Introduction of hospital quality measures may lead to a temporary decrease in patient outcomes

OBJECTIVES

To analyse the impact of hospital quality indicators on hip fracture mortality in Israel.

STUDY DESIGN

A retrospective observational study.

METHODS

Data were collected on all patients aged ≥65 years with an isolated hip fracture in the years 2010-2016 from the Israel's National Trauma Registry. These data were then cross checked with information on co-morbidities and medication intake from the Clalit medical fund. All successfully matched patients constituted the study population. The main outcome measures were in-hospital and 1-year mortality. Trend analysis of surgery on hip fractures within 48 h of hospitalisation (referred to as early hip fracture surgeries) and mortality was performed. The introduction of the proportion of early hip fracture surgeries as an official quality parameter in 2013 was considered an intervention.

RESULTS

The proportion of early hip fracture surgeries continuously increased during the study period and, after the introduction of the quality measure, a significant increase in the uniformity of practice among hospitals was observed. The mortality trend was not related to the early surgeries trend, with a sharp upward spike detected in 2014, followed by a gradual return to previous levels in the subsequent years. The analysis has shown that when adjusting for demographic factors and co-morbidity, both in 2010-2013 and in 2015-2016, a clear benefit in survival existed for patients who were operated on within the first 48 h. In 2014, which was the first year of open publication of achieved quality measures reported in the media, no such benefit was found.

CONCLUSIONS

Even when an improvement in a promoted practice is achieved, its positive impact on clinical outcomes may be delayed, possibly indicating the need for a learning period.

The reliability of the Glasgow Coma Scale in detecting traumatic brain injury: The continuous effect of age

Background: Recent studies noted the limited applicability of Glasgow Coma Scale (GCS) for elderly patients with Traumatic Brain Injury (TBI). However, the dichotomic distinction between "elderly" and "non-elderly" does not cover the full span of influence of age on GCS presentation.Objective: To analyze the influence of age on GCS scores of patients with isolated TBI.Methods: A retrospective study of 18,534 patients hospitalized due to isolated TBI recorded in the Israeli National Trauma Registry in 1997-2017. The GCS scores were compared between four age-groups: 20-44, 45-64, 65-74 and 75+ years old. Additional factors included patient's sex, Abbreviated Injury Scores (AIS) and injury circumstances.Results: GCS scores increased continuously with age at all AIS levels. The trend was significant even after adjustment for patient's sex and injury circumstances. The angle of the trend was different in various injury circumstances, with GCS scores of victims of Road Traffic Accidents sharply increasing after age of 44 and that of the patients hospitalized after falling from own height surging after age of 64.Conclusions: Screening procedures for patients with TBI should give a greater weight to the actual age of adults, as well as to the circumstances of their injury.

New Trends in Terrorism-Related Injury Mechanisms: Is There a Difference in Injury Severity?

STUDY OBJECTIVE

The latest wave of terrorism worldwide has seen significant use by terrorists of mundane, "low-technology" weapons, such as utility knives and civilian vehicles. How do the injuries they produce compare with that of more conventional terrorism mechanisms, such as use of firearms and explosives? We compare injury patterns of the most frequent terrorism-related injury mechanisms in an Israeli data set.

METHODS

This was a retrospective study of 1,858 patients hospitalized because of terrorism events, which were recorded in the Israeli National Trauma Registry between January 1997 and December 2016. The events were divided into 4 groups based on weapon used: explosions, shootings, stabbings, and vehicular attacks. The groups were compared in terms of injuries sustained, use of hospital resources, and clinical outcomes.

RESULTS

Explosion-related and vehicular terrorism resulted in a higher proportion of multiple injuries, whereas stabbings and shootings mostly led to isolated injuries. Victims of vehicular attacks had a high proportion of severe head injuries, whereas stabbing victims had a high volume of vascular injuries. All mechanisms involved significant damage to extremities; however, among stabbing victims injury was mainly to the upper extremities, whereas among vehicular attack victims it was mostly to the lower extremities. The overall injury severity of the compared groups was similar, leading to comparable levels of intensive care use and inhospital mortality. Certain similarities in victims' characteristics were observed between the shootings and stabbings and between explosions and vehicular attacks.

