Reference Patient Ge Ct
IntroductionDiagnostic reference levels were first mentioned by the International Commission on Radiological Protection (ICRP) in 1990 1 and subsequently recommended in greater detail in 1996 2. From the 1996 report:.The Commission now recommends the use of diagnostic reference levels for patients. These levels, which are a form of investigation level, apply to an easily measured quantity, usually the absorbed dose in air, or in a tissue equivalent material at the surface of a simple standard phantom or representative patient. The diagnostic reference level will be intended for use as a simple test for identifying situations where the level of patient dose or administered activity is unusually high. If it is found that procedures are consistently causing the relevant diagnostic reference level to be exceeded, there should be a local review of procedures and the equipment in order to determine whether the protection has been adequately optimized.
If not, measures aimed at reduction of doses should be taken.Diagnostic reference levels are supplements to professional judgment and do not provide a dividing line between good and bad medicine. It is inappropriate to use them for regulatory or commercial purposes. Diagnostic reference levels apply to medical exposure, not to occupational and public exposure. Thus, they have no link to dose limits or constraints. Ideally, they should be the result of a generic optimization of protection. In practice, this is unrealistically difficult and it is simpler to choose the initial values as a percentile point on the observed distribution of doses to patients. The values should be selected by professional medical bodies and reviewed at intervals that represent a compromise between the necessary stability and the long-term changes in the observed dose distributions.
The selected values will be specific to a country or region.Diagnostic reference levels are not the suggested or ideal dose for a particular procedure or an absolute upper limit for dose. Rather, they represent the dose level at which an investigation of the appropriateness of the dose should be initiated.
In conjunction with an image quality assessment, a qualified medical physicist should work with the radiologist and technologist to determine whether or not the required level of image quality could be attained at lower dose levels. Thus, reference levels act as “trigger levels” to initiate quality improvement. Their primary value is to identify dose levels that may be unnecessarily high – that is, to identify those situations where it may be possible to reduce dose without compromising the required level of image quality. Use of Diagnostic Reference Levels to Reduce Patient DoseThe use of diagnostic reference levels as an important dose optimization tool is endorsed by many professional and regulatory organizations, including the ICRP, American College of Radiology (ACR), American Association of Physicists in Medicine (AAPM), United Kingdom (U.K.) Health Protection Agency, International Atomic Energy Agency (IAEA), and European Commission (EC). Reference levels are typically set at the 75 th percentile of the dose distribution from a survey conducted across a broad user base (i.e., large and small facilities, public and private, hospital and out-patient) using a specified dose measurement protocol and phantom. They are established both regionally and nationally, and considerable variations have been seen across both regions and countries 3.
Oct 14, 2015 - Female patients are also thought to be at higher risk for a given exposure, due in. Although there is no chest CT reference dose evaluation in the ACR. On most scanners from GE Healthcare (Milwaukee, Wis) and Toshiba. Reference Books and Articles on Diagnostic X Ray and CT. Assume that the scan is being performed on a GE CT/i CT scanner, and use your kV and mA(s) values. In determining the effective kV, mAs, and slice thickness, average the actual techniques in a way that will provide an accurate value of energy imparted. The workload per patient for. Reference patient size The use of Automatic Exposure Control may decrease or increase CTDI. Tube current modulation REQUIRES CAREFUL CENTERING OF THE PATIENT IN THE. Changing the image thickness may automatically adjust the Image Quality Reference Parameter. GE Systems – changing image thickness will adjust Reference Noise.
Dose surveys should be repeated periodically to establish new reference levels, which can demonstrate changes in both the mean and standard deviation of the dose distribution.The use of diagnostic reference levels has been shown to reduce the overall dose and the range of doses observed in clinical practice. For example, U.K. National dose surveys demonstrated a 30% decrease in typical radiographic doses from 1984 to 1995 and an average drop of about 50% between 1985 and 2000 4,5.
While improvements in equipment dose efficiency may be reflected in these dose reductions, investigations triggered when a reference dose is exceeded can often determine dose reduction strategies that do not negatively impact the overall quality of the specific diagnostic exam. Thus, data points above the 75 th percentile are, over time, moved below the 75 th percentile – with the net effect of a narrower dose distribution and a lower mean dose. CT Diagnostic Reference Levels From Other CountriesDiagnostic reference levels must be defined in terms of an easily and reproducibly measured dose metric using technique parameters that reflect those used in a site’s clinical practice. In radiographic and fluoroscopic imaging, typically measured quantities are entrance skin dose for radiography and dose area product for fluoroscopy.
Dose can be measured directly with TLD or derived from exposure measurements. Some authors survey typical technique factors and model the dose metric of interest.In CT, published diagnostic reference levels use CTDI-based metrics such as CTDIw, CTDIvol, and DLP. Normalized CTDI values (CTDI per mAs) can be used by multiplying them by typical technique factors, or CTDI values can be measured at the typical clinical technique factors. Tables 1 and 2 below provide a summary of CT reference levels from a variety of national dose surveys. CT Diagnostic Reference Levels From the ACR CT Accreditation ProgramBeginning in 2002, the ACR CT Accreditation Program has required sites undergoing the accreditation process to measure and report CTDIw and CTDIvol for the head and body CTDI phantoms. The typical acquisition parameters for a site's adult head (head), pediatric abdomen (ped), and adult abdomen (body) examinations were used to calculate CTDIw and CTDIvol. For the pediatric exam, sites were instructed to assume the size and weight of a typical 5-year-old child, and doses were measured using the 16-cm phantom.
