Can radiological technologists serve as primary screeners of low-dose computed tomography for the diagnosis of lung cancer?

BACKGROUND: The Accreditation Council for Lung Cancer CT Screening of Japan established guidelines for the certification of Radiological Technologists in 2009. OBJECTIVE: To analyze the trends in examination pass rates of the Radiological Technologists and discuss the reasons. METHODS: The cohort comprised 1593 Radiological Technologists (as examinees) based on 10-year of data (with a total of 17 examination runs). First, the examinees' written test results were analyzed. Second, an abnormal finding detection test was conducted using >100 client PCs connected to a dedicated server containing low-dose lung cancer CT screening images of 60 cases. The passing scores were correct answer rate >60% and sensitivity (TP) of >90%, respectively. RESULTS: Overall, 1243 examinees passed with an overall rate of 78%. The average pass rate for the written test was 91%, whereas that for the abnormal findings detection test was 85%. There was a moderate correlation between the test pass rate and average years of clinical experience of the examinees for the abnormal findings detection test (R = 0.558), whereas no such correlation existed for the written test (R = 0.105). CONCLUSIONS: In order for accredited Radiological Technologists to serve as primary screeners of low-dose computed tomography, it is important to revise the educational system according to current standard practices.

Identification of transcription factors responsible for dysregulated networks in human osteoarthritis cartilage by global gene expression analysis.

OBJECTIVE: Osteoarthritis (OA) is the most prevalent joint disease. As disease-modifying therapies are not available, novel therapeutic targets need to be discovered and prioritized for their importance in mediating the abnormal phenotype of cells in OA-affected joints. Here, we generated a genome-wide molecular profile of OA to elucidate regulatory mechanisms of OA pathogenesis and to identify possible therapeutic targets using integrative analysis of mRNA-sequencing data obtained from human knee cartilage. DESIGN: RNA-sequencing (RNA-seq) was performed on 18 normal and 20 OA human knee cartilage tissues. RNA-seq datasets were analysed to identify genes, pathways and regulatory networks that were dysregulated in OA. RESULTS: RNA-seq data analysis revealed 1332 differentially expressed (DE) genes between OA and non-OA samples, including known and novel transcription factors (TFs). Pathway analysis identified 15 significantly perturbed pathways in OA with ECM-related, PI3K-Akt, HIF-1, FoxO and circadian rhythm pathways being the most significantly dysregulated. We selected DE TFs that are enriched for regulating DE genes in OA and prioritized these TFs by creating a cartilage-specific interaction subnetwork. This analysis revealed eight TFs, including JUN, Early growth response (EGR)1, JUND, FOSL2, MYC, KLF4, RELA, and FOS that both target large numbers of dysregulated genes in OA and are themselves suppressed in OA. CONCLUSIONS: We identified a novel subnetwork of dysregulated TFs that represent new mediators of abnormal gene expression and promising therapeutic targets in OA.

VALIDATION OF MONTE CARLO DOSE CALCULATION FOR PAEDIATRIC CT EXAMINATIONS USING TUBE CURRENT MODULATION BASED ON IN-PHANTOM DOSIMETRY.

The aim of this study is to estimate tube current modulation (TCM) profiles in paediatric computed tomography (CT) examinations with a TCM scheme (Volume-EC) and evaluate the estimation accuracy of TCM profiles. Another aim is to validate organ doses calculated using Monte Carlo-based CT dosimetry software and estimated TCM profiles by comparing them with those measured using 5-year-old and 10-year-old anthropomorphic phantoms and radio-photoluminescence glass dosemeters. Dose calculations were performed by inputting detailed descriptions of a CT scanner, scan parameters and CT images of the phantoms into the software. Organ doses were evaluated from the calculated dose distribution images. Average relative differences (RDs) between the estimated and actual TCM profiles ranged from -3.6 to 5.6%. RDs between the calculated and measured organ doses ranged from -4.2 to 13.0% and -18.1 to 4.9% for 5-year-old and 10-year-old phantoms, respectively. These results validate dose calculations for paediatric CT scans using TCM.

Organ Dose Evaluations Based on Monte Carlo Simulation for CT Examinations Using Tube Current Modulation.