CONCLUSION

Despite differences between various terrorist attack mechanisms, the resulting injury severity and inhospital mortality are very similar, with stabbings and vehicular attacks causing injuries as serious as those caused by conventional weapons.

The Differences in Stabbing-Related Injury Profiles of Men and Women

BACKGROUND

Although women comprise only a minority of patients hospitalized due to violence-related injury, the circumstances of attacks against women may make their injuries more severe.

METHODS

We conducted a retrospective study using data of 9173 patients with stabbing-related injuries from 19 trauma centers participating in the Israeli National Trauma Registry between 1 January 1997 and 31 December 2014. Male and female patients were compared in terms of demographic and circumstantial factors, clinical characteristics, and outcomes.

RESULTS

Women were found to have greater injury severity according to the Injury Severity Scale (ISS) - 18% vs. 11% of severe (ISS 16+) injuries - requiring more hospital resources. Injuries that contributed most to injury severity in the female population were head and severe abdominal trauma. Women also sustained injuries to more body sites than men; however, regression analysis showed that the contribution of this factor to the overall difference in injury severity was less important than the injured sites. Regression analysis among severely injured patients pointed at injury to lower extremities as an independent factor related to female mortality. Different from men, among women the stabbing injuries to the upper extremities were not a protective factor in terms of mortality.

CONCLUSIONS

There are significant differences in the injury profiles of male and female stabbing victims, which can be explained by the different circumstances of the injury event.

Equipping Public Spaces to Facilitate Rapid Point-of-Injury Hemorrhage Control After Mass Casualty

In response to increasing violent attacks, the Stop the Bleed campaign recommends that everyone have access to both personal and public bleeding-control kits. There are currently no guidelines about how many bleeding victims public sites should be equipped to treat during a mass casualty incident. We conducted a retrospective review of intentional mass casualty incidents, including shootings, stabbings, vehicle attacks, and bombings, to determine the typical number of people who might benefit from immediate hemorrhage control by a bystander before professional medical help arrives. On the basis of our analysis, we recommend that planners at public venues consider equipping their sites with supplies to treat a minimum of 20 bleeding victims during an intentional mass casualty incident.

The danger of non-exhaustive quality measures: requiring hip fracture repair surgery within 48 hours - a case study

Quality measures are widely used globally in order to measure clinical performance and organizational efficiency of the healthcare systems. However, in a race to achieve certain numerically defined goal, the more important purpose of any organizational step being aimed at improving clinical outcomes could be overshadowed.

The introduction of the requirement to perform most hip fracture surgeries in the first 48 h of hospitalization by the Israeli Ministry of Health (IMOH) provides an interesting example of the complexity of this phenomenon. In 2004, the IMOH decided that hospitals would receive the full DRG payment for hip fractures operations only in cases in which the operation is performed within 48 h of hospitalization. In 2013, the IMOH proceeded to designate the proportion of less than 48 h surgeries as an official quality parameter for comparing hospital performance.

Despite the widely acknowledged and proven clinical benefit of earlier surgery for hip fracture patients, the desired proportion of such surgeries in a given population is not easily defined for a given population, as a significant number of patients may be unsuited for immediate surgery due to medical instability, having a serious co-morbidity or receiving anticoagulant treatment. Rushing these patients to surgery can be therefore expected to have a negative effect on their outcomes, and the subsequent increase in hip fracture mortality recorded in Israel after 2013 may be a result of that.

This example suggests that designating an organizational quality measure without adjusting it for the patient’s medical condition may make it too inaccurate to guide healthcare policy.

