prof. dr. lothar schad - heidelberg university€¦ · • follow-up of osteoporosis management of:...

$: Prof. Dr. Lothar Schad - Heidelberg University€¦ · • follow-up of osteoporosis management of: • metabolic bone diseases • fractures in aging patients Osteoporosis: Bone$
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RUPRECHT-KARLS-UNIVERSITY HEIDELBERG

Computer Assisted Clinical MedicineProf. Dr. Lothar Schad

12/9/2008 | Page 1Master‘s Program in Medical Physics

Chair in Computer Assisted Clinical MedicineFaculty of Medicine Mannheim University of HeidelbergTheodor-Kutzer-Ufer 1-3D-68167 Mannheim, GermanyLothar.Schad@MedMa.Uni-Heidelberg.dewww.ma.uni-heidelberg.de/inst/cbtm/ckm/

Physics of Imaging Systems

Basic Principles of Computer Tomography (CT) III

Prof. Dr. Lothar Schad



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Applications

Applications

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- high black/white contrast

Bones and Lung



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130 kV, 150 mA, 0.8 s5 mm, Pitch 1.5, 50% overlap

Superior Vena Cava Thrombosis

- Siemens Emotion

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4 - phase spiral studyexcellent enhancement

• precontrast

• arterial

• portal-venous

• delayed phase

• 8 mm, Pitch 1.5

• 130 kV, 120 mA, 1.5 s

• 120 ml / flow rate 3 ml/s

Liver Hemangioma Study

- Siemens Esprit



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Siemens Emotion: sagittal reformat Siemens Volume Access: VRT

Ankle Joint: 1 mm Spiral CT

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• low dose of 100 mAs

• 2 x 1.5 mm collimation

• 2 mm slice width

• 99 s spiral duration

• 2 mm, Pitch 2

• low dose ( 90 mA)

Siemens Emotion / Emotion Duo

Spine



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2 x 1 mm, 60 mAs

1.25 mm axial slice

Siemens Emotion Duo

Pediatrics Head

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• life size filming

• semi-automatic

evaluation for the

jaws and teeth

• presurgical planning

for implants

Dental CT: Clinical Option



12/9/2008 | Page 10Brain: Cerebral Infarction I

CT MRI

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12/9/2008 | Page 11Brain: Cerebral Infarction II



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measurement of bone mineral density (BMD) for: • early detection• diagnosis• follow-up of osteoporosis

management of: • metabolic bone diseases • fractures in aging patients

Osteoporosis: Bone Density Evaluation

- CT accuracy of 10% is required due to individual variation of about 30%- but CT reproducibility of better than 2% is necessary in follow-up studies !

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assessment of pulmonarystructure & function

emphysema cystic fibrosis

clinical evaluation of newtherapeutic approaches

lung volume reductionsurgery (LVRS)pharmaceutical treatment

research & therapy in respiratory care (ICU)

Pulmonary CT: Lung Density Evaluation



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source: Aurich and Beck. Institut für Informatik der Heinrich-Heine-Universität Düsseldorf, http://www.eccet.de/sample/colon.html#top

Virtual Coloscopy

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CT Angiography

CT Angiography



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1 mm, Pitch 2Siemens Emotion

2 x 0.5 mm, Pitch 3Siemens Volume Zoom

Cerebral Arteries

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2 x 1 mm, Pitch 3, 1.25 mm SW 130 kV, 100 mA, 0.8 s, 2 mm, Pitch 2

Siemens Emotion / Emotion Duo

Carotids



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130 kV, 143 mAs, 0.8 s, 2 x 1.5 mm, Pitch 4Siemens Emotion Duo

35 cm

Abdominal Aortic Stent Follow-up

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12/9/2008 | Page 19Kidney CTA



