SlideShare a Scribd company logo
IMAGING IN LARGE AND OBESE
Dr Syed Arsalan Raza
MBBS, FRCR, FRCPC
Assistant Professor
Dalhousie University
Consultant Radiologist
Nova Scotia Health Authority
Outline
• Obesity facts
• Imaging Obesity
• Imaging in Obese with different modalities
– Problems
– Suggested strategies
OBESITY FACTS
Definitions
Overweight and obesity are defined as abnormal or
excessive fat accumulation that may impair health
Category BMI (kg/m2
)
Very severely underweight less than 15
Severely underweight from 15.0 to 16.0
Underweight from 16.0 to 18.5
Normal (healthy weight) from 18.5 to 25
Overweight from 25 to 30
Obese Class I (Moderately obese) from 30 to 35
Obese Class II (Severely obese) from 35 to 40
Obese Class III (Very severely obese) over 40
Body mass index (BMI)
• Simple index of weight-for-
height that is commonly
used to classify overweight
and obesity in adults
• Defined as a person's
weight in kilograms divided
by the square of his height
in meters (kg/m2)
Definitions
• Lean body mass
– The combination of cell solids, extracellular and intracellular water, and
mineral mass of the body
– Comprised of everything in your body besides body fat
– Also called fat-free body mass
• Calculated lean body mass:
– Lean Body Weight (men) = (1.10 x Weight(kg)) – 128 x ( Weight2/(100 x Height(m))2)
Lean Body Weight (women) = (1.07 x Weight(kg)) – 148 x ( Weight2/(100 x Height(m))2)
– Predict the lean body weight "average" of a group of people with
similar height and weight
• Measured Lean Body Mass: TBW(1–BFP/100)
– BFP is body fat percentage as measured by using a commercially available body fat
monitor
James WPT. Research on obesity. London. Her Majesty’s Stationery Office.
Hume R. Prediction of lean body mass from height and weight. J Clin Path. 1966; 19
Epidemiology
• Worldwide obesity has more than
doubled since 1980.
• According to the 1985 Canadian
Health Promotion Survey, 6.1% of
Canadian adults were found to be
obese
• 18.1% reported from the 2010
Canadian Community Health Survey
(CCHS)
Current and predicted prevalence of obesity in Canada: a
trend analysis. CMAJ Open. 2014 Mar 3;2(1):E18-26.
Current and predicted prevalence of obesity in Canada: a
trend analysis. CMAJ Open. 2014 Mar 3;2(1):E18-26.
Consequences
• Mortality attributed to
obesity from 5.1% in 1985 to
9.3% in 2000
• Indirect cost to healthcare
• Economic burden of obesity
4.6 - 7.1 billion annually
http://www.phac-aspc.gc.ca
Bariatric Surgery
•Impact on radiology
• Preoperative ultrasound
• Postoperative upper GIs
• Complications
• No optimal imaging modality
• Image quality is severely limited
IMAGING OBESITY
Adiposity Distribution
• High volumes of Visceral Adipose Tissue (AT)
– Reduced insulin sensitivity
– Dyslipidemia
– Impaired glucose tolerance
• Clinical methods suboptimal to assess different AT
compartments and distribution of AT within the body
– Waist-height-ratio (WHtR) –index for abdominal obesity
• Better differentiation and volumetric assessment of
AT compartments required
MRI
Diagnostic imaging in obesity
Best Practice & Research Clinical Endocrinology & Metabolism
(2013) 261–277
High amount of SCAT
(subcutaneous adipose
tissue)
Lower VAT (visceral
adipose tissue)
High amount of VAT
(visceral adipose tissue)
Lower SCAT
(subcutaneous adipose
tissue)
Ultrasound
Mesenteric leaves Preperitoneal fat Subcutaneous fat
Mesenteric fat thickness and cardiovascular risk factor.
International Journal of Obesity (2003) 27, 1267–1273
IMAGING IN OBESE
Individual’s diameter and body weight
is more important than total body fat
or BMI from an imaging perspective
Potential Problems
• Ability of patients to fit on existing imaging
equipment
• Ability to acquire and interpret images
adequately
• Increased radiation dose
• Patient positioning (includes access for image-
guided interventional procedures)
• Injury to technologists and transport personnel
• Increased wear and tear on equipment
Scheduling/transportation/throughput
• Knowledge of a patient’s weight and body diameter is important
before scheduling a patient for an imaging examination
• Appropriate transportation resources
– larger beds
– larger wheelchairs
– adequate nursing and transport
Limitations vary with imaging modality
• For CT, MRI and fluoroscopy
–Can the patient fit on the imaging
equipment?
• For ultrasound, plain radiographs and
nuclear medicine
–Attenuation through excessive fat
Habitus-Limited Reports
Modality
Habitus-limited
reports
Ultrasound 2.0%
Chest x-ray 0.5%
Abdominal CT 0.4%
Abdominal x-ray 0.25%
Chest CT 0.25%
MRI 0.1%
Radiology 2006;240(2): 435–439
ULTRASOUND
Problems
Thickness of
subcutaneous fat
and the sound-
attenuating
properties of fat
present
challenges
Solutions
• “Penetrate” mode
• Tissue harmonic imaging
• Compound imaging
• Speckle reduction filters
Obstetric scans
• Use all available technical tools improving image
quality in obesity
• Consider approaching fetus through the four major
abdominal areas with least subcutaneous fat:
– Periumbilical area
– Suprapubic area
– Right and left iliac fossae
• Transvaginal approach for CNS in fetus with vertex
presentation
• Color Doppler to check cardiac inflows and outflows
• Report limitations
Ultrasound in Obs & Gyne.
Volume 33, Issue 6, pages 720–729, June 2009
Tissue Harmonic Imaging
Ultrasound in Obs & Gyne.
Volume 33, Issue 6, pages 720–729, June 2009
WITH WITHOUT
Color Doppler in Cardiac Assessment
D. Paladini. Ultrasound in Obs & Gyne.
Volume 33, Issue 6, pages 720–729, June 2009
Abdominal Scans
• Modified lateral decubitus position displaces
the fatty panniculus and aids scanning
through the flank.
• Aorta and kidney with coronal or posterior
oblique approach
RADIOGRAPHY
Problems
Problems
• Increased patient thickness leads to increased
photon scatter and reduced contrast
resolution
• Higher peak tube voltage to penetrate excess
tissue reduces image contrast
• Increased exposure time increases the
probability of motion artifact
Solutions
• Tight collimation of the beam to the
region of interest
–Reduces the FOV
–Reduces scatter
Solutions
• Use a grid
– Typically, 85%–95% of scatter photons are
absorbed, in comparison with 40%–50% of
primary photons
– An antiscatter grid with a high grid ratio (8:1 or
10:1) can dramatically reduce scatter and greatly
improve image quality
Solutions
• Use of a grid
Bariatrics Today 2005; 1:31–33
Solutions
• Increasing kVp
• Increasing mAs
• Multiple films to cover the area of interest
(i.e., Segmental/Quadrantic approach)
• Cassette mapping
Abdom Imaging (2013) 38:630–646
High Radiation Dose
• Effective doses from radiographic