The correlation between stabbing-related upper extremity wounds and survival of stabbing victims with abdominal and thoracic injuries

BACKGROUND

When treating patients with stab injuries of the torso, clinicians often lack timely information about the degree and nature of internal organ damage. An externally observable sign significantly associated with characteristics of torso injuries may therefore be useful for practitioners. One such potential sign is the presence of wounds to the hands, sometimes sustained during victims' attempt to defend themselves during the violent altercation. Thus, the primary aim of this study was to evaluate the association between presence of upper extremity wounds and the severity of the thoracic and intra-abdominal injuries due to stabbing.

METHODS

This study was carried out retrospectively using data on 8714 patients with stabbing-related injuries from 19 trauma centers that participated in the Israeli National Trauma Registry (INTR) between January 1st1997 and December 31st 2013. Patients with wounds of upper extremities in addition to torso injuries (UE group) were compared to other patients with torso injuries (TO group) in terms of demographics, injury characteristics and clinical outcome.

RESULTS

The compared groups were found to be homogeneous in terms of age and systolic blood pressure; the number of sustained torso injuries was also identical. The UE group comprised a slightly greater percentage of females, however both groups were predominantly male. Patients with upper extremity injuries had a lower proportion of internal organ damage (36% vs. 38.5%) and lower mortality (0.9% vs. 2%). The higher mortality of patients without upper extremity wounds remained significantly different even when adjusted by other epidemiological parameters (OR 2.46, 95% CI 1.33-5.08).The number of sustained upper extremity injuries was positively associated with deeper penetration of the torso by the stabbing instrument.

CONCLUSIONS

Patients with stabbing-related upper extremity wounds had a significant survival advantage over patients without such injuries. However, a greater number of sustained upper extremity wounds may be an external sign of greater severity of thoracic and intraabdominal stabbing injuries.

Traumatic brain injury: It is all about definition

BACKGROUND

TBI may be defined by different methods. Some may be most useful for immediate clinical purposes, however less optimal for epidemiologic research. Other methods, such as the Abbreviated Injury Score (AIS), may prove more beneficial for this task, if the cut-off-points for their categories are defined correctly.

OBJECTIVE

To reveal the optimal cut-off-points for AIS in definition of severity of TBI in order to ensure uniformity between future studies of TBI.

RESULTS

Mortality of patients with TBI AIS 3, 4 was 1.9% and 2.9% respectively, comparing with 31.1% among TBI AIS 5+. Predictive discrimination ability of the model with cut-off-points of 5+ for TBI AIS (in comparison with other cut-off-points) was better. Patients with missing Glasgow Coma Scale (GCS) in the ED had an in-hospital mortality rate of 11.5%. In this group, 25% had critical TBI according to AIS. Normal GCS didn't indicate an absence of head injury, as, among patients with GCS 15 in the ED, 26% had serious/critical TBI injury. Moreover, 7% of patients with multiple injury and GCS 3-8 had another reason than head injury for unconsciousness.

CONCLUSIONS

This study recommends the adoption of an AIS cut-off ≥ 5 as a valid definition of severe TBI in epidemiological studies, while AIS 3-4 may be defined as 'moderate' TBI and AIS 1-2 as 'mild'.

Policy encouraging earlier hip fracture surgery can decrease the long-term mortality of elderly patients

BACKGROUND

In April 2004 the Israeli Ministry of Health decided to condition DRG payment for hip surgery by time between hospitalisation and operation, giving a fine for every day's delay beyond 48h. An evaluation study performed 2 years after the reform has shown the positive influence of the reform on patient's survival in the hospital. This study evaluates the impact of the reform on the longer-term mortality of patients.

METHODS

A retrospective study based on data from nine hospitals of the national trauma registry available for the years 2001-2007, with surveillance on 2-year survival through data of Ministry of the Interior. The study population includes patients aged 65 and above with an isolated hip fracture following trauma. Mortality curves and Cox regression were utilised to compare the influence of different parameters on long-term mortality.