12/9/2008 | Page 20Lung CTA

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CT Contrast Agent

CT Contrast Agent



12/9/2008 | Page 22Contrast Study Challenges

HU

time (s)

single slice: 40 s

multislice: 5 s

- catching the bolus at the right moment

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pre-monitoringreference scan start injection

monitoring scans spiral scan

CARE Bolus - Automatic Bolus Tracking

patient individual start of the spiral scan



12/9/2008 | Page 24Perfusion CT: ROI Evaluation

1 2

time – density curve

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40 s

5 s

Perfusion CT: Time – to – Peak Map



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perfusion (CBF) time - to - peaknative CT

Early Stroke Diagnosis

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12/9/2008 | Page 27Perfusion CT: Follow-up I

62 years old women, 0.7 h after beginning of symptoms, hemiparesis left

40 sec

5 sec



12/9/2008 | Page 28Perfusion CT: Follow-up II

66 years old women, 1.2 h after beginning of symptoms, hemiparesis right

40 s

5 s

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12/9/2008 | Page 29Perfusion CT: Follow-up III

68 years old women, 2 h and 1 day after beginning of symptoms, hemiparesis left

0. day(2.0 h)

0. day2 h

1. day19 h

5 sec

40 sec



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CT Cardio Imaging

CT Cardio Imaging

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prospective triggeringsequence scans in a single heart phase

- quantification of coronary calcification- motion free images of thorax- imaging of large pulmonary vessels

retrospective gatingspiral acquisition and ECG-recording parallelreconstruction of imaging data at different heart phases possiblenot sensitive to cardiac arrhythmia since retrospective fitting of imaging data to the ECG-curve

high resolution coronary CTA imaging of bypass-transplants quantification of coronary calcification at high reproducibility

Cardio CT



12/9/2008 | Page 32Cardio CT: Retrospective Gating I

ECG

time

z

zr

proj

ectio

n an

gle

θ

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12/9/2008 | Page 33Cardio CT: Retrospective Gating II

= 165 msrotation time2

temp. resolution =

- single source CT: temporal resolution of maximum 165 ms

courtesy: Siemens Medical Solution, Erlangen



12/9/2008 | Page 34Cardio CT: Retrospective Gating III

- single source CT: technical challenge with high heart rates


60 bpm 100 bpm

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source: Blobel et al. Fortschr Röntgenstr 2003

(a) 1 segment (half-scanreconstruction > 200 ms)

(b) 4 segments(c) 2 segments(d) 3 segments

Cardio CT: Multi – Segment Reconstruction



12/9/2008 | Page 36Cardio CT: Retrospective Gating IV

- single source CT: multi-segment reconstruction


1 2

coronary arteries change position =limited image quality

(2 segment recon)varies between = 83 and 165 mstemp. resolution =

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heart beat = 70 b/min heart beat = 85 b/min heart beat = 100 - 110 b/min

Cardio CT: 3D Reconstruction



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3D reconstruction of heart and coronary vessels using four-slice multi-slice CT. Note the stent in the proximal part of the left anterior descending artery

cardiac vessel analysis of the stentedsegment in the same patient (Courtesy of Central Bank Medical Center, Moscow)

source: ECR Newsletter 4/2002

Cardio CT: Stent

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source: Kalender. Computertomographie, Publicis MCD Verlag 2000

Cardio CT: Coronal Angiography



12/9/2008 | Page 40Cardio CT: Heart Function (Pig)

- retrospective ECG gating

~ 70 ms

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Dual Source CT

Dual Source CT



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design of using multiple X-ray tubes with corresponding detectors

has been proposed in the early years of CT to reduce scan time and increase temporal resolution

(adapted according to Boyd, 1981).