examinations in the extremely obese can
exceed 100 mSv from only a small number of
abdominal examinations
• Positioning the patient so that the thinnest fat
layer (anterior or posterior) is closest to the
image receptor – Substantial dose reduction
• Increasing the tube voltage also reduces the
dose.
Radiology: Volume 252: Number 1—July 2009
FLOUROSCOPY
Problems
• Table weight capacity
• Width of the opening (table to image tower)
• Table width
• X-ray tube capacity
Table weight limit
• Approximately 350 lbs
– 300 to 400 pounds with full table movement
capabilities
– 350 to 550 pounds with a static table (no horizontal or
vertical table movement)
• Newer machines – better profile (our
Multipurpose Room machine: 440 lbs vs old
machine: 330 lbs)
• May be possible to perform the study with the
patient in the upright position only
Width of opening and Table width
• The distance from the table top to the digital
image tower
– Standard fluoroscopic equipment: maximum
distance of 45–49 cm
– Newer systems: 76 cm
• Table width
– Standard: 45 cm wide (range 69–80 cm)
– Newer systems: 56 cm (88 cm with extender)
X-ray Tube Capacity
• Greater tube capacity will allow for multiple
exposures without tube overload and
decreased delay between exposures
Additional Problems
• Suboptimal exposures
– Difficult penetration
– Long-exposure time
– Blurry images
• Small fluoroscopic coverage area may limit
fluoroscopic evaluation
– Use overhead images for diagnosis
Overhead Images
COMPUTED TOMOGRAPHY
Challenges in Large Patients
• Table weight limit
• Gantry and FOV
• Image Quality
Table weight limit
• Limitations related to the table motor
• Motor must be able to move the table into the
gantry at a consistent speed to an accuracy of
0.25 mm
• Table weight limit: 450 – 500 lbs
Gantry and FOV
Standard gantry diameter: 130 cm
• More clinically relevant measurement is the vertical diameter with the
table in the gantry: 55 cm
Table width: 68 cm
FoV: Standard 50 cm
• Large-bore CT scanners have an extended field of view up to 82 cm
Part of body
outside the
scan FOV;
may yield
artifacts
Image Quality
Image Quality
Low noise High noise
- Image quality degraded when photons/voxel 
- X-ray beam attenuated by thick layer of
subcutaneous fat: decreased penetrating
capacity of x-ray beam
Optimized CT Protocol
Objective:
• Deliver higher x-ray flux
• More photons / voxel
• Improved contrast-to-noise ratio
Strategy 1:
–  KVP
–  tube current (mA); ‘‘Fixed mAs’’ to ‘‘Automatic mAs’
Strategy 2:
–  slice thickness (mm)
• Thicker collimation or thicker slices reconstruction
Strategy 3:
–  table speed:
•  beam pitch (mm/rotation)
•  gantry rotation time (seconds)
Strategy 4: Combination
CT parameters and Obesity
Automatic tube current modulation
Uppot et al. AJR 2007;188(2):437
xyz-axis modulation according to patient-specific attenuation
High-output X-ray tubes are capable of producing peak tube currents up
to 800 mA to maintain constant image quality over a wide range of patient
Automatic tube current modulation
Automatic tube current modulation
Automatic tube current modulation yields a significant
increase in effective dose in large patients
Inference
• Using the same operator-selected image quality
settings for all-sized patients may results in very
high radiation doses to large patients
• The operator-selected image quality settings (e.g.,
image noise, reference mAs) of automatic tube
current modulation have to be adjusted to large
patients
Manual Modification of CT Protocol
Image quality of abdominal-pelvic CT in large patients can be
improved by manually modifying the protocol without
substantially increasing the radiation dose to deep organs.
Modified anthropomorphic phantom with one or two
circumferential layers of fat equivalent material (- 80 HU)
4 cm
8 cm
Acad Radiol 2007; 14(4):486-94
8 cm of s/c fat
4 cm of s/c fat
CT scanning protocol
At 8 cm of subcutaneous fat thickness, the radiation dose
to the liver using the modified protocol B is actually
decreased as compared to standard protocol A at 0 cm of
subcutaneous fat thickness.
Radiation dose to the liver
0
5
10
15
20
25
C/N
RATIO
4 cm 8 cm
Protocol A
Protocol B
Contrast to Noise Ratio
At 4 cm fat thickness, optimized protocol B increased CNR by 86%
At 8 cm fat thickness, optimized protocol B increased CNR by 137 %
Fat thickness
Modified High Flux Protocol
The modified, high flux CT protocol for obese patients yields
decreased image noise (40% ↓) and increased CNR (76% ↑).
Schindera et al. RSNA 2006
Modified High Flux Protocol
The modified, high flux CT protocol for obese patients
yields increased overall diagnostic acceptancy
High Flux
Regular Flux
Inference
• The abdominopelvic CT protocol manually adjusted
for simulated obese patient:
1. Increased mAs
2. Increased section collimation
3. Diminished table speed
• The manually adjusted abdominal-pelvic CT protocol
yields improved image quality in the simulated
obese patient without increasing the radiation dose
to the abdominal organs
Linear model may overestimate the amount of
contrast material needed in larger patient
– Metabolically inactive body fat does not disperse
or dilute IV contrast
Contrast administration during MDCT
Contrast optimization
Patient’s weight-tailored contrast dose
2.0-2.5 mL/kg of IV contrast material produced
better results than 1.5 mL/kg or a fixed dose
Yamashita et al. Radiology. 2000;216(3):718-723
Contrast optimization
Lean Body Weight (LBW) for calculating the
Iodine concenteration
– More precise and consistent hepatic and vascular
enhancement
– Reduced patient-to-patient variability
Ho et al. Radiology. 2007, 243:431-437
Kondo et al. Radiology. 2008;249(3):872-877
Summed Enhancement Data for Liver, Portal Vein, Aorta
The measured lean body weight is least variable.
Ho et al. Radiology. 2007, 243:431-437
Contrast optimization
Kondo et al. Radiology. 2008;249(3):872-877
No significant correlation between adjusted MHE and BW
positive correlation between adjusted MHE with BMI and BFP
Contrast optimization
CT optimization – Summary
• Optimizing abdominal CT protocols by:
– Increased mAs
– Increasing slice thickness
– Slowing table speed
Result in:
– Decreased image noise
– Increased CNR
– Similar or lower organ dose
CT optimization – Summary
• Automatic tube current modulation for
abdominal CT can result in very high radiation
doses in large patients
– The quality settings for automatic tube current
modulation have to be adjusted in large patients
• Contrast media dose & rate adjusted based on
lean body weight rather than total body
weight in large patients may deliver better
enhancement
Questions or Comments
Thank you