The aims of this study were to estimate tube current values for each X-ray projection angle used in adult chest computed tomography (CT) and abdomen-pelvis CT examinations with tube current modulation (TCM) and to validate organ doses determined using Monte Carlo (MC) simulations through comparisons with the doses measured using in-phantom dosimetry. For dose simulations, dose distribution images were obtained by inputting the geometry of a CT scanner, scan parameters including estimated TCM curves and CT images of an adult anthropomorphic phantom into MC simulation software. Organ doses were then determined from the dose distribution images. For dose measurements, organ doses were evaluated using radio-photoluminescence glass dosemeters located at various organ positions within the phantom. Relative differences between the simulated and measured organ doses were -2.5 to 11.0% and -1.5 to 10.5% for organs in chest and abdomen-pelvis CT scan ranges, respectively. Thus, the simulated and measured doses agreed well.

Dysregulated circadian rhythm pathway in human osteoarthritis: NR1D1 and BMAL1 suppression alters TGF-ß signaling in chondrocytes.

OBJECTIVES: Circadian rhythm (CR) was identified by RNA sequencing as the most dysregulated pathway in human osteoarthritis (OA) in articular cartilage. This study examined circadian rhythmicity in cultured chondrocytes and the role of the CR genes NR1D1 and BMAL1 in regulating chondrocyte functions. METHODS: RNA was extracted from normal and OA-affected human knee cartilage (n = 14 each). Expression levels of NR1D1 and BMAL1 mRNA and protein were assessed by quantitative PCR and immunohistochemistry. Human chondrocytes were synchronized and harvested at regular intervals to examine circadian rhythmicity in RNA and protein expression. Chondrocytes were treated with small interfering RNA (siRNA) for NR1D1 or BMAL1, followed by RNA sequencing and analysis of the effects on the transforming growth factor beta (TGF-ß) pathway. RESULTS: NR1D1 and BMAL1 mRNA and protein levels were significantly reduced in OA compared to normal cartilage. In cultured human chondrocytes, a clear circadian rhythmicity was observed for NR1D1 and BMAL1. Increased BMAL1 expression was observed after knocking down NR1D1, and decreased NR1D1 levels were observed after knocking down BMAL1. Sequencing of RNA from chondrocytes treated with NR1D1 or BMAL1 siRNA identified 330 and 68 significantly different genes, respectively, and this predominantly affected the TGF-ß signaling pathway. CONCLUSIONS: The CR pathway is dysregulated in OA cartilage. Interference with circadian rhythmicity in cultured chondrocytes affects TGF-ß signaling, which is a central pathway in cartilage homeostasis.

Intact attentional orienting towards inverted faces revealed by both manual responses and eye-movement measurement in individuals with Williams syndrome.

BACKGROUND: Individuals with Williams syndrome (WS) exhibit atypical attentional characteristics when viewing faces. Although atypical configural processing of faces has been reported in WS, the relative strengths of configural and local feature information to capture visual attention in WS remains unclear. We previously demonstrated that attentional capture by target-unrelated upright faces differs depending on what response is measured. Whereas eye movements reflected subtle atypical attentional properties at the late stage of visual search, manual responses could not capture the atypical attentional profiles towards target-unrelated upright faces in individuals with WS. Here we used the same experimental paradigm to assess whether sensitivity to configural facial information is necessary for capturing attention in WS. METHODS: We measured both eye movements and manual responses from 17 individuals with WS and 34 typically developing children and adults while they were actively involved in a visual search task with an inverted face distractor. Task measures (reaction time and performance accuracy) and gaze behaviour (initial direction of attention and fixation duration) were analysed for each stimulus. RESULTS: When the target and the inverted face were displayed in the same search array, reaction times and accuracies in individuals with WS showed similar tendencies as typical controls. Analysis of task and gaze measures revealed that attentional orienting towards inverted faces was not atypical. CONCLUSION: Although individuals with WS exhibited atypical gaze behaviour towards upright faces in our previous study, this unusual behaviour disappears if the faces are upside down. These findings suggest that local feature information alone (e.g. eyes) does not contribute to the heightened attention to faces, but configural information appears necessary for drawing attention to faces in individuals with WS, at least in the current experimental paradigm.

MicroRNA-155 suppresses autophagy in chondrocytes by modulating expression of autophagy proteins.

