T T Farman

University of Louisville, Louisville, KY, United States

Are you T T Farman?

Claim your profile

Publications (28)14.89 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To compare the effects of scintillator on the detective quantum efficiency (DQE) of a charge-coupled device (CCD) digital intraoral radiographic system. Three screens composed of 3 different scintillator materials, namely europium-doped lutetium oxide (Lu2(O3):Eu3+), transparent optical ceramic (TOC), thallium-doped cesium iodide (CsI:Tl; CsI), and terbium-doped gadolinium oxysulfide (Gd2(O2)S:Tb; GOS) were compared, in turn, in combination with a CCD detector having square pixels with height and width dimensions of 19.5 microm. DQE was investigated using the slanted-slit-derived MTF and surrogate signal-to-noise ratio (SNR) measurements derived from calculations of the mean and standard deviations from the mean pixel values of multiple random patches from various uniform exposures. An Irix x-ray generator operated at 70 kVp and 8 mA, with a nominal focal spot size of 0.7 mm and 2.5 mm Al equivalent filtration, was used in making all exposures. Using TOC, the peak DQE was 62% at 5 cycles/mm. For CsI, the peak DQE was 22% at 2 cycles/mm. With GOS, the peak DQE was 10% at 1 cycle/mm. Under identical experimental settings, TOC consistently resulted in higher DQE than CsI and commercially available GOS scintillators combined with the same high-resolution solid-state detector.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 03/2006; 101(2):219-23. · 1.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective The conspicuity of cephalometric landmarks may be improved by pseudo color and emboss enhancements of 8 and 16 bit photostimulable phosphor (PSP) cephalograms reviewed by orthodontists. Methods PSP cephalograms of orthodontic patients were obtained. These 8 bit and 16 bit images were viewed in random order in baseline “for processing,” emboss, pseudo color and emboss/pseudo color states. Ten observers viewed the images simultaneously and idependently. Selected soft tissue and hard tissue cephalometric landmarks and of overall image clarity were rated. Repeat images were included to determine intra observer reliability in making ratings. Results Statistically significant differences were found in the preferred image state for both specific cephalometric landmark evaluation and image bit depth. The emboss state was most frequently rated highest for clarity of hard tissue landmarks. Pseudo color state was rated best for soft tissue landmarks. Interrater agreement varied between landmarks but was not altered significantly by bit depth. Intrarater agreement was high. Conclusions Post-processing enhancement of PSP cephalograms is perceived to improve clarity of selected anatomic landmarks in PSP cephalograms.
    International Journal of Computer Assisted Radiology and Surgery 01/2006; 1:105-112. · 1.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective Anatomic landmark clarity of 16 bit photostimulable phosphor cephalograms may be improved by histogram modification and image enhancement. The perceived effects of pixel histogram distribution modifications was investigated. Methods Photostimulable phosphor (PSP) cephalograms were obtained from (n = 40) orthodontic patients using a DenOptix 16 bit instrument. The resulting images were classified according to image histogram characteristics; namely single versus double peak. These images were viewed in random order as baseline, and with embossed, colorized and colorized embossed enhancements. Viewing by ten observers was simultaneous but independent. The clarity of selected soft tissue and hard tissue landmarks and of overall image quality was rated. Repeat images were included to ascertain intra operator reliability in making ratings. Results The observed images differed according to histogram characteristics across a narrow exposure range, and outcomes were not predictable in advance by the operator. Perceived image quality in terms of clarity of selected anatomic details was reduced when a “single peak” histogram image was produced rather than a “double peak” histogram distribution. Emboss and pseudo color enhancements were perceived to aid landmark identification and also improved perception of overall image quality of photostimulable phosphor cephalograms. Emboss enhancement was rated as being best utilized for hard tissue landmarks while pseudo color enhancement was rated to be best utilized for soft tissue landmarks. Conclusions Proprietary PSP systems can substantially reduce the normally wide exposure latitude usually associated with this modality and histogram modification can have influence image quality with significant effects on perception of anatomic landmarks in digital cephalograms.
