1.100 g-1, P < 0.001) and blood flow in the large intestine was unchanged, distribution of intestinal blood flow became more uniform. Overall, blood flow reduction was proportionally greater in GI circulation than in the remainder of fetal circulation. In three additional animals we established that L-NNA reduced blood flow to the mucosal-submucosal layer (P < 0.02) but not to the muscularis serosa of the small intestine. In the same animals, L-arginine (250 mg/kg) restored systemic hemodynamics and partially restored small intestinal blood flow. Our results suggest that NO is an important differential regulator of vascular tone in the developing GI circulation.

Calorie intake in sick versus respiratory stable very low birthweight babies

A comparison between the calorie intake and energy source of sick versus respiratory stable very low birthweight (VLBW, less than 1500 g) babies was made to ascertain the time taken for them to achieve adequate daily calorie intake. It was an observational study of 23 consecutive VLBW babies in which sick respiratory unstable babies were defined as those who required ventilation beyond 72 h of life. Data were collected on the daily fluid and calorie intake for 30 days of life, and beyond if necessary until the babies achieved full enteral feeding and calorie intake of more than 100 kcal/kg per day. Growth parameters at the time of transfer or discharge were also analyzed. In the study, there were 14 sick VLBW and 9 respiratory stable babies with a mean birthweight of 1027 g and 1212 g, respectively. Their mean gestational age (28.7 weeks vs 31.2 weeks), mean age when calorie intake of 100 kcal/kg per day was achieved (19.8 days vs 7.0 days), mean duration of parenteral nutrition (17.1 days vs 2.7 days), mean age when enteral feeds commenced (8.9 days vs 1.7 days) and mean age when full enteral feeding was established (20.6 days vs 7.3 days) were statistically different for the two groups. For the respiratory unstable babies, parenteral nutrition provided more energy than milk until 15 days of life. The average daily energy intake of 100 kcal/kg per day was only achieved by 30 days of life in this group. In the respiratory stable group, milk provided more than 100 kcal/kg per day from 10 days of life. There were no significant differences in somatic growth with regard to bodyweight, length and head circumference for these two groups of babies at the time of transfer or discharge. The daily calorie intake of sick VLBW babies was suboptimal even with the use of parenteral nutrition. The respiratory stable babies, through enteral feeding, easily achieved the recommended daily calorie intake.

Gastric emptying in pre-term infants: the effect of breast milk fortifier

Failure of adequate gastric emptying frequently prevents successful, early enteral nutrition in the pre-term infant. The effect on gastric emptying of adding breast milk fortifier is unknown, but clinical experience suggests that it is less well tolerated by some infants. We therefore compared gastric emptying rates of breast milk and fortified breast milk within pre-term infants, using a previously described ultrasonic technique. Eleven infants were studied on 22 occasions. Median (range) gestation of the group was 28 weeks (25-31) with birth weight 1090 g (714-1360). The human milk fortifier FM-85 (Nestlé, Vevey, Switzerland) was used in all infants. Half-emptying time for unfortified breast milk was less than half that for fortified breast milk. Mean (+/- SEM) half emptying times were 21 min (+/- 3.6) and 48 min (+/- 4.0), respectively. Breast milk emptied faster than fortified breast milk in 10 out of 11 patients. These data demonstrate that the addition of human milk fortifier can significantly slow gastric emptying. This has important implications for the management of infants who have feed intolerance.

BiliBlanket phototherapy system versus conventional phototherapy: a randomized controlled trial in preterm infants

OBJECTIVE

This study compares the use of standard overhead fluorescent phototherapy units with the BiliBlanket a woven fibreoptic pad which delivers high intensity light with no ultraviolet or infrared irradiation in the treatment of jaundice in preterm infants.

METHODOLOGY

We chose to study infants between 800 and 2500 g, with strict criteria for commencing and ceasing phototherapy. Serum bilirubin levels were followed at 12-24 h intervals until 24 h after cessation of phototherapy. Infants were allocated at random to receive either conventional phototherapy or the BiliBlanket.

RESULTS

There were 24 infants in the conventional group and 20 in the BiliBlanket group. Mean duration of phototherapy was compared and was 44 h for the conventional group versus 42 h for the BiliBlanket group.

CONCLUSIONS

We have shown that the BiliBlanket is as effective as conventional phototherapy and was well accepted by nursing staff and parents.