The average and standard deviation of these doses were calculated by year. Summary data for CTDIvol are shown in Table 3 below.In every case except adult abdomen exams in 2003, both the average dose and the standard deviation fell for each consecutive year. Thus, the establishment of CT reference levels in the United States appears to have helped reduce both the mean dose and the range of doses for these common CT examinations.Although dose reduction was observed for adult head CT examinations, feedback from sites undergoing accreditation indicated that sites were systematically reducing dose to below the 60 mGy level, even though complaints with regard to head image quality at this dose level were common.
The purpose of reference levels is to decrease dose levels only when doing so does not compromise image quality or patient care. Changes in technology (multi-detector-row CT) and practice (3-5 mm image widths) have occurred since the U.K. Dose survey that gave rise to the 60 mGy level for the adult head.As can be seen in Tables 1 and 2, these changes have resulted in an increase in the diagnostic reference level for head CT (U.K. 2003 data now specifies CTDIvol reference levels of 65 mGy for the cerebrum and 100 mGy for the posterior fossa). Thus, the ACR CT Accreditation Program used survey data from the inception of the program to establish the most current U.S. Reference levels for head CT (i.e., 2002 data were used to avoid including dose values that were thought to yield inadequate image quality). Beginning January 1, 2008, the ACR CT reference levels were changed to a CTDIvol of 75 mGy (adult head), 25 mGy (adult abdomen) and 20 mGy (pediatric abdomen) 15.
These values will be reassessed periodically. CT Diagnostic Reference Levels for Other CT ApplicationsBecause the practice of CT encompasses many more exam types than routine head and body exams, reference levels for many common CT examinations are important for continuing dose optimization efforts in CT. To this end, several national surveys have begun to assess a broader range of exam types.
Reference Patient Ge Ct Machine
Additionally, the ACR has begun a project to automatically collect CTDIvol data directly from the DICOM header, thus allowing considerably faster accumulation of data sufficient to establish reference levels for additional exam types. This information will extend the value of the diagnostic reference level concept to the majority of CT applications, enabling individual CT users and the community at large to answer the question, 'What doses are typical and what doses are too much?'
Reference Patient Ge Ct Application
. 3-5 episodes of diarrhea of 5 days duration. Recently treated for C Diff. Concern for Mild C. GDH and Toxin Negative. PCR positive for toxigenic strain. Other stool culture negative.
What to do. Treat for reoccurrence.
No treatment for C. Ncr headquarters new vegas. Diff.Treat with anti-diarrheal. Answer: No treatment for C.
Diff at this time as it is asymptomatic carrier. Likely it is post-infectious GI diarrhea. Note: Do not do PCR if either GDH or Toxin are not positive. Reference: CR 33, 37 of. 37 yr old lady.
Mild/Moderate Disease. 1st occurrence GDH +, Toxin +, PCR NAP1/BI/027 - Negative. What abx to use to decrease reoccurrence. PO Vanc. IV Flagyl. Fidoxamicin. Answer: Fidoxamicin (15% reoccurrence with Fidoxamicin vs 25% for PO Vanc).
Note: Better resolution of diarrhea with C. Diff using PO vanco than Metronidazole even at mild / moderate illness. Reference:. 37 yr old lady.
Mild/Moderate Disease. GDH +, Toxin +, PCR NAP1/BI/027 - Positive. What abx to use to decrease reoccurrence.
PO Vanc. IV Flagyl.
Reference Patient Ge Ct Scan
Fidoxamicin. Answer: PO Vancomycin (15% reoccurrence with Fidaxomicin vs 25% for PO Vanc is seen for non- NAP1/BI/027 strain. Among NAP1/BI/027 strain more reoccurrence with Fidaxomicin. Note: Marked rise in Reoccurance with Flagyl on NAP1/B1/027 strain. Reference. DIFF COLITIS - NAP1/BI/027 or not - Initial episode / 1st or 2nd recurrence - Mild / Moderate / Severe / Severe Complicated - Improving / Worsening - Treatment plan.
Recurrence Rate:. First Recurrence: 25% with Metronidazole, and Vancomycin; 15% with Fidaxomicin. Subsequent recurrence:. 65% following standard therapy with Metronidazole and Vancomycin.
Metronidazole (IV) vs. Vancomycin (PO):. Mild to Moderate CDI treatment response rate: 98% with Vancomycin vs 90% with Metronidazole. Severe CDI treatment response rate: 97% with Vancomycin as 76% with Metronidazole; this is statistically significant. Fidaxomicin (PO):. Initial response rate is 88% vs 86% in Vancomycin.
If risk of reoccurrence is higher then Fidaxomycin is preferred BUT Do not use if NAP1/BI/027 as there is more risk of treatment failure on this strain. Rifaximin (PO):. Probiotics:.
FMT (Fecal Microbiota Transplant):. Phamacokinetics:. PO metronidazole is absorbed rapidly and almost completely, with only 6%–15% of the drug excreted in stool. Fecal concentrations of metronidazole likely reflect its secretion in the colon, and concentrations decrease rapidly after treatment of CDI is initiated: the mean concentration is 9.3 mg/g in watery stools but only 1.2 mg/g in formed stools. Metronidazole is undetectable in the stool of asymptomatic carriers of C. Consequently, there is little rationale for administration of courses of metronidazole longer than 14 days, particularly if diarrhea has resolved. In contrast, vancomycin is poorly absorbed, and fecal concentrations following oral administration (at a dosage of 125 mg 4 times per day) reach very high levels: 64–760 mg/g on day 2 and 152–880 mg/g on day 4.
Doubling the dosage (250 mg 4 times per day) may result in higher fecal concentrations on day 2. Fecal levels of vancomycin are maintained throughout the duration of treatment. Given its poor absorption, orally administered vancomycin is relatively free of systemic toxicity.