More Related Content

Similar to Imging in Large and Obese Final.pptx

radiation therapy in ca breast
radiation therapy in ca breast   radiation therapy in ca breast
radiation therapy in ca breast
Isha Jaiswal
 
Redustim - metabolic syndrom
Redustim - metabolic syndromRedustim - metabolic syndrom
Redustim - metabolic syndrom
COSMOSOFT SAS
 
Cervix External Beam Radiotherapy techniques
Cervix External Beam Radiotherapy techniquesCervix External Beam Radiotherapy techniques
Cervix External Beam Radiotherapy techniques
Animesh Agrawal
 
image guided brachytherapy carcinoma cervix
image guided brachytherapy carcinoma cerviximage guided brachytherapy carcinoma cervix
image guided brachytherapy carcinoma cervix
Isha Jaiswal
 
Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018
Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018
Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018
JFIM - Journées Francophones d'Imagerie Médicale
 
Weight loss surgery safe & effective
Weight loss surgery   safe & effectiveWeight loss surgery   safe & effective
Weight loss surgery safe & effective
foregutsurgeon
 
Locally advanced breast cancer
Locally advanced breast cancerLocally advanced breast cancer
Locally advanced breast cancer
Shambhavi Sharma
 
Prostate presentation
Prostate presentationProstate presentation
Prostate presentation
Matthew Buck
 
Optimization of ct scan protocol in acute abdomen 2003 revised aa
Optimization of ct scan protocol in acute abdomen 2003 revised aaOptimization of ct scan protocol in acute abdomen 2003 revised aa
Optimization of ct scan protocol in acute abdomen 2003 revised aa
Hisham Khatib
 
