imaging: when to get mri, ct or pet-ct?

4/3/2014

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Imaging:When to get MRI, CT

or PET-CT?

Alina Uzelac, D.O.Assistant Clinical Professor Neuroradiology

UCSF Department of Radiology and Biomedical Imaging

San Francisco General Hospital

Overview

CT

MRI

PET-CT

Advanced Imaging Techniques

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Imaging Studies

Initial Assessment Head and Neck Ca:

degree of local infiltration

regional lymph nodes involvement

presence of distant metastases second primary tumors

Local Infiltration/Tumor Extent

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59 F w/ trauma.

Inseparable medial rectus

muscle

*

Orbital and Intracranial Extension Sinonasal Undifferentiated Carcinoma

Ax CT

Orbital and Intracranial Extension Sinonasal Undifferentiated Carcinoma

Floor of anterior cranial fossa

Medial rectus

Cor CT

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CT or MRI

All Pts. – initial staging MRI or CT for HEAD and NECK SCCa.

particularly useful in Pts. with clinically N0 neck.

CT vs MRI

CT and MRI are complementary to the clinical examination.

…and may also be complementary to each other.

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Bone window

CT = superior for cortical

bone erosion

Bone window

33 M with an inverted papilloma degenerated into SCCa

Local Invasion

Paraglottic fatextension

56 F w/ epiglottic mass

Ax CT w/

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Ax CT w/ Ax T1

Preepiglottic Space ExtensionBase of Tongue SCCa

CT versus MRI ?CT MRI

Sag CT w/ Sag T1

Preepiglottic Space ExtensionSupraglottic SCCa

CT versus MRI ?

*** *

Motion

CT MRI

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Prevertebral ExtensionPyriform Sinus SCCa

Imaging Studies

Initial Assessment Head and Neck Ca:

degree of local infiltration

regional lymph nodes involvement

presence of distant metastases second primary tumors

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Small Abnormal LNs

**

* * *

Ethmoid Sinus SCCaRecurrence

CT versus MRI ?

Preserved fatty hilum

Thickened cortex

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Clinical N0 neck can be PET negative, given small node volume (<1mL).

PET-CT

PET-CT Tongue SCCA

*

Small LN for PET

Ax CT

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**

CT adequate for ossified cartilage

Thyroid Cartilage InvasionLaryngeal SCCa

Ax CT w/ Ax CT w/

Ax T1 Ax T1 w/ Gd


MRI superior for marrow infiltration

**

*

**

*

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Ax T1 Ax T1 w/ Gd


MRI superior for marrow infiltration

**

*

**

*

Loss of nl fat bright signal Abnormal enhancement

Ax T2

MRI superior marrow infiltration

**

*

Thyroid Cartilage InvasionLaryngeal SCCaLoss of fat suppression

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MRI Cor T2 MRI Cor T1 w/

MRI > CT for distinguishing malignancy from mucus

33 M w/ sinonasal SCCa s/p resection returns w/ brain abscess

MRI Cor T2 MRI Cor T1 w/

MRI > CT for distinguishing malignancy from mucus

SCCa recurrence

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Returns w/ erythema and swellingax CT w/ cor CT w/

SCCa recurrence

perineuralspread cavernous sinus

SCCa recurrence

Ax CT

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Perineural spread of tumor

(use thinner slice thickness - 3 mm)

Intracranial extension

Nasopharyngeal Ca (initial staging and follow up).

MRI over CT

Intracranial ExtensionNasopharyngeal Ca

bone erosion along vidian canal

ax CT Ax T1 w/

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Dural invasion

Cor T1 Gd

Intracranial Direct ExtensionSNUC

*

MRI Staging of NPC

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PET-CT

? Routine PET for initial staging, unless:

Equivocal findings on CT or MRI.

High risk of distant metastatic disease.

Search for 2nd primary.

Nodal SCCa unknown primary.

To be done before Bx: Guide to area of highest yield

Bx can result in high uptake.