    International Journal of Computer Assisted Radiology and Surgery 01/2006; 1:97-103. · 1.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the effects of 2 components (scintillator and x-ray generator) in the imaging chain on the modulation transfer function (MTF) of a charge-coupled device (CCD) digital intraoral radiographic system. Three screens composed of 3 different scintillator materials, namely europium-doped lutetium oxide transparent optical ceramic (TOC), thallium-doped cesium iodide (CsI), and terbium-doped gadolinium oxysulfide (GOS), were compared. Each was used, in turn, in conjunction with a CCD detector having a pixel dimension of 19.5 mum. Two different x-ray generators were also used to evaluate this variable. MTF was investigated using the slanted slit method. The TOC provided a good modulation response for low and middle frequencies, reducing to 0 only at a high cutoff frequency. With CsI and GOS, the system MTF dropped to 0 at a lower cutoff frequency than was the case with TOC. Hence, TOC provided higher spatial resolution than the other 2 scintillators tested under the experimental conditions applied. The differences in MTF attributed to the scintillator type were proportional and consistent. Despite constant pixel dimensions, MTF was affected to a considerable degree by the scintillator applied and the x-ray generator used in conjunction with the same CCD imaging device. TOC shows potential as a possible replacement for CsI and GOS as a scintillator screen material for intraoral digital x-ray imaging using a solid-state detector, providing higher spatial resolution under the given experimental conditions.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 06/2005; 99(5):608-13. · 1.50 Impact Factor
  • Source
    Allan G Farman, Taeko T Farman
    [Show abstract] [Hide abstract]
    ABSTRACT: There has been a proliferation of available dental x-ray detectors over the recent past. The purpose of this short technical report is to provide a basic comparison of spatial resolution, contrast perceptibility, and relative exposure latitudes of 18 current dental x-ray detectors, including solid-state systems (CCD and CMOS), photostimulable phosphors, and analog film. Spatial resolution was measured using a 0.025 mm Pb phantom test grid with a measurement range from 1.5 to 20 lp/mm. For contrast perceptibility, a 7-mm thick aluminum perceptibility test device with wells of 0.1-0.9 mm depth at 0.1 mm intervals and 1 defect of 1.5 mm was used. The relative exposure latitude was determined by expert consensus using clear discrimination of the enamel-dentin junction as the lower limit and pixel blooming or unacceptable levels of cervical burnout as the upper limit. The highest spatial resolution was found with Kodak InSight film, RVG-ui (CCD), and RVG 6000 (CMOS) detectors, each of which achieved 20 lp/mm, followed by the Planmeca Dixi2 v3 at > or =16 lp/mm. Contrast resolution was at least to 0.2 mm through 7 mm aluminum for all 18 detectors, with the best results being found for the Visualix HDI, RVG-ui, RVG 5000, and RVG 6000 detectors and the Schick CDR wired and wireless systems. The greatest exposure ranges were found with photostimulable phosphors and the Kodak RVG 6000 and RVG 5000 detectors. Most current x-ray detectors generally perform well in terms of spatial and contrast resolutions, and in terms of exposure latitude. These findings were independent of the modality applied.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 04/2005; 99(4):485-9.
  • [Show abstract] [Hide abstract]
    ABSTRACT: LCD 4.0 is the first commercially available dental application program to take advantage of DICOM to allow the dentist to perform analyses and diagnoses on images from widely different sensors (CCD, CMOS and PSP technologies). LCD 4.0 interoperability with DICOM images from 11 different dental vendors involved in manufacture or display of digital grayscale images has been demonstrated. LCD interoperability with DICOM images sent over the Internet has also been demonstrated with private practice dentists.
    International Congress Series 01/2005; 1281:1250-1255.
  • Allan G. Farman, Taeko T. Farman
    [Show abstract] [Hide abstract]
    ABSTRACT: Digital radiographic systems for use in dental practice have been available for almost two decades, but internationally most dentists still use analog silver halide X-ray film. This article is a review of the presumed advantages digital radiographic systems have over conventional X-ray film with special emphasis on the costs and benefits of current intraoral and panoramic systems. It is concluded that more evaluations of time and motion for digital imaging in dental practice are needed. Moreover, evidence-based logic should be applied to the determination of the physical properties required by image detectors for the performance of the different diagnostic tasks that are needed when practicing dentistry.
    Oral Radiology 01/2004; 20(1):9-14. · 0.17 Impact Factor
  • CARS 2004. Computer Assisted Radiology and Surgery. Proceedings of the 18th International Congress and Exhibition, Chicago, USA, June 23-26, 2004; 01/2004
  • CARS 2004. Computer Assisted Radiology and Surgery. Proceedings of the 18th International Congress and Exhibition, Chicago, USA, June 23-26, 2004; 01/2004
  • CARS 2003. Computer Assisted Radiology and Surgery. Proceedings of the 17th International Congress and Exhibition, London, June 25-28, 2003; 01/2003
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cerebrovascular accidents (CVA), or stroke, afflict 731,000 Americans each year, with 165,000 of these individuals dying. Stroke is a major cause of death and disability throughout the world, including southern Africa. Atherosclerosis-related formation of thrombi and emboli at the bifurcation of the common carotid artery and proximal internal carotid artery represents a common cause of stroke. The detection of carotid atherosclerosis by dentists using panoramic radiographs recently has been presented to the public through television news stories and the press, but many dentists still do not know how to interpret panoramic radiographs for detection of this condition. This communication illustrates examples in which carotid atherosclerosis was detected using panoramic radiography. Differential diagnoses are presented. Since not every carotid plaque calcifies, panoramic radiography should never be used alone to exclude the possibility of carotid atherosclerosis. It should also be remembered that the mere presence of calcified carotid plaque is not necessarily a reflection on the degree of carotid stenosis. Definitive diagnosis and treatment requires referral of patients deemed to be at risk to an appropriate physician. A variety of advanced diagnostic methods, including gadolinium-enhanced MRI, Duplex Doppler sonography and angiography are used to confirm carotid stenosis.