Ca cervix talk
Ca cervix talkCa cervix talk
Ca cervix talk
Geetika Chahal
 
Radiation therapy gopaul
Radiation therapy gopaulRadiation therapy gopaul
Radiation therapy gopaul
Jamal Malou
 
Ovary 1
Ovary 1Ovary 1
Ovary 1
vrinda singla
 
Breast cancer
Breast cancerBreast cancer
Breast cancer
Nidhil Narayanan
 
Slg bmi 30 35
Slg bmi 30 35Slg bmi 30 35
Slg bmi 30 35
Ruth Escobar
 
Management of hcc sneha
Management of hcc snehaManagement of hcc sneha
Management of hcc sneha
Sneha George
 
Obesity & Surgery
Obesity & SurgeryObesity & Surgery
Obesity & Surgery
Dr. Ibifunke Pegba-Otemolu
 
HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...
HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...
HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...
surimallasrinivasgan
 
Breast cancer webinar LIVE ON YOUTUBE
Breast cancer webinar LIVE ON YOUTUBEBreast cancer webinar LIVE ON YOUTUBE
Breast cancer webinar LIVE ON YOUTUBE
Renu Kori
 
Innovations in Pancreatic Cancer: A Reason to Hope
Innovations in Pancreatic Cancer: A Reason to HopeInnovations in Pancreatic Cancer: A Reason to Hope
Innovations in Pancreatic Cancer: A Reason to Hope
Christopher Kanski
 
New ca stomach mx sneha
New ca stomach mx snehaNew ca stomach mx sneha
New ca stomach mx sneha
Sneha George
 

Similar to Imging in Large and Obese Final.pptx (20)

radiation therapy in ca breast
radiation therapy in ca breast   radiation therapy in ca breast
radiation therapy in ca breast
 
Redustim - metabolic syndrom
Redustim - metabolic syndromRedustim - metabolic syndrom
Redustim - metabolic syndrom
 
Cervix External Beam Radiotherapy techniques
Cervix External Beam Radiotherapy techniquesCervix External Beam Radiotherapy techniques
Cervix External Beam Radiotherapy techniques
 
image guided brachytherapy carcinoma cervix
image guided brachytherapy carcinoma cerviximage guided brachytherapy carcinoma cervix
image guided brachytherapy carcinoma cervix
 
Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018
Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018
Luc Rotenberg mri and management of cervix malignancies jfim ifupi milan 2018
 
Weight loss surgery safe & effective
Weight loss surgery   safe & effectiveWeight loss surgery   safe & effective
Weight loss surgery safe & effective
 
Locally advanced breast cancer
Locally advanced breast cancerLocally advanced breast cancer
Locally advanced breast cancer
 
Prostate presentation
Prostate presentationProstate presentation
Prostate presentation
 
Optimization of ct scan protocol in acute abdomen 2003 revised aa
Optimization of ct scan protocol in acute abdomen 2003 revised aaOptimization of ct scan protocol in acute abdomen 2003 revised aa
Optimization of ct scan protocol in acute abdomen 2003 revised aa
 
Ca cervix talk
Ca cervix talkCa cervix talk
Ca cervix talk
 
Radiation therapy gopaul
Radiation therapy gopaulRadiation therapy gopaul
Radiation therapy gopaul
 
Ovary 1
Ovary 1Ovary 1
Ovary 1
 
Breast cancer
Breast cancerBreast cancer
Breast cancer
 
Slg bmi 30 35
Slg bmi 30 35Slg bmi 30 35
Slg bmi 30 35
 
Management of hcc sneha
Management of hcc snehaManagement of hcc sneha
Management of hcc sneha
 
Obesity & Surgery
Obesity & SurgeryObesity & Surgery
Obesity & Surgery
 
HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...
HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...
HEMANTH ADJUVANT This is adjuvant therapy utilised for education purpose(1) (...
 
Breast cancer webinar LIVE ON YOUTUBE
Breast cancer webinar LIVE ON YOUTUBEBreast cancer webinar LIVE ON YOUTUBE
Breast cancer webinar LIVE ON YOUTUBE
 
Innovations in Pancreatic Cancer: A Reason to Hope
Innovations in Pancreatic Cancer: A Reason to HopeInnovations in Pancreatic Cancer: A Reason to Hope
Innovations in Pancreatic Cancer: A Reason to Hope
 
New ca stomach mx sneha
New ca stomach mx snehaNew ca stomach mx sneha
New ca stomach mx sneha
 

Recently uploaded

The Electrocardiogram - Physiologic Principles
The Electrocardiogram - Physiologic PrinciplesThe Electrocardiogram - Physiologic Principles
The Electrocardiogram - Physiologic Principles
MedicoseAcademics
 
Hemodialysis: Chapter 4, Dialysate Circuit - Dr.Gawad
Hemodialysis: Chapter 4, Dialysate Circuit - Dr.GawadHemodialysis: Chapter 4, Dialysate Circuit - Dr.Gawad
Hemodialysis: Chapter 4, Dialysate Circuit - Dr.Gawad
NephroTube - Dr.Gawad
 
Cell Therapy Expansion and Challenges in Autoimmune Disease
Cell Therapy Expansion and Challenges in Autoimmune DiseaseCell Therapy Expansion and Challenges in Autoimmune Disease
Cell Therapy Expansion and Challenges in Autoimmune Disease
Health Advances
 