PET-CT

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PET-CT Superior to CT

ax CT

Cor PET-CT

Cricoid Cartilage InvasionSubglottic SCCa

Treatment Response

MRI

PET-CT Done 3 months post treatment completion

(prevent false positives).

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Nonsurgical Treatment Response

- radiologic resolution = cure- reduction in size < 50% = failure- 50–75% reduction = indeterminate

(close surveillance)

Advanced Imaging TechniquesPredicting Tumor Response

PET: High SUV = poor response

Diffusion (DWI) MRI.

Dynamic perfusion MRI (vs CT): Tumor hypoxia = radioresistance (and

chemoresistance).

Increased tumor perfusion => improved locoregional control.

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MRIDiffusion Weighted Sequence for

Tx response prediction

Nodal metastasis

*

Staging MRI tongue SCCa

ax DWI ax ADC

*


Tx response prediction


Tx response

Nodal metastasis

*

Staging MRI Follow up

resolution of abnl diffusion

= Tx response

*

ax DWI ax DWI

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Recurrence Imaging

MRI (extent of tumor)

PET-CT (metastases)


recurrenceax DWI ax ADC

Hx mod diff SCCa tongue p-hemiglossectomy, chemoRT, followed by LND. Recurrence, then radical neck dissection w/ pectoralis

flap.

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52 M w/ Hx NPCA s/p XRT in China 4 years prior

RecurrenceMRI for extent of tumor

Solitary NPC metastasis biopsy-proven.

RecurrencePET for metastases

35 M presents with back pain 2 years after NPC treatment

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64-year-old male status post left totalmaxillectomy and free ALT flap for SCCa, post

chemo and radiation therapy.

*flap

RecurrencePET for flap

Treatment ComplicationsImaging

Complications occasionally incidentally imaged.

MRI

PET-CT

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44yo s/p XRT for NPC.

Post XRT ComplicationsSkull base XRT changes

PET negative

44yo s/p XRT for NPC.

Post XRT ComplicationsSkull base XRT changes

PET negative

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Bitemporal XRT necrosisAx T1 w/ Gd Cor FLAIR

Post XRT Complications

Bitemporal XRT necrosisAx T1 w/ Gd Cor FLAIR Ax PET

Post XRT ComplicationsNo abnormal

hypermetabolism

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Brain necrosis 5 years post XRT for NPC


Ax Gd perfusion


Bitemporal XRT necrosis

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Returns 12/2013 w/ L jaw pain and trismus

Oxaliplatin and CyberKnifeCompleted 07/2013 for recurrent

NPC

XRT necrosis central skull base and nasopharynx

*

Oxaliplatin and CyberKnifeCompleted 07/2013 for recurrent

NPC

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XRT necrosis central skull base and NP

*Masticator mm. acute

denervation

Acute Muscle Denervation P-XRT

PET PitfallAcute Muscle Denervation = High Uptake

Right extraocular mucles acute denervation

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PET PitfallAcute Muscle Denervation = High Uptake

84 M recurrent parotid malignancy

perineural spread

cavernous sinus.Right extraocular mucles

acute denervation

Whole BodyPET-MRI

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Whole BodyPET-MRI

Siemens integrated

PET-MRI

= simultaneous imaging

= superior registration

PET-MRI Siemens integrated

PET-MRI

= simultaneous imaging

= superior registration

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Initial Staging: CT or MRI. MRI for NPC

Consider PET-CT:Distant metastases

Positive neck nodes without identifiable primary

Look for second primary

TAKE HOME POINTSHead and Neck Ca Imaging

TAKE HOME POINTSHead and Neck Ca Imaging Predicting response – ADVANCED

imaging:

MRI Diffusion and Perfusion – tumor oxygenation

PET

MRI-PET!

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TAKE HOME POINTSHead and Neck Ca Imaging

Surveillance: MRI

Recurrence: MRI and PET

Thank you!

[email protected]

imaging: when to get mri, ct or pet-ct?

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