Gaussian Boson Sampling

Boson sampling has emerged as a tool to explore the advantages of quantum over classical computers as it does not require universal control over the quantum system, which favors current photonic experimental platforms. Here, we introduce Gaussian Boson sampling, a classically hard-to-solve problem that uses squeezed states as a nonclassical resource. We relate the probability to measure specific photon patterns from a general Gaussian state in the Fock basis to a matrix function called the Hafnian, which answers the last remaining question of sampling from Gaussian states. Based on this result, we design Gaussian Boson sampling, a #P hard problem, using squeezed states. This demonstrates that Boson sampling from Gaussian states is possible, with significant advantages in the photon generation probability, compared to existing protocols.

Driven Boson Sampling

Sampling the distribution of bosons that have undergone a random unitary evolution is strongly believed to be a computationally hard problem. Key to outperforming classical simulations of this task is to increase both the number of input photons and the size of the network. We propose driven boson sampling, in which photons are input within the network itself, as a means to approach this goal. We show that the mean number of photons entering a boson sampling experiment can exceed one photon per input mode, while maintaining the required complexity, potentially leading to less stringent requirements on the input states for such experiments. When using heralded single-photon sources based on parametric down-conversion, this approach offers an ∼e-fold enhancement in the input state generation rate over scattershot boson sampling, reaching the scaling limit for such sources. This approach also offers a dramatic increase in the signal-to-noise ratio with respect to higher-order photon generation from such probabilistic sources, which removes the need for photon number resolution during the heralding process as the size of the system increases.

Driven quantum walks

We introduce the concept of a driven quantum walk. This work is motivated by recent theoretical and experimental progress that combines quantum walks and parametric down-conversion, leading to fundamentally different phenomena. We compare these striking differences by relating the driven quantum walks to the original quantum walk. Next, we illustrate typical dynamics of such systems and show that these walks can be controlled by various pump configurations and phase matchings. Finally, we end by proposing an application of this process based on a quantum search algorithm that performs faster than a classical search.

Bilateral ultrasound-guided supraclavicular block in a patient with severe electrocution injuries of the upper extremities

The performance of bilateral supraclavicular brachial plexus nerve blocks is controversial. We present the challenging case of a 29-year-old male who suffered bilateral high-voltage electrocution injuries to the upper extremities, resulting in severe tissue damage, sensory and motor deficits, and wounds in both axillae. This injury necessitated bilateral below-elbow amputations. His postoperative course was complicated by pain refractory to intravenous narcotics. The decision was made to attempt bilateral supraclavicular brachial plexus blocks. Our concerns with this approach included the risks of pneumothorax and respiratory failure due to phrenic nerve block. Initial attempts at brachial plexus blockade using nerve stimulation were unsuccessful; therefore, ultrasound guidance was employed. With vigilant monitoring in an intensive care unit setting, we were able to safely perform bilateral continuous supraclavicular brachial plexus nerve blocks with an excellent analgesic response and no noted complications.

Intraoperative and Postoperative Blood Glucose Concentrations in Diabetic Surgical Patients Receiving Lactated Ringer's Versus Normal Saline: A Retrospective Review of Medical Records

BACKGROUND

Hyperglycemia is associated with poor postoperative outcomes after carotid endarterectomy. This retrospective study examined the effect of lactated Ringer's and normal saline solutions on intraoperative blood glucose control in diabetic patients undergoing carotid endarterectomy.

METHODS

The anesthetic and surgical records of type 2 diabetic patients who underwent carotid endarterectomy and received either lactated Ringer's solution or normal saline exclusively during the case were reviewed, and 20 patients were randomly selected from each group for further analysis. The outcome of interest was preoperative to postoperative change in blood glucose.

RESULTS

The preoperative to postoperative mean changes in glucose for the normal saline and lactated Ringer's groups were 34.4 ± 70.32 mg/dL and 64.5 ± 61.38 mg/dL, respectively. This slight difference in the mean change in glucose between the 2 groups was not statistically significant (P=0.157).

CONCLUSION

Lactated Ringer's solution does not appear to cause a significant change in the mean blood glucose levels in diabetic patients undergoing carotid endarterectomy compared to patients receiving normal saline. Randomized controlled trials are needed to further determine whether lactated Ringer's solution adversely affects glucose control in diabetic surgical patients.

Acoustic Pharyngometry: A Substitute for Drug-Induced Sleep Endoscopy?

Objective: Upper airway collapse measured using supine acoustic pharyngometry at respiratory residual volume (RV) has previously been correlated with obstructive sleep apnea-hypopnea syndrome (OSAHS) severity. We aim to assess the agreement between sites of maximal upper airway obstruction measured by supine acoustic pharyngometry and drug-induced sleep-endoscopy (DISE) in snoring/OSAHS patients.

Method: In this case series, 50 consecutive patients with known snoring/OSAHS underwent in-office supine acoustic pharyngometry and DISE. Pharyngometric measurements at respiratory tidal volume were compared against the standard normal curve to establish airway landmarks. Sites of minimal cross-sectional-area at respiratory RV were compared with sites of maximal obstruction identified through DISE.

Results: Fifty patients (68% male, 32% female, age 47.3 ± 13.7, mean AHI 37.0 ± 26.8) were evaluated. All endoscopic assessments were performed by a single investigator (M.F.). Regions of maximal upper airway collapse per DISE were classified as retropalatal, mixed retropalatal and retroglossal, retroglossal, mixed retroglossal and retroepiglottic, or retroepiglottic. Graphical and numerical pharyngometric data were assessed by 3 investigators with complete agreement regarding regional collapse. Agreement between sites of maximal upper airway obstruction per DISE and regions of minimal cross-sectional-area per supine pharyngometry was 89.2% (95% CI 74.5, 95.9; P < .001).