OBJECTIVE: Autophagy dysfunction has been reported in osteoarthritis (OA) cartilage. The objective of this study was to investigate the role of microRNA-155 (miR-155), which is overexpressed in OA, in the regulation of autophagy in human chondrocytes. DESIGN: Rapamycin (50 nM) and 2-deoxyglucose (2-DG) (5 mM) were used to stimulate autophagy in primary human articular chondrocytes and in the T/C28a2 human chondrocyte cell line. Cells were transfected with LNA GapmeR or mimic specific for miR-155 and autophagy flux was assessed by LC3 western blotting and by Cyto-ID(®) dye quantification in autophagic vacuoles. Expression of predicted miR-155 targets in the autophagy pathway were analyzed by real-time PCR and western blotting. RESULTS: Autophagy flux induced by rapamycin and 2-DG was significantly increased by miR-155 LNA, and significantly decreased after miR-155 mimic transfection in T/C28a2 cells and in human primary chondrocytes. These effects of miR-155 on autophagy were related to suppression of gene and protein expression of key autophagy regulators including Ulk1, FoxO3, Atg14, Atg5, Atg3, Gabarapl1, and Map1lc3. CONCLUSION: MiR-155 is an inhibitor of autophagy in chondrocytes and contributes to the autophagy defects in OA.

Detection of methicillin-resistant Staphylococcus pseudintermedius ST169 and novel ST354 SCCmec II-III isolates related to the worldwide ST71 clone.

The recent appearance of methicillin-resistant Staphylococcus pseudintermedius (MRSP) is a concern for both veterinary and human healthcare. MRSP clonal lineages with sequence type (ST) 71-spa t02-staphylococcal cassette chromosome mec (SCCmec) II-III and ST68-spa t06-SCCmec V have spread throughout Europe and North America, respectively. The current study compared the molecular characteristics of 43 MRSP isolates from dogs in Japan with those of MRSP from previous reports using multilocus sequence typing based on seven housekeeping genes, SCCmec typing, and detection of antimicrobial resistance genes. Three related clonal lineages, ST71, ST169, and the newly registered ST354, were observed in SCCmec II-III isolates from Japan, despite MRSP SCCmec II-III isolates being thought to belong to a single clonal lineage. The majority of SCCmec II-III isolates belonging to ST169 (9/11) and ST354 (3/3), but not ST71 (0/11), harboured tetM. Four STs were observed for the SCCmec V isolates; however, neither ST68 nor related STs were found in the Japanese MRSP isolates. In conclusion, MRSP SCCmec II-III isolates from Japan belonged to ST71 and related STs (ST169 and ST354). A variety of MRSP SCCmec V clones, including some novel clones, were identified.

Association of the expression levels in the longissimus muscle and a SNP in the CDC10 gene with marbling in Japanese Black beef cattle.

The septin 7 (CDC10) gene, involved in cellular proliferation, has been previously shown to be expressed at different levels in the longissimus muscle (LM) between low-marbled and high-marbled steer groups by differential-display PCR. It is located within the genomic region of a quantitative trait locus for marbling, and thus was considered as a positional functional candidate gene for marbling. In this study, we showed that the CDC10 expression levels in the LM were positively correlated with marbling in Japanese Black (JB) steers (P<0.0001). Further, an association analysis indicated that a SNP in the promoter region of the CDC10 gene was associated with marbling using 99 JB sires (P=0.03) and 542 JB paternal half-sib progeny steers from a sire homozygous for G allele at the SNP (P<0.0001). These findings suggest possible effects of the expression levels in the LM and the SNP of the CDC10 gene on marbling in JB cattle.

Evaluation of organ doses in adult and paediatric CT examinations based on Monte Carlo simulations and in-phantom dosimetry.

The aim of this study was to validate the computed tomography dose index (CTDI) and organ doses evaluated by Monte Carlo simulations through comparisons with doses evaluated by in-phantom dosimetry. Organ doses were measured with radio-photoluminescence glass dosemeter (RGD) set at various organ positions within adult and 1-y-old anthropomorphic phantoms. For the dose simulations, the X-ray spectrum and bow-tie filter shape of a CT scanner were estimated and 3D voxelised data of the CTDI and anthropomorphic phantoms from the acquired CT images were derived. Organ dose simulations and measurements were performed with chest and abdomen-pelvis CT examination scan parameters. Relative differences between the simulated and measured doses were within 5 % for the volume CTDI and 13 % for organ doses for organs within the scan range in adult and paediatric CT examinations. The simulation results were considered to be in good agreement with the measured doses.

Association of the expression levels in the skeletal muscle and a SNP in the CDC10 gene with growth-related traits in Japanese Black beef cattle.