Integrating Ayurveda into Parkinson’s Management: A Holistic Approach
Integrating Ayurveda into Parkinson’s Management: A Holistic ApproachIntegrating Ayurveda into Parkinson’s Management: A Holistic Approach
Integrating Ayurveda into Parkinson’s Management: A Holistic Approach
Ayurveda ForAll
 
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx
Holistified Wellness
 
CHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdf
CHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdfCHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdf
CHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdf
rishi2789
 
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...
Oleg Kshivets
 
Vestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptx
Vestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptxVestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptx
Vestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptx
Dr. Rabia Inam Gandapore
 
LOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loop
LOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loopLOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loop
LOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loop
debosmitaasanyal1
 
Adhd Medication Shortage Uk - trinexpharmacy.com
Adhd Medication Shortage Uk - trinexpharmacy.comAdhd Medication Shortage Uk - trinexpharmacy.com
Adhd Medication Shortage Uk - trinexpharmacy.com
reignlana06
 
Diabetic nephropathy diagnosis treatment
Diabetic nephropathy diagnosis treatmentDiabetic nephropathy diagnosis treatment
Diabetic nephropathy diagnosis treatment
arahmanzai5
 
Top-Vitamin-Supplement-Brands-in-India List
Top-Vitamin-Supplement-Brands-in-India ListTop-Vitamin-Supplement-Brands-in-India List
Top-Vitamin-Supplement-Brands-in-India List
SwisschemDerma
 
Muscles of Mastication by Dr. Rabia Inam Gandapore.pptx
Muscles of Mastication by Dr. Rabia Inam Gandapore.pptxMuscles of Mastication by Dr. Rabia Inam Gandapore.pptx
Muscles of Mastication by Dr. Rabia Inam Gandapore.pptx
Dr. Rabia Inam Gandapore
 
K CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấu
K CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấuK CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấu
K CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấu
HongBiThi1
 
Histopathology of Rheumatoid Arthritis: Visual treat
Histopathology of Rheumatoid Arthritis: Visual treatHistopathology of Rheumatoid Arthritis: Visual treat
Histopathology of Rheumatoid Arthritis: Visual treat
DIVYANSHU740006
 
Tests for analysis of different pharmaceutical.pptx
Tests for analysis of different pharmaceutical.pptxTests for analysis of different pharmaceutical.pptx
Tests for analysis of different pharmaceutical.pptx
taiba qazi
 
OCT Training Course for clinical practice Part 1
OCT Training Course for clinical practice Part 1OCT Training Course for clinical practice Part 1
OCT Training Course for clinical practice Part 1
KafrELShiekh University
 
Part II - Body Grief: Losing parts of ourselves and our identity before, duri...
Part II - Body Grief: Losing parts of ourselves and our identity before, duri...Part II - Body Grief: Losing parts of ourselves and our identity before, duri...
Part II - Body Grief: Losing parts of ourselves and our identity before, duri...
bkling
 
Journal Article Review on Rasamanikya
Journal Article Review on RasamanikyaJournal Article Review on Rasamanikya
Journal Article Review on Rasamanikya
Dr. Jyothirmai Paindla
 
The Nervous and Chemical Regulation of Respiration
The Nervous and Chemical Regulation of RespirationThe Nervous and Chemical Regulation of Respiration
The Nervous and Chemical Regulation of Respiration
MedicoseAcademics
 

Recently uploaded (20)

The Electrocardiogram - Physiologic Principles
The Electrocardiogram - Physiologic PrinciplesThe Electrocardiogram - Physiologic Principles
The Electrocardiogram - Physiologic Principles
 
Hemodialysis: Chapter 4, Dialysate Circuit - Dr.Gawad
Hemodialysis: Chapter 4, Dialysate Circuit - Dr.GawadHemodialysis: Chapter 4, Dialysate Circuit - Dr.Gawad
Hemodialysis: Chapter 4, Dialysate Circuit - Dr.Gawad
 
Cell Therapy Expansion and Challenges in Autoimmune Disease
Cell Therapy Expansion and Challenges in Autoimmune DiseaseCell Therapy Expansion and Challenges in Autoimmune Disease
Cell Therapy Expansion and Challenges in Autoimmune Disease
 
Integrating Ayurveda into Parkinson’s Management: A Holistic Approach
Integrating Ayurveda into Parkinson’s Management: A Holistic ApproachIntegrating Ayurveda into Parkinson’s Management: A Holistic Approach
Integrating Ayurveda into Parkinson’s Management: A Holistic Approach
 
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptx
 
CHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdf
CHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdfCHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdf
CHEMOTHERAPY_RDP_CHAPTER 1_ANTI TB DRUGS.pdf
 
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...
 
Vestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptx
Vestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptxVestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptx
Vestibulocochlear Nerve by Dr. Rabia Inam Gandapore.pptx
 
LOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loop
LOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loopLOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loop
LOOPS in orthodontics t loop bull loop vertical loop mushroom loop stop loop
 
Adhd Medication Shortage Uk - trinexpharmacy.com
Adhd Medication Shortage Uk - trinexpharmacy.comAdhd Medication Shortage Uk - trinexpharmacy.com
Adhd Medication Shortage Uk - trinexpharmacy.com
 
Diabetic nephropathy diagnosis treatment
Diabetic nephropathy diagnosis treatmentDiabetic nephropathy diagnosis treatment
Diabetic nephropathy diagnosis treatment
 
Top-Vitamin-Supplement-Brands-in-India List
Top-Vitamin-Supplement-Brands-in-India ListTop-Vitamin-Supplement-Brands-in-India List
Top-Vitamin-Supplement-Brands-in-India List
 
Muscles of Mastication by Dr. Rabia Inam Gandapore.pptx
Muscles of Mastication by Dr. Rabia Inam Gandapore.pptxMuscles of Mastication by Dr. Rabia Inam Gandapore.pptx
Muscles of Mastication by Dr. Rabia Inam Gandapore.pptx
 
K CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấu
K CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấuK CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấu
K CỔ TỬ CUNG.pdf tự ghi chép, chữ hơi xấu
 
Histopathology of Rheumatoid Arthritis: Visual treat
Histopathology of Rheumatoid Arthritis: Visual treatHistopathology of Rheumatoid Arthritis: Visual treat
Histopathology of Rheumatoid Arthritis: Visual treat
 
Tests for analysis of different pharmaceutical.pptx
Tests for analysis of different pharmaceutical.pptxTests for analysis of different pharmaceutical.pptx
Tests for analysis of different pharmaceutical.pptx
 
OCT Training Course for clinical practice Part 1
OCT Training Course for clinical practice Part 1OCT Training Course for clinical practice Part 1
OCT Training Course for clinical practice Part 1
 
Part II - Body Grief: Losing parts of ourselves and our identity before, duri...
Part II - Body Grief: Losing parts of ourselves and our identity before, duri...Part II - Body Grief: Losing parts of ourselves and our identity before, duri...
Part II - Body Grief: Losing parts of ourselves and our identity before, duri...
 
Journal Article Review on Rasamanikya
Journal Article Review on RasamanikyaJournal Article Review on Rasamanikya
Journal Article Review on Rasamanikya
 
The Nervous and Chemical Regulation of Respiration
The Nervous and Chemical Regulation of RespirationThe Nervous and Chemical Regulation of Respiration
The Nervous and Chemical Regulation of Respiration
 