Conclusion: Acoustic pharyngometry is a completely non-invasive mode of assessment through which numerical and graphical data regarding regional upper airway collapse can be rapidly obtained. Findings demonstrate a high level of agreement with those of DISE in the pretreatment/preoperative evaluation of patients with known snoring and/or OSAHS.

Mandibular Advancement for Obstructive Sleep Apnea: Relating Outcomes to Anatomy

Objective: Previous studies assessing the correlation between airway anatomic factors and success with oral appliance (OA) therapy in the treatment of obstructive sleep apnea (OSA) have failed to reach consensus. We aim to assess the role of regional upper airway obstruction measured by acoustic pharyngometry as a determinant of OA success.

Method: In this outpatient case-series, data from OSA patients (100% CPAP-failures) fitted with a custom OA between 07/2011-01/2012 were reviewed. Regional maximal upper airway collapse was determined on acoustic pharyngometry and classified as retropalatal (RP), retroglossal (RG), or retroepiglottic (RE). Apnea-hypopnea index (AHI) improvement on titration-polysomnography was assessed against regional collapse.

Results: Seventy-five patients (74.7% male, age 49.0 ± 13.6, BMI 29.4 ± 5.2, mean AHI 30.6 ± 20.0) were assessed and their data grouped on the basis of region of maximal collapse on pharyngometry at respiratory residual volume (RP = 29, RG = 28, RE = 18). Overall AHI reduction at OA-titration was –20.2 (95% CI –23.6, –16.8; P < .001) with no significant difference in AHI reduction between groups. There was no significant difference in the rate of response to treatment when defined as >50% AHI reduction plus AHI <20 (RP = 69%, RG = 75%, RE = 83%; P = .545), or rate of cure defined as AHI <5 (RP = 52%, RG = 43%, RE = 72%; P = .146). Correlation of minimum cross-sectional-area and response trended toward significance ( r = .202; –.026, .410; P < .1).

Conclusion: Success with oral appliance therapy is not predicted by identification of the region of maximal upper airway collapse as measured by acoustic pharyngometry. OA therapy achieves reasonable objective response and cure rates in patients with primary retropalatal, retroglossal, or retroepiglottic obstruction at the time of initial titration-polysomnography.

The Utility of Facial Nerve Monitoring for Parotid Surgery

Objective: To assess the utility of facial nerve monitoring in preventing transient and permanent facial paralysis in patients undergoing parotid surgery.

Method: PubMed, MEDLINE, and Cochrane Trial Registry through December 2011 were searched and combined with manual review of relevant article bibliographies. All studies were assessed by 3 reviewers. Systematic review and random-effects meta-analysis were performed of studies comparing the incidence of facial nerve injury in monitored and unmonitored parotid surgery.

Results: Five studies met inclusion criteria and had data suitable for pooling (374 patients). Overall, monitoring provided no benefit in reduction of facial paralysis with an odds ratio (OR) of 0.754 (0.488, 1.165; P = .203). In addition, sensitivity analysis revealed that neither transient nor permanent facial paralysis is significantly reduced with the use of monitoring. Analysis of publication bias revealed a nonsignificant Egger’s regression intercept; however, a single imputed value representing a “missing” study was found to the left of the calculated OR. Addition of this imputed value in no way altered the significance of our findings.

Conclusion: Facial nerve monitoring does not significantly reduce the incidence of transient or permanent facial paralysis in parotid surgery. While few “high-level evidence” studies were available for review, our results were not affected by publication bias. Nerve integrity monitoring should not be considered the standard of care for parotid surgery.

OSA Diagnosis by Peripheral Arterial Tonometry

Objective: To assess the correlation between respiratory sleep indices as measured by portable sleep testing using peripheral arterial tonometry (PAT) and respiratory sleep indices as measured by formal polysomnography (PSG). Thereby assess the validity of PAT devices as diagnostic tools for obstructive sleep apnea in the adult population.

Method: PubMed, MEDLINE, Cochrane Trial Registry (through 12/2011), and relevant article bibliographies were searched. Articles were assessed by 3 reviewers. Systematic review and meta-analysis of studies assessing correlation of respiratory sleep indices between PAT devices and PSG in adults (>18 years) was conducted. Included studies provided an r value for correlation.

Results: Eleven studies met inclusion criteria and had data suitable for pooling (775 patients). Of these, 10 studies were “blinded” in that PAT and PSG were conducted simultaneously in either the home or laboratory setting. One study contained 2 trial phases for the same patient group (n = 21), 1 laboratory and 1 home-based, which were analyzed separately. Overall correlation of respiratory sleep indices was high (r = .867, .836-.892, P < .001). Studies comparing respiratory disturbance index (RDI) had a combined r = .854 (.823-.880, P < .001), and those comparing apnea-hypopnea index (AHI) had a combined r = .890 (.833-.929, P < .001). Analysis of publication bias revealed a nonsignificant Egger’s regression intercept.

Conclusion: Respiratory indices calculated using PAT-based portable devices correlate well with those calculated from the scoring of formal PSG. The strength of this correlation is supported by the “blinded” nature of the majority of the included studies. This technology represents a viable alternative to PSG for confirmation of clinically suspected sleep apnea.

Friedman Staging for Sleep Surgery: Meta-analysis

Objective: 1) Review the available literature reporting on the success of single and multi-level sleep surgery in relation to Friedman Anatomical Staging (FAS). 2) Combine statistical outcomes of multiple studies (where appropriate) to determine surgical success rates (defined by postoperative apnea-hypopnea index [AHI] <20 and 50% reduction) for each clinical stage.

Method: PubMed, MEDLINE, and Cochrane Trial Registry (through 12/2011) were searched, combined with manual review of relevant article bibliographies. All studies were assessed by 3 reviewers. Systematic review and random-effects meta-analysis of studies assessing the success of sleep surgery in relation to FAS were performed. Outcomes are reported as proportional success rates.