Growth performance, as well as marbling, is the main breeding objective in Japanese Black (JB) cattle, the major beef breed in Japan. The septin 7 (CDC10) gene, involved in cellular proliferation, is located within a genomic region of a quantitative trait locus for growth-related traits. In this study, we first showed that the expression levels of the CDC10 gene in the skeletal muscle were higher in JB steers with extremely high growth performance than in JB steers with extremely low growth, using real-time PCR. Further, a single nucleotide polymorphism (SNP), NC_007302.5:g.63264949G>C, was detected in the promoter region of the CDC10 gene and genotyped in three Japanese cattle breeds (known as 'Wagyu' in Japan) and the Brown Swiss dairy cattle breed. All four cattle populations showed a moderate genetic diversity at the SNP of the CDC10 gene. An association analysis indicated that the SNP was associated with growth-related traits in JB cattle. These findings suggest possible effects of the expression levels in the skeletal muscle and the SNP of the CDC10 gene on growth-related traits in JB cattle. The CDC10 SNP may be useful for effective marker-assisted selection to increase beef productivity in JB beef cattle.

Utility of T2 mapping and dGEMRIC for evaluation of cartilage repair after allograft chondrocyte implantation in a rabbit model.

OBJECTIVE: To investigate the effectiveness of quantitative Magnetic resonance imaging (MRI) for evaluating the quality of cartilage repair over time following allograft chondrocyte implantation using a three-dimensional scaffold for osteochondral lesions. DESIGN: Thirty knees from 15 rabbits were analyzed. An osteochondral defect (diameter, 4 mm; depth, 1 mm) was created on the patellar groove of the femur in both legs. The defects were filled with a chondrocyte-seeded scaffold in the right knee and an empty scaffold in the left knee. Five rabbits each were euthanized at 4, 8, and 12 weeks and their knees were examined via macroscopic inspection, histological and biochemical analysis, and quantitative MRI (T2 mapping and dGEMRIC) to assess the state of tissue repair following allograft chondrocyte implantation with a three-dimensional scaffold for osteochondral lesions. RESULTS: Comparatively good regenerative cartilage was observed both macroscopically and histologically. In both chondrocyte-seeded and control knees, the T2 values of repair tissues were highest at 4 weeks and showed a tendency to decrease with time. ΔR1 values of dGEMRIC also tended to decrease with time in both groups, and the mean ΔR1 was significantly lower in the CS-scaffold group than in the control group at all time points. ΔR1 = 1/r (R1post - R1pre), where r is the relaxivity of Gd-DTPA(2-), R1 = 1/T1 (longitudinal relaxation time). CONCLUSION: T2 mapping and dGEMRIC were both effective for evaluating tissue repair after allograft chondrocyte implantation. ΔR1 values of dGEMRIC represented good correlation with histologically and biochemically even at early stages after the implantation.

Hidden osteophyte formation on plain X-ray is the predictive factor for development of knee osteoarthritis after 48 months--data from the Osteoarthritis Initiative.

OBJECTIVE: To examine whether the detection of osteophytes anywhere in the knee could serve as a pre-radiographic biomarker for osteoarthritis (OA) development. METHODS: Baseline magnetic resonance imaging (MRIs) of 132 participants in the Osteoarthritis Initiative (OAI) were studied. Based on radiographs, 66 knees were assessed as osteoarthritis-free (no-osteoarthritis [NOA], or Kellgren/Lawrence [K/L] severity grade 0/1 both at baseline and 48 months), and another 66 knees were assessed as having radiographic OA changes (pre-radiographic osteoarthritis [PROA], or with K/L grade 0/1 at baseline and grade ≥ 2 at 48 months). Using baseline MRI data, we examined eight sites of osteophyte formation: the medial and lateral femoral condyle (MFC and LFC, respectively); medial and lateral tibial plateau (MTP and LTP, respectively); medial and lateral facets of the patellofemoral joint (PM and PL, respectively); tibial spine (TS); and femoral intercondylar notch (IC). Knee joint osteophyte size was assessed via the 8-point marginal osteophytes item of the whole-organ magnetic resonance imaging score (WORMS). The frequencies and distributions of osteophytes were compared between groups. RESULTS: Mild-size osteophytes (defined as score ≥ 2) were observed more frequently at the MFC (P = 0.00278), MTP (P = 0.0046), TS (P = 0.0146), PM (P < 0.0001), PL (P = 0.0012), and IC (P < 0.0001) in PROA knees than in NOA knees. Moderate-size osteophytes (defined as score ≥ 4) were more frequently observed in PROA knees than in NOA knees only at the IC (P < 0.0001). CONCLUSION: Knees with osteophyte formation at the IC, even those of K/L severity grade 0/1, are at risk for the development of radiographic OA by 48 months.

