Number Of CT Scans Research Articles

Stage I testicular tumor: How frequently to scan?

380 Background: Testicular malignancy is the most common cancer affecting men aged between 15 and 44 years. In our centre, almost all low-risk seminoma (LRS) stage-I and non-seminomatous germ cell tumours (NSGCT) stage I (high and low-risk) tumours are followed-up on a surveillance program (SP) for a minimum of 5 years. LRS patients are scanned at 4, 6, and 12 monthly intervals during years 1, 2, and 3 to 5 years respectively. NSGCT undergo computer tomography (CT) scan at 3 monthly intervals in years 1 and 2, 4 monthly in year 3 and 6 monthly thereafter. Clinical examination, Chest X-ray (CXR) and tumour markers (TM) are performed at each visit. This retrospective audit examined if relapses were first detected by raised TM or radiologically, and if there was any difference in detection rate between these investigations to recommend reducing the frequency of CT scans, especially in lower risk groups, and therefore cumulative radiation exposure. Methods: The patient population was obtained from hospital electronic database. Metastatic patients, clinical trials patients and those who received adjuvant treatment upfront were excluded. Results: 396 patients were enrolled from 1999 to September 2013. 153 patients were followed-up in SP. 33 relapses (mean age 37 years, range 17-56) detected in SP. The mean relapse free survival period was 55.3 months (range 9.6-43.3) from date of diagnosis. No relapses were first detected on CXR. 4 patients had only TM elevated and 6 had CT abnormality found post TM elevation. 11 had simultaneous CT and TM abnormalities. For 12 patients, CT abnormality was detected with no TM raise. Of these, 8 were high risk (7 NSGCT and 1 pure seminoma) and 4 were low risk NSGCT. Patients were treated with standard BEP/EP chemotherapy regimen on relapse. All patients are alive to date and continue to be followed-up regularly. Conclusions: 12 patients in our study had relapses detected radiologically with no TM rise. 25% of these patients had low risk NSGCT. Without the CT scan, these patients would have faced potential delay in diagnosis and treatment. Results of prospective randomised trials are awaited to produce evidence to place confidence in less number of CT-scans for these patients during follow- up. Until then we recommend the current standard protocol be followed.

Hinge Fracture during Cervical Open-door Laminoplasty: Does it Affect Clinical and Radiographic Outcomes?

ObjectiveThe purpose of this study was to determine whether the status of the hinge gutter affected clinical and radiographic outcomes of cervical open door laminoplasty.MethodsWe retrospectively analyzed 43 patients who had undergone cervical open door laminoplasty. 23 CT scans were performed at 2 days post-operation. The number of CT scans at 3, 6, 12 and 24 months were 16, 12, 21 and 11, respectively. We collected perioperative and follow-up data, including clinical and radiographic results.ResultsThere were 7 patients without a hinge fracture and 16 patients with one or more hinge fractures at 2 days postoperation. There were 90 hinges, and the rate of ideal greenstick deformation of the hinge was 63% on 2-day-postoperative CT scans. Postoperative VAS scores of neck pain (p=0.012) in patients without a hinge fracture were higher than in patients with hinge fractures. The hinge healing rates were 37% at 3 months, 57.4% at 6 months, 86.4% at 12 months, and 85.4% at 24 months. Among the patients, 14 patients had healed hinges, and 7 patients had one or more hinge(s) that was/were not healed at 12 months post-operation. However, in clinical and radiographic outcomes, there was no difference between these patients.ConclusionCervical open door laminoplasty was safe and provided stable reconstruction of laminar expansion. In radiographs, the difference between hinges that had healed and hinges that had not healed was statistically negligible. Hinge fractures might not influence the clinical and radiographic outcomes of cervical open door laminoplasty.

