RD multisystem formatted Flashcards
- PET is most useful for (FDG PET can tell difference between)
a. Thyroid adenoma vs thyroid carcinoma
b. Brown fat vs liposarcoma
c. Gut uptake vs bladder uptake
d. Postmenopausal uterus & uterine cancer
d. Postmenopausal uterus & uterine cancer T PET has 89% PPV and 91% NPV in patients with endometrial cancer; 87.5% and 97.5% for uterine sarcoma. False positives due to normal cyclic variation (esp. early in menstruation) and post-op changes [StatDx]. The mean endometrial SUV of postmenopausal women receiving hormonal therapy was 1.7 ± 0.7 (range, 1.1–2.6) and that hormonal therapy in postmenopausal women was not associated with a significant alteration in endometrial FDG uptake. Increased FDG endometrial uptake in postmenopausal women may indicate malignancy. [AJR 2010]. Mean SUV for uterine cancer is 13 [StatDx].1. PET is most useful for (FDG PET can tell difference between) Great tables Mettler p380 & p402
a. Thyroid adenoma vs thyroid carcinoma F Normal thyroid has moderate uptake of FDG. While thyroid malignancy may cause focal ↑ uptake, benign thyroid nodules can give a FP. 50% of FDG-avid nodules are benign (usually follicular adenoma). [Mettler, StatDx]
b. Brown fat vs liposarcoma F Hibernoma is a benign but metabolically active tumour of brown fat origin that can result in a false-positive interpretation by exhibiting increased FDG activity with a SUV similar to liposarcoma. [AJR April 2008]
c. Gut uptake vs bladder uptake T? Bladder activity is intense, as FDG is excreted by the kidneys. Activity in the bowel is extremely variable, however it is limited to the mucosa (not intraluminal, not excreted by the liver/biliary tract into bowel). Activity in the small bowel is faint, but activity in the colon can normally be quite intense.
d. Postmenopausal uterus & uterine cancer T PET has 89% PPV and 91% NPV in patients with endometrial cancer; 87.5% and 97.5% for uterine sarcoma. False positives due to normal cyclic variation (esp. early in menstruation) and post-op changes [StatDx]. The mean endometrial SUV of postmenopausal women receiving hormonal therapy was 1.7 ± 0.7 (range, 1.1–2.6) and that hormonal therapy in postmenopausal women was not associated with a significant alteration in endometrial FDG uptake. Increased FDG endometrial uptake in postmenopausal women may indicate malignancy. [AJR 2010]. Mean SUV for uterine cancer is 13 [StatDx].
- Which doesn’t normally take up FDG during PET?
a. Bladder
b. GIT
c. Thyroid
d. Brain
they all uptake
- Which doesn’t normally take up FDG during PET?
a. Bladder T Bladder activity is intense, as FDG is excreted by the kidneys.
b. GIT T Activity in the bowel is extremely variable, however it is limited to the mucosa (not intraluminal, not excreted by the liver/biliary tract into bowel). Activity in the small bowel is faint, but activity in the colon (esp. ascending colon) can normally be quite intense.
c. Thyroid T Normal thyroid has moderate uptake of FDG.
d. Brain T Normal brain demonstrates high FDG uptake.
- Associations which are false
a. Strongyloides with duodenal stenosis
b. VHL with angiomyolipoma
b. VHL with angiomyolipoma F VHL gets renal cysts, clear cell RCC, haemangioblastoma or adenoma. TS gets AMLs.
a. Strongyloides with duodenal stenosis T Helminthic parasite Strongyloides stercoralis. Enters body thru skin/MMs. Causes paralytic ileus (massive intestinal infestation), proximal duodenal dilatation, oedematous irregular mucosal folds, ulcerations & strictures of D3/D4 duodenum. Widespread dissemintation (“hyperinfection”) in immunocompromised host.