RESULTS

Earlier surgery had a significant positive impact on survival through the whole length of the study period. In the period after the introduction of the new reimbursement system for hip fracture surgeries, a significant decrease in the longer-term mortality was observed up to 6 months of follow-up, even when adjusted by patients' age, gender and the receiving hospital. After 6 months there was no further decrease in relative risk, though the survival advantage remained with patients hospitalised after the reform.

CONCLUSIONS

The reform appears successful in decreasing the longer-term patient mortality after hip fracture through influencing surgical practice.

ISS groups: are we speaking the same language?

BACKGROUND

Despite ISS being a widely accepted tool for measuring injury severity, many researchers and practitioners use different partition of ISS into severity groups. The lack of uniformity in ISS use inhibits proper comparisons between different studies. Creation of ISS group boundaries based on single AIS value squares and their sums was proposed in 1988 during Major Trauma Study (MTOS) in the USA, but was not validated by analysis of large databases.

METHODS

A validation study analysing 316,944 patients in the Israeli National Trauma registry (INTR) and 249,150 patients in the American National Trauma Data Bases (NTDB). A binary algorithm (Classification and Regression Trees (CART)) was used to detect the most significantly different ISS groups and was also applied to original MTOS data.

RESULTS

The division of ISS into groups by the CART algorithm was identical in both Trauma Registries and very similar to original division in the MTOS. For most samples, the recommended groups are 1-8, 9-14, 16-24 and 25-75, while in very large samples or in studies specifically targeting critical patients there is a possibility to divide the last group into 25-48 and 50-75 groups, with an option for further division into 50-66 and 75 groups.

CONCLUSIONS

Using a statistical analysis of two very large databases of trauma patients, we have found that partitioning of ISS into groups based on their association with patient mortality enables us to establish clear cut-off points for these groups. We propose that the suggested partition of ISS into severity groups would be adopted as a standard in order to have a common language when discussing injury severity.

Base excess as a predictor for injury severity in pediatric trauma patients

BACKGROUND

Base excess is considered a predictor of mortality and severity of injury in trauma patients. Base excess had been widely examined in different settings. Only few studies have examined the role of base excess in pediatric trauma patients.

OBJECTIVE

To evaluate the value of admission base excess in pediatric trauma patients with respect to intensive care unit (ICU) admission rate and length of hospital stay.

METHODS

A retrospective study of pediatric trauma patients was conducted at a Level II trauma center. All patients aged 0-16 years for which a trauma team was activated over the years 2006-2009 were included. Study database included admission base excess, mechanism of injury, location and nature of injury, injury severity score, length of hospital stay, and ICU admission.

RESULTS

The study group consisted of 359 patients. There was a weak linear correlation between admission base excess, length of stay in the hospital, and ICU admission. Base excess seemed to show a stronger correlation for the youngest age group (0-6 years) and no correlation for the middle age group. There was a positive but weak correlation (R Spearman = 0.26) between admission base excess and Injury Severity Score (ISS). However, 40% of the children with an ISS score >25 had normal admission base excess values. The area under the curve of the receiver operating characteristic curves of base excess for predicting ICU admission was 0.66.

CONCLUSIONS

The admission base excess in pediatric trauma patients seems to be a weak prognostic factor in our facility.

Nationwide trends in abdominal aortic aneurysm repair and use of endovascular repair in the emergency setting

PURPOSE

To analyze nationwide trends in abdominal aortic aneurysm (AAA) repair and the use of endovascular abdominal aortic aneurysm repair (EVAR) in the emergency setting.

MATERIALS AND METHODS

Data were obtained from the Nationwide Inpatient Sample (NIS) using the International Classification of Diseases, Ninth Revision-Clinical Modification (ICD-9-CM) codes for open and endovascular repairs from 2001-2009. Trends in outcome parameters and hospital charges were compared.