Cumulative Total Effective Whole-Body Radiation Dose in Critically Ill Patients

Uncertainty exists about a safe dose limit to minimize radiation-induced cancer. Maximum occupational exposure is 20 mSv/y averaged over 5 years with no more than 50 mSv in any single year. Radiation exposure to the general population is less, but the average dose in the United States has doubled in the past 30 years, largely from medical radiation exposure. We hypothesized that patients in a mixed-use surgical ICU (SICU) approach or exceed this limit and that trauma patients were more likely to exceed 50 mSv because of frequent diagnostic imaging. Patients admitted into 15 predesignated SICU beds in a level I trauma center during a 30-day consecutive period were prospectively observed. Effective dose was determined using Huda's method for all radiography, CT imaging, and fluoroscopic examinations. Univariate and multivariable linear regressions were used to analyze the relationships between observed values and outcomes. Five of 74 patients (6.8%) exceeded exposures of 50 mSv. Univariate analysis showed trauma designation, length of stay, number of CT scans, fluoroscopy minutes, and number of general radiographs were all associated with increased doses, leading to exceeding occupational exposure limits. In a multivariable analysis, only the number of CT scans and fluoroscopy minutes remained significantly associated with increased whole-body radiation dose. Radiation levels frequently exceeded occupational exposure standards. CT imaging contributed the most exposure. Health-care providers must practice efficient stewardship of radiologic imaging in all critically ill and injured patients. Diagnostic benefit must always be weighed against the risk of cumulative radiation dose.

An Exponential Growth in Incidence of Thyroid Cancer: Trends and Impact of CT Imaging

Workup of incidental thyroid nodules detected on CT imaging could be contributing to the increased diagnosis of small thyroid cancers. The purpose of this study was to evaluate recent trends in the incidence of thyroid cancer, and to determine the relationship between annual CT imaging volume and rate of thyroid cancer diagnosis. This retrospective cohort study used data bases for thyroid cancer and CT imaging volume. Thyroid cancer data from 1983-2009 were obtained from the Surveillance, Epidemiology, and End Results data base. National Council of Radiation Protection and Measurements Report No. 160 provided data on hospital and nonhospital CT imaging volume for 1993-2006. Trends in thyroid cancer were modeled for overall incidence on the basis of patient age, tumor histologic features, and tumor size and stage. Linear regression analysis was performed to evaluate the strength of the relationship between annual CT scan volume and the incidence of thyroid cancer by tumor size and histologic type. In 2009, the incidence of thyroid cancer was 14 per 100,000, which represented a 1.9-fold increase compared with 2000. The growth in incidence was exponential compared with a minimal linear increase in thyroid cancer mortality rate. The subgroup with the greatest change was subcentimeter papillary carcinoma, with doubling in incidence approximately every 6.2 years. The linear relationship between annual CT scan volume and the incidence of subcentimeter papillary carcinoma was very strong (R(2) = 0.98; P < .0001). The incidence of subcentimeter papillary carcinoma is growing at an exponential rate without significant change in mortality rate. The strong linear relationship between new cases of subcentimeter papillary carcinomas and the number of CT scans per year suggests that an increase in CT scans may increase the detection of incidental thyroid cancers.

Review of postoperative CT and ultrasound for endovascular aneurysm repair using Talent stent graft: can we simplify the surveillance protocol and reduce the number of CT scans?

Review of postoperative CT and ultrasound for endovascular aneurysm repair using Talent stent graft: can we simplify the surveillance protocol and reduce the number of CT scans?

Reply to ‘Review of postoperative CT and ultrasound for endovascular aneurysm repair using Talent stent graft: can we simplify the surveillance protocol and reduce the number of CT scans?’

Reply to ‘Review of postoperative CT and ultrasound for endovascular aneurysm repair using Talent stent graft: can we simplify the surveillance protocol and reduce the number of CT scans?’