Results: Six studies met inclusion criteria and had data suitable for pooling (521 patients). Success rate (SR) for single-level palatal surgery with FAS-1 was .806 (.630, .910; P = .002). Multi-level surgical data for FAS-1 yielded SR .706 (.458, .872; P = .1). Single-level surgery for FAS-2 yielded SR .379 (.224, .564; P = .197). Multi-level surgical data for FAS-2 yields SR .647 (.527, .751; P = .017). Single-level surgery for FAS-3 yields SR .081 (.037, .169; P < .001). Multi-level surgery for FAS-3 yields SR .412 (.254, .591; P = .334). Analysis of publication bias yielded non-significant Egger’s regression intercepts for studies reporting FAS-2/3 success. Too few studies reported FAS-1 success to allow statistical analysis of publication bias.

Conclusion: These findings demonstrate the utility of FAS in predicting the success of OSA surgery. Findings further reinforce the value of OSA surgery in patients with FAS-1 regardless of disease severity. In addition, they add to the evidence that multi-level surgery is often necessary to treat patients with more advanced staging.

Diagnosing Obstructive Sleep Apnea: Predictive Value of Friedman Tongue Position

Objective: 1) Assess the association between tongue position and risk of obstructive sleep apnea (OSA) as measured by both Mallampati (MP -including classic 3-level and modified 4-level scoring with tongue protrusion) and Friedman Tongue Position (FTP-no tongue protrusion). 2) Determine which of these assessment scales best predicts OSA risk.

Method: PubMed, MEDLINE, Cochrane Trial Registry (through 12/2011), and relevant article bibliographies were searched. All studies were assessed by 3 reviewers. Systematic review and random-effects meta-analysis of studies assessing the association of tongue position and risk of OSA were performed. Outcomes are reported as odds ratios (OR).

Results: Combined data from 5 studies (46,264 patients) revealed an overall OR of 2.436 (1.828, 3.248; P < .001) for presence of OSA with MP/FTP 3 or 4 compared with MP/FTP 1 or 2. Sensitivity analysis revealed OR of 2.185 (1.643, 2.905; P < .001) for MP 3/4 and 4.408 (2.651, 7.327; P < .001) for FTP 3/4, respectively. Combined data from 2 studies (240 patients) revealed an OR for OSA per 1-point increase in MP/FTP of 2.351 (1.430, 3.865; P < .001). Sensitivity analysis revealed OR of 2.5 (1.225, 5.103; P = .012) and 2.219 (1.109, 4.437; P = .024) per 1-point increase in MP and FTP, respectively.

Conclusion: Tongue position 3 or 4, whether classified by MP or FTP, is significantly associated with increased OSA risk. In the clinical assessment of patients with suspected OSA, FTP 3/4 appears to have a higher predictive value for OSA than classic MP 3 or modified MP 3/4.

Friedman and Mallampati Tongue Positions and Obstructive Sleep Apnea Severity

Objective: 1) To assess the association between tongue position, classified by both Mallampati (MP) and Friedman Tongue Position (FTP) scales, and severity of sleep apnea (OSA) as determined by the apnea-hypopnea index (AHI). 2) To determine which of these assessment methods is most closely correlated with OSA severity.

Method: PubMed, MEDLINE, and Cochrane Trial Registry through December 2011 were searched, combined with review of relevant article bibliographies. All studies were assessed by 3 reviewers. Systematic review and random-effects meta-analysis of studies assessing the association of tongue position and OSA severity were performed. Outcomes are reported as correlations.

Results: Ten studies met inclusion criteria and had data suitable for pooling (2515 patients). Overall, increasing tongue position (categorical variable) was significantly associated with increasing OSA severity (continuous variable of AHI) with a correlation of .351 (95% CI .094, .564; P = .008). Sensitivity analysis revealed correlations of .184 (95%CI .052, .310; P = .006) and .388 (95% CI .049, .646; P = .026) for MP and FTP, respectively. Analysis of publication bias revealed a nonsignificant Egger’s regression intercept; however, 4 imputed values to the right of the mean were found using Duval and Tweedie’s trim and fill method. Adding these values yielded an overall correlation of .498 (95% CI .474, .521).

Conclusion: Both the MP and FTP assessment techniques are significantly correlated with OSA severity. Publication bias does not affect or skew our results. The strength of the correlation between AHI and tongue position is greater for FTP than for MP, though the 95% confidence intervals for their respective correlation coefficients overlap.

Volumetric Uncertainty in Radiotherapy

The technologies available to identify anatomical structures (including radiotherapy target and normal tissue 'volumes'), and to deliver dose accurately to these volumes, have improved significantly in the past decade. However, the ability of clinicians to identify volumes accurately and consistently in patients still suffers from uncertainties that arise from human error, inadequate training, lack of consensus on the derivation of volumes and inadequate characterisation of the accuracy and specificity of imaging technologies. Inadequate volume definition of a target can result in treatment failure and, consequently, disease progression; excessive volume may also lead to unnecessary patient injury. This is a serious problem in routine clinical care. In the context of large multi-centre clinical trials, uncertainty and inconsistency in tissue-volume reporting will be carried through to the analysis of treatment effect on outcome, which will subsequently influence the treatment of future patients. Strategies need to be set in place to ensure that the abilities and consistency of clinicians in defining volumes are aligned with the ability of new technologies to present volumetric information. This review seeks to define the concept of volumetric uncertainty and propose a conceptual model that has these errors evaluated and responded to separately. Specifically, we will explore the major causes, consequences of, and possible remediation of volumetric uncertainty, from the point of view of a multidisciplinary radiotherapy clinical environment.