RESULTS

The number of emergency EVAR procedures increased from 382 in 2001 to 1,247 in 2009 (P < .001). During the study period, length of hospital stay associated with total number of EVAR procedures decreased from 3.8 days to 3.4 days (P < .05), and the in-hospital mortality decreased from 2.4% to 2% (P = .32). From 2001-2009, mean hospital charges associated with EVAR increased from $50,630 to $91,401 (74% increase), whereas charges associated with open repairs increased from $54,578 to $128,925 (136% increase). The proportion of patients needing rehabilitation or nursing home placement after EVAR increased from 5.8% to 7.7% (P < .01), and need for home health increased from 6.9% to 10.5% (P < .01).

CONCLUSIONS

There was a significant increase in the number of emergency EVAR procedures during the study period; however, the overall in-hospital mortality associated with EVAR remained unchanged, and the length of hospital stay showed a decreasing trend. The total hospital charges for EVAR were lower than the charges for open abdominal aneurysm repair throughout the study period; the difference in charges between the procedures showed a significant increasing trend with time.

Children and terror casualties receive preference in ICU admissions

OBJECTIVE

Trauma casualties caused by terror-related events and children injured as a result of trauma may be given preference in hospital emergency departments (EDs) due to their perceived importance. We investigated whether there are differences in the treatment and hospitalization of terror-related casualties compared to other types of injury events and between children and adults injured in terror-related events.

METHODS

Retrospective study of 121 608 trauma patients from the Israel Trauma Registry during the period of October 2000-December 2005. Of the 10 hospitals included in the registry, 6 were level I trauma centers and 4 were regional trauma centers. Patients who were hospitalized or died in the ED or were transferred between hospitals were included in the registry.

RESULTS

All analyses were controlled for Injury Severity Score (ISS). All patients with ISS 1-24 terror casualties had the highest frequency of intensive care unit (ICU) admissions when compared with patients after road traffic accidents (RTA) and other trauma. Among patients with terror-related casualties, children were admitted to ICU disproportionally to the severity of their injury. Logistic regression adjusted for injury severity and trauma type showed that both terror casualties and children have a higher probability of being admitted to the ICU.

CONCLUSIONS

Injured children are admitted to ICU more often than other age groups. Also, terror-related casualties are more frequently admitted to the ICU compared to those from other types of injury events. These differences were not directly related to a higher proportion of severe injuries among the preferred groups.

Violence-related injury of children in Israel: age-dependent pattern

OBJECTIVE

To characterize the population of children hospitalized as a result of violence.

METHODS

This retrospective study used data from the Israeli National Trauma Registry on patients aged 0-17 years hospitalized for trauma during 1998-2006. Of 65,430 patients, 2060 (3.1%) had violence-related injuries. Descriptive statistics and bivariate analysis were used to characterize injury patterns and multivariate analysis was used to identify factors associated with severe injury.

FINDINGS

Half the victims of violence < 18 years of age were 15-17 years old. Most were boys. Violence-related trauma occurred more often than other trauma in the street, at school or in a public place or leisure facility, but less often at home. Unarmed brawling and stabbing were the most common types of violence. Brawling affected Jewish children more, while non-Jewish children were more often injured by firearms. The boundaries of age groups with different injury rates corresponded to the 'institutional' childhood stages of the Israeli educational system: the violence-related injury rate dropped after the first year of life, stayed low during kindergarten, rose slightly during elementary school and rose steeply during secondary and high school. The percentage of males increased with each age group. The street became more dangerous with age, while school and home became safer. Adolescents aged 15-17 years, newborn infants and those injured by firearms had the highest risk of severe injury.

CONCLUSION

Age and type of violence were the most important predictors of violence frequency and severity. Ethnicity lost importance when adjusted by these factors. Further research on their influence on violence-related injury is needed.

Percutaneous transosseous translaminar approach for thecal sac access in advanced ankylosing spondylitis with instrumented posterior spinal fusion

A novel transosseous approach for percutaneous access of the lumbar subarachnoid space is described in a patient with advanced ankylosing spondylitis (AS) and instrumented spinal fusion who presented for myelography. Use of a coaxial threaded bone biopsy system to provide transosseous access to the thecal sac, imaging findings, and outcome are discussed. This technique provided access to an otherwise inaccessible subarachnoid space and is an alternative approach in the setting of advanced AS or posterior spinal fusion.