Dual Source CT: Principle I


X-ray fan

stationary detector ring

X-ray sourcealternative: rotating

detector ring

field-of-view

tube 2

tube 1

gantry window

detector 1

dete

ctor

2

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0.33 seconds rotation

Dual Source CT: Principle II- dual source CT: two X-ray sources and two detectors at the same time




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large aneurysm of ascending aorta

triple rule-out examination with artifact-free visualization of right

and left coronary arteries and aortic arch

pulmonary embolism (arrow)

pulmonary embolism

(arrow)

source: www.siemens.com/medical © 04.2007

Dual Source CT: Results I

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= 83 msrotation time4

temp. resolution =

Dual Source CT: Temporal Resolution


- dual source CT: heart rate independent temporal resolution of 83 ms



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60 bpm 100 bpm


Dual Source CT: Retrospective Gating - dual source CT: reliable imaging of all heart rates

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single source CT dual source CTsingle source CT +

multi segment recon.

courtesy: University Medical Center Grosshadern, Munich

Dual Source CT: Results II- dual source CT: patient with varying heart rate between 86 bpm and 122 bpm

heart rate independent temporal resolution of 83 ms



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- heart rate independent - temporal resolution: 83 ms- spatial resolution: 0.33 mm- 5 s for 103 mm- rotation: 0.33 sec- 120 kV, 400 mAs/rotation- heart rate: 73 bpm

courtesy: Erasmus MC, University Medical Center Rotterdam, The Netherlands

Dual Source CT: Results III- dual source CT: precise RCA and LAD in stent visualization with reduced

blooming and without motion artifacts

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courtesy: Nagoya City University Hospital, Nagoya, Japan

Dual Source CT: Results IV- dual source CT: despite high heart rate of 90 bmp, motion free visualization

of the coronary arteries



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courtesy: University Hospital of Munich – Grosshadern, Munich

Dual Source CT: Results V- dual source CT: despite high heart rate of 122 bmp, motion free visualization

of even small coronary arteries

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- heart rate independent - temporal resolution: 83 ms- spatial resolution: 0.33 mm- 17 s for 270 mm- rotation: 0.33 sec- 120 kV, 300 mAs/rotation- heart rate: 64 - 89 bpm


Dual Source CT: Results VI- dual source CT: quick and accurate rule out of myocardial infarction, pulmonary

embolism, and aortic dissection



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Dual Source CT: Results VII- dual source CT: fast visualization of the complete human anatomy in only

42 s with 0.33 mm isotropic resolution

- spatial resolution: 0.33 mm- 42 s for 1889 mm- rotation: 0.5 sec- 120 kV, 120 mAs/rotation- 1889 mm scan range

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Dual Source CT: Results VIII- dual source CT: excellent visualization of the complete peripheral artery tree

showing an occlusion of the left iliac artery

- spatial resolution: 0.33 mm- 31 s for 1389 mm- rotation: 0.5 sec- 120 kV, 200 mAs/rotation- 1389 mm scan range



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Dual Source CT: Results IX

thanks to

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Micro CT

Micro CT



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- pre-clinical in vitro CT imaging

- setup of a μ-CT scanner withfixed micro-focus X-ray tube and areadetector while rotating object

principle of μ-CT scanner

photo of in vitro μ-CT scannerexperimental setup

(IMP Erlangen)


Micro CT: Setup I

rotating objectX-ray tube

detector

rotating axisX-raytube detector

rotating object

cone beam

variable zooming

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imaging of two tungsten wires with 10 µm thickness

3D imaging of bone biopsy osteporosis

3D imaging of a vessel stent for quality control


Micro CT: Resolution



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- pre-clinical in vitro CT imaging

- setup of a μ-CT scanner withrotating micro-focus X-ray tube andarea detector while fixed object

principle of μ-CT scanner

photo of in vitro μ-CT scanner(TomoScope 30s, VAMP

GmbH, Erlangen)

Micro CT: Setup II

mouse couch

detector

rotatinggantry

X-ray tube

detector

mouse couch

rotating gantry

X-ray tube

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whole body scan with about 80 µm resolution

Micro CT: Results I




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ALARA - principle = „As Low As Reasonably Achievable“

Comparison: CT and μ-CT


focus size

x-ray tube power

spatial resolution

scan time

detector

field-of-view

dose

in vitro μ-CT in vivo CT

flat panel detector flat panel detector

not relevant according to ALARA

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12/9/2008 | Page 61Micro CT: Results II

prof. dr. lothar schad - heidelberg university€¦ · • follow-up of osteoporosis management of:...

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