Preventive effects of hyaluronan from deterioration of gait parameters in surgically induced mice osteoarthritic knee model.

OBJECTIVE: Osteoarthritis (OA) leads to pain and loss of function in affected joints. Gait disturbance results from these symptoms of OA, and gait analysis can be important to evaluate the progression of OA. The purpose of this study was to analyze gait pattern in a rodent model of OA and to assess the effects of intra-articular injection of hyaluronan (IAI-HA) by gait analysis, along with histological evaluation. DESIGN: OA was induced by destabilization of the medial meniscus (DMM) of C57BL/6 mice. IAI-HA started 3 weeks after DMM surgery. Mice were allocated to three groups and were given either 800-kDa HA (800-HA), 6000-kDa HA (6000-HA) or saline. We compared these three groups with a sham group by gait analysis using CatWalk. Histological evaluation was performed to assess articular cartilage changes in the knee joints. RESULTS: Mice injected with 800-HA or 6000-HA showed gait patterns similar to that of the sham mice, while the saline-injected group showed gait disturbances 12 and 16 weeks after DMM surgery. Histological changes in articular cartilage were similar among the 800-HA, 6000-HA and saline-treated groups, demonstrating OA progression throughout the experimental time points. Positive gait-related effects of IAI-HA might occur by its pain relieving effect and/or by preventing contracture. CONCLUSION: IAI-HA prevented gait disturbances in the DMM model, but did not prevent histological changes associated with OA progression.

Improvement and quantitative performance estimation of the back support muscle suit.

We have been developing the wearable muscle suit for direct and physical motion supports. The use of the McKibben artificial muscle has opened the way to the introduction of "muscle suits" compact, lightweight, reliable, wearable "assist-bots" enabling manual worker to lift and carry weights. Since back pain is the most serious problem for manual worker, improvement of the back support muscle suit under the feasibility study and quantitative estimation are shown in this paper. The structure of the upper body frame, the method to attach to the body, and the axes addition were explained as for the improvement. In the experiments, we investigated quantitative performance results and efficiency of the back support muscle suit in terms of vertical lifting of heavy weights by employing integral electromyography (IEMG). The results indicated that the values of IEMG were reduced by about 40% by using the muscle suit.

Angiogenic activity of subchondral bone during the progression of osteoarthritis in a rabbit anterior cruciate ligament transection model.

OBJECTIVE: To investigate the longitudinal angiogenic activity of subchondral bone and cartilage during the progression of osteoarthritis (OA) using a rabbit model of OA. MATERIALS AND METHODS: OA was surgically induced by anterior cruciate ligament transaction (ACLT) in left knee of 12 months old female New Zealand white rabbits (n = 33). Histological examination, immunohistochemistry, and angiogenic activity assay was done at 0, 2, 4, 6, 8, 12 weeks after ACLT. Histologic evaluation was performed with haematoxylin and eosin, safranin-O staining to assess the OA change of medial femoral condyle (MFC) and lateral femoral condyle (LFC). CD31 immunohistochemistry was performed to confirm the vascular invasion at osteochondral junction. A co-cultured tubule formation assay was conducted to evaluate angiogenic activity of the subchondral bone and cartilage of MFC and LFC as well as synovium. Association between histological changes, angiogenic activity, and vascular invasion were evaluated. RESULTS: OA changes increased in a time-dependent manner both in MFC and LFC. Angiogenic activity of subchondral bone showed a monomodal change during the OA progression, achieved a peak in the early to progressive stage and decreased to normal level in the late stage of OA. Surge of vascular invasion was observed following the increase of angiogenic activity in the progressive stage of OA. Angiogenic activity of cartilage did not change during the course of OA progression. CONCLUSION: Angiogenic activity of subchondral bone was elevated in the early to progressive stage of OA and vascular invasion into the osteochondral junction followed.

Comparison of sensitivity of lung nodule detection between radiologists and technologists on low-dose CT lung cancer screening images.