Uncertainty of calibrations at the accredited dosimetry calibration laboratories

The American Association of Physicists in Medicine, through a subcommittee (formerly Task Group 3) of the Radiation Therapy Committee, has accredited five laboratories to perform calibrations of instruments used to calibrate therapeutic radiation beams. The role of the accredited dosimetry calibration laboratories (ADCLs) is to transfer a calibration factor from an instrument calibrated by the National Institute of Standards and Technology (NIST) to a customer's instrument. It is of importance to the subcommittee, to physicists using the services of the ADCLs, and to the ADCLs themselves, to know the uncertainty of instrument calibrations. The calibration uncertainty has been analyzed by asking the laboratories to provide information about their calibration procedures. Estimates of uncertainty by two procedures were requested: Type A are uncertainties derived as the standard deviations of repeated measurements, while type B are estimates of uncertainties obtained by other methods, again expressed as standard deviations. Data have been received describing the uncertainty of each parameter involved in calibrations, including those associated with measurements of charge, exposure time, and air density, among others. These figures were combined with the uncertainty of NIST calibrations, to arrive at an overall uncertainty which is expressed at the two-standard deviation level. For cable-connected instruments in gamma-ray and x-ray beams of HVL > 1 mm Al, the figure has an upper bound of approximately 1.2%.

Electron dose calculation using multiple-scattering theory: thin planar inhomogeneities

In this article in our series on electron dose calculation using multiple-scattering theory, we apply the Fermi-Eyges theory to the problem of a thin planar inhomogeneity present in an otherwise-layered medium. We derive expressions for the distribution function P and the location distribution L (which multiplied by the restricted mass collision stopping power is the dose directly deposited by the primary electrons) for various types of incident beams: a completely arbitrary distribution, a Gaussian point source, a pencil beam, an isotropic point source, and a broad parallel beam. We show how divergent-beam dose distributions can be determined from parallel-beam calculations, through use of equivalent configurations dependent upon the depth of dose calculation. Also, we indicate how this work can be applied to the design of wedges (or "compensators") for beam shaping to provide desired dose distributions or to match juxtaposed radiation fields. Explicit formulas for thin plates are then worked out, and we examine the appearance of hot and cold spots distal to the edge of a localized inhomogeneity, for thin half-slabs and for narrow strips. Finally, considering the case of a thin straight wedge-shaped inhomogeneity, we theoretically discover the phenomenon of a "focused hot spot" without an accompanying cold spot, and suggest the design of a "multiple-scattering lens".

Treatment planning with external beams. Introduction and historical overview

In this first of a series of articles on Radiation Treatment Planning based on the Basic Physics Symposium of the American Association of Physicists in Medicine at the 73rd Annual meeting of the RSNA, an attempt has been made to provide a broad overview of the process of designing an optimal radiation therapy regimen. The essentials of treatment planning have been identified and essential terms have been defined. Variables to be selected have been identified and constraints in choosing treatment plans have been noted. The effect of combining multiple beams to achieve the most advantageous distribution of radiation dose within the patient has been discussed and the vital importance of appropriate quality control has been emphasized. Future articles will consider specific aspects of this discipline in detail.

Collimated electron beams and their associated penumbra widths

The Fermi-Eyges multiple-scattering theory for electrons is applied to calculate profiles of collimated electron beams. The dose profile below the collimator is a convolution of the intensity distribution of the electrons at the level of the collimator and the distribution arising from the propagation of a Gaussian point source from the collimator to the level of the calculation. The electrons at the level of the collimator possess an angular distribution characteristic of the configuration of the electron beam at the vacuum window. Hence, the dose profile and its associated penumbra width can be expressed in terms of the angular moments of the distribution of the electrons at the collimator. The dependence of the penumbra width on the configuration-dependent angular spread of the electrons at the collimator accounts for differences in the size of the penumbra between two broad-beam configurations. These differences are also seen experimentally. We have also studied the dependence of the angular moments of the electrons upon scattering foils present above the collimator and the position of the beam-broadening device in the accelerator head.