    SADJ: journal of the South African Dental Association = tydskrif van die Suid-Afrikaanse Tandheelkundige Vereniging 12/2001; 56(11):549-53.
  • A G Farman, T T Farman
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 07/2001; 91(6):619-21.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A retrospective analysis of panoramic radiographs from patients with head and neck cancer, taken prior to radiation therapy, revealed a prevalence of carotid calcifications of 12.6% in men aged 50–59 years, but only 3.3% in women of the same age. By age 70–79 years, the prevalence of calcified carotid atheromas was similar for both genders. Evaluation of the image layer characteristics of a prototype Instrumentarium OP 100D digital panoramic X-ray machine shows this unit to be suitable for detection of calcifications, within the carotid artery at the region of the bifurcation.
    CARS 2001. Computer Assisted Radiology and Surgery. Proceedings of the 15th International Congress and Exhibition, Berlin, Germany, June 27-30, 2001; 01/2001
  • A G Farman, T T Farman
    Dentomaxillofacial Radiology 08/2000; 29(4):254. · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To examine the feasibility of substituting observers determining the accuracy of endodontic measurements for measurements of physical qualities in comparison of digital imaging systems. Sensors from six digital imaging systems were compared for signal-to-noise ratio (SNR), modulation transfer function (MTF) and detective quantum efficiency (DQE). A total of 45 canals in teeth from human cadavers were instrumented to their apical foramina. Endodontic files, ranging in size from size 8 to size 20, were glued in place at random distances from the apical foramina spanning a range of +/- 3 mm. The teeth were imaged with the six digital systems and dental X-ray film. Fifteen dentists independently measured the distance from the end of the file to the apical foramen. Results were expressed as the measurement error. Measurement error was compared to SNR, MTF and DQE for each digital system. CDR (Schick, New York, NY, USA), Digora (Sordex, Helsinki, Finland) and Dexis (Provision Dental Systems, Palo Alto, CA, USA) produced the highest SNR values followed closely by RVG-4 (Trophy, Croissy-Beavborg, France). Sens-A-Ray (Dent-X/Regam Medical Systems, Sundsvall, Sweden), Dexis and the RVG-4 produced the best MTF results. Dexis had the greatest DQE. The mean measurement errors (in mm) were: Film 0.65, Dexis 0.69, CDR 0.71, RVG-4 0.74, Digora 0.89, Sens-A-Ray 0.97, and Visualix-2 (Gendex, Monza, Italy) 0.98. Digital systems closely approximate film in their accuracy when used for endodontic measurement providing that the assessment instruments have similar resolving power. DQE was the best physical predictor of system accuracy when compared with endodontic length measurements. MTF and SNR alone did not accurately predict observer precision.
    Dentomaxillofacial Radiology 08/2000; 29(4):216-22. · 1.15 Impact Factor
  • A G Farman, T T Farman
    [Show abstract] [Hide abstract]
    ABSTRACT: Digital solutions for extraoral and panoramic radiology have been available for more than 15 years. The costs, however, have been too high for adoption in private dental practice. The past 2 years have seen tremendous growth in the number of relatively cost-effective digital options available to the dentist and dental specialist. Furthermore, computer speed and data storage capacities have progressed. This article presents an overview of systems available at present, and their enabling technologies and enhancement capabilities.
    Dental Clinics of North America 05/2000; 44(2):257-72, v-vi.
  • Source
    T T Farman, A G Farman
    [Show abstract] [Hide abstract]
    ABSTRACT: To compare the properties of a new speed group F intra-oral X-ray film with those of three well established types both from groups D and E, and evaluate the impact of six commercially available processing solutions. Four types of dental X-ray film, Flow (Flow X-ray, West Hempstead, NY, USA), speed group F, Ektaspeed Plus (Eastman Kodak, Rochester NY, USA) and M2 Comfort (AgfaGevaert, Morstel, Belgium), both speed group E, and Ultra-speed (Eastman Kodak), speed group D, were exposed under standardised conditions and processed in six different processing solutions. Base plus fog density, characteristic curves, film density, speed, average gradient, contrast and latitude and spatial resolution were calculated. The choice of processing chemistry affected radiographic characteristics including speed grouping. The new F film was consistently the fastest. M2 Comfort could achieve F speed and Ultra-speed achieved E speed using Automat XR chemicals. The speed of Ektaspeed Plus was independent of the automatic processing solution used. Ultra-Speed film had the lowest base plus fog density and the widest latitude. Film contrast was similar irrespective of the film and solution combination. The choice of processing chemistry can affect radiographic characteristics. The new F film reduces patient exposure by one-half compared with E speed film with no detriment to image quality.