Percutaneous lung biopsy: comparison between an augmented reality CT navigation system and standard CT-guided technique

Percutaneous lung biopsies (PLBs) performed for the evaluation of pulmonary masses require image guidance to avoid critical structures. A new CT navigation system (SIRIO, "Sistema robotizzato assistito per il puntamento intraoperatorio") for PLBs was validated. The local Institutional Review Board approved this retrospective study. Image-guided PLBs in 197 patients were performed with a CT navigation system (SIRIO). The procedures were reviewed based on the number of CT scans, patients' radiation exposure and procedural time recorded. Comparison was performed with a group of 72 patients undergoing standard CT-guided PLBs. Sensitivity, specificity and overall diagnostic accuracy were assessed in both groups. SIRIO-guided PLBs showed a significant reduction in procedure time, number of required CT scans and the radiation dose administered to patients ([Formula: see text]). In terms of diagnostic accuracy, SIRIO proved to be more accurate for small-sized lesions ([Formula: see text]20mm) than standard CT-guidance. SIRIO proved to be a reliable and effective tool when performing CT-guided PLBs and was especially useful for sampling small ([Formula: see text]20mm) lesions.

SU-F-BRCD-07: Experimental Validation of Fluence Field Modulation for Noise and Dose Management in CT.

Dose management in CT is a growing concern as the number of CT scans per capita rises. Fluence field modulated computed tomography (FFMCT) is a proposed approach for more optimal dose management, where the incident fluence pattern can change independently for each projection in order to minimize dose while meeting prescribed image quality metrics. This work studies the application of FFMCT for dose and noise management to a small cylindrical phantom. Experiments were carried out on an experimental CT system using a small cylindrical phantom comprised of acrylic spheres, water and teflon rods as the object of interest. Modulation of the incident fluence was optimized using a simulated annealing algorithm that attempts to achieve user-prescribed, regionally varying SNR criteria while limiting dose. The modulated projections were synthesized from projection sets taken at various tube current settings. SNR patterns and predicted dose outcomes were compared to the prescribed values as well as against expected results using a bowtie filter. FFMCT resulted in SNR outcomes with greater agreement to the prescribed regionally varying SNR criteria than achieved by the bowtie filter. Dose reductions were observed for the majority of the object, and reached as high as 60%. Limited regions, coinciding with lower noise, observed dose increases less than 20%. Integral dose reduction over the entire object was greater than 40% when compared to a bowtie filter with comparable image quality in the region of interest. The results support the hypothesis that FFMCT has the potential to meet user-prescribed, regionally varying image quality objectives, while decreasing radiation dose to the patient. These results suggest that given a suitable collimator approach, fluence field modulated computed tomography could reap significant benefits in terms of reducing dose and optimizing image quality. NSERC.

Outcomes of Endoscopic and Percutaneous Drainage of Pancreatic Fluid Collections Arising after Pancreatic Tail Resection

Up to 15% to 30% of patients develop pancreatic fluid collections (PFCs) after pancreatic tail resection. Percutaneous and endoscopic methods have been used to drain these collections, though few data are available that compare outcomes of these modalities. From December 1998 to April 2011, we identified all patients who underwent pancreatic tail resection and developed PFCs requiring intervention. The primary aim was to compare overall success rates in resolution of PFCs using endoscopic and percutaneous modalities. Success rates, hospital length of stay, number of CT scans, sinograms and endoscopies performed, and days with drain(s) in place were compared. Forty-eight patients were identified. Percutaneous drainage was performed a median of 25 days postoperatively, compared with 85 days for endoscopic drainage (p < 0.001). Endoscopic and percutaneous methods had similar rates of technical success (100% vs 97%, p = 0.50) and treatment success (80% vs 81%, p = 0.92), respectively. Recurrence rates were 16.6% for the endoscopic group and 23% for the percutaneous group (p = 0.65), and adverse events occurred in 9.4% of those treated endoscopically vs 13.3% of those treated percutaneously (p = 0.68). Location and characteristics of PFCs did not influence success rates. Recurrences were often treated by "salvage" drainage via the other modality. Median hospital stay was longer after primary percutaneous drainage compared with primary endoscopic drainage (5.5 days vs 2 days, p = 0.046). Primary percutaneous drainage patients also had more CT scans (median 3 vs 2, p = 0.03). Endoscopic drainage and percutaneous drainage appear to be equally effective and complementary interventions for PFCs occurring after pancreatic tail resection. Primary endoscopic drainage may be associated with shorter hospital stay and fewer CT scans.