Imging in Large and Obese Final.pptx

  • 1. IMAGING IN LARGE AND OBESE Dr Syed Arsalan Raza MBBS, FRCR, FRCPC Assistant Professor Dalhousie University Consultant Radiologist Nova Scotia Health Authority
  • 2. Outline • Obesity facts • Imaging Obesity • Imaging in Obese with different modalities – Problems – Suggested strategies
  • 4. Definitions Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health Category BMI (kg/m2 ) Very severely underweight less than 15 Severely underweight from 15.0 to 16.0 Underweight from 16.0 to 18.5 Normal (healthy weight) from 18.5 to 25 Overweight from 25 to 30 Obese Class I (Moderately obese) from 30 to 35 Obese Class II (Severely obese) from 35 to 40 Obese Class III (Very severely obese) over 40 Body mass index (BMI) • Simple index of weight-for- height that is commonly used to classify overweight and obesity in adults • Defined as a person's weight in kilograms divided by the square of his height in meters (kg/m2)
  • 5. Definitions • Lean body mass – The combination of cell solids, extracellular and intracellular water, and mineral mass of the body – Comprised of everything in your body besides body fat – Also called fat-free body mass • Calculated lean body mass: – Lean Body Weight (men) = (1.10 x Weight(kg)) – 128 x ( Weight2/(100 x Height(m))2) Lean Body Weight (women) = (1.07 x Weight(kg)) – 148 x ( Weight2/(100 x Height(m))2) – Predict the lean body weight "average" of a group of people with similar height and weight • Measured Lean Body Mass: TBW(1–BFP/100) – BFP is body fat percentage as measured by using a commercially available body fat monitor James WPT. Research on obesity. London. Her Majesty’s Stationery Office. Hume R. Prediction of lean body mass from height and weight. J Clin Path. 1966; 19
  • 6. Epidemiology • Worldwide obesity has more than doubled since 1980. • According to the 1985 Canadian Health Promotion Survey, 6.1% of Canadian adults were found to be obese • 18.1% reported from the 2010 Canadian Community Health Survey (CCHS) Current and predicted prevalence of obesity in Canada: a trend analysis. CMAJ Open. 2014 Mar 3;2(1):E18-26.
  • 7. Current and predicted prevalence of obesity in Canada: a trend analysis. CMAJ Open. 2014 Mar 3;2(1):E18-26.
  • 8. Consequences • Mortality attributed to obesity from 5.1% in 1985 to 9.3% in 2000 • Indirect cost to healthcare • Economic burden of obesity 4.6 - 7.1 billion annually http://www.phac-aspc.gc.ca
  • 9. Bariatric Surgery •Impact on radiology • Preoperative ultrasound • Postoperative upper GIs • Complications • No optimal imaging modality • Image quality is severely limited
  • 11. Adiposity Distribution • High volumes of Visceral Adipose Tissue (AT) – Reduced insulin sensitivity – Dyslipidemia – Impaired glucose tolerance • Clinical methods suboptimal to assess different AT compartments and distribution of AT within the body – Waist-height-ratio (WHtR) –index for abdominal obesity • Better differentiation and volumetric assessment of AT compartments required
  • 12. MRI Diagnostic imaging in obesity Best Practice & Research Clinical Endocrinology & Metabolism (2013) 261–277 High amount of SCAT (subcutaneous adipose tissue) Lower VAT (visceral adipose tissue) High amount of VAT (visceral adipose tissue) Lower SCAT (subcutaneous adipose tissue)
  • 13. Ultrasound Mesenteric leaves Preperitoneal fat Subcutaneous fat Mesenteric fat thickness and cardiovascular risk factor. International Journal of Obesity (2003) 27, 1267–1273
  • 15. Individual’s diameter and body weight is more important than total body fat or BMI from an imaging perspective
  • 16. Potential Problems • Ability of patients to fit on existing imaging equipment • Ability to acquire and interpret images adequately • Increased radiation dose • Patient positioning (includes access for image- guided interventional procedures) • Injury to technologists and transport personnel • Increased wear and tear on equipment
  • 17. Scheduling/transportation/throughput • Knowledge of a patient’s weight and body diameter is important before scheduling a patient for an imaging examination • Appropriate transportation resources – larger beds – larger wheelchairs – adequate nursing and transport
  • 18. Limitations vary with imaging modality • For CT, MRI and fluoroscopy –Can the patient fit on the imaging equipment? • For ultrasound, plain radiographs and nuclear medicine –Attenuation through excessive fat
  • 19. Habitus-Limited Reports Modality Habitus-limited reports Ultrasound 2.0% Chest x-ray 0.5% Abdominal CT 0.4% Abdominal x-ray 0.25% Chest CT 0.25% MRI 0.1% Radiology 2006;240(2): 435–439
  • 21. Problems Thickness of subcutaneous fat and the sound- attenuating properties of fat present challenges
  • 22. Solutions • “Penetrate” mode • Tissue harmonic imaging • Compound imaging • Speckle reduction filters
  • 23. Obstetric scans • Use all available technical tools improving image quality in obesity • Consider approaching fetus through the four major abdominal areas with least subcutaneous fat: – Periumbilical area – Suprapubic area – Right and left iliac fossae • Transvaginal approach for CNS in fetus with vertex presentation • Color Doppler to check cardiac inflows and outflows • Report limitations Ultrasound in Obs & Gyne. Volume 33, Issue 6, pages 720–729, June 2009
  • 24. Tissue Harmonic Imaging Ultrasound in Obs & Gyne. Volume 33, Issue 6, pages 720–729, June 2009 WITH WITHOUT
  • 25. Color Doppler in Cardiac Assessment D. Paladini. Ultrasound in Obs & Gyne. Volume 33, Issue 6, pages 720–729, June 2009
  • 26. Abdominal Scans • Modified lateral decubitus position displaces the fatty panniculus and aids scanning through the flank. • Aorta and kidney with coronal or posterior oblique approach
  • 29. Problems • Increased patient thickness leads to increased photon scatter and reduced contrast resolution • Higher peak tube voltage to penetrate excess tissue reduces image contrast • Increased exposure time increases the probability of motion artifact
  • 30. Solutions • Tight collimation of the beam to the region of interest –Reduces the FOV –Reduces scatter
  • 31. Solutions • Use a grid – Typically, 85%–95% of scatter photons are absorbed, in comparison with 40%–50% of primary photons – An antiscatter grid with a high grid ratio (8:1 or 10:1) can dramatically reduce scatter and greatly improve image quality
  • 32. Solutions • Use of a grid Bariatrics Today 2005; 1:31–33
  • 33. Solutions • Increasing kVp • Increasing mAs • Multiple films to cover the area of interest (i.e., Segmental/Quadrantic approach) • Cassette mapping
  • 34. Abdom Imaging (2013) 38:630–646