- LEAST LIKELY to be associated with chronic alcoholism?
a. AVN of the femoral head
b. Subdural hematoma
c. HOCM
d. Communcating hydrocephalus
e. Chronic parotitis
c. HOCM F dilated cardiomyopathy assoc/ w/ alcoholism; hypertrophic cardiomyopathy usually familial or sporadic
- Which of the following will increase the signal-to-noise radio in MRI?
a. Decreasing the voxel size
b. Decreasing the number of signal excitations
c. Increasing the number of phase encoding lines
d. Increasing FOV
e. Decreasing field strength
d. Increasing FOV T ↑ FOV & ↓ matrix size → ↑ SNR (more signal per voxel). Trade-off is ↓ spatial resolution.2.
Which of the following will increase the signal-to-noise ratio in MRI?
a. Decreasing the voxel size F ↑ voxel size → ↑ SNR
b. Decreasing the number of signal excitations F ↑ NEX (number of excitations) → ↑ SNR
c. Increasing the number of phase encoding lines F Increasing Ny (number of phase encoding steps) only increases SNR if you also maintain the voxel size by changing the FOV.
d. Increasing FOV T ↑ FOV & ↓ matrix size → ↑ SNR (more signal per voxel). Trade-off is ↓ spatial resolution.
e. Decreasing field strength F ↑ B0 → ↑ SNRSignal-to-noise ratio (SNR) depends on…
• Magnetic field strength – ↑ B0 → ↑ SNRo For small biological samples, if the receiver coil is the dominant source of noise, SNR ∞ B01.75 (∴ doubling B0 leads to 3.3 x’s SNR)
o Tissue RF attenuation causes thermal noise & limits SNR in practice, resulting in an ≈ linear relationship in large biological samples
• Intrinsic signal intensity of tissue (i.e. PD, T1 & T2 parameters) – tissues with short T1 & long T2 provide strong signals & thus improved SNRo Trade-off b/w T1W TR for contrast & noise (short TR to optimise contrast, long TR to optimise SNR)
• Voxel size (pixel size & slice thickness) – ↑ voxel size → ↑ SNR
o Dependent on:
• Pixel size (dependent on FOV & image matrix - ↑ FOV & ↓ matrix → ↑ SNR)
• Slice thicknesso Trade-off is ↓ spatial resolution
• RF receiver bandwidth (BW) – ↓ receiver bandwidth → ↑ SNRo SNR ∞ √1/BW
o The larger the readout (frequency-encoding) gradient, the greater range of frequencies that need to be detected & the lower signal strength at any one frequency, resulting in ↓ SNR
o Trade-off with ↓ receiver bandwidth (& ∴ ↑ SNR) is ↓ spatial resolution
• Use of RF surface coils & their quality
o Improve SNR because they detect noise originating only from the imaging volume within the RF coilo Major advantage is improved spatial resolution
• Number of acquisitions/excitations (NEX) – ↑ NEX → ↑ SNRo SNR ∞ √NEX
o Depends on no. of phase-encoding steps & frequency encoding datao 3D-FT has superior SNR over 2D-FT (all other factors constant)
• Main trade-off with ↑ SNR is ↑ imaging timeNote : improve SNR by- increase magnetic field strength- increase FOV- decrease voxel size- decrease bandwith
- Which of the following statements regarding PET scanning is FALSE?
a. PET has a limited use in assessment of stage I and II myeloma
b. Bronchioloalveolar carcinoma is usually not intensely PET avid
c. PET has a high sensitivity in diagnosing mesial temporal eplipsy
d. PET is superior to MRI in diagnosing cerebral metastases
e. FDG uptake can be seen in active pulmonary tuberculosis
d. PET is superior to MRI in diagnosing cerebral metastases F Normal brain metabolism of FDG (glucose) can hide small metastases. C+ MRI is gold standard. [StatDx]
.3. Which of the following statements regarding PET scanning is FALSE?
a. PET has a limited use in assessment of stage I and II myeloma T see below – may have more than just a ‘limited’ role though
b. Bronchioloalveolar carcinoma is usually not intensely PET avid T BAC, carcinoid & low-grade adenocarcinoma may show low FDG uptake despite aggressiveness
c. PET has a high sensitivity in diagnosing mesial temporal epilepsy T Hypometabolism in abnormal mesial temporal lobe. Can use FDG or flumazenil. More sensitive than MRI. FDG-PET has 89% specificity & 91% sensitivity for TLE.