Cylindrical chamber dimensions and the corresponding values of Awall and Ngas/(NxAion)

Cylindrical ionization chamber descriptions and physical dimensions that are necessary for the calculation of Awall and Ngas are presented. Also included are the corresponding calculated values of Awall and Ngas/(NxAion).

Can the AAPM Task Group 21 protocol lead to optimum ion chamber designs?

The recently published AAPM Task Group 21 protocol for high-energy dosimetry is complicated in that it requires the physicist to obtain the values of about a dozen different physical variables by looking them up in tables or graphs. This should be compared with the procedure of earlier protocols using the concept of a single multiplier C lambda. We have investigated how the physical principles outlined in the improved AAPM protocol could be utilized for the redesign of the therapy-level ion chambers in such a way that one can reduce the number of factors that need to be looked up in tables or graphs for the calibration of high-energy teletherapy photon beams. In our analysis presented in this paper we found that one such design could be for an ion chamber having a wall acrylic or Bakelite of a thickness not exceeding 0.1 g/cm2 and having an inner diameter of 6 mm, and used in conjunction with a cobalt-60 buildup cap of thickness 0.35 g/cm2 made of acrylic, Bakelite, or Tufnol. If a chamber of such a design is used in a water phantom, the dosimetry practically reduces to the simplicity of the former protocols of depending on a single value of energy-dependent multiplier to be obtained from a table. With the above design parameters, it becomes possible to eliminate the explicit need to incorporate the factors Pwall, Prepl, Awall, beta wall, and the variable alpha, representing the fraction of ionization due to electrons from the wall material of the chamber.

Quality assurance of radiation dosage: usefulness of redundancy

Regulations for maintaining the calibration of radiation-measuring instruments generally require that they be recalibrated periodically, and some also specify periodic spot-checks. There is a finite probability that changes in the instrument sensitivity will occur between these calibrations or periodic checks. Routine spot-checks of the output of a therapy unit, made with a given instrument, should detect changes in either device. Comparisons of reliability obtained by these and other procedures for checking on instrument sensitivity are made using calculations based on estimates of the mean time between failures for sources and instruments. These comparisons demonstrate that significantly greater reliability and efficiency should result from considering each machine spot-check and recalibration as a check on the stability of both the machine and the instrument, as opposed to placing complete dependence upon the instrument during the period between separate checks of its sensitivity.

Product representations of teletherapy dose distributions

Product representations are frequently used for teletherapy dose distributions. For example, the dose in a central plane is often written as the product of two factors, one dependent on the depth and the other on the transverse variable. We have answered the following question: given a (two-dimensional) set of data, how closely is it possible to represent these data by a product of two such factors, and what factors would give a best-fit representation? We thus have developed a quantitative test with which to judge any proposed product representation, for a given set of data. As an example, we have applied our method in analyzing the accuracy of a model proposed by van de Geijn for representing central-plane Cobalt-60 dose data through a product representation on decrement lines intersecting the source.

Cutaneous metastases from carcinoma of the cervix

Metastases to the skin from internal malignant neoplasms are an uncommon and often preterminal event. Cutaneous metastases from a carcinoma of the uterine cervix, however, have rarely been reported, even in the advanced stages of the disease. A patient was initially seen with cutaneous metastases and was found to have an extensive tumor in the pelvis, which proved to be a squamous cell carcinoma arising in the cervix.