  • 35. High Radiation Dose • Effective doses from radiographic examinations in the extremely obese can exceed 100 mSv from only a small number of abdominal examinations • Positioning the patient so that the thinnest fat layer (anterior or posterior) is closest to the image receptor – Substantial dose reduction • Increasing the tube voltage also reduces the dose. Radiology: Volume 252: Number 1—July 2009
  • 37. Problems • Table weight capacity • Width of the opening (table to image tower) • Table width • X-ray tube capacity
  • 38. Table weight limit • Approximately 350 lbs – 300 to 400 pounds with full table movement capabilities – 350 to 550 pounds with a static table (no horizontal or vertical table movement) • Newer machines – better profile (our Multipurpose Room machine: 440 lbs vs old machine: 330 lbs) • May be possible to perform the study with the patient in the upright position only
  • 39. Width of opening and Table width • The distance from the table top to the digital image tower – Standard fluoroscopic equipment: maximum distance of 45–49 cm – Newer systems: 76 cm • Table width – Standard: 45 cm wide (range 69–80 cm) – Newer systems: 56 cm (88 cm with extender)
  • 40. X-ray Tube Capacity • Greater tube capacity will allow for multiple exposures without tube overload and decreased delay between exposures
  • 41. Additional Problems • Suboptimal exposures – Difficult penetration – Long-exposure time – Blurry images • Small fluoroscopic coverage area may limit fluoroscopic evaluation – Use overhead images for diagnosis
  • 44. Challenges in Large Patients • Table weight limit • Gantry and FOV • Image Quality
  • 45. Table weight limit • Limitations related to the table motor • Motor must be able to move the table into the gantry at a consistent speed to an accuracy of 0.25 mm • Table weight limit: 450 – 500 lbs
  • 46. Gantry and FOV Standard gantry diameter: 130 cm • More clinically relevant measurement is the vertical diameter with the table in the gantry: 55 cm Table width: 68 cm FoV: Standard 50 cm • Large-bore CT scanners have an extended field of view up to 82 cm Part of body outside the scan FOV; may yield artifacts
  • 48. Image Quality Low noise High noise - Image quality degraded when photons/voxel  - X-ray beam attenuated by thick layer of subcutaneous fat: decreased penetrating capacity of x-ray beam
  • 49. Optimized CT Protocol Objective: • Deliver higher x-ray flux • More photons / voxel • Improved contrast-to-noise ratio
  • 50. Strategy 1: –  KVP –  tube current (mA); ‘‘Fixed mAs’’ to ‘‘Automatic mAs’ Strategy 2: –  slice thickness (mm) • Thicker collimation or thicker slices reconstruction Strategy 3: –  table speed: •  beam pitch (mm/rotation) •  gantry rotation time (seconds) Strategy 4: Combination CT parameters and Obesity
  • 51. Automatic tube current modulation Uppot et al. AJR 2007;188(2):437 xyz-axis modulation according to patient-specific attenuation High-output X-ray tubes are capable of producing peak tube currents up to 800 mA to maintain constant image quality over a wide range of patient
  • 53. Automatic tube current modulation Automatic tube current modulation yields a significant increase in effective dose in large patients
  • 54. Inference • Using the same operator-selected image quality settings for all-sized patients may results in very high radiation doses to large patients • The operator-selected image quality settings (e.g., image noise, reference mAs) of automatic tube current modulation have to be adjusted to large patients
  • 55. Manual Modification of CT Protocol Image quality of abdominal-pelvic CT in large patients can be improved by manually modifying the protocol without substantially increasing the radiation dose to deep organs.
  • 56. Modified anthropomorphic phantom with one or two circumferential layers of fat equivalent material (- 80 HU) 4 cm 8 cm Acad Radiol 2007; 14(4):486-94 8 cm of s/c fat 4 cm of s/c fat
  • 58. At 8 cm of subcutaneous fat thickness, the radiation dose to the liver using the modified protocol B is actually decreased as compared to standard protocol A at 0 cm of subcutaneous fat thickness. Radiation dose to the liver
  • 59. 0 5 10 15 20 25 C/N RATIO 4 cm 8 cm Protocol A Protocol B Contrast to Noise Ratio At 4 cm fat thickness, optimized protocol B increased CNR by 86% At 8 cm fat thickness, optimized protocol B increased CNR by 137 % Fat thickness
  • 60. Modified High Flux Protocol The modified, high flux CT protocol for obese patients yields decreased image noise (40% ↓) and increased CNR (76% ↑). Schindera et al. RSNA 2006
  • 61. Modified High Flux Protocol The modified, high flux CT protocol for obese patients yields increased overall diagnostic acceptancy High Flux Regular Flux
  • 62. Inference • The abdominopelvic CT protocol manually adjusted for simulated obese patient: 1. Increased mAs 2. Increased section collimation 3. Diminished table speed • The manually adjusted abdominal-pelvic CT protocol yields improved image quality in the simulated obese patient without increasing the radiation dose to the abdominal organs
  • 63. Linear model may overestimate the amount of contrast material needed in larger patient – Metabolically inactive body fat does not disperse or dilute IV contrast Contrast administration during MDCT
  • 64. Contrast optimization Patient’s weight-tailored contrast dose 2.0-2.5 mL/kg of IV contrast material produced better results than 1.5 mL/kg or a fixed dose Yamashita et al. Radiology. 2000;216(3):718-723
  • 65. Contrast optimization Lean Body Weight (LBW) for calculating the Iodine concenteration – More precise and consistent hepatic and vascular enhancement – Reduced patient-to-patient variability Ho et al. Radiology. 2007, 243:431-437 Kondo et al. Radiology. 2008;249(3):872-877
  • 66. Summed Enhancement Data for Liver, Portal Vein, Aorta The measured lean body weight is least variable. Ho et al. Radiology. 2007, 243:431-437 Contrast optimization
  • 67. Kondo et al. Radiology. 2008;249(3):872-877 No significant correlation between adjusted MHE and BW positive correlation between adjusted MHE with BMI and BFP Contrast optimization
  • 68. CT optimization – Summary • Optimizing abdominal CT protocols by: – Increased mAs – Increasing slice thickness – Slowing table speed Result in: – Decreased image noise – Increased CNR – Similar or lower organ dose
  • 69. CT optimization – Summary • Automatic tube current modulation for abdominal CT can result in very high radiation doses in large patients – The quality settings for automatic tube current modulation have to be adjusted in large patients • Contrast media dose & rate adjusted based on lean body weight rather than total body weight in large patients may deliver better enhancement