Contrasting fates for 6-alpha-methylpenicillin N upon oxidation by deacetoxycephalosporin C synthase (DAOCS) and deacetoxy/deacetylcephalosporin C synthase (DAOC/DACS)

6-alpha-methylpenicillin N was synthesised via known routes from 6-aminopenicillanic acid, and tested as a substrate for recombinant DAOCS and DAOC/DACS. Incubation with DAOCS resulted in conversion of 2-oxoglutarate without oxidation of the penicillin substrate ('uncoupled turnover'). Incubation with DAOC/DACS resulted in oxidation to the cephem aldehyde. This is the first example of substrate-induced 'uncoupled turnover', which has been proposed to be an editing mechanism for these enzymes.

Pilot study of high-frequency ultrasound to assess cutaneous oedema in the conservatively managed breast

Cutaneous oedema is a relatively frequent complication in patients treated conservatively for breast cancer. The factors that contribute to this complication have not been precisely determined. We performed a pilot study to assess the usefulness of high-frequency ultrasound as a quantitative measure of cutaneous oedema. Eleven patients undergoing breast-conserving therapy for breast cancer were studied. Both the treated and untreated breasts were examined. Total cutaneous thickness provided a useful measure of cutaneous oedema. The treated breast was significantly thicker than the untreated breast (P < 0.001). The medial aspect of the breast was thicker than the lateral aspect in both the treated and untreated breast (P < 0.001). The increase in cutaneous thickness predated radiotherapy in those patients who had undergone an axillary dissection. Intrapatient variation in skin thickness was much less than interpatient variation in skin thickness (coefficient of variation 6.4% vs. 18.2% for the untreated breast; coefficient of variation 13.9% vs. 30.9% for the treated breast). Increasing cutaneous thickness was associated with decreasing cutaneous echodensity. We were unable to derive quantitative estimates of echodensity. Cutaneous oedema is an important outcome variable following conservative treatment of breast cancer. High-frequency ultrasound is able to quantify this accurately. It can readily detect changes invisible to the naked eye. High-frequency ultrasound should enable the effects of different treatment options (e.g., extent of surgery, radiotherapy, and chemotherapy) on cutaneous oedema to be differentiated and for the time course of oedema to be accurately characterised.

Functional importance of motif I of pseudouridine synthases: mutagenesis of aligned lysine and proline residues

On the basis of sequence alignments, the pseudouridine synthases were grouped into four families that share no statistically significant global sequence similarity, though some common sequence motifs were discovered [Koonin, E. V. (1996) Nucleic Acids. Res. 24, 2411-2415; Gustafsson, C., Reid, R., Greene, P. J., and Santi, D. V. (1996) Nucleic Acids Res. 24, 3756-3762]. We have investigated the functional significance of these alignments by substituting the nearly invariant lysine and proline residues in Motif I of RluA and TruB, pseudouridine synthases belonging to different families. Contrary to our expectations, the altered enzymes display only very mild kinetic impairment. Substitution of the aligned lysine and proline residues does, however, reduce structural stability, consistent with a temperature sensitive phenotype that results from substitution of the cognate proline residue in Cbf5p, a yeast homologue of TruB [Zerbarjadian, Y., King, T., Fournier, M. J., Clarke, L., and Carbon, J. (1999) Mol. Cell. Biol. 19, 7461-7472]. Together, our data support a functional role for Motif I, as predicted by sequence alignments, though the effect of substituting the highly conserved residues was milder than we anticipated. By extrapolation, our findings also support the assignment of pseudouridine synthase function to certain physiologically important eukaryotic proteins that contain Motif I, including the human protein dyskerin, alteration of which leads to the disease dyskeratosis congenita.

Is there more than one late radiation proctitis syndrome?

PURPOSE

To investigate the significance of the various late rectal symptoms that appear after radical prostatic irradiation.

PATIENTS AND METHODS

Patients with localised prostate cancer treated between 1987 and 1994 at the Mater Hospital, Newcastle with radical megavoltage irradiation were recalled for examination and to complete a detailed questionnaire concerning late radiation-induced symptoms and their effects on normal daily life. The influence of patient age treatment related variables and acute proctitis symptoms occurring during therapy or the late symptoms recorded were assessed and the relationship between late symptoms and late EORTC/RTOG score and impact on normal daily life were studied.

RESULTS

The presence of symptoms of acute proctitis was the only factor to predict any of three late symptoms (urgency, frequency and diarrhoea) and late EORTC/RTOG score in this series (odds ratios: 1.7-2.57, P-values: 0.009-0.0007). Cluster and discriminant function analyses revealed the presence of five subgroups of patients with varying permutations of different late rectal symptoms, including one group with minimal symptoms (P < 0.0001). While bleeding and rectal discharge were the major contributors to late EORTC/RTOG score (P < 0.0001 and 0.04), faecal urgency and bleeding were the most important factors to impact on normal daily life (P < 0.0001 and P < 0.0003). A relatively low concordance was found between late EORTC/RTOG score and the patients' self assessment on the effect of their symptoms on their normal daily lives. Some late symptoms, including bleeding and rectal discharge become less prevalent after 3 years of follow-up with a resulting improvement in EORTC/RTOG score.

CONCLUSIONS

There may be more than one late (chronic) proctitis syndrome which may be linked in greater or lesser degrees to acute proctitis symptoms occurring during therapy. Urgency is a common late symptom which often has an important impact on normal daily life and deserves recognition in late normal tissue scoring systems. Assessment of the incidence of bleeding as a measure of late rectal morbidity following prostate irradiation may underestimate the impact of these chronic effects. Confirmatory studies are necessary.