Prognosis in infants with birth asphyxia

The risk of neurodevelopmental disability from birth asphyxia secondary to intrapartum complications and obstetric mismanagement is generally overestimated. Between 8-17% of all cerebral palsy is associated with adverse perinatal events suggestive of asphyxia. Less than 10% is probably due directly to birth asphyxia itself. Studies have shown that different methods of intrapartum assessment of fetal well-being (fetal heart rate monitoring, fetal scalp pH, presence of meconium) do not correlate well with each other or with neonatal parameters (acid-base status at birth, Apgar scores, seizures, neurological behaviour) and outcome measures (death, cerebral palsy, mental retardation). The prevalence rate of cerebral palsy in most communities of 2.0-2.5 per 1000 children is not falling in spite of increasing use of obstetric and neonatal interventions aimed at preventing or treating birth asphyxia. Prediction of neurodevelopmental outcome of birth asphyxia is difficult because of a limited ability to measure birth asphyxia quantitatively in the antenatal and neonatal period. The terminology used to describe the condition is often confusing. It has been recommended that substantial cerebral hypoxia can only be presumed when four criteria are met: the infant has an Apgar score < or = 3 at 10 minutes, metabolic acidosis at birth, hypotonia for several hours and seizures. For the paediatrician, a number of clinical observations and laboratory investigations have been suggested as helpful in the prediction of death or disability among term infants with birth asphyxia.

Avoidance of red blood cell transfusion in an extremely preterm infant given recombinant human erythropoietin therapy

To avoid red blood cell (RBC) transfusions, recombinant human erythropoietin (rHuEPO) was given to an infant born at a gestation of 26 weeks and a birthweight of 830 g to parents who were Jehovah's Witnesses. The infant had hyaline membrane disease and required 52 days of assisted ventilation and 19 days of oxygen therapy. He received theophylline therapy for 61 days for recurrent apnoea and bradycardia. He developed bilateral intraventricular haemorrhage (IVH) and left-sided periventricular leucomalacia (PVL). Intravenous rHuEPO was started on day 1 at 200 U/kg per day for 1 month followed by subcutaneous rHuEPO 400 U/kg three times a week for 6 more weeks, supplemented with Vitamin E, folic acid and iron. Blood sampling was kept to a minimum and non-invasive blood-gas monitoring was used consistently. Consequently, the estimated cumulative volume of blood loss from sampling was only 21 mL during his hospital stay. His haemoglobin (Hb) was 150 g/L at birth and this fell to below 100 g/L from day 25 onwards. His lowest leucocyte count was 3.6 x 10(9)/L. He was discharged on day 83 with a Hb of 95 g/L, Hct of 29%, reticulocyte count of 2.8% and weight of 2400 g. At a postnatal age of 3 months, he had a Hb of 113 g/L. At 6 months, investigations showed: Hb 121 g/L, haematocrit 33%, reticulocyte 1% and a weight of 4.4 kg. He was readmitted to hospital once for an episode of vomiting and follow up to date showed developmental delay.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose conversion from aminophylline to theophylline in preterm infants

Twenty two preterm infants were prospectively evaluated to assess the need for dose adjustment when converting enteral and parenteral routes of methylxanthine administration.Serum theophylline concentrations remained unchanged in 18 infants after conversion from intravenous aminophylline to theophylline by mouth without dose reduction, as is currently recommended [corrected]. Intravenous aminophylline and theophylline by mouth may therefore be prescribed at equivalent doses, with a possible reduction in drug errors, and improved stability of serum concentrations.

Chronic lung disease in preterm infants

The increasing significance of chronic lung disease (CLD) in the neonatal intensive care unit (NICU) is a result of the increased survival of extremely small and preterm infants and a more aggressive management policy for respiratory failure. Many survive with persistent pulmonary dysfunction, the aetiology of which remains poorly understood. CLD consists of several descriptive categories which have a number of clinical features in common.

Improving health status in extremely low birthweight children between two and five years

The 5-year outcome of 101 extremely low birthweight (ELBW, < 1000 g) children discharged from the Neonatal Intensive Care Unit was reported. Over this period, there were four post-discharge deaths. The neurodevelopmental impairment rate was 18% overall: cerebral palsy 7%, blindness 3%, deafness 3% and developmental delay 10%. Seventy-one percent of children were readmitted to hospital. The mean number of admissions was 2.4 per child and the mean duration of total hospital stay was 11.3 days per child in the 5-year period. A trend was observed in a reduction in the readmission rate and hospital days in the 2-5-year period compared to the period between discharge and 2 years, though the differences were not statistically significant. The most common reason for readmission was for surgical procedures, primarily aural ventilation tube insertion and tonsillectomy and adenoidectomy. Significant health problems included recurrent wheezing episodes, stridor and croup in the period up to 2 years and otitis media and tonsillitis between 2 and 5 years. There was some catch-up growth, especially in height, between 2 and 5 years. Children with < 800 g birthweight had similar rates of neurodevelopmental impairment and hospital readmission to those of 800-999 g birthweight. However, they experienced more otitis media and pneumonia, had more ear, nose and throat operations, and at 5 years of age, more were below the 3rd centile for weight. This study showed that the health status of ELBW children had improved between 2 and 5 years, but they continued to experience recurrent health problems and hospital readmissions which would have resulted in added financial and emotional burdens to their families.