Comparison of MRI Sequences to CT in Identification of Calcified Subependymal Nodules in Tuberous Sclerosis Patients (P03.134)

Objective: To determine if MRI is as effective as CT in identification of calcified subependymal nodules in tuberous sclerosis (TS) patients, so that the number of CT scans that TS patients undergo may be able to be reduced, leading to less radiation exposure and less cost. Background CT has been used to look for calcifications in TS patients, especially if they have enlarging subependymal nodules concerning for subependymal giant cell astrocytomas. However, CT has been found to be a source of significant radiation, and MRI techniques have advanced. Design/Methods: TS patients who underwent both a CT and MRI within a 120 day period were evaluated. CT and MR studies from the same patient were compared. CT was considered the gold standard in identification of calcification. Calcification on CT was considered a true positive (TP). Results: Neuroimaging from 9 patients has been reviewed. Patient ages ranged from 2 months to 7 7/12 years, with an average of 3.9 years. Only 2 patients had SWI sequences, which was a limitation of this study. Fifty-five subependymal nodules were identified. MRI overall detected 52 of 55 lesions. The sensitivity for detecting subependymal nodules was 94.5% for T2-weighted imaging, 85% for B0 sequences, and 87% for SWI. The overall sensitivity of CT for detecting subenpendymal nodules was 94.5%; however, most of the lesions were calcified. The sensitivity of CT for uncalcified subependymal nodules was 25%. Among the MRI sequences, the sensitivity for detecting calcifications on T2-weighted sequences was 78%, B0 sequences was 82%, and SWI was 87%. Conclusions: CT is more sensitive than MRI at detecting calcified subependymal nodules. However, it is not sensitive for uncalcified nodules. Traditional MRI (without SWI) tended to underestimate calcified subependymal nodules. However, addition of SWI, which appeared to be the most sensitive MRI sequence to calcification, may allow closer approximation to CT findings. Disclosure: Dr. McGregor has received royalty payments from MedHumor Publishing. Dr. Caron has nothing to disclose. Dr. Perkins has nothing to disclose. Dr. Wheless has received personal compensation for activities with Abbott, UCB, GSK, Novartis, Ortho-McNeil, Cyberonics, Abbott, Cyberonics, Inc., Novartis, Ovation Pharmaceuticals, Marinus Pharmaceuticals, Questcor, Valeant, Pfizer Inc as a consultant and/or participant on an advisory board. Dr. Wheless has received research support from Abbott Laboratories, Cyberonics, Inc., Ortho-McNeil Pharmaceuticals, Novartis, UCB Pharma and Ovation Pharmaceauticals. Dr. Choudhri has nothing to disclose.

A coverage probability based method to estimate patient-specific small bowel planning volumes for use in radiotherapy