Response of human hair cortical cells to fractionated radiotherapy

Hair cortical cell counting (HCCC) represents a non-invasive, in-vivo measure of cell kill in the human integument. Sixty-six patients undergoing conventionally fractionated, external beam radiotherapy for early stage carcinoma of the prostate had groin hair samples counted. This technique is a sensitive and reproducible measure of radiation effect and may have applicability as an in-vivo prediction tool or in the field of biological dosimetry. A repopulative follicular response occurring at 3-4 weeks may explain flattening of the dose response curve.

Mucosal regeneration during radiotherapy. Trans Tasman Radiation Oncology Group (TROG)

BACKGROUND AND PURPOSE

Regeneration of the aerodigestive mucosa is known to occur during conventionally fractionated radiotherapy. The circumstances surrounding its time of onset and magnitude are not well understood, however.

MATERIAL AND METHODS

Mucosal reactions were observed in 100 patients undergoing conventionally fractionated treatment at 2 Gy/day over 7 weeks and 88 receiving accelerated treatment at 1.8 Gy twice daily over 3 1/2 weeks on the Trans Tasman Radiation Oncology Group head and neck cancer trials. Similar observations in 61 patients treated palliatively at dose rates between 0.8 and 240 Gy/h using ten 3.0-4.2 Gy fractions over 2 weeks are compared.

RESULTS

Several findings emerged from these studies: 1. Reactions evolved more quickly at oropharyngeal sites than in the hypopharynx. 2. Reactions at both sites evolved more rapidly at greater rates of dose accumulation. 3. The timing of reactions suggested the presence of a strong regenerative mucosal response that started before the manifestation of "patchy' (grade II) mucosal reactions. 4. The regenerative response was strong enough to "make good' damage accumulated at a rate of 2 Gy/day in over a third of cases. 5. The linear quadratic model without time correction failed to provide an adequate prediction of the frequency or intensity of mucosal reactions produced by any of the regimes. A simple model of the regenerative response is presented.

CONCLUSIONS

This study suggests that the timing and magnitude of the regenerative response vary between sites and individuals but are linked to the amount of epithelial cellular depletion occurring during treatment.

Assessment of mucosal underdosing in larynx irradiation

PURPOSE

Mucosal underdosing as a result of electron disequilibrium at the air cavity may affect local recurrence rates for T1 and T2 larynx cancers. Secondary build-up properties of high-energy beams have been demonstrated in a slab phantom. It was the aim of this investigation to determine whether significant surface underdosing exists for the mucosa under clinical conditions.

METHODS AND MATERIALS

Measurements were made using a thermoluminescent dosimetry (TLD) extrapolation technique in an anatomic larynx phantom. The larynx phantom was constructed using tissue and cartilage equivalent material, based on patient cross-sectional anatomy. Three different thicknesses of LiF ribbons, 0.14, 0.39, and 0.89 mm, were placed reproducibly at 12 different positions at the anterior, posterior, and lateral walls on the endolarynx surface. Measured doses were plotted and an extrapolation was made back to the mucosal depth to obtain the dose received at each of the positions. Results were obtained for two different field configurations, opposed laterals and oblique fields, for 6-MV X rays and opposed lateral fields from a telecesium unit. In addition, the larynx surface doses of field sizes from 4 x 6 cm2 to 7 x 6 cm2 were investigated.

RESULTS

Surface underdosing was observed owing to the secondary build-up and build-down effect of the air cavity, and the dose measured for the three extrapolation TLDs at any position varied by up to 18%. An average variation of 6% was observed. The surface underdosing was most apparent for the 6-MV opposed lateral beam technique, where mucosa doses down to 76% of the prescribed dose were observed. Mucosal underdosing at the measurement positions was less marked with oblique techniques, telecesium treatment, and increasing field size.

CONCLUSION

Because of underdosing, some surface positions receive < 80% of the prescribed dose. This may contribute to the potential for higher recurrence rates observed with high-energy photons.

Underprediction of human skin erythema at low doses per fraction by the linear quadratic model

BACKGROUND AND PURPOSE

The erythematous response of human skin to radiotherapy has proven useful for testing the predictions of the linear quadratic (LQ) model in terms of fractionation sensitivity and repair half time. No formal investigation of the response of human skin to doses less than 2 Gy per fraction has occurred. This study aims to test the validity of the LQ model for human skin at doses ranging from 0.4 to 5.2 Gy per fraction.

MATERIALS AND METHODS

Complete erythema reaction profiles were obtained using reflectance spectrophotometry in two patient populations: 65 patients treated palliatively with 5, 10, 12 and 20 daily treatment fractions (varying thicknesses of bolus, various body sites) and 52 patients undergoing prostatic irradiation for localised carcinoma of the prostate (no bolus, 30-32 fractions).

RESULTS AND CONCLUSIONS

Gender, age, site and prior sun exposure influence pre- and post-treatment erythema values independently of dose administered. Out-of-field effects were also noted. The linear quadratic model significantly underpredicted peak erythema values at doses less than 1.5 Gy per fraction. This suggests that either the conventional linear quadratic model does not apply for low doses per fraction in human skin or that erythema is not exclusively initiated by radiation damage to the basal layer. The data are potentially explained by an induced repair model.

Factors influencing outcome following radio-chemotherapy for oesophageal cancer. The Trans Tasman Radiation Oncology Group (TROG)

BACKGROUND AND PURPOSES

To define new directions, the Trans Tasman Radiation Oncology Group (TROG) has conducted a detailed analysis of its unrandomised experience with radio-chemotherapy in oesophageal cancer.

METHODS AND PATIENTS

Since 1984, 373 patients with oesophageal cancer have been treated on three prospective, but unrandomised, protocols involving radiation with concurrent cisplatin and infusional fluorouracil. Centres in Australia and New Zealand have contributed patients. Reasons for case selection have been examined in detail and prognostic models have been examined in the light of biases exposed.