Analytic representation of electron central-axis depth dose data

We have examined a number of analytic representations of electron central-axis depth dose data current in the literature, testing them against sets of standard depth dose data. One of them, a two-parameter model of Shabason and Hendee, is recommended in situations in which good accuracy (approximately 2%) is desired, with the values of the parameters determined by an approximation formula which we have developed elsewhere. For higher accuracy, we have developed a polynomial model which gives, typically, a standard deviation of the fitting polynomial from the data points of 1%, and a maximum deviation of 2%. Fitting polynomials obtained with this method possess the property of having zero slope at the position of actual maximum dose, and generally a fifth-order polynomial (requiring four nonzero coefficients) provided the most acceptable fit. The four parameters involved are determined through inversion of a 4 x 4 matrix, and we have tabulated these four coefficients for the standard data sets. The polynomial model is designed for interpolation in the range between the 100% dose depth and the 10% dose depth, and another fitting curve of the same type can be adjoined to cover depths less than the 100% dose depth.

Application of fission track detectors to californium-252 neutron dosimetry in tissue near the radiation source

Fission track detectors were applied to a unique problem in neutron dosimetry. Measurements of neutron doses were required at locations within a tumor of 1 cm diameter implanted on the back of a mouse and surrounded by a square array of four 252Cf medical sources. Measurements made in a tissue-equivalent mouse phantom showed that the neutron dose rate to the center of the tumor was 2.18 rads micrograms-1 h-1 +/- 8.4%. The spatial variation of neutron dose to the tumor ranged from 1.88 to 2.55 rads micrograms-1 h-1. These measurements agree with calculated values of neutron dose to those locations in the phantom. Fission track detectors have been found to be a reliable tool for neutron dosimetry for geometries in which one wishes to know neutron dose values which may vary considerably over distances of 1 cm or less.

Californium-252 dosimetry in phantoms of various dimensions

By using a tissue-equivalent (TE) ionization chamber filled with TE gas and a magnesium ionization chamber filled with argon gas as the dosimeter pair for the twin-chamber method, the authors obtained the neutron and gamma-ray components of the radiation dose from californium 252 (252Cf). The distribution of dose components as a function of different phantom dimensions was determined. The effect of neutron absorption and scattering was evaluated, as well as the absorption and production of gamma rays in the phantom. The results can be used for improvement of 252 Cf dosimetry when using a body of finite dimensions.

Hidrotic ectodermal dysplasia with diffuse eccrine poromatosis

Eccrine poromatosis (EP) of remarkable severity has been observed in a patient with hidrotic ectodermal dysplasia (HED), a member of the kindred originally described by Clouston. Neither the EP nor its association with HED has been previously reported.

On the application of a liquid-dielectric ionization chamber to 252 Cf dosimetry

Our investigations of an iso-octane-filled liquid-dielectric ionization chamber indicate that this dosimeter is well suited for the measurement of dose distributions at distances close to 252Cf interstitial implant sources. Initial research has shown that such an instrument provides good discrimination between the radiation components of a mixed field and possesses excellent sensitivity. Calculations indicate that iso-octane will yield a neutron and gamma-ray dose response independent of energy over a major part of the 252Cf spectral range, while transmission measurements have demonstrated that the liquid causes little perturbation of the radiation field.

An assessment of RBE of Californium-252 for C57-Black/6 mouse fibrosarcoma by a precise afterloading technique

Afterloading techniques were developed for the in vivo assessment of the RBE of californium-252 with respect of radium-226 using a fibrosarcoma in mice. The afterloading holder positions sources so that the tumor is uniformly irradiated. Using the end points of tumor volumetric studies up to 150 days after irradiation, it was found that the RBE ranged from 5-8 at clinically relevant dose rates and total doses.

Maintenance of condenser-ion chamber calibration

Readings made with condenser-ionization chamber systems are frequently suspect because significant changes in calibration can occur without being evident in the normal use of the instruments. These changes can be traced to physical causes that alter the voltage sensitivity of electrical capacitance. Thus, measurement of these electrical parameters will indicate whether or not a change in calibration has occurred. Formulas are presented of calculating such changes and determining which parameter is responsible. Good agreement was obtained between the results of calculations with these formulas and the results of radiation measurements made with a Victoreen Condenser R-Meter after several components had been deliberately maladjusted.