Background and purposeThe aim of this work was to develop a statistical method for generation of patient-specific planning organ-at-risk volumes (PRVs) for the small bowel (SB), by efficient use of a few repeat CT scans. Materials and methodsThe PRVs are generated from a coverage probability (CP) matrix of the small bowel wall (SBW) by thresholding. To estimate the CPs, we extend a previously published ‘relative frequency of coverage’ approach by adding a ‘soft margin’ around each SBW instance. This prevents the CP matrix from containing any holes, thus making it more robust. As the number of CTs approach infinity, the ‘soft margin’ approaches zero and the CP matrix converges to the ‘relative frequency of coverage’. The PRVs were evaluated by using the bootstrap method in three patients with different degrees of SB motion: The PRVs from randomly sampled subsets of CTs were compared to the PRVs generated from all 10–11 CT scans, by analysis of sensitivity and specificity. Furthermore, the PRVs generated for CP=0.005 (i.e. generous patient-specific PRVs) and for CP=0.03 (i.e. tight patient-specific PRVs) were compared to an intestinal cavity (IC) approach and a population based PRV approach of 10 and 30mm isotropic planning margins around SB. ResultsThe sensitivity and specificity of the PRVs depend on the number of CT scans and the CP threshold. With three CT scans and a threshold of 0.03, an average sensitivity of 94–96% and specificity of 86–97% was obtained. All investigated SB planning volumes had an average overlap >89% of both SB and SBW. The tight patient-specific PRVs and the 10mm margins had the lowest relative volumes, followed by the generous patient-specific PRVs, the 30mm margins and the ICs. ConclusionsBased on a few CTs, our method generates patient-specific SB PRVs which are both sensitive and specific. Compared to conventional approaches, the patient-specific PRVs are either similar or better in predicting for SB voxels, and at the same time they occupy a smaller or similar volume in the patient.

Composition and associated factors of radiological examination in major trauma patients

Objective To explore the determinant factors influencing the constituent parts of radiological examination in severe trauma patients so as to provide scientific basis for optimized strategy of radiological examination. Methods A prospective study was carried out from April to July 2010 in a tertiary hospital. Clinical data of 60 severe trauma patients admitted to emergency department and ICU were recorded. The type, number and site of trauma under radiological examination were described and compared among different stages of treatment. The correlation between number of radiological examinations and age, number of injured site, injury severity score (ISS), Glasgow Coma Scale (GCS), ICU stay and overall length of hospital stay were analyzed. Results (1) The majority of radiological examinations in 60 patients were radiography and CT, with a corresponding median number of 6.0(3.0～ 11.0, IQR)and 10.0(8.0 ～ 13.8, Qr) times per patient. (2) The numbers of radiography examinations requested in emergency room, emergency ICU and general ward were quite approximately equal (x2 =4.043 ,P =0. 132), while CT examinations were mainly requested in emergency room and emergency ICU (x2 = 20. 274 , P < 0. 001). (3) The numbers of radiological examinations requested for different sites of injury were quite significantly different between radiography and CT during different stages of treatment (x2 = 114.609, 75.932, P < 0.01). (4 ) The number of CT scan requested was positively correlated with number of injured site, ISS, ICU and overall length of hospital stay (r =0.273,0.369,0.523,0.417,all P <0.05). Conclusions The sum of radiological examinations in severe trauma patients was great mainly in radiography and CT, and CT was more predominantly requested. The number of CT scans examinations was positively correlated with severity of injury and length of ICU stay. Further study is warranted to optimize radiological examination in severe trauma patients. Key words: Major trauma; Radiological examination; Associated factors

New knowledge about CT usage and dose optimisation in children, but a major question is still unanswered