RESULTS

Cause specific survival in 92 patients treated pre-operatively with 35 Gy, infusional fluorouracil and cisplatin was 25.5 +/- 6.0% at 5 years and similar to the 5 year expectations of 169 patients treated with 60 Gy and two courses of the same chemotherapy (23.8 +/- 4.7%). Analysis of failure in these groups suggests that local relapse precedes the development of metastases and competes as a cause for ultimate failure. Although patients treated surgically were less likely to relapse locally, survival was no better because more developed metastases. Some of the 112 patients treated "palliatively" with 30-35 Gy concurrent with chemotherapy without surgery have become long-term survivors with 5 year survival figure in this group 7.7 +/- 3.4%. Apart from variables related to disease stage and performance status at presentation, tumour site emerged as a strong predictor of outcome. Prognosis worsens the nearer the tumour is to the stomach. In addition, indications of a radiation dose response relationship emerged.

CONCLUSIONS

Concurrent radio-chemotherapy protocols can improve outcome in patients fit enough to tolerate these approaches. New strategies remain necessary, however.

Low dose rate teletherapy: updated tumour response

This report presents an update of tumour response experience in patients with locally advanced head and neck cancer treated on the low dose rate teletherapy project at the Mater Misericordiae Hospital, Newcastle. Long-term progression-free survival figures are disappointing in all dose rate/total dose groupings and offer little encouragement that an improvement in therapeutic ratio can be achieved for head and neck cancer patients using teletherapy apparatus adjusted to treat at low and intermediate dose rates.

Clinical use of carbon-loaded thermoluminescent dosimeters for skin dose determination

PURPOSE

Carbon-loaded thermoluminescent dosimeters (TLDs) are designed for surface/skin dose measurements. Following 4 years in clinical use at the Mater Hospital, the accuracy and clinical usefulness of the carbon-loaded TLDs was assessed.

METHODS AND MATERIALS

Teflon-based carbon-loaded lithium fluoride (LiF) disks with a diameter of 13 mm were used in the present study. The TLDs were compared with ion chamber readings and TLD extrapolation to determine the effective depth of the TLD measurement. In vivo measurements were made on patients receiving open-field treatments to the chest, abdomen, and groin. Skin entry dose or entry and exit dose were assessed in comparison with doses estimated from phantom measurements.

RESULTS

The effective depth of measurement in a 6 MV therapeutic x-ray beam was found to be about 0.10 mm using TLD extrapolation as a comparison. Entrance surface dose measurements made on a solid water phantom agreed well with ion chamber and TLD extrapolation measurements, and black TLDs provide a more accurate exit dose than the other methods. Under clinical conditions, the black TLDs have an accuracy of +/- 5% (+/- 2 SD). The dose predicted from black TLD readings correlate with observed skin reactions as assessed with reflectance spectroscopy.

CONCLUSION

In vivo dosimetry with carbon-loaded TLDs proved to be a useful tool in assessing the dose delivered to the basal cell layer in the skin of patients undergoing radiotherapy.

Factors influencing the degree of erythematous skin reactions in humans

Dose-response relationships have been studied using an ordinal visual scale and reflectance spectrophotometry data from 123 treatment sites on 110 patients treated with 10 dose fractions over 12-14 days. Dose rates varied between 3 and 240 Gy/h and total doses of between 25 and 41 Gy were given using teletherapy apparatus. We found qualitative scoring of erythematous skin reactions to be subject to considerable inter- and intra-observer variation. Reflectance spectrophotometry provided more reproducible information, some of which was undetectable by naked eye. Baseline erythema readings were significantly higher in male patients and at anatomical sites of previous heavy UV exposure. In addition, a pronounced decline in erythema readings during the second week of therapy and 'reciprocal vicinity' (abscopal) effects adjacent to the field, undetected by the eye, were observed in a subset of patients. Meaningful dose-response relationships could be derived only from reflectance data with peak change from the pretreatment baseline measure providing the best discrimination. Peak erythema measures following treatment were found to depend on the age and gender of the patient as well as the treatment site and its baseline erythema measurement. This was independent of the total dose administered or the instantaneous dose rate at which it was delivered. The rate of erythema development was also dose rate dependent but only weakly dependent on the biological dose intensity (Gy equiv./day) of the treatment course. The data raise the question of whether irradiation-induced erythema is exclusively a secondary phenomenon occurring as a result of basal cell killing. The short repair half time value of 0.06 h obtained by direct analysis is perplexing and may reflect a dose rate-dependent physiological vasodilatory response to irradiation and/or a multi-component cellular repair process.

Combined modality therapy for esophageal carcinoma: preliminary results from a large Australasian multicenter study

PURPOSE

This report updates local control and survival experience and focuses on treatment toxicity in 294 patients with esophageal cancer who have been treated at six Australasian centers using three prospective unrandomized protocols that used concurrent radiation, cisplatin, and modest dose infusional fluorouracil.

METHODS AND MATERIALS

Protocol 1--"definitive" chemoradiation. One hundred and thirty-seven patients have been treated with "definitive" radiation to 60 Gy in 6 weeks plus two courses of cisplatin (80 mg/m2) and infusional fluorouracil (800 mg/m2/day over 4 days) during the first and fourth weeks of radiation. Protocol 2--"preoperative" chemoradiation and surgery. Seventy-eight patients received chemoradiation using the same chemotherapy, but 30-35 Gy in 3-4 weeks prior to surgery. Protocol 3--"palliative" chemoradiation. Seventy-nine patients deemed incurable were treated "palliatively" with the same chemoradiation protocol without surgery. Follow-up ranges from 6 months to 7 years (mean 22 months) in live patients.