d. PET is superior to MRI in diagnosing cerebral metastases F Normal brain metabolism of FDG (glucose) can hide small metastases. C+ MRI is gold standard. [StatDx].
e. FDG uptake can be seen in active pulmonary tuberculosis T Active granulomatous disease is FDG avid [StatDx]
Durie-Salmon staging system (Multiple myeloma)
• Stage I
o Small number of myeloma cellso Slightly ↓ hemoglobino Plain films with ≤ 1 lesion or area of bone involvemento Normal calcium
o Small amount of monoclonal immunoglobulin in blood/urine
• Stage II
o Moderate number of myeloma cellso Labs and plain films intermediate between stage I and III
• Stage III
o Large number of myeloma cellso Severely ↓ hemoglobino Hypercalcemia
o ≥ 3 sites of bone involvement on plain films
o Large amount of monoclonal immunoglobulin in blood/urineMultiple myeloma imaging
• FDG PET useful foro Evaluation of disease activityo Detection of extraosseous disease involvemento Direction of local therapy (e.g., radiation)
o Assessment of patients with nonsecretory myeloma
o Evaluation of response to therapy
• FDG PET/CT with contrast
o Superior to MR in the detection of focal lesions
• MR better for diagnosis of diffuse disease pattern
o Limited window (spine and pelvis) reduces sensitivity
o Generally reserved for evaluation of bone marrow in spine and pelvis
o Improved ability to detect both focal and diffuse disease
• Protocol advice
• For detection of diffuse disease, obtain PET/CT from top of head to toes
• For patients not affected by renal failure (which is common in MM), use oral and IV contrast-enhanced CT
- MR pulse sequence FSE or TSE has the following characteristics on 3T or higher field MR scanners?
a. Increased imaging speed is limited mainly by the TE
b. Increased imaging speed is limited mainly by the TI
c. Increased imaging speed is limited mainly by the gradient switching
d. Increased imaging speed is limited mainly by the specific absorption rate
e. Increased imaging speed is limited mainly by the TR
d. Increased imaging speed is limited mainly by the specific absorption rateBJR 2007:Generally, TSE techniques require high radiofrequency (RF) power, because many refocusing pulses are necessary to build the echo train. Doubling the field strength (e.g. from 1.5 to 3.0 T) results in a fourfold increase in RF power; consequently, the specific absorption rate (SAR) limits are exceeded earlier in the highfield environment. Therefore, the signal gain from highfield MRI cannot be easily transferred into faster TSE sequences, because the repetition time (TR) and the echo spacing cannot be chosen as short as technically possible.In T1 weighted sequences, the need to choose a short TR limits echo train length. The risk of artifacts and the large quantity of radiofrequency energy deposited by 180° pulses restricts the parameters (TR, effective TE, echo train length) of this type of sequence. [Imaios]The shorter the TE, the higher the Signal-to-Noise Ratio (SNR), and as the TE increases, the SNR will steadily decrease. Echo train length (ETL) is the number of 180 refocusing pulses that are in one TR of the FSE sequence.
- Regarding MR pulse sequence STIR (short tau inversion recovery), which of the following statements is MOST CORRECT?
a. Produces fat suppression through chemical shift phenomena
b. Produces fat suppression through relaxation phenomena
c. Produces water suppression through relaxation phenomena
d. Produces fat suppression through magnetization transfer phenomena
b. Produces fat suppression through relaxation phenomena
• STIR (Short TI IR): used for fat suppression
o TI is selected to null the signal from fat (e.g. 150 – 180 ms in 1.5 T magnet)
o Tissues with long T1 values appear bright
o Enables multi-slice acquisition
• FLAIR (fluid-attenuated IR): used for CSF suppressiono TI is selected to null the signal from CSF (e.g. 1500 – 2200 ms)
o May improve detection of peri-ventricular lesions, e.g. plaques