OBJECTIVES: The objective of this study was to compare the sensitivity of detection of lung nodules on low-dose screening CT images between radiologists and technologists. METHODS: 11 radiologists and 10 technologists read the low-dose screening CT images of 78 subjects. On images with a slice thickness of 5 mm, there were 60 lung nodules that were ≥5 mm in diameter: 26 nodules with pure ground-glass opacity (GGO), 7 nodules with mixed ground-glass opacity (GGO with a solid component) and 27 solid nodules. On images with a slice thickness of 2 mm, 69 lung nodules were ≥5 mm in diameter: 35 pure GGOs, 7 mixed GGOs and 27 solid nodules. The 21 observers read screening CT images of 5-mm slice thickness at first; then, 6 months later, they read screening CT images of 2-mm slice thickness from the 78 subjects. RESULTS: The differences in the mean sensitivities of detection of the pure GGOs, mixed GGOs and solid nodules between radiologists and technologists were not statistically significant, except for the case of solid nodules; the p-values of the differences for pure GGOs, mixed GGOs and solid nodules on the CT images with 5-mm slice thickness were 0.095, 0.461 and 0.005, respectively, and the corresponding p-values on CT images of 2-mm slice thickness were 0.971, 0.722 and 0.0037, respectively. CONCLUSION: Well-trained technologists may contribute to the detection of pure and mixed GGOs ≥5 mm in diameter on low-dose screening CT images.

Effects of climatic elements on Campylobacter-contaminated chicken products in Japan.

Japanese weather data for areas that produced Campylobacter spp.-positive chicken products were compared with those for areas producing negative samples. Regarding samples produced during the period of rising temperature (spring and summer), the mean weekly air temperatures for Campylobacter-positive samples were higher than those for negative samples for the period of the week in which the samples were purchased (18.7 °C vs. 13.1 °C, P = 0.006) to a 12-week lag (12 weeks before purchasing samples; 7.9 °C vs. 3.4 °C, P = 0.009). Significant differences in weekly mean minimum humidity and sunshine duration per day were also observed for 1- and 2-week lag periods. We postulated that the high air temperature, high humidity and short duration of sunshine for the chicken-rearing period increased Campylobacter colonization in chickens during the period of rising temperature. Consequently, the number of Campylobacter-contaminated chicken products on the market in Japan may fluctuate because of the climatic conditions to which reared chickens are exposed.

Computed tomography dose assessment for a 160 mm wide, 320 detector row, cone beam CT scanner.

Computed tomography (CT) dosimetry should be adapted to the rapid developments in CT technology. Recently a 160 mm wide, 320 detector row, cone beam CT scanner that challenges the existing Computed Tomography Dose Index (CTDI) dosimetry paradigm was introduced. The purpose of this study was to assess dosimetric characteristics of this cone beam scanner, to study the appropriateness of existing CT dose metrics and to suggest a pragmatic approach for CT dosimetry for cone beam scanners. Dose measurements with a small Farmer-type ionization chamber and with 100 mm and 300 mm long pencil ionization chambers were performed free in air to characterize the cone beam. According to the most common dose metric in CT, namely CTDI, measurements were also performed in 150 mm and 350 mm long CT head and CT body dose phantoms with 100 mm and 300 mm long pencil ionization chambers, respectively. To explore effects that cannot be measured with ionization chambers, Monte Carlo (MC) simulations of the dose distribution in 150 mm, 350 mm and 700 mm long CT head and CT body phantoms were performed. To overcome inconsistencies in the definition of CTDI100 for the 160 mm wide cone beam CT scanner, doses were also expressed as the average absorbed dose within the pencil chamber (D100). Measurements free in air revealed excellent correspondence between CTDI300air and D100air, while CTDI100air substantially underestimates CTDI300air. Results of measurements in CT dose phantoms and corresponding MC simulations at centre and peripheral positions were weighted and revealed good agreement between CTDI300w, D100w and CTDI600w, while CTDI100w substantially underestimates CTDI300w. D100w provides a pragmatic metric for characterizing the dose of the 160 mm wide cone beam CT scanner. This quantity can be measured with the widely available 100 mm pencil ionization chamber within 150 mm long CT dose phantoms. CTDI300w measured in 350 mm long CT dose phantoms serves as an appropriate standard of reference for characterizing the dose of this CT scanner. A CT dose descriptor that is based on an integration length smaller than the actual beam width is preferably expressed as an (average) dose, such as D100 for the 160 mm wide cone beam CT scanner, and not as CTDI100.