RESULTS

Durable palliation of dysphagia in all three treatment groups has been reflected by encouraging 3-year survival expectations of 43.2 +/- 5% in definitively treated patients, 40.3 +/- 7.65% in surgically treated patients, and 8.5% +/- 3.9% in the palliatively treated patients. There are early indications that female patients have fared better than males. Toxicity levels were modest in all three groups. Following definitive treatment, severe myelotoxicity (World Health Organization grades 3 and 4) occurred in 19%, severe esophagitis (World Health Organization grade 3) in 11%, and moderate or severe benign stricture in 17%, depending upon age and sex of the patient (being worse in female patients).

CONCLUSIONS

These studies demonstrate that the concurrent addition of modest dose cisplatin and infusional dose fluorouracil to radiation in the definitive, preoperative, and palliative settings contribute to high rates of durable dysphagia-free survival, with overall survival comparable to (and possibly better than) the chemoradiation arm of the recently reported Intergroup Study, but at the cost of less morbidity.

Acute reaction parameters for human oropharyngeal mucosa

The purpose of this study was to determine the influence of changes in dose rate over the range 0.8-240 Gy/h on acute oropharyngeal mucosal reactions in human subjects, and to estimate the values of the important parameters that influence these reactions. Sixty-one patients requiring radiotherapy to palliate incurable head and neck cancer were treated on a telecaesium unit, using opposing lateral portals to total midline doses, varying between 30 and 42 Gy in 10 daily fractions over 2 weeks, at dose rates of 0.8, 1.8, 3.0 and 240 Gy/h according to a central composite study design. The severity and time course of reactions were charted at least twice weekly for each patient, using the EORTC/RTOG acute mucosal reaction grading system. Duration of reaction at each grade was observed to provide a more sensitive reflection of effect than the proportion of patients reaching any particular reaction grade. Analysis of duration by direct and indirect methods suggest alpha/beta ratios in the range 7-10 Gy and half-time (t1/2) values in the range 0.27-0.5 h, if mono-exponential repair kinetics are assumed. The t1/2 values are short and raise the question as to whether the repair kinetics of this tissue are well described by a mono-exponential function. Further prospective studies involving multiple daily fraction treatment regimes delivered at high dose rate, in which interfraction interval is deliberately varied, are needed to find out whether the parameters derived from this project are applicable to fractionated treatment courses at high dose rate.

Simultaneous adjuvant radiation therapy and chemotherapy in high-risk breast cancer--toxicity and dose modification: a Transtasman Radiation Oncology Group Multi-Institution study

PURPOSE

To establish the toxicity profile of simultaneously administered postoperative radiation therapy and CMF chemotherapy as a prelude to a randomized controlled study addressing the sequencing of the two modalities.

METHODS AND MATERIALS

One hundred and thirty eight breast cancer patients at high risk of locoregional, as well as systemic relapse, who were referred to three centers in Australia and New Zealand were treated with postoperative radiation therapy and chemotherapy simultaneously. Acute toxicity and dose modifications in these patients were compared with 83 patients treated over the same time frame with chemotherapy alone. In a separate study the long-term radiation and surgical effects in 24 patients treated simultaneously with radiation therapy and chemotherapy at Newcastle (Australia) following conservative surgery were compared with 23 matched patients treated at Newcastle with radiation therapy alone.

RESULTS

Myelotoxicity was increased in patients treated simultaneously with radiation therapy and chemotherapy. The effect was not great, but may have contributed to chemotherapy dose reductions. Lymphopenia was observed to be the largest factor in total white cell depressions caused by the simultaneous administration of radiation therapy. Postsurgical appearances were found to so dominate long-term treatment effects on the treated breast that the effect of radiation therapy dose and additional chemotherapy was difficult to detect.

CONCLUSION

Studies addressing the sequencing of radiation therapy and chemotherapy will necessarily be large because adverse effects from administering the two modalities simultaneously are not great. The present study has endorsed the importance in future studies of stratification according to the extent and type of surgery and adherence to a single strict policy of chemotherapy dose modification.

Dosimetry of high energy electron therapy to the parotid region

Well-known inadequacies in currently available electron planning systems, and two cases of temporal lobe necrosis following electron therapy of the parotid stimulated a comprehensive head and neck phantom dosimetric study of the use of high energy electrons for parotid treatments. A typical electron field employed for the treatment of parotid malignancy was examined in an anthropomorphic head phantom from which air cavities had been excavated. Thermoluminescent dosimeter measurements were compared with predicted point doses obtained from a Theraplan Treatment planning system (V05). Data was examined for three different electron energies: 12, 16 and 20 MeV and with the addition of contoured bolus for 20 MeV. A number of significant discrepancies between the measured and predicted dose were observed. Measured doses were seen to exceed predicted doses by up to 23% in the temporal lobe. Further under-predictions of dose were found behind the mandible and in the nasal cavity. Over-predictions of dose by the planning algorithm of up to 22% were observed beside the oropharynx. Some of these discrepancies were found to relate to Theraplan under-estimation of the dose in the fall-off region. Other errors are attributable to the difficulties in predicting dose at density interfaces. Localised over- and under-predictions of this magnitude must be accounted for by the clinician prescribing treatment in terms of possible late effects on the temporal lobe and, in particular, the nominated dose specification point.

Radiotherapy planning for lung cancer: can we do better?

Modern radiotherapy planning and treatment techniques allow the delivery of treatment with considerable geographic and dosimetric precision. Uncertainties and variability in the radiotherapy process prior to this stage, that is, localization of the target volume, has received little systematic study. The results of a planning study in non-small cell carcinoma of the lung are presented to highlight the possible variability in the planning process, both at an inter-clinician and intra-clinician level. The implications of this survey, both in terms of treatment outcome and training issues, are discussed.