During the last few years, we have seen some worrying articles describing both the significant increase in CT usage in adults and children and estimations of considerable cancer risk from CT in children. The articles by Brenner et al. [1–3] in particular have sparked new awareness and concerns regarding radiation dose. Currently, an article or report on these issues appears in a scientific journal, in a newspaper or on TV almost monthly. This places enormous responsibility on those radiologists who provide CT to children and adolescents. Paediatric radiologists not only have to promote the enormous advances of CT for disease management in childhood, they also need to make every effort to highlight to radiologists, imaging technicians and clinicians in all subspecialties that, before any use of CT in children, two main criteria must be fulfilled: justification, and optimisation of radiation protection. The articles by Pearce et al. [4] and by Goo [5] in this issue of Pediatric Radiology reflect this continuously increasing awareness, and the concerns within and outside the radiological community regarding the increasing number of CT scans in children and the corresponding substantial radiation exposure. While a number of previous publications have described trends in the use of CT primarily in adult populations, very little has been published regarding temporal trends and other patterns of CT usage in young people. The article by Pearce et al. [4] describes patterns in CT usage among young people aged less than 22 years in Northern England from 1993 to 2002. The results show that the number of CT studies increased, in particular in the years 1997–2000. This was around the time of the introduction to clinical practice of helical CT and multidetector CT. These important technical advances improved the overall performance of CT, in particular speed, facilitating large area scans within seconds and multiphase studies. As a result, CT has become an indispensable part of medical imaging. These important technical inceptions and trends in the late 1990s may be the reason for the observed increase in the number of CTs per patient in this study (the median doubled from 1 in 1993 to 2 in 1999). Since we know very little about the utilisation of CT in young populations around the world, it is indeed crucial to report such trends and patterns. Beyond the necessary description of trends in the use of CT in children and young adults, research on optimisation of paediatric CT techniques, particularly of radiation dose, is of major importance. The article by Goo [5] is an example of this important research. This describes an individualised approach that does not rely on age and body weight but rather on cross-sectional area and the mean density of a specific body region to achieve uniform image noise in contrast-enhanced paediatric chest CT. Individualised volume CT dose can thereby be determined. This interesting approach allows a high degree of tailored CT technique in children. On the other hand, it illustrates that paediatric CT is indeed a challenge. The complexity of the technique and approach described leads to a discussion of whether high-quality paediatric CT is perhaps best performed exclusively in dedicated centres R. Fotter (*) Department of Paediatric Radiology, University Hospital, Medical University Graz, Auenbruggerplatz 34, Graz, Styria 8036 Austria e-mail: richard.fotter@medunigraz.at

262 oral A COVERAGE PROBABILITY BASED METHOD TO ESTIMATE PATIENT-SPECIC SMALL BOWEL PLANNING VOLUMES FOR USE IN RADIOTHERAPY

Abstract Background and purpose The aim of this work was to develop a statistical method for generation of patient-specific planning organ-at-risk volumes (PRVs) for the small bowel (SB), by efficient use of a few repeat CT scans. Materials and methods The PRVs are generated from a coverage probability (CP) matrix of the small bowel wall (SBW) by thresholding. To estimate the CPs, we extend a previously published ‘relative frequency of coverage' approach by adding a ‘soft margin' around each SBW instance. This prevents the CP matrix from containing any holes, thus making it more robust. As the number of CTs approach infinity, the ‘soft margin' approaches zero and the CP matrix converges to the ‘relative frequency of coverage'. The PRVs were evaluated by using the bootstrap method in three patients with different degrees of SB motion: The PRVs from randomly sampled subsets of CTs were compared to the PRVs generated from all 10–11 CT scans, by analysis of sensitivity and specificity. Furthermore, the PRVs generated for CP=0.005 (i.e. generous patient-specific PRVs) and for CP=0.03 (i.e. tight patient-specific PRVs) were compared to an intestinal cavity (IC) approach and a population based PRV approach of 10 and 30mm isotropic planning margins around SB. Results The sensitivity and specificity of the PRVs depend on the number of CT scans and the CP threshold. With three CT scans and a threshold of 0.03, an average sensitivity of 94–96% and specificity of 86–97% was obtained. All investigated SB planning volumes had an average overlap >89% of both SB and SBW. The tight patient-specific PRVs and the 10mm margins had the lowest relative volumes, followed by the generous patient-specific PRVs, the 30mm margins and the ICs. Conclusions Based on a few CTs, our method generates patient-specific SB PRVs which are both sensitive and specific. Compared to conventional approaches, the patient-specific PRVs are either similar or better in predicting for SB voxels, and at the same time they occupy a smaller or similar volume in the patient.