    Dentomaxillofacial Radiology 02/2000; 29(1):41-5. · 1.15 Impact Factor
  • A G Farman, T T Farman
    [Show abstract] [Hide abstract]
    ABSTRACT: The RVG-ui is a solid-state system for dental x-ray imaging combining a charge-coupled device (CCD) of small pixel size (19.5 microns) with a caesium iodide (CsI) scintillator. It features two sizes of sensor with receptive areas that approach the size of No. 1 and No. 2 periapical x-ray films. The spatial resolution of the RVG-ui exceeds 20 lp/mm, rivaling direct-exposure intra-oral x-ray film when the latter is optimally exposed and processed. The recording latitude of the RVG-ui for clinically acceptable images is 25:1, making exposure error unlikely. In features such as speed of image acquisition, reduction in radiation dose, retrieval of data, and organization and storage of images, the RVG-ui system surpasses traditional x-ray film. Furthermore, it is possible to make accurate length measurements very quickly, and to apply an artificial intelligence program to determine the probability of proximal dental caries in enamel and dentin.
    International journal of computerized dentistry 08/1999; 2(3):183-96.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Accurate assessment of intraosseous lesion dimensions is useful in determining strategies for treatment of periradicular pathoses of dental causation. To compare the efficacy of digital versus analog imaging for the measurement of mesiodistal and vertical dimensions of periapical lesions in patients that require apical surgery. Fourteen examiners assessed the dimensions of 28 lesions with a millimeter ruler and Ektaspeed Plus radiographs (Eastman Kodak, Rochester, N.Y.), and with the Visualix-2 (Gendex/Dentsply, Milan, Italy) in unenhanced, contrast-stretched and equalized modes with proprietary software mouse-driven measurement algorithm. Impregum F (Premier Dental Products) impressions at surgery were used as the "gold standard." Ten randomly chosen images were reread 2 weeks later to assess intra-operator reliability. As the Mauchly sphericity test was significant for all tests, a multivariate analysis of variance was used to assess accuracy. To explain the exact difference between means, the Bonferroni test was applied. Intra-observer reliability was assessed with Friedman's two-way analysis of variance; inter-observer effects were determined with Cronbach's alpha. For accuracy in measurement, the closest to the "gold standard" were achieved with the Visualix-2 with image equalization. The contrast-stretched Visualix-2 and unenhanced Visualix-2 measurements were less accurate; conventional film was consistently the least accurate (p < 0.002). On the other hand, subjective preference placed film radiographs above the unenhanced Visualix-2 images; contrast-stretched Visualix-2 images were preferred over all other modalities. Charge-coupled device-based images with the Visualix-2 are preferable to film-based radiographs for measuring periapical lesion dimensions.
    Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 02/1998; 85(2):203-9.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To determine the consequences for entrance exposure of varying the beam energy and operating current for panoramic radiography using a charge-coupled device receptor. Images were made of a RANDO average man phantom (Alderson Research Laboratories, Stamford, CT) at kVcp settings of 60, 66, 70 and 80 and an mA of 2.0, 3.2, 6.4 and 10.0. The exposure cycle was set as recommended by the manufacturer at 17.6 s. Diagnostic image quality was rated by a panel of two oral and maxillofacial radiologists and one oral and maxillofacial pathologist. Entrance exposures were assessed using a 3 cc ionization chamber placed at the beam entry points while imaging the molar, premolar, and anterior teeth both using the DigiPan (Trophy Radiologie, Vincennes, France) CCD receptor and conventional T-Mat G film/Lanex Regular screens (Eastman Kodak, Rochester, NY, USA). Acceptable image quality was attained with combinations of 60 kVcp and 3.2, 6.4 or 10 mA, 70 kVcp and 2.0, 3.2 or 6.4 mA; at 80 kVcp irrespective of the mA it was unacceptable. The maximum reduction in entrance dose was 77%, averaged over the three sites, at 70 kVcp and 2 mA. The DigiPan receptor produces satisfactory images with saving in entry exposure saving of approximately 70% when compared with a conventional film/rare earth screen combination.
    Dentomaxillofacial Radiology 02/1998; 27(1):36-40. · 1.15 Impact Factor