A comparison of three electron planning algorithms for a 16 MeV electron beam

PURPOSE

We report results of a comparison of three electron planning algorithms, an Age-Diffusion Pencil beam algorithm and two (2-D) and three dimensional (3-D) Hogstrom pencil beam algorithms, using simple 2 x 2 cm air and hard bone inhomogeneities and a complex anthropomorphic head and neck phantom.

METHODS AND MATERIALS

The simple inhomogeneities have variable dimensions outside the plane of calculation to test the effects of out of plane scattering on 2-D algorithms, compared with dose measured by film below the inhomogeneity in the dose fall-off range. Comparisons are also made of a parotid treatment field for 16 MeV electrons, and the dose measured by high sensitivity thermoluminescent dosimeters in the head and neck phantom.

RESULTS

Behind the simple inhomogeneities, the electron algorithms are found to underestimate the dose behind the air cavity by up to 40% and overestimated the dose behind bone by up to 30%. In the head phantom, the presence of inhomogeneities also presents problems for the algorithms, with overestimations of dose of up to 20% found behind bone-tissue interfaces, apparently due to shielding by high density bone. Overestimations of up to 17% are also found beside interfaces parallel to the beam. Underestimations of dose of up to 10% are found on the beam-side of interfaces, due to under-prediction of backscattered electrons. All three investigated algorithms underestimate the dose by up to 20% behind extreme surface curvature. One algorithm is found to underestimate the dose in the falloff region while another overestimates the dose around the 90% isodose.

CONCLUSION

Clinicians should be aware of the limitations of their planning systems.

Objective decision-making following a portal film: the results of a pilot study

PURPOSE

To discriminate between random and systematic treatment setup errors using portal films.

METHODS AND MATERIALS

A bi-dimensional analytic techniques using multiple analyses of variance based on Hotelling's T2 statistics to derive numerical and graphical measures of daily portal film accuracy and precision has been trialed using 88 daily portal films from seven patients' treatment.

RESULTS

A demonstration is provided of how a reasonable approximation of random variation from the intended (Simulator) field center, and systematic displacement of the mean position of the portal film centers may be derived from a minimum number of portal films. If a random error as great as 10 mm exists, at least six or seven portal films are considered necessary to reliably detect and quantify the size of a systematic error.

CONCLUSION

Our results suggest that a modest systematic error could go undetected until the end of a 5 or 6 week course of treatment if only one portal film is obtained each week. A greater number of portal films should be performed during the first week of treatment to reduce the frequency of such errors. Efforts to separate and quantify both random and systematic errors in setup are worthwhile and will lead to improvements in outcome at the individual patient level and at a departmental level in the development of quality assurance programs.

Low dose rate teletherapy and tumour response

Tumour responses in 25 patients with locally advanced head and neck cancer, treated on an experimental fractionated low dose rate (FLDR) teletherapy program are reported. Treatment was given at dose rates ranging from 1.8 to 3 Gy/h to a range of total doses from 32-38 Gy, with palliative intent. The total doses delivered have been predicted by the linear quadratic formula to be equivalent to 33-41 Gy using conventionally fractionated high dose rate treatment, in terms of acute normal tissue effects. A complete response rate (no visible or palpable disease 2 months after treatment) was observed in 28% of cases. Analysis of these response rates suggests that the linear quadratic formula may underestimate the anti-tumour effect of FLDR teletherapy at the various dose rates and total dose permutations in this study.

Phase I/II study of concurrent weekly carboplatin and radiation therapy in advanced head and neck cancer

Thirty-two patients with locally advanced head and neck cancer have been treated with concurrent weekly carboplatin and conventional radiation therapy (RT) (2 Gy fractions 4-5 days/week to a total dose of 64-70 Gy over 7-8 weeks) in a Phase I/II study. Carboplatin was administered weekly during RT at doses of 75-150 mg/m2/wk as a 1-hour infusion. The maximum tolerated dose of carboplatin was 130 mg/m2/wk, with myelosuppression, predominantly neutropenia, being dose limiting. Other systemic toxicities were insignificant and no overlapping toxicity was evident. Ultimate locoregional control and survival probabilities were disappointing. It is suggested that either further studies using radiation and carboplatin at the dose 130 mg/m2/wk, or variations on dose and scheduling be performed prior to the instigation of Phase III studies.

Pelvic radiotherapy with concurrent 5-fluorouracil modulated by leucovorin for rectal cancer: a phase II study

Combined modality treatment for cancer of the rectum has been shown to reduce recurrences and improve overall survival. We wished to find out if we could safely give concurrent radiotherapy and 5-fluorouracil (5-FU) modulated by leucovorin (LV) in 3 settings: pre-operatively, adjuvantly and in recurrent disease. A total of 39 patients were treated, 11 preoperatively, 17 adjuvantly and 11 with recurrent disease. There were 26 males and 13 females with a median age of 64 years. The median radiotherapy (RT) dose was 45 Gy/25 fractions/1.8 Gy per fraction (range 25-63 Gy). Chemotherapy consisted of LV 80 mg/m2 i.v. infusion over 1.5 hours followed by 5-FU 400 mg/m2 i.v. bolus, both given once a week. The median number of cycles was 8 (range 3-12). Diarrhoea was the main toxicity, and was encountered in 30 patients (77%): grade 1 in 3 (8%), grade 2 in 12 (30%), grade 3 in 11 (28%), and grade 4 in 4 (10%). This required 18 (46%) patients to have modifications to their RT (20% had breaks and 26% ceased at doses < 45 Gy). Nine patients (23%) had modifications in the chemotherapy (10% had breaks and 13% received < 6 cycles). Encouraging responses were seen in the preoperative setting. Concurrent RT and 5-FU/LV, as given in this schedule, results in an unacceptable incidence of diarrhoea, limiting both the total dose of RT and chemotherapy that can be delivered, particularly in patients who have had previous surgery.