Toward an individualized target motion management for IMRT of cervical cancer based on model-predicted cervix–uterus shape and position

Background and Purpose To design and evaluate a 3D patient-specific model to predict the cervix–uterus shape and position. Methods and Materials For 13 patients lying in prone position, 10 variable bladder filling CT-scans were acquired, 5 at planning and 5 after 40 Gy. The delineated cervix–uterus volumes in 2–5 pre-treatment CT-scans were used to generate patient-specific models that predict the cervix–uterus geometry by bladder volume. Model predictions were compared to delineations, excluding those used for model construction. The prediction error was quantified by the margin required around the predicted volumes to accommodate 95% of the delineated volume and by the predicted-to-delineated surface distance. Results The prediction margin was significantly smaller (average 50%) than the margin encompassing the cervix–uterus motion. The prediction margin could be decreased (from 7 to 5 mm at planning and from 10 to 8 mm after 40 Gy) by increasing (from 2 to 5) the number of CT-scans used for the model construction. Conclusion For most patients, even with a model based on only two CT-scans, the prediction error was well below the margin encompassing the cervix–uterus motion. The described approach could be used to create prior to treatment, an individualized treatment strategy.

724 Head Injuries in Children: Is it Nice to Ct Scan?

Introduction: Trauma is commonest cause of hospital admission in children and head injuries account for 75% of children admitted. Head injury is a common cause of acquired neurological and cognitive disability in childhood. Indications for CT scan in children with head injury are well documented in NICE Guidelines, UK.Aim: To evaluate our practice for children attending A&E department with head injury at district general hospital in comparison with NICE guidelines.Method: This was a retrospective audit of case notes of children over a 2months period, attending the emergency department with head injury. Case notes were analysed to record Glasgow coma scale, children admitted for neurology observation and whether the NICE guidelines for CT scan was followed.Results: Of 120 children with head injury who attended A&E, 107 full case notes were available. In total 13/107 children (12%) met the criteria for CT scan. However 6/13 children (46%) were sent home after clinical assessment by a doctor. 7/13 (54%) were admitted for 24 hours neurology observation of which 3/13 underwent CT scan. Head injury leaflet was given to all children sent home.Conclusions: This study reiterates continual awareness of NICE guidelines amongst physicians for highest quality care. However as evident in this study, it may require a four fold increase in the number of CT scans done. This may not be possible at a district general hospital due to local constraints of radiology and can be circumvented by proper clinical assessment and follow up with a head injury advice booklet

Using scientifically and statistically sufficient statistics in comparing image segmentations.

Automatic computer segmentation in three dimensions creates opportunity to reduce the cost of three-dimensional treatment planning of radiotherapy for cancer treatment. Comparisons between human and computer accuracy in segmenting kidneys in CT scans generate distance values far larger in number than the number of CT scans. Such high dimension, low sample size (HDLSS) data present a grand challenge to statisticians: how do we find good estimates and make credible inference? We recommend discovering and using scientifically and statistically sufficient statistics as an additional strategy for overcoming the curse of dimensionality. First, we reduced the three-dimensional array of distances for each image comparison to a histogram to be modeled individually. Second, we used non-parametric kernel density estimation to explore distributional patterns and assess multi-modality. Third, a systematic exploratory search for parametric distributions and truncated variations led to choosing a Gaussian form as approximating the distribution of a cube root transformation of distance. Fourth, representing each histogram by an individually estimated distribution eliminated the HDLSS problem by reducing on average 26,000 distances per histogram to just 2 parameter estimates. In the fifth and final step we used classical statistical methods to demonstrate that the two human observers disagreed significantly less with each other than with the computer segmentation. Nevertheless, the size of all disagreements was clinically unimportant relative to the size of a kidney. The hierarchal modeling approach to object-oriented data created response variables deemed sufficient by both the scientists and statisticians. We believe the same strategy provides a useful addition to the imaging toolkit and will succeed with many other high throughput technologies in genetics, metabolomics and chemical analysis.

The effects of a media campaign on beliefs and utilization of imaging examinations in Norwegian patients with low back pain

Aims: Several authors have reported an overuse of imaging examinations for unspecific low back pain conditions. In this study, we examined the influence of a media campaign for better understanding and management of back pain in the general population on utilization of imaging examinations. Methods: The media campaign Active Back ran for three years (2002-2005) in two Norwegian counties and the results were compared to the adjacent control county. Numbers of imaging examinations were collected manually from every radiology department in each of the three counties, while belief measures were collected through a telephone survey before, during and after the campaign. Beliefs of the health care providers were collected through questionnaires. Results: We observed a decrease of X-rays by 35% in the intervention counties and by 33% in the control county. The number of CT scans decreased by 51% and 57% respectively. The number of MRI scans increased by 152% in the intervention counties and by 596% in the control. Combining all modalities, the number of imaging examinations increased by 3% in the intervention counties and by 56% in the control county. There was a tendency both in the general public and among the health care providers towards less trust in the usefulness of X-rays in all counties during the study period. The health care providers in the control county seemed to recommend imaging more often than their colleagues in the intervention counties. Conclusion: Despite slightly increased scepticism among the general public and health care providers, we observed an overall increase in utilization of imaging modalities. The dramatically increased utilization in the control group was likely explained by an increased capacity for MRI examinations obtained by the opening of a new radiology clinic, and not as an effect of the media campaign.

The ‘Image Gently’ campaign: increasing CT radiation dose awareness through a national education and awareness program

ALARA (As Low As Reasonably Achievable) has been a guiding principle for pediatric radiologists for decades. The Society for Pediatric Radiology (SPR) has long been a leader in promoting safety in radiology practice in children. However, the ALARA principle has taken on new meaning in the past several years as the number of CT scans in children has skyrocketed. For example, it is estimated that since the 1980s when CT was beginning its ascendancy there has been up to an 800% increase. CT scans in children provide great benefit in patient care when used appropriately. However, increased use requires a team approach to ensure that only indicated exams are performed and at the Pediatr Radiol (2008) 38:265–269 DOI 10.1007/s00247-007-0743-3

Medical Research Council trial of 2 versus 5 CT scans in the surveillance of patients with stage I non-seminomatous germ cell tumours of the testis

4519 Background: Surveillance is a standard management approach for stage 1 non seminomatous germ cell tumours (NSGCT), yet there is no agreement on the number of CT scans that are required to detect relapses. A randomised trial of 2 versus 5 CT scans was performed to determine whether the number of scans influenced the prognostic group (J Clin Oncol 15:594–603, 1997) at relapse. Methods: Patients with clinical stage 1 NSGCT opting for surveillance were randomised to chest and abdominal CT scans at either 3 and 12 or 3, 6, 9, 12, and 24 months, with all other investigations (clinical exams, markers, chest X-rays) carried out at equal frequency in the two arms. 3/5 patients were allocated to the 2 scan schedule. 400 patients were required to exclude a 3% increase in the proportion of patients relapsing with IGCCCG intermediate or poor prognosis disease with 90% power at the 5% significance level (1-sided). Results: 247 patients were allocated to 2 CT scans and 167 to 5 CT scans. With a median follow up of 40 months 37 (15%) relapses have occurred in the 2 scan arm and 33 (20%) in the 5 scan arm. No patients were poor prognosis at relapse but 2 (0.8%) of those relapsing in the 2 scan arm were intermediate prognosis compared to 1 (0.6%) in the 5 scan arm a difference of 0.2% (90% CI −1.2%, +1.6%). The mean diameter of abdominal mass at relapse was 2.1 cm in the two scan arm and 2.2 cm in the five scan arm. After chemotherapy a residual mass was present in 35% in the 2 scan and 36% in the 5 scan arm. No deaths have been reported. Conclusions: This study can exclude with 95% probability an increase in the proportion of patients relapsing with intermediate or poor prognosis disease of more than 1.6% if they have 2 rather than 5 CT scans as part of their surveillance protocol. CT scans at 3 and 12 months after orchidectomy should be considered as the new standard and will be associated with a reduction in radiation exposure. No significant financial relationships to disclose.